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Title: The Courtship of Animals
Author: Pycraft, W. P. (William Plane)
Language: English
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Hutchinson’s
Nature
Library
THE COURTSHIP OF ANIMALS
[Illustration: Plate 1.
LOVE-MAKING.
Frontispiece.]
The
Courtship of Animals
BY
W. P. PYCRAFT
OF THE
ZOOLOGICAL DEPARTMENT OF THE BRITISH MUSEUM: FELLOW OF THE ZOOLOGICAL
SOCIETY OF LONDON; ASSOCIATE OF THE LINNEAN SOCIETY: MEMBER OF THE
ROYAL ANTHROPOLOGICAL INSTITUTE; MEMBER OF THE BRITISH ORNITHOLOGISTS’
UNION; HON. MEMBER OF THE AMERICAN ORNITHOLOGISTS’ UNION; ETC., ETC.
Author of “A History of Birds,” “The Natural History Museum,” “Pads,
Paws and Claws,” “The Infancy of Animals,” etc., etc., etc.
_With 40 Plates on art paper Containing over 80 Illustrations_
_THIRD EDITION_
LONDON
HUTCHINSON & CO.
PATERNOSTER ROW
I DEDICATE THIS VOLUME
TO
H. ELIOT HOWARD
WHOSE OBSERVATIONS OF THE COURTSHIP OF BIRDS RECORDED IN HIS “HISTORY
OF THE BRITISH WARBLERS” CONSTITUTE A BEACON FOR ALL ENGAGED IN THE
STUDY OF ANIMAL BEHAVIOUR
PREFACE
That “one touch of Nature which makes the whole World kin” is surely
nowhere more obvious than in the “Courtship” of Animals. For the
“Beasts that Perish,” no less than Man himself, are stirred by the
same emotions; the Fever of Love runs as high in them as in ourselves;
and its modes of expression are not so different, though they may
superficially appear to be so. The nature of these differences and
their interpretation, it is the purpose of this book to set forth.
Charles Darwin laid the foundation for the study of this phase of
Animal behaviour in his masterly work on the “Descent of Man,” a work
which has been much criticized and much misunderstood since Carlyle’s
crude abuse of it as the “Gospel of Dirt.” Darwin was the first to show
us that the fierce battles, and strange antics, which characterize so
many of the “Lower Orders of Creation” under the exaltation of the
Sexual emotions are manifestations fraught with tremendous consequences
to the race.
The facts which he brought to light, and the discussions to which
they have given rise, have, however, unfortunately been too commonly
regarded as merely interesting to those who have a liking for Natural
History.
This is a most unfortunate mistake. For such facts have a vitally
important bearing on the very problems of social well-being which now
loom so largely among us. “Reform” is in the air. Its protagonists
are busy amongst us with schemes for our regeneration, among which
“Sex-problems” are made to occupy a very conspicuous place. But no
good can come of their cogitations so long as they fail to realize the
springs of behaviour in this regard. The facts herein set down will, it
is hoped, help much towards this end.
My labours in the preparation of these pages have been materially
lightened by the help and counsel of many friends. To them I desire now
to record my very grateful thanks. More especially am I indebted to my
friends Mr. H. Eliot Howard, Professor Lloyd Morgan and Mr. John Cooke.
I must also thank those who have contributed towards the illustrations
which enliven these pages. The delightful Frontispiece, and many of the
plates scattered through this work, I owe to the generosity of Messrs.
Rowland Ward, Limited. The excellent rendering of the Birds of Paradise
adapted in part from the work of Mr. G. E. Lodge and the late J. G.
Keulemans, and partly drawn from specimens in the British Museum, is
the work of Mr. Roland Green. The very difficult, and less fascinating,
technical figures I owe to the skill of Mr. Philip Whelpley. The
wonderful photographs illustrating the “Display” of the Sun-bittern and
the Kagu were taken by my friend Mr. D. Seth-Smith.
Finally I have to thank Mr. Roger Ingpen for the immense amount of
trouble which he has taken in seeing these pages through the press.
W. P. Pycraft.
October, 1913.
CONTENTS
CHAPTER
INTRODUCTION
The nature of Life and its power of reproduction—The
stuff of which Life is made—The Emotions—The simplest
living things—Where is neither Birth nor Death yet the
Population increases—The First Marriage—The beginning
of sex—The two dominating instincts—The conditions
of survival—The Oyster’s narrow world—“Fiddling
work”—Amorousness—The superior Male—Where Death
begins—“Germ-plasm” and what it means—Sex and “Secondary
sexual Characters”—Some theories—“Hormones” what are
they? 1
CHAPTER II
“MANKIND IN THE MAKING”
The use of the term “Courtship”—Primitive Man and
the Foundations of Society—“Amorousness” as a motive
force—Polygamy—Our half human ancestors—Standards of
Beauty—Disquieting signs 21
CHAPTER III
MAN’S COUSINS THE APES
The Man-like Apes and their mode of Life—Their
“Courtships”—Musical Chimpanzees—How the Orang-utan
improves his voice—His likeness to Caliban—The truculent
visage of the Gorilla—“Ornament” in the lower Apes—The
Concerts of the Howler Monkeys 40
CHAPTER IV
AT DAGGERS DRAWN
The Birth of Weapons—All Flesh is Grass—Utility and
Ornament—The Fever of Love—The “Challenge” of the
Deer—What it means-More about “Hormones”—“Hummel”
Stags—The Age of Deer—The “Courtship” of the Moose—Types
of Antlers—Antlered Females—Fighting Topi—The Lance
of the Oryx in the Lion’s Flanks—Happiness and
Hartebeestes—Odoriferous Suitors—The Bloody Sweat
of the Hippopotamus—The Elephant in Love—Concerning
Tusks—Polygamy 49
CHAPTER V
THE LION AND HIS KIN
A Surprising Relationship—The Lion’s Mane—The
Sabre-toothed Tiger—Some Theories about Origins—Sea-lions
in Love—Some Strange Ornaments—Whales and Weapons 77
CHAPTER VI
COURTSHIP AMONG BIRDS
Generalities—Darwin v. Wallace—The Peacock in his
Pride—The “Display” of the Peacock Pheasant—The
Splendour of the Argus Pheasant and the Marvel of
its Eyes—The Frill of the Amherst Pheasant—Birds of
Paradise in the Toils of Love—Inflated Suitors-Ruffs
and Reeves—Fearsome Weapons and their Uses—Birds which
dance-Musical Birds—The Bird’s Voice-box—The “Lek” of
the Capercaillie—Instruments of Percussion—The Curious
Performance of the Woodpecker 92
CHAPTER VII
THE SEXUAL SELECTION THEORY AS APPLIED TO BIRDS
Where the Rôle of the Sexes is reversed—Polygamy and how
it is brought about—Coloration and Courtship—Instinctive
Actions—The Importance of Landed Possessions—The Meaning
of “Display”—The Springs of “Behaviour”—A New Light
on the Wild-duck—The “Display” of the Great-crested
Grebe—Some Neglected Factors 134
CHAPTER VIII
SOME “COLD-BLOODED” LOVERS
The Courtship of the Crocodile—Amorous Lizards—Horned
Chameleons—A Flagellating Terrapin—The Frog that would
a-wooing go—Some Musical Frogs—Some marvellous instincts
in Newts 161
CHAPTER IX
LOVE-MAKING AMONG THE FISHES
Germinal variations—Fishes and Mate-hunting—Some
Remarkable Sexual Differences displayed by the Teeth
of “Rays”—The Double-eyed Fish—The Coloration of the
Dragonet—Some Curious Facts about Salmon—The Strange Use
of the Kidney in the Stickle-back—The Stickle-back and
Parental Duties—Siamese Fighting-fish 175
CHAPTER X
SOME OF THE “LOWER ORDERS”
Butterflies and Moths, and the Coloration of their
Wings—Female Choice and “Fine Feathers”—When Male
Butterflies are Dominant—Sexual Selection among
Butterflies—Abortive Experiments—Wallace and the Sexual
Selection Theory—The Sense of Smell in Butterflies and
Moths—Fragrant Butterflies—Wingless Moths and their
Lures to Lovers—Methods of Pairing among Butterflies and
Moths—More Experiments 185
CHAPTER XI
BEETLES THAT “BLUFF”
The Coloration, and other Forms of Ornament in Beetles,
and the Significance thereof in regard to the Sexual
Selection Theory—The Courtship of Grasshoppers and their
Kin—The Remarkable Ears of Locusts and Grasshoppers—The
Field-cricket and the Katydid as Troubadours—The
Wonderful Performances of the Cicadas—The Duels of
Long-horned Locusts—Dragon flies—The May-flies’ “Dance of
Death”—The Jaws of the Giant Alder-fly and their Strange
Use—Some Curious Facts about Stone-flies 208
CHAPTER XII
SCORPIONS, SPIDERS AND CRABS
Musical Lovers among Spiders and Scorpions—Colour
among Spiders, and its uses—The Spiders’ Dance of
Death—Spiders and Conjugal Bliss—How Pairing is
accomplished—Scorpions in Love—Musical Crabs—Quarrelsome
Fiddler-crabs—Crabs and Courtship in the Deep Sea-Amazons
among Prawns—Brine-shrimps and Water-fleas—“Natural” v.
“Sexual” Selection 236
CHAPTER XIII
SOME STRANGE MARRIAGE-CUSTOMS: AND VIRGIN BIRTHS
The Courtship of the Cuttle-fish—The Sumptuous Cradle of
the Argonaut—The Love-darts of the Snail—Hermaphrodites
and the Dangers of Self-fertilization—Oysters and
Beauty—Sex reduced to its Lowest Terms—Parthenogenesis
and Virgin Birth—The Story of the Hive-Bee—The Departure
of the Queen—The New Queen and her Marriage-flight—The
Celebration of the Nuptials and its Surprising Sequel—The
Widowed Queen turns Executioner—The Queen as Mother—The
Queen’s Daughters—Nursemaids’ Duties—Change of Work—The
Drones and their Career—Food and Sex—The Bumble-bee and
its Life-story 265
CHAPTER XIV
PARTHENOGENESIS AND ITS SEQUEL
Courtship among the Ants—The Great Renunciation—Maternity
carried to Extremes—Where Males are
Superfluous—Degenerate Males—Keeping Death at Bay—Where
Females are Unknown 296
LIST OF ILLUSTRATIONS
Love-making Frontispiece
Facing page
The Gorilla preparing for hostilities 42
The barometer of maleness—among the Apes 44
Weapons of offence 52
Manchurian Wapiti “calling” 54
Group of Beisa Oryx 60
Eland Cows 64
American Bison 64
Elephants 70
Head of male Wart-hog 72
Male and female Babirusa 72
Somali Zebras 72
Giraffe 72
Californian Sea-lions, or Eared Seals 82
Elephant Seal 88
Northern Elephant Seal 88
“The Peacock in his pride” 96
Peacock Pheasant 96
Patterns which puzzled Darwin 98
The “Strutting Turkey” 100
The display of the Great Bustard 100
Some of Fortune’s favourites 104
The love-making of the Prairie Hen 110
Grades of evolution in the syrinx or organ of voice in
the males of Surface-feeding and Diving-ducks 126
Fighting for territory 140
The display of the Grasshopper Warbler 142
The display of the Sun-bittern 142
The Kagu in display 142
A male-Savi’s Warbler 152
Another aspect of the Kagu’s “display” 154
Some strange accompaniments of courtship:
The White-headed Bell-bird 156
The Umbrella-bird 156
Skull of the American white-beaked Pelican 156
Head of a Puffin, showing the moulting of the beak
sheath 156
The Satin Bower-bird and its bower 158
The “bower” of the Bower-bird 158
The Bearded Lizard 166
Bright colours which cannot be attributed to “sexual
selection” 200
Stridulating organs, etc. 218
Crickets and May-flies 220
Male Astia displaying before the less brilliant female 242
Male Icius displaying 242
Scorpions 252
Death of the male Scorpion 254
The female Mantis devouring her mate 254
The “Fiddler-crab” among mangrove roots 258
The “Fiddler-crab” 258
Some remarkable devices 262
Some remarkable methods of “courtship” 268
THE COURTSHIP OF ANIMALS
CHAPTER I
INTRODUCTION
The nature of Life and its power of reproduction—The stuff of which
Life is made—The Emotions—The simplest living things—Where is neither
Birth nor Death yet the Population increases—The First Marriage—The
beginning of sex—The two dominating instincts—The conditions of
survival—The Oyster’s narrow world—“Fiddling work”—Amorousness—The
superior Male—Where Death begins—“Germ-plasm” and what it means—Sex and
“Secondary sexual Characters”—Some theories—“Hormones” what are they?
The nature of life is generally regarded as affording a theme which
possesses no more than an academic interest: but there is one aspect
of this great subject which must attract us all, and that is its power
of reproducing itself. Life begets Life, as Love is said to beget
Love. The nature of this mysterious power we can only dimly realize,
and the forces which underlie its manifestations few even suspect,
save perhaps in a vague way. Yet the tree of Knowledge bears no fruit
more vitally important to our well-being, than that which will make us
“as Gods, knowing good and evil” in all that concerns the processes
of reproduction. But curiously enough, this is a forbidden fruit, and
those who eat thereof are expected to maintain a discreet silence on
the subject. These enlightened ones, however, cannot remain altogether
dumb. But they speak, in the veiled language, of Art and Poetry,
Literature and the Drama. They talk round the subject rather than of
it. Love, Hate, Jealousy, and Envy, are but attributes thereof. We
profess to believe that “Knowledge is Power” and to desire to increase
its force among us by raising the standard of our system of education.
But education which does not, of set purpose, reveal the sources of our
being and of our emotions, good and evil, is no more than a travesty
of education; and they who seek to foist upon the community Knowledge
thus emasculated, are unworthy to wield the power which has been placed
in their hands. If social well-being be the aim of the high-priests
of Education, then something more than copybook maxims like “Be good
and you will be happy” must henceforth be preached. Of what avail is
it to exalt the name of Knowledge, while the straightest road thereto
is barred across and marked “No thoroughfare!” These blind leaders of
the blind seem to imagine that the social well-being they profess to
desire can only be attained by side roads, leading anywhere, save in
the direction of this Pool of Siloam.
The stuff of which living things are made is called “Protoplasm.”
Text-books of Physiology give its chemical constituents with fearsome
accuracy, and each of these constituents can be isolated in the
laboratory, but “all the king’s horses and all the king’s men” cannot
build these up again into living matter. Its consistent inconsistency
defies us; every statement we make of it has to be qualified by
reservations and saving clauses. Its permanency is attested by the
fact that it has endured through millions of years, yet we are daily
reminded of its evanescent nature. Its power of reproducing itself
according to type, none can doubt, yet no two individuals are exactly
alike.
The purely physical phenomena of life, to be rightly appreciated, must
always be considered in relation to the psychical phenomena which
are the soul of life. These subtle and intangible forces cannot be
experimented with in the laboratory, or expressed in formulæ; we
cannot denote their strength in horse-power. Just as the physical
manifestations of life begin with lowly types, so the psychical begin,
and they gather strength and complexity with the bodies they pervade.
These manifestations we call behaviour, and in their more intense
developments, “emotions.”
These emotions present an infinite range of variety in the higher
animals, and they attain their maximum of intensity wherever the
reproductive activities are concerned. The part which these activities
play in controlling behaviour is by no means always apparent, and
is commonly not even suspected. Even man himself is subject to this
control. And it is this fact which lifts the “Courtship” of the lower
animals out of the category of merely curious phenomena. For the
springs of his conduct, his behaviour and “emotions” under varying
circumstances, can only be understood, and even then but imperfectly,
by comparison with other creatures lower in the scale, so far, of
course, as comparison is possible.
This line of inquiry, then, takes one back to the simplest living
things, among which there is neither marrying nor giving in marriage,
neither birth nor death. Life is reduced to its simplest terms—a speck
of animated jelly is all that confronts one, and this is only to be
seen under a high power of the microscope. It has neither mouth nor
organs of digestion, no visible means of locomotion are traceable,
and the special senses of sight and hearing are wanting; but taste
and smell, of a nebulous kind, are there. Shape it cannot be said to
have, for its bodily outline is constantly changing, thereby it moves.
A long tongue of its jelly-like substance, or “protoplasm” as it is
called, is thrust forwards, and the rest of the body is, as it were,
dragged after it. Whatever animal, or vegetable, matter it passes
over, in the course of its wanderings, is drawn up into the semi-fluid
substance of this diaphanous body, and its juices extracted, the
undigestible residue is left behind in the course of the morning’s
walk! In due time it becomes adult; further growth is impossible. When
this stage is attained a strange thing happens. A certain minute, more
solid portion of this body, which lies in the very centre of the mass
and is known as the “nucleus,” begins to assume an hour-glass shape.
Speedily the constriction becomes apparent across the whole body and
rapidly increasing, cuts it in two, as if by the tightening of some
invisible thread. Here Death is cheated, and records of births are
unknown! And just as there are no parents so there are no children.
But a foreshadowing of what is to be occurs even here. For every now
and then two individuals, to all appearances identical, meet and
promptly begin to merge the one into the other till they twain become
one flesh in very truth. Here is the most primitive form of marriage
in Nature. And here, in this union, or fusion, of separate entities of
Germ-plasm, we have the beginning of sex. Such unions are common among
these primeval forms of life. In many cases this “marriage” takes place
between two particles of Protoplasm of which one is rather larger than
the other. In such case the smaller is regarded as male, the larger as
female. Here we have the first sign of “sexual differentiation” or the
evolution of “male” and “female” individuals.
Some such union, some such process of “rejuvenation” by the importation
of “fresh blood” seems to be imperative for the continuance of
existence throughout the whole animal world, even though it may take
place at rare intervals of time. Why should this be? Is this strange
meeting and commingling a matter of chance, or is the one seeking the
other possessed by a ravenous mate-hunger?
As we ascend higher in the scale it becomes apparent that life has
gathered force. That primitive speck of jelly, the Amœba, with which
we started, gave but two signs of animation—the power of movement,
and hunger. Whether these responses to internal stimuli can be called
instinctive is open to argument. But there can be no question about
the instinctive nature of the behaviour of these higher animals.
After the instinct to feed the two most powerful are the desire for
self-preservation—the avoidance of danger—and the desire to mate. These
two are the dominating instincts throughout the rest of the animal
world, not even excepting man himself.
The tremendous power of “mate-hunger” has been overlooked by a strange
confusion between cause and effect. Almost universally its sequel, the
production of offspring, has been regarded as the dominant instinct in
the higher animals. This view has no foundation in fact. “Desire” for
the sake of the pleasure it affords, and not its consequences, is the
only hold on life which any race possesses. And this is true both in
the case of man himself and of the beasts that perish. Wherever this
instinct becomes weak, or defective, extinction speedily and inevitably
follows. This “Amorousness” is the motive power of “Courtship” wherever
it is met with; manifesting itself in the eccentric, and often
grotesque posturings, or in the loud and often musical cries which
constitute the study of courtship. Intensity of desire is indispensable
to survival.
Only the lowly and sedentary types, of which the Oyster may be taken
as an example, lack this fire; and here because it is unnecessary. For
the reproductive germs of this animal are discharged into the water,
to take their chance of attaining their object. They are liberated
unconsciously, discharged like the undigested residue of the food,
without effort, and without cognizance of the act. This must be so,
for the Oyster merely lives—vegetates. Sightless, and without power
of movement, after its larval wanderings are over, it lives merely
to eat. And even in this, choice is denied it. The currents of water
mechanically brought to afford the necessary oxygen for the maintenance
of life, bring with them the food which is to restore the slowly
wasting tissues. To such a creature there can be no “outer-world,” no
consciousness of the existence of individuality other than its own.
The desire for sexual intercourse is met with only where the
co-operation of two individuals is necessary to ensure the production
of offspring. Such individuals being free to roam, must have some
incentive to seek one another at the time when their germ-cells have
attained maturity. And this incentive is furnished by the glands in
which these elements are produced: supplemented by the secretions
of certain ancillary glands. These stimulating juices, known as the
“Hormones,” will be presently described.
But if we owe our existence to the gratification of what may be called
our lower instincts, it is no less certain that all that is best in us
we owe to our offspring. We meet with the beginnings of altruism, which
the begetting of offspring entails, far down in the animal kingdom, and
it attains to its full perfection in the human race. Here only, in its
best and truest sense, Love begins: though affection may be found, and
in a high degree, in many of the lower animals.
Living things are as clay in the hands of the potter. But it is as if
they made themselves, for the designer and the guiding hand are alike
invisible. No vessel is exactly like its neighbour, either in the
quality of its substance or in the details of its construction. And
this because the clay of which it is made possesses that mysterious
property we call life. A property which endows each new feature as
it appears, with an individuality of its own, whose survival, or
suppression, depends entirely on its relationship to surrounding parts;
on its harmony with its environment, in short. Colour, size, shape,
temperament, behaviour, may each be regarded as so many entities
depending for survival on whether or not they can exist in harmony with
their environment—the several parts which make up what we call the
individual.
In like manner the individual—the complex bundle of parts and
qualities—must attain, and maintain, a certain harmony with its
environment—the outer world. The process of change, both in quality
and quantity, which is for ever going on among the several parts of
every separate individual, brings about the elimination of unfavourable
variations; and “selects” those which vary in the right direction:
that is to say, which serve to maintain a place in the sun for the
individual in which these momentous changes are going on. But it is not
enough that the individual should be in “working order”; it must be in
harmony with all the conditions on which existence depends. And the
standard of this harmony is set by that very exacting arbiter of life
and death, “Natural Selection.” It is not enough that the instincts
in regard to this or that habit should be keen, or that this or that
particular organ of the body should be efficient—a certain minimum,
all-round, standard of efficiency is demanded, or elimination follows.
It is through this instability of “temperament,” this tendency to vary
in infinite directions, that the balance between the individual and
the environment is maintained. Evolution follows the line of least
resistance.
The little boy who remarked that it must be “fiddling work, making
flies,” was more sage than he knew. The complex web of factors which
even a fly represents are beyond the grasp of human understanding. But
it is clear that the reproductive instincts, and the emotions they
beget, have played, and play, a tremendous part in the evolution of the
higher animals.
Those whose business it is, for one reason or another, to study
these emotions know well that “mate-hunger” may be as ravenous as
food-hunger, and that, exceptions apart, it is immensely more insistent
in the males than in the females. But for this, reproduction in many
species could not take place: for the sexes often live far apart, and
mates are only to be won after desperate conflict with powerful rivals
no less inflamed. Thus it is idle to speak of an equality between the
sexes in this matter, in regard to the human race. Dogmatism, and the
frequent repetition of pretty platitudes, will not alter what Nature
has ordained. The failure to realize this is painfully obvious in
the utterances of many who speak in the name of the newly-founded
“Eugenics” society, which seeks the means to ensure the well-being
of the race by the spread of a more intimate knowledge of this
all-important subject. The existence of what Mr. Heape has recently
called a “sex-antagonism” is beyond dispute, for the instincts of the
male and female are fundamentally different. The male is dominated
by the desire to gratify the sexual appetite; in the female this is
counteracted by the stimulation of other instincts concerned with the
cares of offspring.
Amorousness, then, is the dominant feature of the males among all
animals: and this sex presents yet another characteristic which is to
be borne in mind. In all that concerns the evolution of ornamental
characters the male leads. In him we can trace the trend which
evolution is taking; the female and young afford us the measure of the
advance along the new line which has been taken. Why this should be is
inexplicable. But sooner or later the females assume, or will assume,
all the features originally possessed by their lords; and finally the
young also follow suit. That is to say, the females and young tend to
retain the ancestral characters. In the course of time the ability to
develop new features by the male loses its impetus, and not till then,
apparently, do the females, and still later, the young, begin to share
his glory. These remarkable features are strikingly illustrated among
the birds, as these pages will show.
Nature is nothing, if not perverse. And hence it happens that there
are many exceptions to every rule which one formulates. Among the
birds, for example, there are species wherein the rule that the female
follows her mate in the acquisition of new characters is, so to
speak, set aside. She follows a line of her own. This is true, at any
rate, of superficial characters, such as coloration. By some curious
change in her “metabolism,” as the conversion into living tissue of
the substances taken as food is called, this coloration may attain
a brilliance in no way inferior to that of the male, but strikingly
different. The beautiful Orange Fruit-pigeon (_Chrysoenas victor_)
furnishes a case in point, the male being of a gorgeous orange-yellow,
the female of a no less vivid green. But the differences are not so
great as they appear at first sight. For the male was originally green,
and the female has thus but intensified the ancestral livery. Green,
it should be remarked, of a more or less olive shade, always precedes
yellow in development; and yellow may yield to red, but this order is
never reversed. A no less striking case is that of the Upland Goose
(_Cloephaga magellanica_), the male of which is pure white, while the
female wears a livery of chestnut and brown. But so sharply are the
colours defined that it would be difficult to say that one was of a
higher order of coloration than the other. To what causes or factors
are these departures due?
Reproduction in the simplest living things takes place by a simple
division of the body into two as soon as its maximum size or adult
condition has been attained. In such simple types the body consists
only of a single “blob,” or particle, of jelly. But a new era began
when large numbers of such particles, or “cells,” began to form
coherent masses, different parts of the mass performing different work
for the mutual benefit of the community. Some have come to form what
we call the body, which is born, and in due course dies. Others are
alone concerned with the task of reproduction. They are nourished by
the body, and on attaining maturity, give rise to new bodies. These
reproductive cells are excessively small. The male, or “sperm” cell,
can only be distinguished under the highest powers of the microscope.
The female cell, or “Ovum,” is always larger than the male, because, in
addition to the germinal matter which it contains, it is furnished with
a store of food in the shape of yolk. This accounts for the relatively
enormous size of the egg of the hen. Within the hardened shell the
germ develops into the chick, deriving food for its growth from this
generous store. Where this yolk is limited in quantity the growing
body is hastily fashioned, and launched forth into the world in the
form of a “larva,” when it must forage for itself till it has attained
its adult form. Or it is retained within the body of the mother until
development is complete.
The reproductive cells are the bearers of the Germ-plasm, the stuff
of which man and the beasts of the field alike are fashioned. Only a
portion of this germ-plasm gives rise to a new body; the rest is, as it
were, held over and stored within the new body to give rise to another
in due course. That which produces the body we call the “Somatoplasm,”
because it is the “plasm” or stuff of which the “Soma,” or body,
is made. As to the nature of this Germ-plasm and its mysterious
properties, a wide divergency of opinion exists among _savants_. But the
views which find most favour to-day are those of the veteran Professor
August Weissmann, as set forth in his work on the “Germ-Plasm, a Theory
of Heredity.”
The excessively minute quantity of this germ-plasm which suffices
to form a new body is incredible. By what miracle of miracles is
the essence of a man distilled? His body arises from the union or
commingling of two particles of living matter so minute as to be
invisible to the naked eye. One of these particles is the “sperm”—cell
furnished by the male parent; the other, the “ovum,” furnished by
the mother. True the ovum may measure as much as the one-hundred and
fiftieth part of an inch, but the bulk of this is yolk-food necessary
to furnish the tender germ with life and energy till it shall have
attached itself to the walls of the womb, whence all its future
nourishment is derived.
By no process of analysis known to us could the germ-plasm of man be
distinguished from that of, say, a jelly-fish; and in the matter of
quantity there is no more difference. Yet, identical to our senses, in
potentiality how amazingly different are these two particles of jelly!
In the lowliest animals, such as jelly-fish, one cannot distinguish
male and female at sight. The appearance of separate male and female
individuals begins somewhat high in the scale marking an epoch in
the history of animal life. For the birth of sex inaugurated not
merely individuals producing distinctive “male” and “female” germs,
but individuals which, by virtue of their sex, developed differences
of behaviour and mentality which were to be followed by tremendous
consequences. Certain aspects of this behaviour are to furnish the
theme of these pages; others, and no less important, those who will may
discover in Professor Arthur Thomson’s “Evolution of Sex.”
We are far, indeed, from being able to explain the attributes of sex.
At most, we can but endeavour to interpret the behaviour associated
therewith. This was the task which Darwin set himself to achieve in
his theory of sexual selection. He was influenced in the train of
thought which he followed up with such brilliant success by what he had
observed in the behaviour of highly-ornamented species, such as the
Peacock and the Birds of Paradise. The strange antics of these birds
when under the influence of sexual excitement persuaded him that they
were at least dimly conscious of their splendour, and of its power
to fascinate. The female, on the other hand, was supposed to be coy,
and to bestow her person on the finest performer. In this way the
dullest birds and the poorest performers were gradually eliminated.
Here, indeed, was sexual selection. The frills thus begotten he called
“Secondary Sexual Characters,” a term which is also used, and was used,
by him, to include any feature whereby the sexes can be distinguished
apart from the character of the genital organs.
Horns, tusks, and spurs are other forms of secondary sexual characters.
And these stand for another form of sexual selection—that of selection
by battle. Herein victory falls to the strongest and most pugnacious
male who, as the spoils of victory, annexes the females which formed
the subject of the duel. This theory, which must be discussed at
greater length in the course of these pages, has had many critics,
and among them men of mark. But whatever modifications may be deemed
necessary, they will be such as are demanded by the results of later
discoveries rather than to the force and subtlety of the arguments of
his opponents.
One of the most formidable of the opponents of the Sexual Selection
theory was Wallace. But his arguments were far from convincing, and
often inconsistent. He attributed the more frequent occurrence in male
animals of brilliant coloration and exaggerations of growth such as
give rise to manes, beards, long plumes, and so on, to a “surplus of
strength, vitality and growth-power which is able to expend itself
in this way without injury,” or, as he sometimes expresses it, to
superabundant vitality. He was evidently striving to find words for
the faith that was in him, and he was nearer the truth than he knew
or than his critics supposed. He was seeking facts which only the
physiologist could furnish. And these made their appearance long years
after with Professor Starling’s discovery of Hormones. We are far from
understanding the origin of these mysterious juices which must be so
frequently alluded to in these pages, but they are evidently intimately
associated with the expenditure of energy. This may sometimes find an
outlet in increased stature, sometimes in pure luxuries of growth. The
force of Wallace’s arguments was crushed out by the weight of detail
they were made to bear.
Mr. J. T. Cunningham a few years ago entered the lists and failed to
achieve his purpose no less completely. His was a theory which assumed
too much. In the first place it was based on the transmissibility of
acquired characters, of the truth of which there is at present no
evidence.
He contends, for example, that the vivid hues of scarlet, blue, yellow
and violet which colour the naked skin of the neck of the cassowaries
and of both sexes, and the curious horny casque which surmounts the
head, are the outcome of the constant laceration of the skin inflicted
by the males during their conflicts for the possession of the females.
He assumes that such conflicts take place, and he assumes that such
“acquired characters” are transmitted. Now, as a matter of fact, these
birds do not fight with their beaks, but with their feet. And to this
end the claw of the inner toe is enlarged to form a great spur. But
there is no evidence that the skin of the neck is ever damaged in such
conflicts as they may engage in. No scars are ever found, at any rate,
to lend support to this theory. The casque, which is similarly supposed
to be a mark of honourable conflict, is an “ornament” of great frailty,
for it is composed of a delicate filigree-work of bone covered with a
thin sheath of horn. In like manner, the long plumes which surmount the
heads of birds like the Peacock, and many Birds of Paradise, and the
wattle which surmounts the beak of the Turkey, are supposed to have
had their origin in similar pugilistic encounters in the past. Mr.
Cunningham is surely pushing the theory of the transmission of acquired
characters a little far. For what has been transmitted in these cases
is not a number of scarred surfaces, but a series of hypertrophied
structures. An amazing array of ornamental characters, symmetrically
disposed, and often vividly coloured, in short, has been produced from
lacerated tissues which in kind and extent can have varied but little.
Evidence has been accumulating during the last few years which would
have rejoiced the heart of Darwin. Had he known that birds of sober
hues “display” with the same animation and with as much elaboration
of posture as the Peacock and the Pheasant, his theory of “Sexual
Selection “would probably have left little for those who came after him
to criticize. Since his time it has been discovered that both permanent
and recurrent secondary sexual characters, such as the antlers of
deer and the temporary nuptial plumage of birds, such as the Ruff for
example, are controlled as to their growth by the stimulating action
of the “secretions or juices formed by certain of the ductless glands
“; that is to say, of glands having no apparent connection with their
surrounding tissues. We owe much of our knowledge of this subject to
Professor Starling, who has called these secretions “Hormones.”
Darwin knew that the essential sexual glands, the testes and the
ovaries, in some mysterious way controlled, in a large degree, the
development of these “hall-marks” of sex, for it was known in his
time that castrated stags failed to produce antlers, and that hen
pheasants, for example, in extreme old age, or when the ovaries were
damaged by disease or injury, at once assumed the plumage of the cock;
but the part played by these ductless glands was quite unsuspected.
They are the Thyroid, and the Thymus glands, which are attached to
the outer walls of the trachea or windpipe. The Pituitary body, which
forms part of the brain, and the Suprarenal bodies, attached to the
kidneys. It would be foreign to the purpose of these pages to enter
into the functions of these glands; suffice it to say, that the juices
formed therein are taken up by the blood, and distributed over the
system. Their action is only very imperfectly understood. We know
that any derangement in their efficiency results in disease, and that
they play a very important part in the reproductive system, as will
become abundantly evident in the course of these pages. Much hitherto
attributed to the action of “Sexual Selection” alone, it is now evident
is largely due to their action.
The all-sufficiency of the “Sexual Selection” theory to account for
the development of armature, such as horns, antlers, and the huge
spine-like outgrowths which form so conspicuous a feature of many
of the extinct Land-dragons, or Dinosaurs, has been by no means
universally accepted. Some authorities like Dr. A. Smith Woodward and
Professor Osborne interpret these after another fashion. They hold
that these are the “expression points” of inherent growth forces, a
process of concentration marking the final stages of evolution prior
to extinction. From which it may be inferred that there is a term to
the life of a species as there is to the life of the individual. In
many cases it is suggested the very exuberance of growth has been the
exterminating factor, as in the case of the huge antlers of the Irish
“elk,” whose enormous weapons hampered his endeavours to escape his
enemies. This is the theory of “Orthogenesis,” or direct development.
According to this, new structures, arising in the germ-plasm as
“variations,” will of their own inherent vitality go on increasing in
each generation unless, and until, checked by “Natural Selection.”
Changes in the character of the “Hormones” might very well bring
about these excesses of growth. It is well known that the exuberance
of growth which produces giants among the human race is due to a
derangement of the secretions or hormones of the pituitary body which
largely control growth.
Another factor of Sexual Selection which is commonly ignored, but which
is of profound importance, is to be found in the part played by the
emotions in regard to sexual relationships; the part which the “mind”
has played, and plays, in the mating of animals, at any rate of the
higher types.
Darwin touched but lightly on this theme. Later writers have almost
entirely ignored it. Almost all that is worth knowing on the subject
we owe to Professor Lloyd Morgan, who was one of the first to take up
this difficult line of investigation, and to Professor Groos. Their
researches have shown that there can be no doubt but that the emotions
have played and are playing an important part in the phenomena we are
striving to analyse. Sexual selection, in short, is concerned not
merely with the evolution of the physical characters of the body, but
also, and no less, with the psychological attributes thereof. Many new
and extremely valuable facts in this regard have been brought to light
by Mr. H. Eliot Howard in the course of his remarkable studies on our
native warblers. Not until the psychology of sex in the lower orders
of creation has been further investigated shall we have a properly
balanced account of the part played by sexual selection in the scheme
of evolution.
By now it will have become apparent that the study of the “Courtship”
of animals is one of alluring interest and full of pitfalls for the
unwary. And this because of the apparent difficulty in drawing any
hard-and-fast line between the part played by “Natural” and the part
played by “Sexual” Selection, at any rate in some cases.
To this aspect of the theme Professor Lloyd Morgan has drawn particular
attention. “It is difficult,” he remarks, to accept the view that
individual choice has played no part where the sexual instincts are
concerned. But supposing that it has played its part ... the effects
will be wrought into the congenital tissue of the race if, and only
if, there are certain individuals which, through failure to elicit the
pairing response, die unmated. Is preferential mating, supposing it to
occur, carried to such a degree that some individuals fail to secure
a mate? That is the question. If so, sexual selection is a factor in
race progress; if not, though it may occur in nature, it is inoperative
as a means of evolutionary development. The whole question, in itself a
difficult one, is further complicated by the fact that the males which
are possessed of the most exuberant vitality, and are therefore by
hypothesis rendered the most acceptable through emotional suggestion,
are likely to compete with other males of less exuberant vitality by
direct combat. Such competition, by which the weakest are excluded from
mating through no choice on the part of the female, falls under the
head of natural selection, and not of sexual selection, if by that term
we understand preferential mating.
“This serves to bring out the difference ... between natural selection
through elimination and conscious selection through choice....
Sexual selection by preferential mating begins by selecting the most
successful in stimulating the pairing instinct.... The process is
determined by conscious choice. It is in and through such choice that
consciousness has been a factor in evolution.”
Herein Lloyd Morgan, like Darwin, recognizes the existence of a
dual machinery in determining survival, where this depends on the
co-operation of two individuals leading separate existences—Natural,
and Sexual, Selection—sometimes the one and sometimes the other
prevailing. In the former, the females are seized by force; in the
latter, won by displays.
But is this really so? In these pages it is contended that a sharp
line must be drawn between all those attributes and characters which
are necessary to achieve individual survival, the survival of the
Ego, and all those which, on the other hand, are necessary to achieve
reproduction and the survival of the race. The former are governed, or
determined, by Natural, the latter by Sexual, Selection.
The sphere of influence of these two factors may be delimited, if
we regard natural selection as the factor accountable only for the
qualities necessary for the survival of the individual—necessary to
ensure success in the struggle for existence. Then it will become
apparent that the qualities and attributes necessary to achieve the
survival of the _race_ are of a different kind, and these are the
factors which are embraced under the term “Sexual Selection.”
It is a mistake to regard animals in relation to the selection theory
as if they were so many tailors’ “mannikins.” Yet a large number of the
critics of the selection theory seem to fall into this error, ignoring
all but the most superficial characters.
The peculiarities of colour, structure and behaviour, that is to say,
the characters and qualities which distinguish the individuals of any
given race, are due to inherent qualities of the germ-plasm. Each of
such qualities, therefore, may be regarded as entities. Selection
determines their survival. Intracellular selection is the first sieve
through which they have to pass, natural and sexual selection are
others, as circumstances may determine.
As a rule the sex of an individual is attested by more or less
conspicuous external features. These are known as the “Secondary Sexual
Characters.” But no hard-and-fast line can be established for these,
at any rate, so far as colour and ornament are concerned, for such, as
will become apparent in the course of these pages, tend to appear first
in the male, and then, later, to be acquired by the female, until in
many cases the two sexes become again indistinguishable.
CHAPTER II
“MANKIND IN THE MAKING”
The use of the term “Courtship”—Primitive Man and the Foundations
of Society—“Amorousness” as a motive force—Polygamy—Our half human
ancestors—Standards of Beauty—Disquieting signs.
Our ideas on the subject of the “Courtship” of animals are of necessity
largely framed on what has been observed by each of us in regard to our
own race; and without any very careful analysis of motives, or thought
of what lies behind. But no real insight into this most tremendous
subject can be gained which does not strive to penetrate beyond what is
actually seen; which does not endeavour to get at the source of conduct
in this regard.
“Courtship” is the word we commonly employ to describe the act of
wooing; and in civilized human society at any rate, the intensity of
the emotions which inspire the desire to woo are held in restraint by
a variety of causes—and hence the “Courtship.” In the lower animals it
is a moot point whether the term “Courtship” can be accurately applied.
They are governed by no conventions, for them there is neither modesty
nor immodesty. Desire with them is not made to walk delicately,
veiled according to custom; nor is it artificially fostered as among
civilized communities by stimulating food and the crowding together of
large numbers of both sexes in artificial surroundings. Rather it is
a natural, rhythmical, highly emotional state, which gathering force
inhibits the ordinary emotions, or, rather, overrides them, begetting
an intensity of passion which brooks no control. It demands, without
parleying, or mincing matters, what is really the object of courtship
among the civilized human communities—the consummation of the nuptial
ceremony. The term “Courtship” is a Euphemism. Nevertheless, bearing
this in mind, it may conveniently be used in these pages.
We cannot hope to understand the springs of courtship in the human race
from what we observe in present-day society, or even from what we have
gleaned thereon from the records of remote ages. We must get back, so
far as is possible, to the very dawn of the human race: to that period
of man’s evolution when his conduct was controlled by purely savage
instincts. But even then the mark of the beast must have been fading
out. His most valuable asset, his larger brain, even then gave him an
advantage over the Apes, his near relations, and over the beasts of
the field which he had begun to bring into subjection. We may assume
that like his anthropoid relations, he was of a solitary, nomadic
disposition, wandering in small parties from place to place as fancy
or food determined. His advance to this stage started when, by the
activity of his enlarging brain, he began to be oppressed by the gloom
of the forest, and drawn by the fascination of more open country, and
the ever-varying scenes which exploration brought him. But this life
begot new needs and new desires. Hitherto, hunger, self-preservation
and self-perpetuation were the only stimulants which roused his
activities; and they were also the three forces, and powerful forces,
which shaped his love of solitude. The proximity of his fellows
threatened his three most vulnerable points—they competed for his food,
they endangered his life, and threatened the possession of his family.
This more varied and adventurous existence roused new centres of
activity in his brain; he began to perceive, though dimly, the
possibilities of a larger life, though doubtless one which would
minister to his own comfort rather than to that of his family—the
natural and only road to better things. He began to devise more
expeditious means of securing food, and circumventing his enemies,
among whom the most formidable was his fellow-man, because in him he
met his match. In the course of his wanderings he had learned the use
of stones as weapons—which he could never have done in the forests—and
he had also discovered the value of his family as ministers to his
comfort, if only by setting them to collect such food as did not
require strength and cunning in its capture. An inherent love of the
chase for the sake of the excitement which this afforded probably made
him nothing loth to regard hunting as his own peculiar duty. A little
later the advantages of neighbourliness were borne in on him, largely
for the sake of the greater ease wherewith the animals of the chase
could be captured by their combined efforts; but this begat comradeship
and some of the graces which follow therefrom.
Thus was laid the foundation of Society and “civilization” with all its
attendant barbarities. Then, as now, whatever discordant notes were
heard, were those struck by the twin Demons Envy and Jealousy. These
disturbers of the peace are parasites on Society, their very existence
depends on it. They have played a larger part in fashioning its rules
and regulations than is generally realized. Their influence is as
powerful to-day as ever in the past. It expresses itself in varying
degrees in different individuals, and is roused by varying causes. But
the most potent of all is jealousy in regard to sexual matters.
Amorousness, a word with a deep meaning, was, and is, the underlying
factor which shaped, and is sustaining, human society; and is no
less powerful among the beasts that perish. The motive force in this
has not been the desire for offspring, but for the satisfaction of
the elemental animal passion, the gratification of the purely sexual
emotions which at their height are irresistible. There may be some
who will see in this contention a degrading aspect of life. But this
view will obtain only among those who prefer the man-made sophistries
of life to its Divine mysteries. This dominance of what are popularly
called the animal passions is the outcome of a perfectly natural
process, whereby those in which these passions were defective died
without offspring, while those who tended to excess were similarly
eliminated. The desire for offspring for its own sake may exist among
our own species to-day but, normally, offspring follows as an effect
not as a cause. Many of our social problems would straighten themselves
out if these facts were once faced and acknowledged; we are apt to
concern ourselves with what should be—according to our ideals—rather
than what is. Let it be granted that this rendering is true, and much
else that mystifies becomes clear.
Whether primitive man was monogamous or polygamous, or whether he
practised promiscuity, are themes which have exercised the minds of the
most ingenious since the custom of making books began, and the most
diverse conclusions have been arrived at. In coming to any conclusion
on this subject probability based on what we know of the higher apes
can be the only standard of argument. In these animals monogamy is
the rule, the male and female with their young roaming at large in a
family party. Occasionally, however, a male is seen accompanied by two
females, and this is only what we should expect. The Apes are not very
prolific animals nor are they numerous in individuals, hence, should
any male be killed either in combat with a rival or by any other means,
his mate probably wanders in search of another male, by whom, when
found, she is probably readily adopted even if he should be already
mated.
In like manner lived our half-human progenitors. But with them family
parties no longer wandered aimlessly searching for food, but with
a purpose. No longer forest dwellers, or vegetarians, food would
require more zeal and discrimination in collecting, and shelter of
some kind had probably to be devised, partly as a protection against
predatory animals, and partly for personal comfort, since it would
now have become apparent that this could be appreciably increased by
the exercise of a little effort and ingenuity. This appreciation of
creature comforts formed a cement holding the family together; a sense
of safety in Society helped still further. Rude tools chipped from
flints were among their earliest and most cherished possessions for
the sake of the advantages they secured. Here was the earliest form
of wealth and the birth of labour and a further step on the road to
progress. Little would now occur to derange the harmonious routine
of the daily life, save only the ever-present jealousy of the head of
the family which was assailable both from within and without. His sons
and daughters were probably now regarded as a portion of his wealth,
for they ministered to his comfort, and aided in the daily work which
had now become a necessity. As his sons attained to maturity, so they
became rivals to be watched with a jealous eye, and finally driven
off, while his daughters at the same time became potential mates.
This danger of close inter-marriage was a real one, though it cannot
be supposed that it was in any way realized. The risk was evaded by
perfectly natural means. The jealousy of the head of the family which
drove him to expel his sons as they attained maturity provided the
means. These young bachelors sought their mates from neighbouring
families, and it is probable that they would not be hard to lure from
their parental control, but in such matters force was able to effect
where persuasion failed.
These mate hunting excursions are to be regarded as extremely powerful
factors in securing the betterment of the race. They were adventures in
which all must fail who did not possess courage, cunning, and brawn,
for, paradoxical as it may seem, evolution depends, not so much on the
qualities of the individual as on the elimination of the unfit. As
yet might was right. But the strife of combat, fierce and merciless,
had its beneficial results not only in weeding out the physically and
mentally deficient, but in stimulating affection between the victor and
his prize.
As the advantages of neighbourliness dawned upon these children of
nature, rules and regulations, for the control of the individual on
behalf of the good order of the community, came into being; and among
the earliest laws to be framed, we may be certain, were those for
the regulation of marriage. These, as we may gather from the history
of savage races to-day, did not concern themselves with chastity, at
any rate before marriage, it was enough if they secured the right
of possession, and excluded the dangers of close intermarriage.
Promiscuity in the past was never the practice of any race, its
existence to-day, among both savage and civilized people, is due in part
to imperfections in the social scheme, and in part to the vagaries of
individuals.
That the sexual instincts form the bed-rock on which depends the
survival of all races of animals, which, for their propagation, require
the co-operation of separate sexes, is beyond dispute. And it is no
less certain that in so far as the evolution of man is concerned,
jealousy has been a powerful integrating factor.
Among the higher animals apart from Man, both polygamy and polyandry
are met with, and this with no apparent detriment to the race. It
is significant, however, that polyandry is never met with among the
mammals, and but rarely among the birds, when, as will be shown,
this form of sexual relationship has been accompanied by a profound
modification of the behaviour of the sexes in regard, not only to
courtship, but to the offspring. The male has lost his masculinity,
and the female her femininity. In human society both forms of marriage
prevail, and there can be no doubt, from the history of such customs,
that of the two types, polygamy is much to be preferred. It is certain
that no race which practices polyandry can do more than hold its
own, and that in a low grade of development. This cannot be said of
polygamy, which might indeed be commended as a solution of some of our
own social problems, were it not almost certain that the remedy would
prove as bad as the disease.
The subject of “Courtship” in so far as it applies to the human race
is one concerning which little can be said. Westermark, Letourneau,
Sutherland, and last but by no means least, Darwin, have brought
together a mass of facts bearing on the status of women among
communities, savage and civilized, ancient and modern, and from these
much may be inferred. To this harvest, however, Darwin himself still
remains the most important contributor on all that directly concerns
the “Sexual Selection” theory. Other writers seem to have paid more
attention to the laws governing the possession of women than to the
discussion of the motives which may have controlled the choice of
mates. Instances of amatory dalliance, such as are met with among
the inferior apes, and the birds, seem to be wanting. This negative
evidence seems to show that, even among the most ancient, the most
Ape-like, half-human races of man such dalliance was unknown. And this
because primitive man, in his love-making as in everything else, was
accustomed to take what he wanted, or die in the attempt. It is to
this forcefulness of character that the human race owes its progress
throughout the ages. But did he, when desire possessed him, exercise
any sort of choice, when this was possible? What were his standards?
These are unanswerable questions; at most we can but infer what his
behaviour may have been from observations on existing races of mankind.
These seem to demonstrate that while some races profess admiration for
certain of their physical peculiarities, these cannot be attributed to
the action of sexual selection.
It has been suggested that the low, beetling brows, protruding mouth,
and flat, broad nose which characterized the earliest human peoples,
were slowly eliminated by the æsthetic taste displayed by the females
in their choice of mates. Now in the first place, it is highly
improbable that they had any choice allowed them, and if they had,
these are just the characters which were most marked in the males and
might, or probably would, in consequence, have been deemed “manly” and
desirable, for it is hardly to be supposed that such people would be
capable of conceiving ideas of a possible refinement of their personal
appearance if they could but add to the height of their foreheads
and reduce the size of their faces. These graces settled down on
them as the brain enlarged and habits changed. But the process of
transformation must have been infinitely slow, and quite imperceptible
from one generation to another.
The absence of secondary sexual characters in man, such as the brightly
coloured areas which are so conspicuous a feature of many of the lower
apes, is to be explained by his fundamentally different mode of life.
Such vivid hues obtain only in species which live in troops, and
they serve as aphrodisiacs, ensuring mating to every female forming
a part thereof, which would be by no means certain were there no
external signs of her condition. Primitive man, like the higher apes,
was instinctively monogamous, and of necessity solitary, till he had
acquired a tolerable measure of self-control and neighbourliness. When
lust possessed him, he was obliged, in making his maiden venture to
scour the country in the search for the object of his desire. This
found, and won, probably only after desperate conflict with the head of
the family, the nuptial ceremonies would be short.
The greater physical strength of the male and his higher brain capacity
are probably the result of Natural, rather than of Sexual Selection.
The former would weed out all the weakly and dull-witted in the
ordinary course of the struggle for existence, the latter, during the
early days of man’s development, would award the prizes of life to the
most amorous and cunning, and to the most ambitious of the competitors.
The secondary sexual characters of the female are chiefly negative
characters, the absence of those which are conspicuous in the male. She
retains more of the primitive characters of the race. This is the rule
in regard to the animal kingdom. Wherever we desire to find the onward
tendency of evolution, the latest developments of the race, we turn
to the male; when we desire to learn something of the past history of
the species we turn to the female and young. This standard, of course,
yields by no means uniform results, for we find every gradation of
progress on the part of the latter, till male and female and young are
externally indistinguishable. But the order is almost invariably the
same—first the male, then the female, then the young. Thus progress is
more or less automatic or “Orthogenic,” as the scientific text books
have it, new characters, as they appear, tending to go on increasing
in amplitude till checked by Natural selection. It is to be noted,
however, that this transference is limited, for the female never
inherits characters which are concerned with aggressiveness to the same
degree as in the males, as witness, for example, the brow-ridges and
huge canines in the case of the gorilla.
Darwin believed that the beards of men have developed by the selective
choice of the women who preferred bearded men, while the secondary
sexual characters of the women indicate the lines of male choice.
There is, however, no evidence to show that in the past—for these
characters are as old as man himself—woman had any choice whatever in
the choice of her mate, save under exceptional circumstances. He was
led to this conclusion by one or two striking instances apparently
demonstrating this choice, and on these he seems to have based his
version of the influence of sexual selection in man. The first of
them is furnished by the Hottentots wherein, in both sexes, there is
a marked “Steatopygy,” or accumulation of fat on the buttocks. In the
female this is excessively developed, and it is said that such females
are highly prized by the males. Darwin cites an instance of a woman
in which this accumulation was so enormous, that she could only rise
with the greatest difficulty from a sitting position. But there is no
evidence to show that less favoured females remained unmarried.
In other tribes the breasts attain excessive proportions, so much so
that they can be slung over the shoulder to feed the infant strapped
to her back. These may have been increased by sexual selection, the
preference of the males for such mates as possessed this feature in
the most marked degree; but there is good reason to believe that such
characters, which, it must be remembered, are the outward manifestation
of germinal variations, once having appeared, would of themselves, of
their own inherent vitality, have gone on developing. They won favour
from long familiarity, which has imparted a semblance of increment
from choice. These increments of growth in any given generation would
be imperceptible, but variations in excess of the average would be
conspicuous, and excite admiration from their very strangeness.
The part which sexual selection has played in determining the physical
characters of the human race has without doubt been overestimated.
Its influence may be said to have ceased with the development of the
emotional side of his nature. This momentous process began with the
male and had its roots in the ebullitions of his inherently amorous
nature which has been the dominating factor in his career, and will be
to the end, however much its influence may be disguised by the complex
conditions of civilization.
These emotions, varying in kind and intensity, are such as are embraced
in the term “Love” in the highest sense. They control the selection
of mates, but this selection takes no account, save by accident, of
qualities which have any value as factors of race-survival. In the
lower animals these are determined by natural selection, and sexual
selection adopts as it were the material furnished thereby. It
“selects” only in so far as it eliminates the non-sexually inclined,
and those which lack the qualities essential to ensure reproduction,
such as weapons for example. In human communities natural selection
is largely avoided, and “mate-hunger” seems now to be swayed by more
than the mere desire for its satisfaction. With the development of
human faculty new factors have been introduced, complex emotions have
come into being, whose influences are as yet only vaguely understood.
Whither are they tending? What will be their effect on race-progress?
These are matters of grave importance to us all, and to the student of
Eugenics in particular.
Of man’s higher emotions, which, it is contended, now govern his
conduct, probably the earliest to assert itself was the æsthetic. His
quickening mentality could not fail to be captivated by the bright
hues of birds and butterflies, and flowers, the glorious colour-effects
of dawn and sunset, the seasons in their changes and so forth. And as
this sense of the beautiful slowly gathered force he would seek to
decorate his naked body with such of the more brightly-coloured objects
around him as were suitable or rather with such as could be affixed
thereto.
As a signal mark of his favour and affection, he would occasionally
transfer some one, or another, of his most lasting ornaments to
his mate, and the additional charm this would give her ensured a
continuance of such gifts, and paved the way for tribal fashions. But
then, as now among savages, the males take the lead in this matter
of ornamentation, but in proportion as affection grows, they are
transferred from him to her, so that among civilized races to-day,
the custom is entirely reversed, the women, not the men, wearing the
finery. So soon as families began to be neighbourly and to combine
for the sake of company and mutual help, the spirit of rivalry, so
essential to progress everywhere, would tend to increase the number
of such gifts, and to set “fashions.” With the foundation of society
“selection”—by the elimination of the unsocial, would ensure, not
only the survival of such fashions, but their multiplication and
diversification, producing results which, to our eyes, have often been
hideous. The immediate effect of this form of selection, however, was
not a change in physical characteristics, but in the evolution of
personal ornaments and development of the æsthetic sense. Progress
in this direction must have been infinitely slow, and the lower races
of to-day furnish us with instructive object-lessons in its course.
In many cases uglification rather than refinement has attended their
efforts.
It is indeed more than probable that the various types of ornamentation
obtaining among savage races had their origin in outbursts of sexual
exaltation. One of the earliest methods of personal decoration was
probably to daub the body with paint, as is the custom during the
performance of various religious and semi-religious rites among the
Australian aborigines. A desire to find a permanent substitute for
paint led to the practice of cicatrization, and the later and more
refined custom of tattooing. But personal mutilation has taken many and
strange forms, such as knocking out the front teeth, filing them to
saw-like points, inserting gold or jewels, or staining them. No less
extraordinary are the various types of lip and ear ornaments, and the
suspension of ornaments from the nose. The various fashions of dressing
the hair are also traceable to this origin.
That these modes of personal decoration designed for special occasions
should in course of time become permanent, and should, in many cases,
have lost their original associations is but natural. To-day among
savage and barbaric races many of these modes of transfiguration have
become associated with religious and semi-religious ceremonies, but
many have been retained solely to enhance the personal appearance, even
though in our eyes an exactly opposite effect has been attained. Among
the natives of the Congo, for instance, the face is covered with raised
patterns formed by cicatrization; that is to say, by cuts made with
a knife, which are made to form scars on healing by means of pungent
juices or heated iron. Further, the teeth are filed to form saw-like
cutting edges, producing a revolting effect according to European
ideals, but charming according to the standards of those thus patterns
which adorn the tattooed face of the Maori present a result more nearly
pleasing. Many of the natives of East Africa pierce the lobes of the
ear and hang ornaments therein so heavy, that in due course a hole
large enough to run the arm through results. These are mutilations of a
purely ornamental character. Curiously enough, precisely similar forms
of mutilation occur among people dwelling in different continents, as
in the case of the lip and ear ornaments worn by natives of Africa and
South America. There can have been no means of communication between
these races, and hence we must conclude they were independently derived.
More striking still is the practice of deforming the head which
prevailed among the Peruvians, the Caribs of the West Indies, and the
natives of Vancouver, and the Chinook Indians, wherein it attained
its maximum. Among some tribes, the head was depressed from above
downwards, giving the skull a cone-shape, the apex pointing backwards;
among others the pressure was applied to the back and front of the
head, giving a more or less globular shape, and causing the sides of
the head to bulge ominously. Now these distortions are to be attributed
solely to the whim of Fashion. But how could this have arisen? No adult
could have started it, for the form of the skull cannot be altered
once its growth is completed. The conception of this diabolical custom
apparently then arose in the brain of some fiendishly ingenious person,
who realized that to effect its realization pressure must be applied
to the head of the infant at its birth and for some considerable
time after, by squeezing the head between boards, or tying it round
with thongs of hide. That disastrous results would follow from this
tampering with the brain would seem an unavoidable conclusion; yet
such was not the case. During the moulding process, travellers who
have witnessed it tell us, children display no sign of suffering, even
though their eyes seemed to be starting from their sockets from the
pressure. But they cried when the thongs were loosened. On attaining
to man’s estate, such victims to parental folly seemed to be in every
way as intelligent as the men of neighbouring tribes which had no such
insane customs.
How deeply rooted was the prejudice in favour of this extraordinary
fashion is shown by the fact that when, during infancy, from sickness,
or other cause, the bandaging was neglected or omitted, and the child,
in consequence, attained to man’s estate with a head of the shape
designed by nature, he was seriously hampered in the struggle for
existence, for no honours among his tribe were possible. Indeed, as
often as not he was sold as a slave. But thus did Public Opinion bring
disaster on its advocates, for those misguided people have been swept
off the face of the earth by their own folly. Those who survived the
ordeal, it is true, seemed in no way mentally deficient, but the infant
mortality must have been great, and none of the adults could ever have
attained to their full potentiality.
These people were, however, not the only lunatics at large. For this
extraordinary practice found its devotees in many other widely sundered
parts of the world. Deformed heads of various types have been found
in rock-tombs near Tiflis, in the Crimea, Hungary, Silesia, in South
Germany, Switzerland, and even in France, Belgium and England! How did
it spread from one nation to another? Since means of communication
were extremely limited centuries ago, one can only suppose that in
most cases it arose independently. It is possible that the idea
started with the unintentional deformations of the head which follow
the practice of carrying the child during early infancy. It is well
known that if a child be constantly carried on one arm, so that one
side of the head continuously presses against the shoulder, a more or
less marked asymmetry of the skull results. It would be enough for
the head of one of the chief’s children to show a rather unusually
marked asymmetry of this kind for every mother to endeavour to copy the
defect, for imitation ever was the sincerest form of flattery!
To place these superficial, non-transmissible, artificially created
features, such as deformed heads, mutilated teeth and ears, and so
on, in the same category as the “secondary sexual characters” of the
lower animals which are physical, inherent and transmissible features,
is to ensure confusion of thought. The one represents a physical, the
other an emotional development. The persistence of certain forms of
mutilation esteemed beautiful in human society is not to be attributed
to Sexual selection, or to “preferential mating,” for these things
are not only non-transmissible features, but outside the sway of the
amorous instincts, as is shown by the case of those individuals who,
living in a community where deformed heads are _de rigueur_, have heads
of normal shape. So soon as such perversions become a part and parcel
of everyday life, they become essential to the general well-being and
comfort of their possessors, enabling them to follow their normal
avocations without exciting the dislike or wounding the prejudices of
their neighbours. The absence of the “tribal sign” alienates the esteem
and comradeship of his neighbours and brings an unenviable notoriety.
In like manner albinos among birds, for example, are hunted down by
their fellows and killed, and birds of exotic species conspicuous by
reason of their unfamiliar appearance are treated in the same manner.
The sexual instincts have no part in this.
It will have become obvious in the course of this chapter that Sexual
selection as a factor in shaping the evolution of the human race has
not played a very conspicuous part. Nevertheless, the balance of
opinion to-day is probably in favour of the view that the physical
peculiarities by which we distinguish one race from another are, for
the most part, due to the influence of this form of selection. A more
careful survey of the facts will show that this view is untenable.
And there is no more striking demonstration thereof than that it has
been inconsequently applied to account for features in one race, which
in another are attributed to environment or to Natural Selection.
It may safely be asserted that colour, the shape of the nose, the
prominence of the jaws, and the character of the hair, are no more the
result of “Sexual Selection” than stature, for example. These are the
manifestations of inherent growth forces, or “tendencies,” which owe
their survival, and development, to the influence of Natural selection.
Sexual selection has brought about the dominance of the male, by
the struggle between males for mastery, originally for females. It
“selected” for survival, in primitive races, those males with the
thickest skulls and the strongest physique; it determined the survival
of the keenest witted and most aggressive and most amorous males, and
it eliminated those in which the latter features were too active. It
assured victory, in short, to those only who possessed just those
qualities on which life or death depend in moments of conflict. In the
case of the females, it assured survival only to those who possessed
strongly developed maternal instincts and submissiveness.
It is by no means realized that the incidence of moulding forces
has changed and is changing with the environment of the race. So
long as physical force, as between man and man, determined survival,
as among savage races to-day, so long does it ensure to such races
strong men and strong children, for in conflict with neighbouring
tribes victory rests with the most powerful of physique and endurance
and the most prolific. This last is an all-important concomitant if
repeated conflicts are to be successfully waged. Among civilized
peoples such contests began to lose their value in this regard when,
by the introduction of arms, physical personality became a steadily
diminishing factor. Victory now rests rather with those peoples who are
most skilful in devising engines of destruction. The brain, not brawn,
tells. But man cannot live by brains alone. With the inevitable decline
in his physical nature man’s hold on existence is seriously imperilled.
Civilization is making for extinction as much as over-specialization in
the case of the lower animals. Hitherto, save in the case of decaying
nations, women have played but a minor part in what we may call the
“tribal” affairs of the race. Among the civilized nations of to-day,
in proportion as the “maleness” of the community becomes more and more
effete, the victims of sophistry, and the slaves of shibboleths, so
the influence of the females asserts itself. And recent events among
us show plainly enough that that influence is the reverse of good.
Having its roots in personal vanity, and the love of notoriety, it is
intolerant alike of reason and self-restraint, and that way madness
lies.
CHAPTER III
MAN’S COUSINS THE APES
The Man-like Apes and their mode of Life—Their “Courtships”—Musical
Chimpanzees—How the Orang-utan improves his voice—His likeness to
Caliban—The truculent visage of the Gorilla—“Ornament” in the lower
Apes—The Concerts of the Howler Monkeys.
We are none of us given to boasting of our poor relations, and most
of us indignantly repudiate our kinship with the Apes. But facts are
stubborn things: the relationship is there, whether we admit it or
not: and those who love truth for truth’s sake will not shirk the
comparison between themselves and their remote cousins. Unhappily,
from our present point of view, this cannot be carried very far, for
the “Love idylls” of the Apes have yet to be written. Such facts,
however, as have been gleaned are interesting. Of the higher, man-like,
or “Anthropoid” species only the most meagre information is to be
obtained; but this nevertheless is interesting. For the most part we
have to be satisfied with inferences drawn from a study of the external
differences between the sexes—from the “Secondary Sexual Characters,”
in short, and from the records of travellers who have encountered these
creatures in their native wilds.
The species which throw most light on this theme are the Gorilla,
the Chimpanzee and the Orang-utan. Of these the Chimpanzee has most
in common with the human race. But it may satisfy the qualms of many
to know that between the Ape and the Man there is a great gulf fixed.
The brain of the largest Ape is less than half the size of that even
of the lowest of mankind. Man is a reasoning, and for the most part a
reasonable, creature; he is a tool-making animal. This is more than
can be said of any of the apes, even the most intelligent. Their teeth
and immensely powerful arms must serve their every need. No ape ever
fashioned for himself either a knife, a vessel to carry water, or any
means of transport; and herein we have a measure of his brain capacity.
The huge jaws and great canine teeth are no less conspicuous “marks of
the beast.”
These, however, man himself has but recently lost, as was proved by
the sensational discovery of the skull of an ape-like man at Piltdown,
in Sussex, during 1912. Herein the jaw was essentially that of an ape,
while the base of the skull was as markedly human. The cheek teeth, or
molars, were of the human type; but the canine was ape-like, though
much inferior in point of size. That the men of this remote age—which
was possibly that of Pliocene times and certainly not later than early
Pleistocene—had begun to use rudely-fashioned tools, is proved by the
roughly-chipped flints found with the remains. With the invention of
tools the decline in the size of his “eye” teeth began.
In all the large apes these “eye” teeth are of great size. Their
purpose, it would seem, is primarily to serve as weapons in conflicts
between rivals. Such conflicts are apparently unintentionally, and
unavoidably, provoked by the loud cries uttered by the males in their
endeavours to discover the whereabouts of females desiring mates. Of
necessity roaming far in search of food, the unmated have no means of
making their whereabouts known, save by thus giving tongue to desire.
Evidently the normal methods of voice production do not suffice for
their urgent needs, for the carrying power of the voice is immensely
fortified by means of great air sacs, or chambers, formed in part by an
enlargement of the body of the hyoid, or the bone which supports the
tongue, and in part by dilatations of the inner walls of the larynx.
The females, it is to be noted, are by no means so well equipped
in this matter. It is not necessary that they should be. All that
those desiring mates have to do is to follow up the cries of avid
males, a by no means difficult task, especially when under the spell
of the emotions which possess them. But the mechanism which serves
the Chimpanzee and the Gorilla by no means fulfils the needs of the
Orang-utan. In this uncouth creature the system of resonating chambers
is immensely increased by great, thin-walled, membranous pouches
extending round the neck and under the armpits, so that when inflated
these areas have a most extraordinarily swollen appearance. When the
Orang chooses to lift his voice even the deaf must hear.
Where fighting instead of fondling is the sequel to these impassioned
cries the conflict is probably not of long duration, for it is
certainly severe. This is attested by the fact that captured specimens,
if adult, are commonly found to be minus one or more fingers, which
have been bitten or torn off in these love affairs.
[Illustration: Plate 2.
_From a drawing by I. Thornton._
THE GORILLA PREPARING FOR HOSTILITIES.
Note the “beetling” brows, the large size of the canine teeth, and the
great development of the arms in these arboreal creatures, which play
an even more important part in locomotion than the legs. The latter in
this illustration are, however, relatively too small.
[Face page 42.]
An added ferocity of expression is given to the male Gorilla by the
development of enormous brow ridges and the huge canines. The former
are regarded by some authorities as adaptations to afford increased
powers of mastication. But if this were so, then such ridges should
be equally developed in both sexes, and this is far from being true.
Hideousness, rather than ferocity, has been given to the Orang-utan by
the out-growth of enormous ridges on each side of the face, and these,
when the great wind-bags encircling the neck are inflated, impart a
repulsiveness of expression attained by no other animal living.
Of the normal every-day life of the great Apes but little is known. It
would seem, however, that they live in family parties—an adult male
accompanied by a female and one or more young of different ages, of
which one is commonly an infant in arms. It is difficult to procure
positive evidence on the point, but it is commonly believed that the
young remain with their parents till they are several years old, when
they are gradually driven off to fend for themselves. This is a common
procedure with all animals. The dominant impulse in this is something
akin to greediness, an indefinable perception that too large a family
party will entail too great a strain on the food supply, hence the now
no longer helpless young are regarded as a danger to the safety of
the family, and are turned adrift. Incidentally this procedure is of
immense benefit to the race, for it ensures its distribution, enlarges
its chances of survival, and lessens the danger of in-breeding.
Attention must now be turned to the lower Apes. In these it is to be
remarked the secondary sexual characters differ conspicuously from
those of the man-like species. Manes and beards and brightly-coloured
areas of bare skin are now the dominant feature. But canine teeth, in
proportion rivalling those of the Gorilla, are found in the Baboons,
while in some of the New-world monkeys voice production of quite
remarkable power takes the place of ornament.
The precise part played by ornament among these animals can only be
inferred from Darwin’s observations on captive animals, and then only
in so far as they refer to colour. Manes, beards and moustaches, such
as are shown in the adjoining illustrations, are borne only by the
males, and sometimes take extravagant forms.
Darwin suggested that the mane of the Baboons, for example, served as
a shield when fighting with rivals, protecting the great blood-vessels
from injury. Incidentally this end may be attained, but from what we
know of similar developments in other animals, this cannot be regarded
as the primary function of the mane. One is tempted to look upon it
as a protective device because of its position, but it is probably
no more so than is the long flowing hair which adorns the flanks of
the Guereza. This is of a purely ornamental character, although,
according to some, it is to be reckoned as an instance of protective
coloration, the long white hair matching the long pendant masses of
lichen which hang from the boughs of the trees in the damp forests
where these creatures live, and so concealing them from their enemies.
Of beards and moustaches many examples might be cited, but the most
striking must suffice. These are furnished by the Satan Monkey or
Black Saki (_Pithecia satanas_), and the little Tamarin Monkey (_Midas
imperator_)—one of the Marmosets. In the first-named the beard is thick
and full, but in the latter scanty. This, however, is atoned for by the
enormous upwardly curled moustache giving the face a most comically
human appearance.
[Illustration: Plate 3.
_From drawings by I. Thornton._
THE BAROMETER OF MALENESS—AMONG THE APES.
All the Man-like Apes possess great canine teeth and powerful voices.
In the Orangutan the Compass of the voice is enormously heightened by
means of a huge wind-bag which encircles the neck. The wind-bag is seen
in fig. 1, which also shows the great folds of skin developed by adult
males on each side of the face. In other species, as in the Tamarin
Marmoset (_Midas imperator_) (fig. 2), and the Satan monkey (_Pithecia
satanus_) (fig. 3), “ornaments” in the shape of beards and moustaches
are developed, while in the Mandrill (fig. 4) the face is vividly
coloured.
[Face page 44.]
In the development of brilliantly-coloured areas of bare skin
the monkeys stand alone among the Mammalia. The hues displayed are
remarkable for their brilliancy, and this varies in intensity, waxing
and waning with the varying moods of their possessors, and attaining
their maximum during periods of sexual excitement. Blue, green, red,
and violet are the dominant colours, and these are confined to the
face, buttocks, and genital organs. The same hues are commonly present
in both sexes, though in the female they are less brilliant. Normally
the male appears to be unconscious of the conspicuous patches of
colour, but when under the irrepressible stimulus of sexual excitement
he seems to endeavour to make the utmost possible capital out of such
adornments, more especially presenting his buttocks to his mate in an
apparent endeavour to stimulate her desire. In some species, as with
the Baboons for example, the naked area of this hinder part of the body
is a much more conspicuous feature in the female than in the male,
becoming enormously swollen and carunculated, and from its vivid red
colour presents a positively revolting appearance, according to our
standard of what is beautiful. The most vividly coloured species of
all is the Mandrill, which, in this matter exceeds all other living
Mammals. The face, in the male, is produced forward to give the head a
dog-like shape, while the whole of the upper surface of the muzzle has
been transformed into a swollen, deeply fluted mass by the excessive
inflation of the underlying bone. The bare skin covering this is of a
brilliant cobalt blue, with lines of violet in the furrows, while the
nose is of a bright scarlet. The naked skin of the buttocks, and the
genital organs, are suffused with brilliant tints of scarlet and blue.
In spite of the purity and brilliance of the coloration the effect is
to make the creature really hideous.
Of the display Cuvier writes: “La partie postérieure du corps n’est ni
moins extraordinaire ni moins révoltante. Sous une courte queue sans
cesse relevée est un anus entouré d’un gros bourrelet d’écarlate; de
larges fesses nues, que l’animal semble montrer sans cesse avec autant
de lascivité que d’impudence, sont colorées d’un rose vif nuancé sur
les côtés de lilas et de bleu. Les parties genitales enfin sont d’un
rouge de feu d’autant plus tranché qu’elles sont absolument nues, et
qu’elles viennent a la suite d’un abdomen revêtu de poils blancs.”
While we cannot suppose these animals to possess any standard of
beauty or ugliness, it must not be forgotten that they are more or
less conscious, not only of the existence of these brightly-coloured
areas, but of the effect they produce, as Darwin showed long since in
the cases of a captive Mandrill, and some other smaller species of
Monkeys, among them a Rhesus Monkey. These, when shown a looking-glass,
at once presented their hinder ends to what they supposed to be the
new arrival. A similar mark of friendliness was shown towards their
keeper, and visitors introduced by him. Periodically, under the sexual
stimulus, this desire becomes intensified and becomes an invitation to
mating.
In this connection it is interesting to note that in some of the
Macaque Monkeys we have signs of a reversal of the usual sequence of
coloration. For in the Pigtailed Macaque the young of both sexes are
more brilliantly coloured than the adults, in regard to the bare skin
areas, while in the Hairy-eared Macaque (_M. lasiotis_) and the Rhesus
Monkey (_M. rhesus_) the face of the female is brighter than that of
the male. This surely means that this coloration is in process of
suppression, for according to the rule the male is the first to develop
new characters, then the female, and finally they are transmitted to
the young. The extra brightness in the young, then, is to be regarded
not as an incipient, but as an ancestral character in process of
elimination.
As a rule, among the Mammals at any rate, brilliant coloration and
weapons of offence are not associated in the same animal. The Baboons,
and the Mandrill in particular, are exceptions, for these animals are
provided with most formidable “tusks,” the canines of both upper and
lower jaws being of great size, and opposed one to another in such a
way that they wear away to form sharp, angular cutting-edges, more
murderous than the fangs of the Tiger.
Reference has been made already to the existence of large sound
resonators for the purpose of increasing the volume of the voice in
the Orang, Gorilla and Chimpanzee. Some of the Gibbons are also well
provided in this direction. But the most striking instances of the
kind are furnished by the Orang, and the monkeys known as Howlers. In
these last the base of the hyoid, as the skeleton for the support of
the tongue is called, is fashioned into a deep bony cup, which has the
effect of intensifying the volume of the voice to a most surprising
extent. But more than this, apparently for the protection of this bony
voice-bowl the upright branches of the lower jaw have become remarkably
deepened, and widened, a correlation of growth between unrelated parts
which is fraught with deep significance. “Terrific,” “terrible” and
“harrowing” are terms which have been used by travellers like Bates,
Belt and Wallace in describing the cavernous roar of these animals, a
roar which will easily carry two miles. It would seem that these vocal
efforts are not merely confined to what we may call the “Courting”
season, as is the roar of the stag, but that they are heard nightly
at dusk. They may be resumed again at dawn, and re-awakened when
thunder-clouds gather. They have become the normal method of giving
vent to excitement, and probably are intensified when isolated males
are desirous of discovering the whereabouts of females equally anxious
to find a mate.
Among the Apes we meet, as with the human species, with both monogamy
and polygamy. But it would be dangerous to assume that the reasons
for polygamy are the same in both. Polygamy, indeed, has by no means
always the same significance. In the most primitive, half-human races
of the past, as with the man-like Apes to-day, polygamy is determined
by accident rather than choice. These extinct peoples, like the great
anthropoids, were normally monogamous, but on the death of a male in
conflict with his neighbour, or from other causes, his mate would
probably of her own free will seek out the nearest male and even if he
were already mated would be at once adopted into the family circle.
This certainly happens in the case of the Gorilla and Chimpanzee
to-day. But among living races of mankind, both savage and civilized,
multiplicity of wives is a matter of choice on the part of the male,
and in many cases to achieve this females from other tribes have to
be secured—either by purchase or conquest. With the lower apes, or
“monkeys,” polygamy only obtains among gregarious species; and either
because the birth-rate of the females exceeds that of the males, or
because a considerable number of young males are killed annually
by exciting the jealousy of the older males, who are exceedingly
pugnacious.
CHAPTER IV
AT DAGGERS DRAWN
The Birth of Weapons—All Flesh is Grass—Utility and Ornament—The
Fever of Love—The “Challenge” of the Deer—What it means—More about
“Hormones”—“Hummel” Stags—The Age of Deer—The “Courtship” of the
Moose—Types of Antlers—Antlered Females—Fighting Topi—The Lance of
the Oryx in the Lion’s Flanks—Happiness and Hartebeestes—Odoriferous
Suitors—The Bloody Sweat of the Hippopotamus—The Elephant in
Love—Concerning Tusks—Polygamy.
From Apes to Antelopes is a far cry, but contrasts are always helpful.
Antelopes and Deer, Zebras and Elephants, Rhinoceroses and Swine, are
types, taken at random, of that great and important group of animals
known as the “Ungulates,” or “Hoofed” animals. These illustrate in
a very striking manner what is meant by the term “Secondary Sexual
Characters.” They demonstrate no less forcibly what is meant by the
term “Sexual Selection.” They are valuable in this connection, because
of the often formidable weapons, in the shape of horns and tusks, which
so many species have developed during the struggle for mates.
But “Sexual Selection” will not explain their origin, and it is
difficult, in the present state of our knowledge, to discover any
clues which will reveal this. In seeking these there are certain broad
aspects of the problem which are not to be lost sight of. In the first
place, horns, at any rate, are confined to the hoofed animals. That the
various types of hoofed animals, living and extinct, have had a common
ancestry, no one at the present day will probably call in question. The
relationship, however, of the various living types, one to another, is
by no means always apparent: the missing links are to be sought in the
records of the rocks.
When the whole of the evidence comes to be surveyed, and not till
then, it becomes apparent that this wonderful diversity is the result
of complex factors. That the conditions of existence have controlled
the results is beyond question; but it is equally certain that these
conditions have been merely controlling and not causative. In other
words, we must regard each of these different groups or types—Deer,
Antelopes, Horses, Elephants, Swine, and so on—as witnesses of what
we call “Heredity.” They are so many “Diathetic types.” That is to
say, the forms, or individuals, belonging to each type have inherited
certain peculiarities in common; they display a “Diathesis” as the
doctors call it: an inherent, inborn tendency, or habit of growth, in
a definite direction: a tendency which, ever and anon, develops new
qualities, takes new directions. And thus it is that we get Oxen—using
this term in its widest sense and not in its special sense—Antelopes,
Goats and Sheep, for example. These have, among other things, a
“diathesis” in the direction of horn production, and each, too, of
a different type. What is meant by this apparently mystifying term
“diathesis” will perhaps be made clear by taking the case of the Ox and
the Sheep. While very different in appearance, these live on precisely
similar food; yet no one has any difficulty in discriminating between
the taste of beef and mutton. In the marvellous chemical laboratory of
the body the grass gathered in the same field is converted into flesh
which even in its uncooked state is easily distinguishable. Though for
the purposes of this illustration domesticated animals have been used,
the same is true of their wild relations. Sportsmen tell us that the
various types of Antelopes and the Zebra, which may be seen feeding
together, have yet flesh of very different qualities. These qualities
are to be attributed neither to “Natural” nor to “Sexual” selection;
they are “accidents.” Similarly, their horns are the witness of a
horn-producing “diathesis”: the various divergencies in curvature,
and in the form of their spirals, or the number of their encircling
rings—as in the horns of Antelopes—are to be interpreted in like
fashion. These twists and turns vary in the same way that the taste of
the flesh varies, and for the same reason; that is to say, they are not
the outcome of “Sexual Selection,” nor have they been brought about by
“Natural Selection” to serve the purpose of “Recognition marks,” as
Wallace would have us believe.
But horns, as horns, apart from their “accidents” of curvature
and ornament, must certainly be regarded as the product of Sexual
selection, for having once started into being those individuals had
the best chance of leaving descendants which were best armed. The
possession of horns was not necessary to the maintenance of the
species; but such armature was essential among the males in securing
possession of the females. Other things being equal, the male with the
biggest horns wins the prize. Since these are also used as weapons of
offence, or rather of defence, in warding off the attacks of beasts
of prey, it might be contended that they are as much the product of
Natural selection as of Sexual selection.
It soon becomes apparent that this interpretation must fail. In the
first place, if it were true, the females should be similarly armed.
In the second, in the presence of many of their enemies they are
useless. The Cape hunting-dog, for example, is more than a match for
any antelope. This ferocious animal kills his victim by running it
down, persistently tearing at its flanks, until at last the entrails
protrude and the horrid chase is ended. Furthermore, the horns are a
comparatively late acquirement of the species, as is shown in the case
of the Deer; for the earliest known fossil species were hornless. That
the females among the Oxen and many of the Antelopes possess horns is
an interesting fact, but it can only be regarded as another instance
of a character first acquired by the male and later, in successive
generations, transferred to the female. And it is to be noticed that
this transference is never found save in the cases where the character
in question has attained its maximum in the male. The transference
of weapons to the female is the more remarkable because there is no
evidence that they play any part in the struggle for existence, either
in securing mates or in warding off the attacks of enemies. Moreover,
these weapons in the female may exceed those of the male, in length,
though they are never so massive. They are to be regarded solely in
the light of ornaments. There are few more striking instances indeed
where the purely ornamental and the strictly utilitarian are so closely
associated.
[Illustration: Plate 4.
_By the courtesy of Rowland, Ward, Ltd._
WEAPONS OF OFFENCE.
Horns of various types furnish the most conspicuous of the “Secondary
Sexual Characters” of the ruminants. In the Deer only are these
branched. In the “hollow-horned” ruminants they are either lance-like
or more or less spirally curved, or they may form more or less open
loops.
1. Black-tailed Deer. 2. Hangul or Kashmir Barasingha Deer.
3. Greater Kudu. 4. Black-buck. 5. Saiga Antelope, remarkable also for
its curiously swollen nose. 6. Marco-Polo’s Sheep.
[Face page 52.]
Attention may now profitably be turned to the behaviour of these
interesting tribes when under the alluring influences of love.
Tradition and the poets have contrived to persuade us that the fever
of Love becomes epidemic in the spring. This, however, is by no means
true, at any rate in so far as what we are pleased to call the “lower
animals” are concerned. For with many, as for example the Deer and the
Bats, this fever is not aroused till the time of autumn plenty. With
regard to the deer, we can find a reason for this. It is determined in
part by the period of gestation, and in part by the peculiar character
of the most conspicuous of the male secondary sexual characters—the
antlers. The deer, at any rate of the northern hemisphere, carry their
young about eight months. Now it is important that they should make
their entry into the world just as the food supply is increasing and
the temperature is rising. With the summer before them the young have
time to gather strength for the encounter with their first winter. We
have a striking witness to the truth of this contention in the fact
that when the Indian Spotted Deer, or Chital, was first introduced into
Europe, nearly all the fawns perished owing to having been born in
winter; later, the females took to calving in spring, and from thence
onwards the species has held its own among us.
As touching the stags. The antlers, as everybody knows, are shed
annually, and their renewal entails a very considerable strain on the
system. As a consequence, it is necessary that this period of stress
should fall after the trial of winter is overpast, and with the genial
summer before them. From the end of March, when the old weapons are
shed, till July, the masterful males of the community wander at large,
seeking seclusion and avoiding all occasion of quarrel; for they
are not only defenceless, but threatened with disaster should any
accident befall the growing horns, which, during their formation, are
exceedingly sensitive. Even a slight blow would not only spoil their
shapely proportions, but, further, might render them useless in the
warfare that is before them.
With some species this desire to go into retreat is more marked than in
others. The Red-deer, and the Wapiti, on the one hand, and the Moose on
the other, well illustrate this. The two first-named pass the winter in
herds, in the case of the Wapiti numbering many thousand individuals;
no other species, indeed, is so markedly gregarious. With the advance
of the spring, however, all is changed, for the males withdraw from
their companions to suffer humiliation in seclusion. As chill October
arrives, a striking alteration in their demeanour becomes apparent,
at any rate in the case of the older males. The new antlers are now
hardened, and the blood supply, which has hitherto been building up the
new weapons, is cut off. As a consequence, the “velvet,” which till now
has been directly concerned with the growth of the antlers, dies, and
peels off the underlying bone. To facilitate this work of cleaning,
the animal rubs them, first against the stems of saplings, and, later,
against larger trees, and even rocks, till at last they are ready for
“battle, murder and sudden death.” The “rutting” season, in short, has
commenced. And with the final completion of the antlers other signs
of that approaching frenzy, which is soon to establish itself, become
apparent. The most striking of these are the swelling of the neck, and
a marked increase in the mane thereof; while the voice enlarges its
compass enormously, whereby the females, so long neglected, are now
feverishly sought for.
[Illustration: Plate 5.
_Photo by G. W. Wilson Co. Ltd., from “The Living Animals of the World.”_
MANCHURIAN WAPITI “CALLING.”
The “stags” do not begin to call for mate’s until the horns have more
or less completely shed their velvet.
[Face page 54.]
The Red-deer, maddened with desire, scours the country, calling as he
travels with a loud musical roar, ever and anon impatiently listening
for the tremulous response of females hardly less anxious to mate
than himself. One after another is speedily added to his harem, but not
without conflict. For sooner or later he catches the call of another
stag in like case. A jealous fury at once takes possession of him, and
the call, intended as a message to mateless hinds, becomes translated
into a challenge to fight for the mates possessed. Each of the now
infuriated challengers makes all haste to come to blows, and speedily
they are rushing headlong on one another to meet in a crash of antlers.
Then follows a test of strength, a sort of tug-of-war reversed, for
each strives to push the other to his knees, and succeeding, to deal
a deadly sideways thrust at the kneeling adversary’s heart with the
spike-shaped brow-tines. This attempt, however, is rarely achieved. Yet
not seldom such encounters become a duel to the death, and one in which
both die, for in the remorseless tilt at one another the antlers of one
may spring apart, and then close in on those of the other. Once this
happens, it seems to be rare indeed that they can be extricated from
this close embrace. With heads thus locked, they sway, and twist, and
tug, not now for the mastery, but for life itself. But as the hours run
they become more and more exhausted by their efforts, weaker and weaker
from loss of food and rest, till finally death releases both.
A male having once succeeded in forming a harem, will commonly contrive
to repeat his success year after year, withstanding all comers. But
sooner or later his vigour wanes and he is ousted by another and
younger male. Not else would the stamina of the race be preserved. It
is considered a moot point, however, whether physical strength and
sexual potency run at the same pace; for it is believed by some that
a stag will often contrive to hold a harem against all rivals after
his fertility has declined. This, however, is extremely improbable. A
lowering of fertility means a decline in the potency of the hormones,
and in the development of the secondary sexual characters, among which
are the antlers, which are by no means negligible factors. That they
are not all-important, however, seems to be shown by the fact that,
occasionally, stags appear in a herd which are congenitally unable to
produce antlers—a reversion to the ancestral condition—and such are
said, occasionally at any rate, to be able to oust their formidably
armed rivals. This may be so, but the fact that “hummel” stags, as they
are called, are so rare is surely to be regarded as eloquent testimony
of the disadvantages of their unarmoured state. They become speedily
eliminated, in short, by “Sexual Selection.”
After this outburst of sexual activity has spent itself, the various
harems, with their lords, amalgamate; all living in peace through the
winter. The stags retain their antlers at this season, partly as a
protection against predatory enemies, such as wolves, and other large
carnivores, which would otherwise play havoc in their ranks, and partly
because the cold of winter and scanty fodder would inhibit the growth
of new antlers or reduce their size. With the return of spring the
dangers of attack are lessened, temperature rises, and food becomes
once more plentiful. Then the inevitable disarmament takes place.
The Red-deer, though mature at six, does not reach his prime till his
eleventh year, and from thence till his fifteenth or sixteenth year is
at his best. The hinds mature earlier, and appear to be fertile for a
much longer period. At any rate, a wild hind in Jura, known by certain
peculiarities of its ears, during twenty-one years produced twenty
calves. She was killed at last with a calf at her side, but was thin
and haggard-looking. She was, therefore, not less than six-and-twenty
at her death. The calves, it may be mentioned, are born in May and June.
Old stags shed their antlers, it is remarked, earlier than young ones.
And this is an advantage to the species, since it prevents premature
breeding on the part of sexually precocious but immature males, and
limits competition to the adults.
What obtains in the case of the Red-deer obtains also with minor
variations due to environment, climate, and so on, in the case of all
other deer. The life-history of the Wapiti, as might be supposed,
differs only in detail from that of the Red-deer. But during the winter
they form vast herds, numbering thousands. It may be that in primitive
times the Red-deer was no less numerous. But in this country, at any
rate, conditions favourable to the maximum development, either in
bodily size, or in the massiveness of the antlers, have long since
passed away. Even in the Highlands of Scotland the conditions of
existence have entirely changed owing to disafforestation. Deer are
essentially forest dwellers. But the “deer forests” are such only in
name, and for the most part the wild stags of to-day must get what
shelter they can from rocks and inequalities of the ground. From
this cause, and from the very natural desire of the owners of such
“forests” to secure the finest heads in each year, the whole race
has deteriorated. How great a change has come over it may be seen by
comparing the heads of British Stags with those from German forests,
where the conditions of existence are more favourable. If we turn to
the records of the past we find that the antlers found in the fens,
turbaries, and caverns of our islands are vastly larger, heavier, and
carry a greater number of points on the sur-royals, than do those of
the existing Scotch stags.
Having regard to the fact that hundreds, and in the distant past
thousands, of antlers were shed annually, the comparative rarity of
these weapons in the haunts of deer excites comment. This is accounted
for by the fact that they are greedily eaten by their late owners,
apparently, though unconsciously, for the sake of their bone-producing
qualities.
By way of contrast with the Red-deer and Wapiti, we may take the Moose
(_Alces machlis_), which at no time, and nowhere, attains to large
herds. This is explained by the relatively restricted food supply which
obtains in the haunts of these creatures. For they frequent the margins
of streams, feeding largely on willows and birch. From the shortness
of their necks, and the great length of their legs, they cannot crop
grass and other short herbage, for unless they kneel they cannot reach
the ground. Hence it is obvious that though their geographical range
may be wide, their numbers are kept rigidly in check. They would be
fewer still but for the fact that, unlike other deer, they glean no
small amount of food from the water, wading out to feed upon aquatic
vegetation. The roots of water-lilies are especially sought for, and to
obtain these the animal will often disappear entirely under water.
As a consequence of the limited food supply the Moose lead solitary
lives. On the Eastern side of America, where the winter is severe, a
few individuals, generally a family party, will “yard up,” or make a
fortress for their mutual protection by trampling down the snow over a
restricted area. But in the Yukon district, my friend Mr. F. C. Selous
tells me this is never done.
The rutting season of the bulls begins as soon as the antlers begin
to “peel.” What follows is practically a repetition of what has
already been related in regard to the Red-deer and Wapiti. And in this
connection it is interesting to note that the natives take advantage of
the period of desire in the bull to entice him to his death. Generally
this is done by imitating the call of the cow in response to the bull’s
anxious bellowing. But in Southern Alaska the opposite side of his
nature is played upon. This is done by scraping or beating the bushes
with the shoulder-blade of a Moose in such a way as to reproduce the
sound of a bull cleaning his horns. The very suspicion of a rival
enrages him, and, rushing in a blind fury in the direction of the
tell-tale sounds, he speedily falls a victim to the trick which has
been played him.
That the mating period is the most critical, and most searching in
the whole life-history there can be no doubt. Every faculty during
this time is put to the test, and from the time of sexual maturity
until old age is at last attained it is an annual test. Alertness is
all important. Other things being equal, success falls most certainly
to those individuals with the keenest perception, and quickest
interpretation of sight, sound and smell.
One is puzzled at what seems a concession of Darwin’s to the Lamarckian
theory of the inherited effects of use in this connection. For in
discussing the bellowing of the stag in “The Descent of Man,” he
remarks that it “does not seem to be of any special service to him,
either during courtship or battles, or in any other way. But may we not
believe that the frequent use of the voice, under the strong excitement
of love, jealousy and rage, continued during many generations, may
at last have produced an inherited effect on the vocal organs of the
stag, as well as of other male animals?” All the evidence goes to show
that the production of sound, and the instant interpretation of its
significance, is a matter of the highest importance. In the case of the
Moose, for example, the noise occasioned by the cleaning of antlers
provokes the same frenzy as at another time is aroused by the voice.
Dullness of perception not only in these matters, but at all times, is
fatal.
As touching the less conspicuous secondary sexual characters of Deer
more must be said presently. For the moment the antlers must retain
our attention. Time was when the Deer lacked these appendages. When
they first appeared, in the now extinct species of the Middle Miocene
period, they were no more than short prongs. Later, one of the prongs
became elongated, and developed short branches or “tines,” which, in
succeeding species, became more numerous, while at the same time, with
the gradual evolution of more and more species, these antlers assumed
new features both in the matter of size and in the character and number
of the “tines,” a development which has reached its maximum to-day. But
apart from these specific variations, which have given us such types as
those of the Roe-deer, Red-deer, Wapiti, Caribou, Moose, Fallow-deer,
Sambar, Schombergk’s deer, the strange Milou-deer, Elds-deer and
Mule-deer, each species displays a quite remarkable range of variation
in regard to its particular type of antler. Nowhere, perhaps, is this
more strikingly marked than in the case of the Caribou and Moose. No
doubt this feature is due largely to the fact that the horns are shed
annually, and that the variations are due, in part at any rate, to
temporary environmental conditions, such as food and weather. But
these apart, individual peculiarities are constant, reappearing with
more or less exactness each year.
[Illustration: Plate 6.
_Photo by Lord Delamere, from “The Living Animals of the World.”_
GROUP OF BEISA ORYX.
The lance-like horns of these animals can be used with deadly effect,
even against lions.
[Face page 60.]
In contemplating these facts one asks: What are the underlying factors
of this variability? What is the significance of the branching? What
end is attained by the annual shedding? That the antlers constitute
very effective weapons of offence there can be no doubt, and one is
inclined to regard the branching as the outcome of natural selection,
on the assumption that branched antlers would be less deadly than
lance-like weapons. It would perhaps be tempting to accept this
interpretation as all sufficient were it not for the evidence afforded
by the hollow-horned ruminants. The Oryx and the Kudu, for example, are
lance-bearers, and therefore show conclusively that stags similarly
armed might well have continued to survive in spite of the foils which
the “tines” provide. Darwin, long since, guardedly suggested that
while these weapons primarily served for offensive purposes, their
elaborate systems of branching might have been brought about by sexual
selection. That is to say, the extreme beauty of the weapons may excite
the admiration of the females as well as our own. Granting this, he
inferred they might have played an important part in elaborating the
branching by constantly displaying a preference to mate with those
males possessed of the largest and most branched antlers. But there
are many and serious objections to this suggestion, and the most
important of all is the fact that the female is allowed no choice in
the selection of her lord and master. We can, then, only regard the
antlers of deer as another instance of the survival of a “fortuitous”
but inherent variation, which survived because, whatever the defects
thereof, they proved advantageous in the struggle for existence.
Having regard to the fact that so many of the females among the
hollow-horned ruminants have acquired horns, it is somewhat remarkable
that in the Reindeer alone among the deer are these weapons normally
possessed by the female. The gradual transference to the female of
features which were originally secondary sexual characters in the
male is an occurrence which is met with in every group of animals. In
writing “The Infancy of Animals” I gave a number of instances of this
kind. But the case of the Reindeer affords a more than usually striking
illustration of this curious sequence; and this because rudiments of
antlers are to be met with among the females in several different
species of Deer to-day. They have been found in the females of both
Roe- and Red-deer, though such cases are rarely met with. As a rule
this assumption of the male secondary sexual characters by the female
occurs only in very aged animals, or as one of the sequelæ of diseased
ovaries and consequent sterility. But at least one instance is on
record of a doe Roe-deer which possessed small antlers while pregnant.
Thus, then, we gain a further insight into the process by which the
female slowly assumes the outward attributes of the male; that is
to say, the secondary sexual characters appear first in the male,
and as seasonal characters. Sooner or later they become permanently
established. By the time they have become firmly fixed in the male, and
apparently not till then, they appear in a dilute form during senility,
or in consequence of ovarian disease, in the female. Having once
started, however, they appear earlier and earlier in the life-history
of succeeding generations of females, and at last in the juvenile
stages of both sexes.
The hollow-horned ruminants, which must now be considered, afford some
very striking facts in regard to these “secondary sexual characters,”
more especially in so far as horns are concerned. In the first place
these weapons are permanent structures, taking the form of a bony core
ensheathed in horn, with which we may compare the temporary covering
of velvet in the deer: in the second, they are unbranched. The only
exception to this rule is furnished by the Prong-horned Antelope,
wherein the sheath is both annually shed, and branched. The branching,
however, is very slight, taking the form of a short forwardly directed
prong about half-way up the sheath, which is borne on a long bony
pedicle recalling that of the Muntjac. The shedding is due to the
formation of new horn material at the base of the old sheath, which
is gradually forced off by the growth of the new tissue. Structurally
the horn of this remarkable Antelope differs somewhat from that of its
relatives.
As may be seen in Plate 4, in the form of the horns the typical
hollow-horned ruminants present an exceedingly varied range, and one
often of great beauty in the matter of curvature. That they serve as
formidable weapons of offence was demonstrated during 1912, when,
according to the Annual Report of the Government Game Reserves,
published by the Pretoria Government, the game warden, Major Stevenson
Hamilton, reported of the Antelopes that “many carcases of males of
almost all species, killed in single combat with rivals, were found
during the mating season, untouched by anything except vultures.” As
a rule, however, these animals, like the Sheep and Goats, and their
larger relatives the Cattle, seem to avoid a duel to the death. One
or two instances as to the general character of these combats for
the possession of mates must suffice. Thus the late A. H. Neumann,
a hunter of experience, remarks that he once or twice saw conflicts
between the Topi (_Damaliscus jimela_), an ally of the Hartebeestes.
The two rivals would stand a little apart, affecting, apparently, to be
unaware of one another’s presence. Suddenly they would rush headlong at
one another, bringing their heads together with a clash, each, at the
same moment, falling on his knees.
Major Powell Cotton, again, once witnessed an affray between two Beisa
Oryx. Here the master bull of the herd was infuriated by the advent of
an intruder in his harem. Time after time they dashed at each other,
their foreheads meeting with a thud; then, with horns interlocked,
they wrestled fiercely; then, separating, they charged again. Yet
neither, he remarks, tried to use his lance-points, as they do when
cornered by man or beasts of prey. Nevertheless, encounters of a more
sanguinary character appear to be by no means rare, for it is no
uncommon experience of hunters to kill bulls of this species in which
one eye has been burst by a horn-thrust. Another peculiarity of these
animals is the extreme thickness of the hide of the neck and withers,
which seems to afford a shield against such spear-thrusts during
these battles. How powerful is the thrust of these weapons, and how
efficiently they can be used, is shown by the fact that lions in making
an attack on an old bull are often severely wounded, or even killed.
And there are many instances on record of cases where both the lion and
his intended victim have died together, the Antelope having been unable
to withdraw his horns from his adversary’s body. The beautiful Pala
Antelope fights furiously with rival rams, and the vanquished, as with
so many of the Antelopes, form herds by themselves, till one by one
they gather strength and skill enough to establish their right to mate.
[Illustration: Plate 7.
_Photo by courtesy of the Duchess of Bedford, Woburn Abbey._
ELAND COWS.
Among antelopes the females commonly bear horns, which may be even
longer than in the males, though less massive.
[Face page 64.]
[Illustration: Plate 8.
_Photo by courtesy of the Duchess of Bedford, Woburn Abbey._
AMERICAN BISON
The “Secondary Sexual Characters” of the male are here conspicuously
developed, and are seen in the massive fore-quarters and enormous
head.]
The Elands present some puzzling features, for both sexes bear large
horns, and they are very massive in the bulls. Yet these animals
are generally described as the most inoffensive of all the horned
ruminants. That the horns are used to any extent in conflicts between
rival males seems doubtful, inasmuch as this species is remarkable for
the development of an enormous “dewlap,” a thin pendulous fold of skin
which runs from the throat to the chest. Such a form of “ornament”—for
in this light we must regard it—would be dangerous, indeed, when much
fighting was to be done. Nevertheless, it would be contrary to all
our experience to conclude that weapons so well developed as are the
horns of the bull Eland were entirely useless. This is a matter which
decidedly calls for further investigation.
That our knowledge of that most important period of life of the larger
mammals, the period of sexual exaltation, is lamentably incomplete will
be realized by anyone who seeks enlightenment on this subject. Most
of the meagre information we possess has been collected by travellers
and sportsmen, neither of whom have the time to devote to the long and
laborious watches that a fuller history demands. Every now and then a
glimpse is afforded of this period of the life-history which brings
home in a very convincing fashion, how little is really known. It
seems certain that the fighting hitherto described is to be regarded
as but a phase of a cycle of events which takes place at this time.
Thus, for example, the old naturalist and traveller Schweinfurth tells
how he once encountered a herd of Hartebeest which were apparently
effervescing with animal spirits, for they kept running around in
couples, like horses in a circus, using a clump of trees as a pivot.
Others, in groups of three or four, stood by, interested spectators.
After a time these, in turn, took their places and ran round, two at a
time, in their own circuit, and in the same fashion. Their evolutions,
he says, were so regular as to suggest the guidance of some invisible
ring-master. These gyrations may be regarded as an erotic dance. The
Sambar, under like excitement, will stalk about with erected tail,
outstretched muzzle and everted face glands, and the Black-buck, among
the antelopes, behaves in like fashion.
It cannot be supposed that these quaint performances are peculiar to
the species in which they have been observed, but rather it may be
inferred that similar antics, besides others yet to be discovered,
are performed by all. Their purpose seems plain enough, for they must
be regarded surely as aphrodisiacs, excitants to pairing. They recall
the erotic dances of savages, or the ceremonial orgies of ancient
civilizations. Such performances, on an even more elaborate scale, are
to be met with among the birds.
So far, in describing the horned ruminants, the horns only have been
considered; but these animals display yet other secondary sexual
characters, which, while less conspicuous, are yet no less important
during this critical period of life. Some, as for instance the canine
teeth possessed by some of the deer, are decidedly puzzling. While
absent, or vestigial, in most, in a few they are greatly developed, and
this, too, in species which possess relatively large horns, as in the
Muntjac. It seems difficult to believe that the co-existence of these
very different kinds of weapons can be of vital importance to their
possessors; yet unless this be so, one or other would surely have
degenerated. It is significant that in the hornless Musk-deer these
teeth attain to a very considerable length, at their maximum as much
as three inches. That they are used by rival males, and with effect,
is shown by the fact that the hides of these animals are often found
scored by deep lines cut by these tusks. In those aberrant ruminants,
the Camels, quite formidable tusks are present both in the upper and
lower jaws, and these are used with effect whenever occasion demands,
and often when it does not.
The armoury necessary for successful love-making contains yet other
weapons, evolved to supplement physical force, and more subtle in their
effect. Such are certain skin glands which, at the rutting season,
secrete a copious flow of a creamy, or semi-fluid matter, and pungent
odour. In the deer the more important of these are found in the deep
pit, or “larmier,” which opens in front of the eye. In the Musk-deer,
however, this secretion has a most powerful odour of musk, and is
formed in a pouch, or “pod,” of about the size of a small orange, under
the skin of the abdomen. The secretion, which is formed by the male
only, is of a chocolate colour, and of about the consistence of moist
gingerbread. It has a most pungent scent, and when diluted forms the
basis of many of our most powerful and most highly-prized perfumes, on
which account, it may be mentioned, this animal has for generations
been submitted to a most unrelenting persecution. But that is another
story.
In most of the antelopes the principal scent gland is seated in a pit
in front of the eye, as in the deer. In some, as in the Gnu, it forms
instead a swollen, tumid area, oblong in shape, instead of lying in a
pit. In the Reedbuck it is placed around the bases of the horns; and
in the Rocky-Mountain Goat it forms a great bare cushion behind the
horns. All have more or less well-developed glands seated in the skin
between the toes. But, wherever placed, the secretions thereof are more
or less completely suspended save during the breeding season, when they
are poured forth abundantly. The precise rôle they play is by no means
certainly known. It seems reasonable to suppose that, in the first
place, the odour they disperse enables the males to announce their
whereabouts to the females seeking mates, should they fail to hear
their bellowing. But the antelopes, for the most part, unlike deer, do
not, the year round, lose touch with one another; so that it must be
concluded that these odours serve as excitants to the act of pairing,
and we know that the sense of smell plays a very important part at
this time, which, so far as these animals are concerned, is the only
period which comes more or less exactly within the meaning of the term
“courtship.”
That scent among the antelopes holds a really important place is shown
by the fact that the bull of the common Eland intensifies his natural
odours by micturating upon the mass of long hair which grows upon the
forehead. To do this the head is bent down and turned tailwards, in
order that the tuft should receive its due urinary spray! And goats in
captivity exhibit the same curious habit. In them, indeed, it is often
pushed to such an excess that blindness results, so that the animal has
to be slaughtered.
While in many cases these odours are imperceptible to human nostrils,
in others this is far from being the case. Among the ruminants the goat
is particularly odorous. So also are the giraffe and the water-buck,
both of which may be detected by their smell at considerable
distances. And these emanations are most noticeable in the males and at
the breeding season. The bull elephant, both in the Indian and African
species, during the breeding season produces a copious flow of aromatic
matter from a gland which opens above the eye in the form of a tubular
aperture large enough to admit a pencil. This aperture in the African
elephant is remarkable for the fact that it is invariably found to be
“plugged” with numerous spines of the acacia, which have from time to
time found their way in as the animal was forcing its way through the
dense undergrowth. This extraordinary fact was first noticed by Mr. F.
C. Selous, and has since been confirmed by Dr. Einar Lonnberg.
It is probable that the “bloody sweat,” which at times covers the hide
of the Hippopotamus just after leaving the water, is associated with
the period of rut. This mysterious exudation is accompanied by small
crystals; but though red in colour, it contains no blood. So far no
reasonable explanation for this remarkable phenomenon has ever been
given, but probably it will be found to be associated with the sexual
activities and is possibly odoriferous. A precisely similar exudation
occurs in the neck of the male of the Red Kangaroo.
That these secretions play an important and perhaps variable part
in the selection of mates seems demonstrated in the case of an
incident related to me by my friend Mr. John Cooke, who some time
ago was watching a flock of some three hundred sheep while it was
being driven by the shepherd and his dogs into a field. As soon as
they were securely shut in, and the shepherd had gone, three rams
who were included in the flock at once began a three-cornered fight.
One, presumably the youngest, was soon vanquished. The other two
soon settled their differences, and the clashing of horns was at once
followed by a very different performance. The master ram began to run
in and out among the ewes, sniffing at each, and driving out those
whose odour most pleased him. Having at last satisfied himself with a
harem of about one hundred, the second ram was allowed to make a like
choice, and behaved in a like manner, leaving the remainder to the
ram which was first vanquished. May we take it that the strongest and
oldest rams selected the youngest ewes, and the oldest were left to the
youngest, and first conquered ram? By some such rough and ready method
of selection Nature may contrive that the immature male shall do as
little harm to the race as possible by mating with the oldest, and in
many cases barren females.
Our survey of the “hoofed” animals has so far been confined to the
ruminants. Space must now be found for a brief review of what obtains
under like circumstances in the case of the great pachyderms—the
Elephant, Rhinoceros and Hippopotamus; the Pig and the Camel.
[Illustration: Plate 9.
_Photo by Lord Delamere, from “The Living Animals of the World”_
ELEPHANTS.
The sexes differ but little in general appearance: and chiefly in the
superior size of the male and his more massive tusks.
[Face page 70.]
As to actual “courtship” among these animals practically nothing
is known; but the varied and formidable weapons which they possess
are enough to show that the secondary sexual characters play a very
important part in the preliminary capture of mates. That they may
also be used for the more prosaic purpose of securing food is nothing
to the point. In the Elephant, for example, the tusks are sometimes
of enormous size and weight, specimens of eleven feet in length and
weighing as much as two hundred and fifty pounds are on record. They
are used for cutting through the bark of machabel trees, which is then
seized by the trunk and torn off, for elephants are extremely fond of
this bark; and they are also turned to account in breaking up roots
which have been exposed by digging with the fore-feet. But this is
certainly not the main purpose of such weapons. On the contrary, their
use is primarily as weapons of offence between rival bulls. As one
would expect, they never attain to a very large size in the female, but
that they are large enough to serve her at need is shown by the fact
that a portion of a tusk, evidently of a cow-elephant, was once found
embedded in the jaw of a bull. There can be little doubt but that this
was broken off in an endeavour to repel the advances of a too amorous
male, for, as with all animals, pairing is impossible without the
consent of the female, and this is never accorded until she is desirous
that it should take place. As a preliminary to this, an amorous
dalliance is perhaps the invariable rule among animals, and this takes
many and often strange forms. The Elephant affords a case in point. For
the late A. H. Neumann once came upon a pair which were evidently, as
he says, “love-making.” Creeping upon them noiselessly, he found the
male fondling his mate with his trunk, and then, standing side by side,
they crossed their trunks, and put the tips thereof into each other’s
mouths, the elephantine form of kissing. Deer, cattle and horses, cats
and dogs, constantly lick one another under like circumstances.
Superficial secondary sexual characters are wanting both in the
Hippopotamus and the Camel. Both, however, possess a formidable
armature of teeth which are capable of inflicting very severe wounds.
In the Hippopotamus the canines are of enormous size, and their
punishing power is further strengthened by the fact that they work
in opposition to a pair of similar teeth in the lower jaw; they cut
like a pair of shears, the upper closing upon the lower pair with
the precision of scissors-blades. In addition, the lower jaw develops
two long, blunt-pointed, ivory spikes, which are scarcely less to
be dreaded. With these weapons the bulls fight furiously, and it is
no uncommon thing to find vanquished males frightfully mauled, the
hide being lacerated from head to tail. Protection, in a measure, is
afforded by its enormous thickness, but the great folds and pleats of
skin seen in the Rhinoceros are never developed. The females, however,
are similarly armed, and the teeth are nearly as large as in the males,
which is a rather unusual occurrence.
The Swine, which are near relations of the Hippopotamus, in like manner
develop huge pointed canines, and these reach their maximum in the
great Wart-hogs of Africa. But in the swine the mechanism differs,
for although the canines are closely opposed, the shaft of the upper
teeth curves upwards, and the lower teeth are much smaller than the
upper. In fighting, these animals do not bite, like the Hippopotamus,
but use the upper canines to rip up their antagonist with a sudden,
swift upward and sideways movement of the head. How dangerous is the
wound thus inflicted those who have hunted the wild-boar know well. A
curious exaggeration of this arrangement of the teeth is seen in the
Babiroussa. Herein the upper canines grow directly upwards, actually
piercing the upper lip as in the case of the downwardly growing tusks
of the elephant. That these teeth, however, are of any service in
fighting is doubtful, for the upper tooth curves upwards and backwards
in a semicircle so that the points are harmless. The tusks of the lower
jaw, however, are extremely long and pointed, though their wounding
power is limited by reason of the upper teeth. This may account for
the fact that the head, the part mostly attacked by enraged
boars, presents no sort of armature designed for defence; while in the
Wart-hog, on the other hand, great solid bucklers of hide stand out
on either side of the head below the eyes, giving the animal a most
repulsive appearance, but affording him a very present help in time
of trouble. In the wild-boar, where the tusks are shorter, no such
protective armature is needed.
[Illustration: Plate 10.
HEAD OF MALE WART-HOG.
In the “Swine” family the canine teeth are always greatly developed,
but they attain to their maximum, relatively, in the Wart-hog.]
[Illustration:
_Photos by Scholastic Photo Co., from “The Living Animals of the World.”_
MALE AND FEMALE BABIRUSA.
A characteristic of this pig is the peculiar development of the tusks
in the male, the upper pair of which grow through the lips and curve
upwards.
[Face page 72.]
[Illustration: Plate 11.
_Photo by Lord Delamere, from “The Living Animals of the World.”_
SOMALI ZEBRAS.
The Zebras, unlike their cloven-hoofed relations, have no weapons, save
for inter-tribal conflicts. Yet they have been as successful in holding
their own against lions and other predatory animals as species provided
with horns.
[Face page 72]
[Illustration: Plate 12.
_Photo copyright by A. H. Bishop._
GIRAFFE.
The horns of this animal can prove formidable weapons of offence on
occasion, though they are useless against predatory animals.]
While the ungulates, or hoofed animals, are peculiar in the development
of horns as weapons of offence, they are by no means singular in the
use of teeth for this purpose. In some cases, as in the Muntjac, both
forms of armature are present. The only other instances where teeth
in this group of animals are used for offensive purposes are those
furnished by the Camel and the Horse. But here they do not exhibit
that excessive size which is met with in the Elephant, and some of
the Swine. In both the Camel and the Horse it is the canine which is
used, and both jaws are similarly armed. Since the camel has no upper
incisors, the part played by the teeth is beyond dispute; but it has
been contended that the horse uses his incisor or “front-teeth” alone
when fighting. But this is not so; the canines can, and do, inflict
ugly wounds, as is shown by the necks of zebras.
A further method of defence among the larger Ungulates, at any rate,
is resorted to when hard pressed: and this is the use of the hoof in
kicking. Giraffes kick both after the usual fashion and in striking
downwards with the fore-foot. And an interesting demonstration of this
has been furnished by Mr. F. C. Selous in his delightful “African
Nature Notes.” He relates that on one occasion he came across a calf
only a day or two old, with its back broken. From scratches on the
calf, and the footprints on the ground in its vicinity, he was at once
enabled to gather the cause of its terrible plight. In a word, it had
been attacked by two leopards, and the mother, in an endeavour to beat
off the assailants with a blow of her fore-foot had accidentally struck
her offspring. Horses, Cattle, Antelopes, Camels and Elephants can all
kick with precision and effect. So far as the evidence goes, however,
this is a method of defence used against beasts of prey, and is rarely,
if ever, employed in conflicts between rival males. Females persecuted
by the undesired attentions of amorous males, however, do, as we know
from the case of domesticated animals, use this device to defend
themselves.
It is not difficult to account for the origin of such secondary sexual
characters as manes, beards, tusks, and brightly-coloured areas of
skin, though whether our interpretations are really correct is another
matter. But no attempt to explain the origin of horns has yet achieved
a like degree of persuasiveness. These weapons appear only in the
Ungulates, a group which has, in past times, given birth to some very
extraordinary types of head armature of this kind. These must be
excluded from the present discussion; suffice it to say that, as usual,
they were the adjuncts of the males. According to current theories it
is supposed that these weapons arose as the result of the action of
sexual selection. It is assumed that the hornless ancestors of now
horned ruminants fought for their mates by “butting” with the forehead.
Naturally, other things being equal, the thickest skulled combatants
obtained the mastery. Any tendency to develop frontal “bosses” of bone
would further enhance the chances of success, and would, indeed, soon
become necessary for survival. And from such “bosses” the passage to
horns and antlers forms an easy transition. Just such incipient horns
or “bosses” actually make their appearance in the domesticated horse:
but these animals never butt at one another. If, however, we regard
horn-production as an inherent diathesis of the ungulate somatoplasm,
we have an intelligible basis for the explanation of horn development.
The formidable horns of the Rhinoceros are of a totally different
character, being solid structures formed by hairlike agglomerations,
firmly fixed upon a roughened area of the nasal region. These weapons
play a very important part in settling disputes between rival males,
but on other occasions demanding offensive tactics the Indian
Rhinoceros at any rate seems to depend rather on his power of wounding
by means of the chisel-shaped lower incisors. These, by means of a
swift lateral movement of the head can be made to inflict most terrible
gashes, as those who hunt with elephants well know. It is quite
possible, however, that the teeth are also thus used during struggles
for supremacy. And this may perhaps account for the enormous bucklers
of skin developed by the Indian Rhinoceros, but only indicated in the
case of the African species.
All the larger Ungulates, and many of the smaller species, are
polygamous. The Rhinoceros, and all of the swine-group save the
Hippopotamus, among the larger species are exceptions to the rule. The
preponderance of females which this implies is generally supposed to
be due to the losses sustained among the males by fighting during the
struggle for mates. The case of horses, however, seems to militate
against this view, for though they undoubtedly fight furiously, no
evidence is forthcoming to show that such conflicts terminate fatally.
Were it possible to secure the necessary data it would probably be
found that polygamy, and polyandry, are determined solely by the
numerical proportions of the sexes: the excess of males or females
being due neither to “Natural” nor “Sexual” Selection, but to inherent
peculiarities of the germ-plasm tending to produce an excess of males,
or females, as the case may be.
Finally, all the evidence goes to show that it is a mistake to
suppose that polygamy is due to the excessive sexual avidness of the
males, which impels them to first essay the overthrow of all possible
rivals, and then to appropriate every female within their sphere of
influence, holding them by force. On the contrary, this plurality of
mates is thrust upon them. And this because the females, impelled by
“mate-hunger,” attach themselves to the nearest male within call: the
size of the harem depending on the number of available males. The
battles which are fought between rival males are no more sanguinary
than in the case of monogamous species. This contention is well
illustrated by the African Wydah-birds (_Vidua_), which are markedly
polygamous, though they have no special weapons of offence. In
districts where males are numerous the harem will not exceed eight, or
ten, females; where males are scarce this number may be increased to
fifty. In like manner the varying number of hinds accompanying a stag
are to be regarded, not as an index of his prowess, but of the scarcity
or abundance of males in the neighbourhood.
CHAPTER V
THE LION AND HIS KIN
A Surprising Relationship—The Lion’s Mane—The Sabre-toothed Tiger—Some
Theories about Origins—Sea-lions in Love—Some Strange Ornaments—Whales
and Weapons.
That the Lion and the Lamb could possibly have been derived from the
same stock seems incredible: yet such is the case, though the pedigree
is now well-nigh lost in the mists of a hoary antiquity. It is not
surprising, then, that in their present-day garb they should show so
little in common. Nor is it strange that among their many points of
divergence the one should differ so conspicuously from the other in the
matter of secondary sexual characters. For when these are conspicuous
among the Ungulates they usually take the form of horns, of which the
Carnivores have no need, for the teeth and claws whereby they win their
daily portion of meat make equally serviceable weapons of offence when
turned against their own kind.
Among the larger Carnivora, the Lion alone displays any obvious
distinction between the sexes in the matter of ornament, and this in
the form of the well-known mane. Darwin, and later authorities, have
regarded this as a shield to protect the great blood-vessels from
injury during battles between rivals. But it is not very clear that
this alone is sufficient to explain its presence, inasmuch as the Tiger
in this respect is defenceless. Mr. F. C. Selous long ago pointed out
that the varying abundance of the mane is due to climatic causes. Lions
which live in districts where the nights are very cold, as in high
table-lands, have large manes; those which occupy lower ground, where
the nights are relatively warm, have but a scanty mane. It is clear,
however, that the abundance of the mane is not determined by the need
for warmth, otherwise it would have been as well developed in the
female. Rather we must regard a low temperature as conducive to the
growth of long hair when a natural tendency to produce this is present.
There are few men who can claim to have so great a first-hand
acquaintance with Lions as Mr. Selous, and he has pointed out to me
one significant fact which seems to show not only that the mane has
not been developed to serve as a shield when fighting, but that fights
between rival males must be rare. And this because of the absence
of any evidence in the shape of scars on the skin. With claws so
formidable as those of the lion, ugly wounds would certainly be made in
any prolonged conflicts, for the skin of this animal is very thin.
In the now extinct Sabre-toothed Tiger the upper canines were of
enormous length, and it is not improbable that they, on this account,
exceeded the bounds of usefulness; that, while as weapons of offence
they may have proved exceedingly effective, yet they hampered the
animal when feeding. In many ways one is reminded by these weapons of
the huge tusks of the Walrus. These are blunt-pointed, and are said
to be used very largely for digging up the large clams and other
burrowing shell-fish on which this animal mainly feeds. They are also
used as levers to drag the huge body out of the water on to the ice.
As fighting weapons they are formidable, and the wounds they inflict
are sometimes serious. The polygamous habits of this huge creature may
account for the fact that they are so much larger in the males, wherein
they may attain a length of thirty inches, and a weight of eight pounds
a-piece.
In connection with the monstrous tusks of the Sabre-toothed Tiger there
is a point which so far seems never to have attracted the attention it
deserves. And this concerns two small flanges of bone which project
from the lower border of the end of the lower jaw. In themselves they
are unimportant: they lie, it is to be noticed, parallel with the
points of the great upper teeth which descend on either side of them.
Their full significance is not apparent till we turn to the skull of
another extinct animal of quite another type—the huge Dinoceros, one
of the Ungulates. This animal was also armed with an enormous pair
of tusks, which also, when the mouth was closed, descended on either
side of a flange. In this case, however, the flange was developed to
such an extent that its free edge descended to the level of the point
of the tusk, thus affording it protection against injury. The really
striking feature of this curious down-growth is not apparent till an
attempt is made to explain its presence. What determined its growth?
It seems to furnish us with another of the many instances which are
to be found of the correlation of growth between unrelated parts, for
there is apparently no traceable connection between the growth of this
pair of teeth in the upper jaw and the development of the flanges of
the lower border of the jaw which are embraced by these teeth. In the
Sabre-toothed Tiger the inciting cause to this flange growth, whatever
it may have been, seems to have been much weaker than in the case of
Dinoceros.
Naturally one asks, can the whole thing be explained by the theory of
Kinetogenesis promulgated years ago by Cope? That is to say, are these
curious down-growths the result of a response to a stimulus set up in
the lower jaw by constant lateral blows dealt by the tusks against
the side of the jaw during the lateral movements of the jaw when
feeding or ruminating? Such movements in an Ungulate would be frequent
and constant: hence perhaps the more striking result. On account of
the scissor-like action of the jaws in the Sabre-tooth such lateral
movements were far less extensive, and less powerful. But though this
explanation sounds plausible, it presents many difficulties. In the
first place it seems to commit one to the admission that the responses
of the Somatoplasm during the life of the individual are transmitted
to the germ-plasm: that, in short, the characters acquired by the
individual during its lifetime are transmitted to its offspring. And
there are insuperable difficulties in the way of such a theory. Yet,
it must be admitted, it is no less difficult to believe that this
correlation of growth is due solely to fortuitous variation, for one
cannot really conceive of a variation of this kind taking place in two
such different structures independently. Such a conception would have
been less difficult if the case of Dinoceros alone were known to us.
We could have supposed that, somehow, the lower jaw started to produce
its flange just as the teeth began to develop an excess of growth which
carried their points beyond the level of the jaw. But the Sabre-tooth
shows that the tusks had assumed a growth relatively exaggerated as
in Dinoceros, and yet the flange never attained to more than feeble
development. We cannot rest content with the theory that the flange is
due to the constant stimulus of blows struck against this region of the
jaw during the lateral movements which take place when feeding. Were
these animals alive to-day it could be tested by extracting the tusks
during infancy, when, the stimulus being removed, the flanges should
not appear.
There are yet other aspects of the skull of Dinoceros which may well
be considered here. The first concerns the excessive armature of
horns, there being no less than three pairs supported on massive bony
cores; and the second the ridiculously small brain cavity which is
proportionately smaller than that of any other known mammal, recent or
fossil. This poverty of brain-power was probably one, if not the chief,
factor among the causes which brought about the extinction of this
strange beast. Even more formidable horns were borne by the extinct
Arsinoetherium. But this animal did not display the double armature of
horns and tusks.
Among the Carnivora monogamy is the rule, though the Lion is
occasionally polygamous. But the Eared-seals (_Otaria_), or Sea-lions,
and Sea-bears afford a striking example of polygamous species and
of the ferocity they display when sexually excited. These animals,
moreover, are capable of the most astonishing powers of endurance and
vitality, exceeding indeed that of all other mammals. Since the habits
of the Northern Fur-seal (_Otaria ursina_) have been more carefully
studied than those of any others, it may serve as a sample of the rest.
Living for the greater part of the year in the open sea, the old
bulls—animals of six or seven years old—are the first to seek the
“rookeries,” or breeding grounds, taking up their territory a full
month before the cows arrive. Later, the younger bulls appear, and the
more daring endeavour to force their way through the ranks of those
who have already taken up positions. This often leads to fighting, but
more usually nothing further than “bluffing” is indulged in, though
it is commonly supposed that very severe engagements take place. This
seems, however, to be only occasionally true. In due course, generally
about the second week in June, the cows begin to arrive, at first in
straggling numbers, but soon the main body puts in an appearance, and
before the end of the month many thousands of both sexes are crowded
along the foreshore. But yet, contrary to the generally accepted
belief, no serious fighting takes place. The bulls quietly seize the
females as they arrive. It would seem that the first arrival serves as
a focus of attraction for all later comers landing in the vicinity. The
bull holding the most advantageous post—that is to say, that nearest
the best landing-place—starts the collection and, unintentionally, the
distribution of the cows. Having seized the first arrival, he places
her by his side. As the later females arrive he gives each a most
cordial welcome, and then proceeds to round up his harem. But soon he
has more wives than he can continue to control. Do what he will, he
cannot be in two places at once; and thus it is that in rushing off to
chastise some covetous neighbour, one or more bulls on the opposite
side of his harem proceed to make captures from his horde. And this
system of abduction goes on over the whole rookery till all the cows
have been appropriated, leaving a crowd of envious bachelors in the
background who have not yet developed either courage or strength to
secure mates for themselves.
[Illustration: Plate 13.
_Photo by New York Zoological Society, from “The Living Animals of the
World.”_
CALIFORNIAN SEA-LIONS, OR EARED SEALS.
The “bulls” of the Eared Seal are much larger than the “cows”; they
have otherwise no very conspicuous “Secondary Sexual Characters.”
Face page 82.]
But within forty-eight hours of their landing the cows give birth to
their “pups.” And it is for this purpose, and not for mating, that they
come to land. Within a few days of the birth, however, the females
are “in use” again. This is the critical period in the life in the
rookery. For the bulls now become frenzied with excitement and fight
most viciously one with another, each hoping to possess himself of his
opponent’s harem. Each tries to seize the other by the fore flipper,
and, failing in this, the fangs are buried in the back. They hold
tenaciously, each trying to force the other to relax his hold; but
commonly this vice-like grip is maintained till the skin gives way,
leaving great bleeding rents. Sometimes the contest rages till one or
both is fatally wounded. Often during such duels an idle bull, hitherto
unable to secure a harem, will rush in and capture that of one of the
combatants!
In the management of the harem the bull is an adept. Whether he has
five cows or fifty, he is, says Dr. Lucas, “master of the situation.”
His will is law. Not that it is always tamely accepted as such, but
the result is the same. If a cow becomes restless, and moves about, a
warning growl usually quiets her. If the movement is persisted in and
an attempt to escape evident, the bull is up at once with a show of
fierceness and in chase. He may simply strike her down with his open
mouth. Often in doing so his sharp canines tear a gash in her skin. He
may even seize her in his mouth and deliberately throw her, or carry
her back into the harem. If the cow thinks she has a chance to get away
she may try to outrun him. If she miscalculates the distance he seizes
her, after a few swift bounds, by the skin of the back, or by the hind
flipper, and tosses her, often torn and bleeding, into the family
circle. As a rule, however, she avoids this seizure by turning and
facing her lord and master, and biting him in the breast and throat.
But all to no purpose. In spite of her violent protests he pushes her
backwards before him into the fold.
Sometimes in her efforts to improve her position she runs up to, and
is seized by, a rival bull. Her lord speedily asserts his ownership by
getting a grip wherever he can on the would-be truant. Then begins a
tug-of-war between the two bulls, during which the wretched victim of
their rage may be torn in pieces. By the elimination in each generation
of the more querulous and discontented, the peculiarly gentle and
passive nature so characteristic of the females has been developed.
After the first ten days’ sojourn ashore the female is allowed to go
to sea to feed, returning presently to suckle her young. The bull, on
the other hand, can enjoy no such privilege. For three long months he
must keep watch and ward fasting—at first, in order that he may retain
his territory; later, that he may retain his harem. This fast, having
regard to the loss of energy and blood which this strenuous period
entails, is wonderful; for in the case of all other animals fasts
are always associated with absolute rest and sleep. Not so with the
Sea-lion; he arrives at the breeding-ground fat and well-liking, he
leaves a starved and battered wreck.
The foregoing summary of the habits of these most interesting and much
persecuted animals is taken from the exhaustive report of Dr. F. A.
Lucas and Mr. Charles Townsend. These two distinguished naturalists
accompanied the United States contingent of the Fur-seal International
Commission despatched in 1896-97 to inquire into the threatened
extermination of these animals. Major Barrett Hamilton accompanied
the British contingent, and also made a report. And it is curious to
note that on some points he is diametrically opposed, not only to
the American naturalists, but to all other writers on this theme. He
contends, for example, that “nothing could better illustrate the fact
that it is the cows, and not the bulls, which have the real control of
the harem-system.” He traced the rapid growth of two harems from four
or five to as many as eighty cows. And he tells these were completely
out of control and free to move about as they wished. “The bulls, in
spite of all their bluster, had the flimsiest of nominal dominion, and
the cows were always able to, and frequently did, leave the harems
daily to dally with the cowless bulls on the outside. Yet ... as long
as they chose to sit massed together on the ground which had been
appropriated by the two stronger bulls, no weaker rivals could approach
to within ten yards of them. The master of the harem had no control
over its occupants, but he was absolute lord of the ground on which
they sat.” This is certainly curious, but more so is the fact that
these females were allowed to return by the “cowless bulls” outside
the charmed circle. Later in the season he tells us he witnessed an
even better illustration of this singular behaviour. At this time “the
division of the cows into harems was a very unequal one, the smaller
bull being only able to keep a very few cows, while the larger one
claimed the greater part of the rookery. But the cows could pass over
to the smaller bull’s ground as often as they liked; and he probably
was father to a great many more of the pups born in 1898 than those of
the half-dozen cows over whom he claimed control.” In regard to two
other bulls in another cart of the island, there came a time when the
inequality of the harems reached such a pitch, that the newly-arriving
cows “had to lie in scattered groups outside the main mass, and thus
permitted the weaker bulls to form new harems out of the reach of the
two strong old bulls.” But perhaps the most singular feature of all
was the indifference which one old bull displayed towards a little
bachelor, permitting him to enjoy the most intimate relations with one
of his cows without displaying the least sign of annoyance, as if he
could scarcely regard one so young as a rival.
There is much evidence to show that the erotic side of the male-seal
develops early. “I saw,” he says, “the little black pups acting to each
other in a way that made it certain that their sexual feelings had
already made themselves felt.” This one can well understand, for only
animals of strong sexual tendencies could survive the strenuous life
which the period of sexual activity entails.
The very different interpretation of the behaviour of these animals
at this very important stage of their life-history must be due to the
fact that different colonies were studied which were living, too, under
somewhat different conditions. It seems clear, for example, that the
landing of the females so graphically described by Dr. Lucas was a
landing under exceptional circumstances, the master bulls having taken
up positions at the only spot where access to the desired breeding
quarters was to be found; while Major Barrett Hamilton was probably
fortunate in seeing phases which were wanting in the “rookeries”
examined by Dr. Lucas. And both these observers again differ in the
accounts they give of the life of such “rookeries” with those by Mr.
Elliot, who explored these teeming colonies some years earlier when the
number of animals forgathered there was far larger and the fighting,
apparently in consequence, was far more severe.
In the matter of secondary sexual characters the most remarkable of the
seal-tribe are those of the Elephant Seal and the Bladder-nosed Seal,
and this because of the extraordinary development of inflatable tissue
above the muzzle which these animals display. Of their life-history
we know little enough, and this despite the fact that for generations
the Elephant Seal was mercilessly hunted and slain for the sake of its
oil. Millions were slaughtered during the last century, yet only scraps
of information on the economy of the creatures has come down to us.
All that is of any value, and especially in regard to the “Courting”
period, we owe to Mr. Charles Townsend, of the New York Aquarium, and
this in regard to the northern species, _Macrorhinus angustirostris_
of Guadelupe, though it may safely be inferred that the Southern,
Antarctic species, _M. leoninus_, differs in no essential respects.
According to Mr. Townsend, the adult bull, having taken possession of
his territory and formed a harem, is constantly called upon to wage
duels for both with less fortunate rivals. And the severity of such
combats was attested by the deep wounds and festering sores of the
necks of these old warriors—which, at their maximum, attained in the
days of their prosperity a length of nearly thirty feet and a girth of
sixteen feet; but the last survivors of the race to-day seem rarely to
exceed twenty-two feet. The weapons used in fighting are the canines,
and the only armour they possess is that formed by the thickening of
the skin of the neck, which forms a great massive shield, so that
really dangerous wounds are rare. The great fleshy proboscis, the most
vulnerable part, is carefully guarded by the upturned position of the
head. The use of this trunk-like organ, which may attain a length
of about fifteen inches, is not clear; it seems to serve mainly as
an “ornament,” at times, too, furnishing a very definite indication
as to the temper of its owner. While the animal is slowly moving its
great carcase from place to place, this remarkable organ is relaxed,
and pendent; but when fighting it is closely contracted so as to be
out of harm’s way. Whether it plays any useful part in the capture of
food is not known; but it is probably much displayed during phases of
sexual excitement. In young animals, it is significant to notice, as
well as in the adult female this trunk is entirely wanting, which seems
to suggest that this peculiar feature has only been recently acquired,
the young and the adult female, as is the rule, standing nearer to the
early forebears of this strange type. There is an enormous difference,
it should be remarked, between the sexes in the matter of size, the
female not attaining more than half the bulk of her lord. A further
interesting point concerns the coloration of the young, which are
black, while the adults are brown. Doubtless this is connected with the
requirements of the young, the black coat attracting more heat than the
lighter-coloured coat of the adult.
As touching that curious creature, the Crested, or Hooded Seal
(_Cystophora cristatus_), a native of the colder regions of the North
Atlantic. This animal is remarkable for the development, in the males
alone, of a great crest or casque on the head, which is formed by a
large inflatable air-sac over the ridge of the nose, and communicating
with the nostrils. When fully inflated, it covers the head as far back
as the eye. Its purpose is a matter of conjecture. It seems to be
inflated either when he animal is greatly excited, as when challenging
rival males, or when threatened with danger from other causes, as
when attacked by man. The males are exceedingly pugnacious, and fight
with one another for the possession of females with great ferocity,
such contests being accompanied by cries which can be heard for miles.
From the difficulty which Esquimaux and sealers find in killing the
animal with clubs it certainly seems as if this strange wind-bag were
more than merely ornamental.
[Illustration: Plate 14.
_Photo copyright, W. P. Pycraft._
ELEPHANT SEAL.
This is a young animal. Note the great size of the eyes, and the
general “seal-like” character of the head as compared with that of the
adult.]
[Illustration: _Photo by courtesy of Charles Haskins Townsend, Director
of New York Aquarium._
NORTHERN ELEPHANT SEAL.
Adult male and female, and yearling. The male shows the enormously
inflated snout.
[Face page 88.]
That those extraordinary creatures the Cetacea—the Whales and their
kin—are derived from the same common stock as the typical carnivora
there can nowadays be no doubt, widely as they have departed from
their land-dwelling relatives in almost every possible feature of
their organization. In the matter of their “Courtship” we know
nothing, but we may infer certain incidents in this critical period
of their life-history from the peculiar nature of the secondary
sexual characters which some species display. Thus in the Pilot
Whale (_Globicephalus_) and the Bottle-nose Whale (_Hyperoödon_) the
forehead, in the bulls, is enormously swollen by a mass of fibrous
tissue so dense as to turn the blade of the sharpest knife, as I
know well from attempts to dissect this region. Now the only use,
surely, for such a cushion is that of a battering-ram by rival males
in charging one another, as rams and other horned animals will do. In
the Bottle-nose Whale this cushion is backed up by an enormous mass of
solid bone thrown up by the maxillæ. The origin of this bony growth
is interesting, for it appears first as a slight swelling in the rare
species _Berardius_; it is seen at a further stage of growth in the
female “Bottle-nose” (_Hyperoödon_), and attains its maximum in the
male, where it stands unique. There are two other species which demand
notice here. The first is Layard’s Beaked Whale (_Mesoplodon_); the
second the Narwhal. The former is the only vertebrate which in a wild
state wears a muzzle! In this species the teeth have totally vanished
save for a pair in the lower jaw, which are found towards the end of
the jaw. These in the adult, or perhaps we should say senile, male
grow upwards and inwards, finally meeting one another above the upper
jaw, so as to make it impossible for the animal to open its mouth more
than the fraction of an inch! Surely here we have a secondary sexual
character carried to an excess, and so proving not only disadvantageous
to the animal, but positively disastrous, for it seems clear that so
hampered the creature can feed only on the most minute forms of animal
life, which could only be captured and swallowed with difficulty. It
is true that the Rorquals feed on excessively minute Crustacea, but
they are able to take in enormous quantities at a time, the “whalebone”
serving the office of a sieve to prevent their escape. The Mesoplodon
has no such aids. One is tempted to believe that the skulls displaying
this most curious feature are abnormal, comparable to those, say, of
rabbits wherein the teeth have grown so excessively long as to close
the mouth, on account of the displacement of the cutting surfaces by
accident. But there is nothing to afford support to this view, and one
must therefore fall back on the suggestion of senility.
The Narwhal has long been celebrated for the enormous size of the
canine teeth, the only teeth present in the jaws. As a rule, only
one leaves its bony socket, the other, commonly the right, remaining
as a mere vestige, seven or eight inches long within the skull. The
protruding tooth, which is spirally fluted, may attain a length of
nine feet. Occasionally both teeth are developed, and in this case
the spiral is the same, differing in a very striking manner from
the spiral horns of ruminants, wherein one presents a right, the
other left-handed spiral. But what purpose do these teeth serve? This
question has never yet been definitely settled. Some hold that it is
used to break open breathing holes in the ice, for the animal lives
in the far north: others that it is used as a spear in hunting prey.
Some aver that it serves as a weapon of offence, being used by rival
males in their struggle for mates. Scoresby, the explorer, indeed, says
he has seen young males in mock-battle, fencing with these remarkable
weapons. But until we have more satisfactory data, we must regard this
armature of the Narwhal as affording another instance of a secondary
sexual character of doubtful value to its possessor.
CHAPTER VI
COURTSHIP AMONG BIRDS
Generalities—Darwin v. Wallace—The Peacock in his Pride—The “Display”
of the Peacock Pheasant—The Splendour of the Argus Pheasant and the
Marvel of its Eyes—The Frill of the Amherst Pheasant—Birds of Paradise
in the Toils of Love—Inflated Suitors—Ruffs and Reeves—Fearsome Weapons
and their Uses—Birds which dance—Musical Birds—The Bird’s Voice-box—The
“Lek” of the Capercaillie—Instruments of Percussion—The Curious
Performance of the Wood-pecker.
The fact that so little is known about the mammals during that period
when the all-important work of securing mates is going on, and of the
subsequent events, is largely due to the difficulties which close
observation of this phase of their life-history entails. With the birds
matters are far otherwise; their haunts are more accessible; they
are far more numerous, and much more easily kept under observation.
Consequently, we have a tolerably complete knowledge of the lives
of some species, at any rate, during the reproductive period; that
is to say, as to the sequence of events from the beginning of the
reproductive activities onwards; but the interpretation of what is seen
is another matter. No attempt which has yet been made to fathom the
psychology of sex has yielded more than a slight insight into what is
taking place. Nevertheless, this is an aspect of the subject which
has a far more important bearing on the problems of evolution than
is generally realized. But these pages are concerned rather with the
relations between the sexes, than with the subtle forces which have
fashioned and control conduct in this regard.
In all that concerns the problems of sex, which is to say of
reproduction, birds, speaking generally, display a briefer and more
condensed sequence of events than the mammals; and, moreover, many
species compel the attention even of the most incurious, to their
behaviour at this time, through the development, either of song, or
of fantastic displays of their amorous feelings: while others force
themselves no less conspicuously under notice by their habit of nesting
in large, and often enormous colonies.
In the matter of the development of secondary sexual characters birds
stand conspicuous among the Vertebrates, and easily eclipse the
mammals; among which bright, strongly contrasted, colours are the
exception. Among the birds they may almost be said to be the rule.
Also, in this category we have to reckon song, and the production of
more or less musical sounds by the agency of internal resonators or of
specially modified feathers; as well as quaint forms of posturing which
may be included under the head of dances. Further, some species have
developed formidable weapons of offence. These things are interesting
enough in themselves, but they become still more so when we reflect
that they formed the corner-stone of Darwin’s theory of “Sexual
Selection,” and that Wallace’s criticisms thereof were inspired by
evidence from the same source.
The interests of this chapter will best be served if the evidence
on which this theory was founded be first surveyed: when Darwin’s
deductions and the criticism which they have aroused will be the more
readily appreciated.
Definitions are always liable to exceptions; and concrete cases are
better than abstract terms. Birds, then, perhaps better than any
other group, illustrate what is meant by the term “secondary sexual
characters,” if only because examples are so constantly at hand. Save
among experts, sex among birds cannot be determined except by the
differences in plumage, or sometimes in size, which the sexes display.
But even here, it is only among species which occupy what we may call a
mid-evolutionary phase in which this discrimination is possible. Among
“generalized” species, wherein the plumage is of sombre hue, there is
no external distinguishing mark between male and female; and the same
is true with species which have attained to the maximum of resplendent
plumage; as for example many Parrots and Kingfishers, where again both
sexes, and at all ages, display the same vivid hues. Thus, in the
case of either of the two extremes, the study of behaviour during the
breeding season is one of great difficulty and no less uncertainty.
Where the sexes are sharply distinguished by differences of coloration,
however, as with the Peacock, the matter is otherwise. This bird, from
time immemorial the symbol of vanity, illustrates in a singularly
effective manner the broad features of what is commonly meant by
“courtship” among birds, while it furnishes a no less striking example
of the development of “secondary sexual characters.”
One might have supposed that birds, under the spell of that
irresistible desire for sexual intercourse, would behave differently in
regard to their “courtship” according to whether they were monogamous,
polygamous, or polyandrous: but while their behaviour during this
period of the life-history presents an extraordinary variety, it is
only at any rate slightly determined by the plurality or otherwise of
mates; and the same rule holds in regard to the brilliancy or otherwise
of coloration.
The most common manifestation of sexual desire among birds takes the
form of strange posturings which are, in some species, enormously
exaggerated by the display of vividly coloured frills, tufts, or other
conspicuous modifications of the normal plumage. The Peacock affords
a most excellent example of this combination of the contortionist and
the beau, though the nature of this display is by no means generally
understood. This applies more particularly to artists, who from time
immemorial to the present day, in essaying to paint the Peacock in his
pride, have invariably fallen into the error of treating the great
ocellated train as if it were the tail, placing it where, of course,
the tail ought to be, at the end of the body! As a matter of fact it
is nothing of the kind; these gorgeous plumes are really exaggerated
tail-coverts which, when set on end, appear to arise from an oval
shield of metallic green scales—the central back-feathers. When this
trailing glory is erected, the bird throws the body forwards and
downwards, so that the outermost train-feathers fall downwards on
either side in front of the wings, which are more or less trailed: so
that from the front only the head and neck are visible, the rest of the
body being hidden _behind_ the screen, as may be seen by a reference to
the accompanying photographs. The manner of this display is extremely
interesting, for the bird seems to be conscious of the effect produced:
though it cannot be supposed that this is really the case.
When displaying, the bird gradually approaches the nearest female
and slowly erects these extraordinary plumes. So soon as this is
accomplished he begins to walk backwards towards the object of his
attentions, presenting nothing but a great round shield of dull brown
feathers, backed up by the tail-feathers, and the dull-coloured wings.
So soon as he judges himself near enough, however, he suddenly swirls
round, confronting her in all his splendour, and heightening the effect
with a loud scream accompanied by a rapid, vibratory, motion of the
train-feathers which produces sounds like the pattering of rain on
leaves. Then he stands before her, with bowed head, as if to give her
an opportunity of drinking in his splendour to the full. Commonly,
however, she appears to be utterly indifferent, and either walks away
or continues a real, or affected hunt for food, as if no such thing as
a love-sick suitor were within a hundred miles of her! But sooner or
later his suggestive attitudes beget an answering response, and pairing
takes place.
The display of the beautiful Peacock Pheasant differs conspicuously
from that of the Peacock, and recalls that of the Argus Pheasant. In
the Peacock Pheasant, as will be seen from the adjoining photograph,
the wings, and tail, are alike bedecked with ocelli. The display is
made by the bird as it crouches close to the ground, with the wings and
tail raised to form a continuous, patterned surface, the head being
swiftly moved during the performance; hence its blurred outline in the
photograph.
[Illustration: Plate 15.
_Photo by D. Seth-Smith._
PEACOCK PHEASANT.
The display of this bird differs conspicuously from that of the Peacock
and recalls that of the Pigeon in some respects. The “ocelli” on the
wings afforded Darwin the interpretation he sought for as to the
meaning of the notch in the “eye” of the Peacock’s tail-feather.]
[Illustration: Plate 16.
_Photos by the Author._
“THE PEACOCK IN HIS PRIDE.”
In the upper figure it will be noticed the “train,” when erected,
encircles the base of the neck; the lower figure shows the train
supported by the tail and dropping on each side in front of the wings.
[Face page 96.]
The Argus Pheasant is an even more wonderful performer than the two
preceding species. In this bird, it should be remarked, the tail and
the secondary wing-feathers are enormously lengthened, the latter to
an extent met with in no other bird, showing that the struggle for
existence cannot be very severe with this species. For if long
journeys had to be undertaken in search of food, or to avoid extremes
of climate, or enemies had to be swiftly escaped, such cumbersome
wings would lead to speedy extermination. But an even more remarkable
feature of these wings is their wonderful coloration. The primaries
have blue shafts, and a most delicately mottled pattern formed by spots
of reddish chocolate on cream-coloured ground, while the secondaries
have their broad webs ornamented with large ocelli, to be described in
greater detail presently. When under the influence of sexual excitement
Darwin tells us, the wings are so spread as to form a deep concavity,
an effect which is gained by pressing the primaries close to the
ground, and turning the elbows upwards. Within this concavity lie the
ocelli, in radiating vertical rows. But to produce this effect the bird
has to turn its head under its wing, so that it lies behind the screen.
Hence it cannot see the female which is the object of these captivating
antics. As a consequence, to discover whether he has an audience for
she will often walk disdainfully away—he has constantly to thrust his
head through the curtain, and hence many of the feathers in this region
get much worn.
By nature it would seem the Argus Pheasant is a very solitary bird,
though we must assume it is polygamous. As the breeding season
advances, however, the male proceeds to choose some open space in the
depths of the forest—which it never leaves—and therefrom to clear all
the dead leaves, and twigs, for a space of some six or eight yards
square, so that nothing but the bare earth remains, and thereafter
this area is kept scrupulously clean. Here, in solitary state, for a
short season he remains, calling at frequent intervals to advertise the
fact that an eligible male is in the neighbourhood desiring mates. A
dozen times in succession he will break the stillness of the forest
gloom with a loud, “How-how, how, how, how!” Sooner or later comes a
responsive, “How-owoo, how-owoo!” and in a short time, guided by the
sound, one or more females discover the object of their quest. But the
pairing desire has not yet reached its full intensity, and doubtless to
kindle this the display just described is enacted, and not once, but
a dozen times probably, before the desired state of frenzy has been
aroused. Not seldom another male answers the cry, and this inevitably
leads to a duel whereby the fittest and strongest male is speedily
discovered.
A word as to these ocelli. This pattern is rare among birds, and Darwin
brought to light some extremely interesting facts regarding it. He was
led to investigate the matter by his curiosity as to the meaning of
the notch in the ocelli of the Peacock’s train-feathers. At last he
noticed that among the different species of Peacock Pheasants there was
one (_Polyplectron chinquis_), in which the ocelli were paired, one
lying on either side of the shaft, in another (_P. malaccense_) these
approached and partly fused with one another. Now, to get the indented
ocellus of the Peacock, we have only to imagine the fusion of two such
ocelli, whose long axes inclined obliquely to one another, to get the
“eye” of the Peacock with its indented lower edge; for such fusion
would give a continuous upper and an indented lower border.
The “eyes” of the Argus Pheasant are more interesting still, for, as
Darwin pointed out, these have the appearance, if the feathers are
held more or less vertically, of a number of balls lying each within
a socket, or cup: for each of these balls has a light area which
exactly simulates the light glancing across the upper pole of a sphere,
leaving the rest in shadow; and, singularly enough, this effect is
produced in the living bird only when the feathers are erected for
display. The probable steps in the evolution of these ocelli from
simple spots, and through elliptical bars, Darwin traced with his usual
skill and insight, and those who would follow this up should turn to
that wonderful book, “The Descent of Man.”
[Illustration: Plate 17.
PATTERNS WHICH PUZZLED DARWIN.
The notch in the “eyes” of the Peacock’s train-feathers puzzled Darwin
till he met with the ocelli of the Peacock-pheasant. The left-hand
lower figure represents the ocellus of the Argus, the right-hand that
of the Peacock-pheasant.
[Face page 98.]
It is probable that the erroneous interpretation of the display of the
Peacock is due to the more lasting and easily remembered impression
of what obtains in the case of the Turkey under like emotions. This
bird in his exultant moods, most people have seen. Herein the tail
plays a very important part, being raised and spread to form a great
half-circle, while at the same time the back-feathers, or at least
those of the lower back, are set on end, and the wings are trailed on
the ground. The effect is heightened by the suffusion of blood to the
bare skin of the head and neck, and the sudden inflation of a long,
pendent, fleshy wattle from the forehead, which hangs down over the
beak. Great display is made with this, and an additional importance is
added by the spasmodic vocal efforts which can best be described by
the “gobble” rapidly repeated, as the bird struts about with mincing
gait, turning the wheel-like tail now to one side now to the other.
But the Turkey possesses yet another “ornament” which commonly escapes
notice. This is the curious tuft of long, black, coarse, bristles which
projects forward in front of the breast. It is difficult to discern
what part this tuft may play, since it is quite inconspicuous. It seems
as though this must be added to the number of structural characters
which appear to survive without any apparent use.
The game-birds, it is significant to remark—and significant because
they are commonly polygamous—afford a quite remarkable series of
displays, only some of which can be summarized in these pages. In every
case, too, they are accompanied by conspicuous coloration and a more
or less excessive development of brightly-coloured plumes, or areas
of bare skin. In some, as in those wonderful birds the Tragopans, the
development of bare skin, vividly coloured, and produced into pendulous
folds, has attained a degree met with nowhere else among this group.
These flaps, or finger-like wattles, as the case may be, under the
influence of sexual excitement become turgid, and their hues enormously
intensified: though beyond this fact but little else is known of their
performances. In Swinhoe’s Pheasant the face is bare, the skin being
covered, as in the case of the common Pheasant, with tiny villi of a
vivid red colour. But when excited by the presence of a female the
upper part of this face area rises high above the head like a pair of
horns. With these turgid, and erect, the bird makes a series of short,
semicircular rushes around his prospective mate, accompanying each of
these gyrations with an angry hissing sound. The Golden, and Amherst
Pheasants are among the most gorgeously clad of birds. Not their least
conspicuous ornament is a cape-like frill of long, highly coloured
feathers of which the birds seem to be extremely conscious; for when
endeavouring to excite the female nearest him to the necessary pitch of
sexual desire, he places himself sideways before her, drawing the frill
round to the side facing her, and dropping the wing, in order, as it
would seem, that she may miss nothing of his resplendent livery. This
side of his nature he reserves for her. Intruding rivals are treated
after quite another fashion, for like most of the gallinaceous birds
his legs are armed with formidable spurs which can, and do, inflict the
most terrible wounds: as, indeed, has been shown from the evidence of
the Cock-pit in the case of game-cocks.
[Illustration: Plate 18.
THE “STRUTTING TURKEY.”
This should be contrasted with the Peacock. Herein the tail itself
is the principal ornament, the effect of which is heightened by the
erection of the back-feathers, and the vivid play of colour of the
“wattles” of the head.]
[Illustration: _Photo copyright by W. H. Quentin._
THE DISPLAY OF THE GREAT BUSTARD.
This is effected by the inflation of a great wind-bag in the neck, and
the eversion of the wing and tail feathers as described in the text.
[Face page 100.]
By way of contrast with the several displays just described, it would
be hard to find a more striking illustration than that afforded by
the Lesser Bird of Paradise (_Paradisea minor_), inasmuch as here the
display is associated with rivalry between a number of individuals.
For much of our knowledge on this subject we have to depend on the
descriptions of natives; but happily this has now been supplemented by
observations made by Mr. Ogilvie Grant on a captive in the Gardens of
the Zoological Society of London.
Impelled by the surging wave of sexual desire, as yet only seeking
consummation, these birds gather together at frequent intervals, on
certain of the forest trees of the Aru Islands, selected apparently
because they present an immense head of spreading branches, and large
but scattered leaves. Here ample space is found for the revels, which
take the form of “Sacaleli,” or dancing-parties, comparable to the
erotic dances of many barbaric races.
By the time the ball opens, the birds, to the number of twenty or more,
have worked themselves up into a state bordering on frenzy, and each
commences his performance with quivering wings and loud, penetrating
cries which may be syllabled as _walk—walk—walk—walk—walk—walk_,
rapidly repeated. Then the wings are suddenly held out on either side,
the tail is bent forward under the branch, and with a quick, barely
perceptible rustle, the gorgeous, golden, diaphanous side-plumes are
thrust upward and forward on each side of the body, forming an arched
cascade above the back. With every muscle tense the performer will
remain in this attitude from ten to twenty seconds, slightly quivering
the wings, and from time to time imparting a tremor to the upraised
plumes. Then follows a second phase. Each bird, seemingly possessed,
commences to dance and hop wildly backwards and forwards along the
bough, and with head bent forward, wings spread horizontally, and the
side plumes raised to their utmost, he gives vent to a series of loud
harsh cries—“ca! ca! ca! ca!” For some seconds he remains in a sort
of ecstasy, rubbing his beak on the bough, and occasionally glancing
backwards below his feet, and with the back fully arched. The climax
passed, he reverts once more to the earlier, more erect stage of the
display, when the paroxysm either gradually subsides or is renewed.
No less extraordinary is the behaviour of the King-bird of Paradise
(_Cicinnurus regius_), which has been described by Sir William Ingram,
who for a time had a captive in his aviaries. As the illustration
shows, its posturing is quite remarkable. Before this is described,
however, a brief description of its coloration should be given,
which, it must be remarked, cannot possibly convey more than a very
vague idea of its sumptuous character. Picture a bird no bigger than
a thrush, but of a wonderful cinnabar red, with a gloss as of spun
glass: the head clothed in short, velvety, orange-hued feathers; and
with a white breast, having the softness and sheen of satin, and
crossed by a band of deep metallic green, contrasting with the red
of the throat. Add a yellow beak, and legs of cobalt blue, and you
will have the features which catch the eye at the first glance. But a
little closer examination will reveal yet other points for wonderment.
Along each side of the body the upper flank-feathers become elongated
and delicately tinted, and, furthermore, they are erectile: so that
they can be raised up on each side of the body to form an almost
circular shield of delicate ash grey, bordered with buff and emerald
green. These play a most important part during the sexual frenzy,
and the effect thereof is not a little heightened by the middle pair
of tail-feathers, which have been modified to form a pair of slender
stalks, some ten inches long, bearing at the ends a curious disc of
emerald green formed by coiling upon itself—like a watch-spring—the
only piece of the vane of the feather which remains.
So much for its fine feathers; now for the manner of their use. “He
always commences his display,” writes Sir William Ingram, “by giving
forth several short notes and squeaks, sometimes resembling the call
of a quail, sometimes the whine of a pet dog. Next he spreads out
his wings, occasionally quite hiding his head; at times, stretched
upright, he flaps them, as if he intended to take flight, and then,
with a sudden movement, gives himself a half turn, so that he faces the
spectators, puffing out his silky-white lower feathers; now he bursts
into his beautiful melodious warbling song, so enchanting to hear but
so difficult to describe. Some weeks ago I was crossing a meadow and
heard the song of a skylark high up in the heavens, and I exclaimed at
once: ‘That is the love-chant of my King-bird.’ He sings a low bubbling
note, displaying all the while his beautiful fan-like side-plumes,
which he opens and closes in time with the variations of his song.
These fan-plumes can only be expanded when his wings are closed, and
during this part of the display he closes his wings and spreads out
his short tail, pressing it close over his back, so as to throw the
long tail-wires over his head, while he gently swings his body from
side to side. The spiral tips of the wires look like small balls of
burnished green metal, and the swaying movement gives them the effect
of being slowly tossed from one side to the other, so that I have
named this part of the display the ‘Juggling.’ The swaying of the body
seems to keep time with the song, and at intervals, with a swallowing
movement of his throat, the bird raises and lowers his head. Then comes
the finale, which lasts only a few seconds. He suddenly turns right
round and shows his back, the white fluffy feathers under the tail
bristling in his excitement; he bends down on the perch in the attitude
of a fighting cock, his widely-opened bill showing distinctly the
extraordinary light apple-green colour of the inside of the mouth, and
sings the same gurgling notes without once closing his bill, and with a
slow dying-away movement of his tail and body. A single drawn-out note
is then uttered, the tail and wires are lowered, and the dance and song
are over.
“The King-bird has another form of display which he very rarely
exhibits, and only on three or four occasions have I seen him go
through this performance. Dropping under the perch, the bird walks
backwards and forwards in an inverted position with his wings expanded.
Suddenly he closes his wings and lets his body fall straight downwards,
looking exactly like a crimson pear, his blue legs being stretched
out to the full length and his feet clinging to the perch. The effect
is very curious and weird, and the performance is so like that of
an acrobat suddenly dropping on to his toes on the cross-bar of a
trapeze that I have named this the ‘Acrobatic’ display. It has been
witnessed on different days to his ‘Juggling’ display. While giving his
‘Acrobatic’ performance he sings the whole time, but never shows his
side-plumes, and when he is in the pendulous position his body sways
gently as if it were influenced by a fitful breeze. The whole of this
performance takes but a very few seconds.”
[Illustration: Plate 19.
_From a Drawing by Roland Green, Jun., adapted from G. E. Lodge and
others._
SOME OF FORTUNE’S FAVOURITES.
The Birds-of-Paradise have few rivals in the matter of ornament. In the
centre of this plate are seen the Lesser and the King Bird-of-Paradise
displaying (after G. E. Lodge). The first-named is distinguished by
the enormous development of the side plumes, which can be raised high
above the back. In the second, the ornaments take the form of erectile
frills on each side of the breast, and strangely modified tail-feathers
which end in curious discs. At the top left-hand corner is the
King of Saxony’s Bird-of-Paradise; on the right is the Long-tailed
Bird-of-Paradise; at the bottom of the page, from left to right, are
Hunstein’s, the Six-wired, and Superb Bird-of-Paradise.
Face page 104.]
Naturally one needs to witness such a display to appreciate its beauty
and its weirdness; but the wonderful sketches which my friend, Mr. G.
E. Lodge, made during one of these performances, should go far towards
helping the reader to visualize what really takes place.
While it would be untrue to say that the Birds of Paradise are of a
more amorous, or more excitable disposition than other less resplendent
birds, one cannot but be impressed with the fact that they exhibit
a range of variation in the matter of feather-ornament probably
unequalled, and certainly unsurpassed, by any other group of birds.
From what has been observed of the few species which have been kept
in confinement, they seem to enjoy no less distinction in matters of
display. On this latter subject no more of importance can be said, and
exigencies of space forbid any attempt to describe the exquisite beauty
of coloration which a survey of all the known species reveals. It would
be hardly more profitable to attempt to describe the varied character
of the shields, crests, frills, streamers, which are to be met with
in different species: but a glance at the accompanying illustrations
will show that it would be hard, indeed, to exaggerate the splendour
of the ornamentation which these birds have developed. Even here,
where no indication can be given of the glowing, vivid colours, often
indescribably beautiful, it is obvious that these birds well deserve
their name. St. John’s imaginary Paradise would probably have been
described in far more enticing language had he known of the existence
of these wonderful birds.
Among all the known species the dullest is Wallace’s Bird of Paradise,
the general coloration being of a dull brown hue; but even here, a pair
of wing-coverts are produced into long, broad streamers, unique among
birds; while the feathers of the throat and flanks are of a marvellous
metallic green, the flank-feathers being produced to form a long,
pointed tuft.
To what factors must we attribute the growth of these wonderful
colours, these strange outgrowths, frills, and tufts, and streamers,
the like of which is almost unparalleled? In a group numbering some
fifty or more species there is not one that does not display some
strange feature. We cannot attribute it to the environment, for in such
case the results should have produced uniformity; nor can we invoke
the aid of sexual selection save in a very indirect manner, and in a
sense other than generally understood by this term. It seems, then,
not unreasonable to suggest that they are the expression points of the
internal metabolism: the manifestations of that tendency to vary which
is inherent in every fibre of the organism. But no attempt shall be
made to elaborate this theory till more evidence has been taken. The
humming-birds, and the game-birds, are perhaps the only other groups
which exhibit quite such a prodigality of ornament; of the latter,
instances have already been cited.
So far the displays which have been described have been such as
are confined to the use of more or less resplendent plumage. There
are, however, many species which contrive to secure most startling
results, not so much by the parade of coats of many colours as by
grotesque changes of shape produced by wind-bags of various kinds. The
Pouter-pigeon affords a case in point. This bird possesses the power of
inflating the gullet to an enormous size, so as to produce a strangely
distorted form, at any rate, to our eyes. The “Pouter,” it is hardly
necessary to mention, is an artificial product of the “fancier,” who
has taken advantage of the natural tendency, seen in the Wild Pigeon,
to inflate the neck during moments of excitement. By the selection from
each generation of the finest performers in his stock, the Pouter of
to-day has been developed. But there are many birds which, while not
even remotely related, have developed the same strange device. The most
striking illustration of this kind is furnished by the Great Bustard, a
bird once common on the fen-lands of Great Britain, but now, unhappily,
exterminated within these islands.
The means of inflation in this case is afforded by a large thin-walled
sac of a very remarkable character. Opening by a small slit just under
the tongue, it is continued down the front of the neck immediately
under the skin, which in this region is thickened by an accumulation
of fat and blood-vessels. Between the arms of the furcula, or
merry-thought, its cavity is constricted, to expand again immediately
to form a pear-shaped termination. How it is filled is something of
a mystery. But once inflated, the bird draws its neck downwards and
backwards, so that the head is brought to rest between the shoulders
and is there almost buried, partly by pressure on this curious
air-cushion and partly by the erection of a number of bristle-like
feathers, which in calmer moments project backwards on each side of
the head. At the same time the tail is drawn forwards to lie upon the
back, thus exposing a billowy mass of white feathers forming the under
tail-coverts. The tips of the wing-feathers are used to hold the tail
in position. Meanwhile the scapulars are set on end, and the long inner
secondary quills are similarly erected. The feathered contortionist,
having completed his preparations, now approaches his partner with a
mincing gait, then halts before her and solemnly utters a series of
low grunts like “oak, oak, oak.” Having thereby declared his passion,
and commonly without gaining any answering response, he returns to his
normal shape again!
It is curious that a near relative of this bird, the Great Australian
Bustard (_Eupodotis australis_), also captures the wind to declare
his love; but it is disposed of after a quite different fashion,
being drawn into the gullet, though the precise manner in which it
is manipulated demands further investigation. The display Dr. Murie
described many years ago. It begins, he tells us, with a swelling
of the throat, while the head is thrown upwards. Immediately after,
the neck swells, and the feathers of the lower part of the neck, set
all on end, are carried downwards, apparently surrounding a huge bag
which reaches nearly to the ground. During all this time the head and
neck are held rigid and point skywards, the head surmounting a great
feathery column. Meanwhile the tail, as with the Great Bustard, is
drawn forwards over the back. In this peculiar attitude the bird struts
about in a stiff, waddling manner, the elongated neck-bag swaying to
and fro and the feathers of the throat standing out in the shape of a
great rounded swelling. The acme of inspiratory effort completed, the
bird begins to snap the jaws together, producing loud noises, which are
accompanied by a soft dove-like cooing.
The Pectoral Sandpiper in like manner inflates its gullet. But, unlike
the Pigeon and the bird just described, the neck is not markedly
straightened, nor is the body raised. As the air is drawn in, the
gullet expands, till it forms a great spherical drum. Then the excited
performer runs along the ground uttering a resonant “too-u tooo-u”
repeated seven or eight times in rapid succession, all the while he
approaches nearer to the apparently very much-otherwise-engaged female.
This effort failing, he will then often rise on quivering wings twenty
or thirty feet into the air, and dive gracefully down again immediately
afterwards, deflating this curious balloon to await a more favourable
opportunity.
In some species where wind-bags are employed as aphrodisiacs the outer
skin is brilliantly coloured and exposed during the display. The
Prairie-hen affords a case in point. In this species the air-chamber
is furnished, not by the gullet, but by the air-sacs of the neck. When
these are inflated they appear as two large orange-coloured bodies
standing boldly out among the feathers. Their effect is heightened by
a tuft of long stiff feathers which are thrust forward like a pair of
horns, on each side of the head, while at the same time the feathers of
the back are set on end, the tail is spread like a great fan, and the
wings are half opened and trailed like those of the Turkey.
The displays take place in the early hours of the morning, when parties
of from a dozen to fifty, of both sexes, meet on some slight knolls
where the grass is short. Having duly assembled, the more ardent cocks
immediately begin to prepare for the morning revels, the first part of
the performance apparently being of a comparatively passive nature—the
parade of the air-sacs and the erection of the feathers.
Then some “proud cock, in order to complete his triumph, will rush
forward at his best speed ... through the midst of the love-sick
damsels, pouring out as he goes a booming noise ... which may be
heard for at least two miles in the morning air. This sound is by no
means harsh or unpleasant. When standing in the open prairie at early
dawn listening to hundreds of different voices pitched in different
keys, coming from every direction and from various distances, the
listener is rather soothed than excited.
“Every few minutes this display is repeated. I have seen not only one,
but more than twenty cocks going through this funny operation at once;
but then they seem careful not to run against each other, for they have
not yet got to the fighting point. After a little while the lady birds
begin to show an interest in the proceedings by moving about quickly, a
few yards at a time, and then standing still a short time.
“The party breaks up when the sun is half an hour high, to be repeated
the next morning, and every morning for a week or two before all make
satisfactory matches. It is towards the latter part of the love-season
that the fighting takes place among the cocks, probably by two who have
fallen in love with the same sweetheart....”
There is much that is extremely interesting in this account and a
little that seems to have been misinterpreted. The fact that these
antics are repeated during many days until at last the females are
moved to display some interest is just what we should expect if this
demonstrative behaviour on the part of the males acts, as we believe,
as an aphrodisiac. And that actual fighting occurs is highly probable,
but there can be no doubt that in such case the whole aspect of the
bird must be changed, for anything in the nature of fighting with the
delicate air-sacs inflated would greatly endanger the most important
aid to success in achieving this object which these birds possess.
[Illustration: Plate 20.
_Photo from The Museum of Natural History, New York._
THE LOVE-MAKING OF THE PRAIRIE HEN.
During the “display” large, yellow, air-sacs in the neck are inflated.
The bird in the foreground shows one of these, and the ornamental
feather frill, very clearly.
[Face page 110.]
No less remarkable is the performance of the Frigate-bird (_Fregata_),
a tropical species allied to the Pelicans and Boatswain-bird, and to
our own more familiar Cormorants and Gannets. It might well be called
a marine Swift, having excessively short legs and small feet, and a
wonderful expanse of wing. As with the Swifts, of course most of its
time is spent on the wing; the feet are only useful for supporting the
body when ashore, they are never used for walking, at any rate, for
more than a few steps. The wings afford the only means of locomotion.
Our knowledge of these birds when under the stress of sexual excitement
we owe to Dr. C. W. Andrews, who had the good fortune to study the
species known as the Great Frigate-bird (_Fregata aquila_) during his
task of surveying Christmas Island (Indian Ocean).
“About the beginning of January,” he remarks, “the adult males begin
to acquire a remarkable pouch of scarlet skin beneath the throat; this
they can inflate till it is nearly as large as the rest of the body,
and a dozen or more of these birds sitting on a tree with outspread,
drooping wings and this great scarlet bladder under their heads are a
most remarkable sight. When a hen bird approaches the tree the males
utter a peculiar cry, a sort of ‘wow-wow-wow-wow,’ and clatter their
beaks like castanets, at the same time shaking their wings. When
they take to flight the air is allowed to escape from the pouch, but
occasionally they might be seen flying with it partly inflated.”
Here again there can be no doubt about the purpose, or perhaps one
should say the stimulus, of this strange performance. This pouch,
I have been enabled to ascertain from dissection, is not formed by
inflating the gullet, but, as in the case of the Prairie-hen, by the
enlargement of the air-sacs of the neck.
These air-sacs, which are present in all birds, are only enlarged to
further the ends of sexual display in a few species, and, curiously
enough, these are in no way related one to another. The Adjutant
storks, it may be remarked in this connection, have used the air-sacs
which are fed by the nasal system instead of those fed by the lungs,
as in all the species so far described. When deflated this pouch forms
a quite inconspicuous conical swelling in front of the neck; under the
stimulus of excitement, it awakens as it were into activity, and is
suddenly transformed into a great red or red-and-black bag, encircling
the neck and projecting far downwards in front of it, only to be
deflated an instant later with a speed which leaves one gasping.
The specialization of the air-sacs, that is to say their transformation
to perform new functions subservient to the ends of sexual activities,
is not exclusively confined to display. In at least one instance an
air-sac has been specially developed to act as a voice resonator.
This is furnished by the Emu, wherein the wind-pipe, near the middle
of its length and on its anterior aspect, has a number of incomplete
rings forming a long slit. The lining of the windpipe escapes from
this slit in a hernia-like pouch, and takes up a position beneath the
skin. Even when inflated this pouch gives no very obvious sign of its
existence, but it serves to produce a curious hollow, drumming sound,
like the boom of a big drum softly beaten. But why it should have been
developed, when the Ostrich and the Cassowary produce similar but
louder “music” without any special apparatus whatever, is a mystery. At
least one species of Cassowary can emit a roar which would do credit
to a lion.
In the males of all healthy animals the periodic stimulus to
reproduction finds expression in more or less striking eccentricity
of conduct. Sometimes, as the foregoing instances have shown, this
has been exaggerated by the development of long, resplendent plumes:
sometimes by brilliant coloration, displayed either by the plumage or
by bare areas of skin, or by both, while in not a few cases attitudes,
to our eyes grotesque and made still more so by the aid of inflatable
pouches, are the outward and visible sign of the raging fires within.
For the completion of this chapter yet other instances of this kind
must be cited, instances which reveal a further elaboration of some
of the more striking of these tricks of posturing; or which concern
the growth of the aggressive instincts, which are proclaimed by the
development of armature often of a very formidable character. As the
sequel shows, however, there are no hard and fast dividing lines
between these several modes of expression.
That remarkable bird, the Ruff (_Machetes pugnax_), now, alas! no
longer to be met with in our fens, exhibits a curiously composite
character in the phases of its love display.
Preparations for this are begun in the early spring by the assumption
of what is called a “nuptial dress,” which is worn only by the male,
and which contrasts in a very conspicuous manner with the plumage worn
during the rest of the year. The most striking features of this dress
are the great, erectile, Elizabethan ruff which encircles the neck
immediately behind the head, and the long, tongue-shaped “ears” which
surmount the head itself. These exhibit a most remarkable diversity
in their coloration, and it is no exaggeration to say that no two are
ever alike. Red, cream-colour, buff, black, white; spotted, streaked,
freckled and barred are the only descriptions that can be applied to
them, for the combinations of their hues and patterns seem infinite.
Having grasped this fact, the eye next turns to the colouring of the
rest of the body, and it will be found that here too is the same
diversity, though less conspicuously so; and finally it will be noticed
that at this time the feathers around the base of the beak have been
replaced by yellow or orange-coloured papillæ. The females also now
wear a dress differing from that of the so-called “winter plumage,”
but it does not present any very striking features nor any form of
ornamentation comparable to that of the males.
The Ruff is a polygamous bird, which, in its display, presents some
curious and puzzling features, one of which consists of a sort of
tournament between rival males. At the break of day the performers,
selecting such eminences as the fen-lands afford, assemble apparently
to display their finery, for a couple of males will often stand facing
one another with frills erected and beaks touching the ground, silent
and immovable, for perhaps half a minute. Sooner or later, however,
they will commence to spar, and this presently leads to blows, during
which one of the combatants will attempt to seize the other by the
wings. However, no damage seems to be inflicted during such encounters,
which are by no means aimless or profitless, for during such bouts the
weaker, less vigorous birds are driven from the field, and the victor
in consequence wins for himself a larger harem.
When the actual pairing time arrives the parade of the frills begins
again. The amorous instincts, it is important to notice, are awakened
earlier in the males, so that by the time the females have attained to
a like condition the least mettlesome males have been driven off. What
follows is not the selection by the females of the finest performers
so much as a process of sorting out, whereby the females discover and
cleave to those males which are readiest for mating. This display
succeeds in revealing both the most mettlesome males and the most
amorous females, who, however, would seem to require great persistence
and much demonstration on the part of the males before they can be
finally aroused to the pitch necessary for pairing. Again and again a
male may be seen to approach an apparently very unconcerned female,
and then to crouch down before her with his beak pressed to the ground
and his frill and “ears” set off to their fullest. For some seconds
he will remain lost in apparent contemplation, then with a dazed,
far-off, expression he will look up, to find, as often as not, that
she is still apparently feeding, quite unmoved by his protestations;
or that she has even flown off and left him. Pursuit speedily follows,
and the performance is repeated until at last she too catches the flame
of passion and permits, or rather invites, the final act of sexual
congress.
Though these birds on occasion will fight, and savagely, they cannot
inflict serious damage on one another by reason of the relative
feebleness of their beaks and legs, which are but ill-adapted for
violent measures. Inasmuch as the Ruff is a polygamous species,
these bloodless battles have a peculiar interest. They show that
the preponderance of females, which polygamy implies, is not, as is
commonly supposed to be the case, due to a high death-rate among the
males by fighting. The same is true of the Wydah-birds, and their kin,
the only polygamous species among the Passeres.
In this connection it is to be remarked that fighting, of a more or
less sanguinary character, is apparently universal among birds, the
conflicts being waged not so much in the way of squabbles for the
possession of females as for the acquisition and retention of territory
and all that this entails during the breeding season and, to a much
less extent, in the defence of the eggs and young. But to this point
we must return. For the moment it will be more profitable to focus
attention on the character of this fighting. In the first place, it
is by no means necessary that the combatants should be armed. The
“dove of peace” at this time of the year appears in a new and not
always pleasing light, for not only will he fight his neighbours,
but he does not always show that gentleness towards his wife with
which tradition has credited him. The little Humming-bird would seem
to be as little capable of fighting as a bird could be, yet few are
more pugnacious. The naturalist Gosse tells of a pair which had torn
one another’s tongues out in their blind fury; and everybody knows
that Robins and Tits fight savagely to preserve their chosen haunts
from invasion by their neighbours. In some birds this pugnacity has
become an overmastering passion. Some of the Quails, and a species
of Rail (_Gallicrex cristatus_), a near relation of the Moorhen, are
commonly kept by the natives of the East, as our forefathers kept
Fighting-cocks, for the sake of seeing them fight one another. Yet,
save in the case of the Fighting-cock, neither of these birds possesses
any aggressive weapons.
Among the game-birds, however, powerful armature, in the shape of
long, pointed, spurs on the legs are met with. In the Jungle-fowls
and Pheasants only a single pair are found on each leg, but in other
species, as in the Francolins, there are several pairs, and these
birds, it is instructive to notice, are notorious for the ferocity
of their encounters. It is said that in the Indian Swamp-Francolin
(_Francolinus gularis_) nearly every individual is marked by scars and
wounds received in duels with rivals.
Certain members of the Plover-tribe, and certain Anserine birds, have
developed spurs of a very formidable character on the wings. Among the
Plover-tribe the best example of such armoured species is the Egyptian
Spur-winged Plover (_Hoplopterus_). This bird, after the fashion
of its unarmoured relatives, such as the Common Lapwing, fights by
turning suddenly in the air and striking with the wings. In the case
of the formidably armed Egyptian bird the result is often fatal; but
with our Lapwing a fatal result is rare, since but slightly swollen
knobs take the place of spurs. In Hoplopterus and in the Jacana this
spur arises from the base of the thumb, but in the Spur-winged Goose
(_Plectropterus_) it is borne by one of the wrist bones (the radial)
while in the aberrant Geese-like birds (_Palamedea_ and _Chauna_) there
are two spurs on each wring, one at each end of the metacarpus. That
these weapons have come into being in response to need seems a very
natural conclusion, but it is one which presents many difficulties
when more closely examined. The wing spurs, differing widely in their
nature as they do, in one case borne on a carpal bone, in others on the
metacarpus, seem rather to owe their origin to fortuitous variations
which have become, so to speak, adopted by selection, than to a
response to the oft-repeated stimuli incidental to fighting. The latter
explanation is Lamarckian and to-day finds favour with but few. The
stimulus theory seems to be effectually discounted by the existence
of the spurs on the legs of gallinaceous birds. That these owe their
origin to impacts, or blows, seems more than doubtful: and one can
hardly see how they could have served any useful purpose until they had
attained a sufficient length to serve as weapons. Even if we suppose
that the spurs of, say, the Jungle-fowl or the Francolin have been
derived from tuberosities such as are found on the legs of the French
Partridge (_Caccabis rufa_), we should still lack evidence that the use
of the legs in fighting caused the origin of the tuberosities.
There is yet another puzzling feature in regard to the armature of
the wings, and one which may yet help to a better understanding of
the puzzles presented by spurs. A Jacana, one of the Plovers, has the
radius broadened or flattened out from its middle onwards to form a
flat plate or blade, but the use thereof is unknown. It may possibly
serve as a weapon of offence, enabling the bird to beat its rivals with
its wings, but from the nature of the structure, and of the effect
such a use of the forearm would have upon the hand, it seems doubtful
whether it serves any aggressive function. If used at all in fighting
it is probably during fights in mid-air, when, after the fashion
pursued by the Spur-winged Plover, and even in the case of our own
Lapwing, a blow is struck by the uppermost bird at its rival, and often
with fatal effect. It is significant to remark, by the way, that in
the Lapwing a tubercle answers to the spur of Hoplopterus just as the
tubercles of the French Partridge (_Caccabis_) answer to the spur of
the Jungle-fowl or Pheasant: but the flattened radius of the wing of
the _Metopidius jacana_ has no parallel.
With birds, as with men, there must always remain the ability to
appeal to force when some important end cannot otherwise be gained.
The species which adopts the crazy tactics of the Quaker is doomed to
extinction, sooner or later. The foregoing instances display force, as
we may say, aggressively. But even the peacefully disposed birds can
fight when aroused.
Reference has already been made to dancing in this chapter; but so far
no very striking instances thereof as a form of sexual display have
been cited. The subject has been deferred because this peculiar type of
activity is not always directly associated with the _furor amantium_.
With some species, which, it should be remarked, also lack distinctive
colouring, the erotic state is manifested apparently not so much by the
display of expanded wings and tail as by frenzied dances. The Jacanas,
aberrant members of the Plover tribe resident in South America, are
expert performers, displaying moreover a curious spontaneity during
such outbursts. A flock will be apparently sedulously feeding when
suddenly and with quick, excited gestures all will cluster together in
a group and go through a singular and pretty performance, holding their
wings outstretched and agitated, some with a fluttering and others with
more leisurely movement, like that of a butterfly sunning itself. The
performance over, all scatter and feed again.. The Honourable Walter
Rothschild, in his “Avi-fauna of Laysan” tells us of the stately
Albatross, which breeds, or rather bred there—for the Japanese display
a singular callousness in regard to animal life where commercial
interests are concerned in thousands: “First they stand face to face,
then they begin nodding and bowing vigorously, then rub their bills
together with a whistling cry. After this they begin shaking their
heads and snapping their bills with marvellous rapidity, occasionally
lifting one wing, straightening themselves out and blowing out their
breasts; then they put their bills under the wing or toss them in the
air with a groaning scream, and walk round each other often for fifteen
minutes at a time.”
Cranes are much given to dancing. Mr. Nelson, an American
ornithologist, has described with much vigour the dancing of the
Sandhill Crane in Alaska. As he lay in a “hunting-blind” he was
suddenly aroused by the arrival of a crane, followed speedily by
a second, uttering his loud note as he came, until he espied the
first-comer on the ground, when he made a circuit and dropped close
by. Both birds then joined in a series of loud rolling cries in quick
succession. Suddenly, the last-comer, which seemed to be a male,
wheeled his back towards the female and made a low bow, his head nearly
touching the ground, and ending by a quick leap into the air. Another
pirouette brought him facing his charmer, whom he greeted with a still
deeper bow, his wings trailing loosely by his sides. She replied by an
answering bow and hop, and then tried to outdo the other in a series
of spasmodic hops and starts, mixed with a set of comically grave and
ceremonious bows. The pair stood for some moments bowing right and
left, when the legs appeared to become envious of the large share
taken in the performance by the neck, and then would ensue a series
of skilled hops and skips, like the steps of a minuet. Such antics
are characteristic of the Cranes of all species, and sometimes a
whole flock will join in such dances. But, it is to be noted, they are
not necessarily signs of the _furor amantium_: they certainly always
accompany this, but frequently they are indulged in, apparently, solely
as an outlet for exuberance of feeling.
Before the theme of dancing can be dismissed the performance of a small
species of perching bird, one of the South American Manakins, must be
described. The natives call it the “Bailador,” or dancer. In an account
of his travels in Nicaragua Mr. Nutting tells us: “I once witnessed one
of the most remarkable performances it was ever my lot to see. Upon a
bare twig ... at about four feet from the ground, two male ‘bailadors’
were engaged in a song and dance act that simply astonished me. The two
birds were about a foot and half apart and were alternately jumping
about two feet in the air and alighting exactly on the spot whence they
jumped. The time was as regular as clockwork, one bird jumping up the
instant the other alighted, each bird accompanying himself to the tune
of to-le-do—to-le-do—to-le-do, sounding the syllable to as he crouched
to spring, le while in the air, and do as he alighted. This performance
was kept up without intermission for more than a minute, when the birds
suddenly discovered they had an audience and made off.” Here again we
have no evidence of the _furor amantium_; nor that any females were
spectators of the scene.
It is important to notice that Mr. Howard, in the course of his study
of the Warblers, witnessed a performance having some likeness to this
on the part of three young Sedge Warblers but newly escaped from
the nursery. And this not in some solitary instance, but on several
occasions. Just after leaving the nest, he remarks, they are very
playful, “their games sometimes taking the form of a tilting match.
Three take part; two sit on convenient twigs facing one another, and
the third, from the central position, might almost be called an umpire.
Numbers One and Two lower their heads, each in anticipation of the
other moving; one of them, call him Number One, then springs into
the air and darts at Number Two: Number Two dodges and occupies the
position vacated by Number One; each of them then faces round ready to
continue the fray, the change of positions becoming quite rapid.” But
no recurrence of these antics has been noted during the course of the
adult sexual display, which is confined to posturing and displaying the
outspread wings and tail. Nevertheless there can be no doubt but that
such games in later life are incorporated, in the case of many species,
with the love display.
That the reproductive glands have played, and still play, a by no means
unimportant rôle in Evolution is shown by the history of the secondary
sexual characters. Among the birds, at any rate, the early stages of
physical changes belonging to this “figuration” are to be seen in
various forms of posturing, which in their more elaborate developments
we call “dances.” In many cases, as for example among the Warblers, the
periods of sex-emotion are marked by posturing alone. But in a number
of species, as has already been shown, the products of the sexual gland
seem to have undergone some further elaboration which has resulted in
the additional phenomena of gaudy coloration, in hypertrophied plumes,
and in weapons of offence.
But not yet is the list of such sexual products exhausted, for no
mention has so far been made of the development of the many wonderful
devices for the production of peculiar and arresting sounds, musical
and otherwise. These are of two kinds: one wherein certain feathers
have been modified to produce rhythmical notes either by percussion or
by vibration; the other wherein the internal organs have been modified
to produce musical notes or loud, resonant cries.
Instances of the latter kind are innumerable, and as a consequence no
more than one or two can be cited in these pages. The facts associated
with the production of vocal, as distinct from instrumental, music are
both curious and puzzling. To begin with, this music is produced by
the lower end of the trachea or windpipe, which has become modified in
various ways, though not so strictly in relation to the sounds produced
as is commonly supposed. The anatomical details of these modifications
cannot, or rather need not, be described now, save in the most general
terms.
Briefly the syrinx, or organ of voice, of birds, is formed in part by
the lowermost rings which form the tubular windpipe, and in part by
the smaller pair of tubes which, running therefrom to the lungs, form
the bronchi. These last are formed of semi-rings only, the inner wall
of the tube being formed by very delicate translucent membranes. As
air is forced from the lungs along the bronchi and up the windpipe,
the modulation of the voice is effected by muscles which regulate the
amount of air driven through the syrinx, and the height of the column
in the tube; the latter being effected by muscles which alternately
lengthen and shorten it.
So far so good. Next it is to be noted that this syrinx presents
a great variety of modifications, or types, differing not only in
plan, but also in the number and distribution of the muscles for its
manipulation. The most accomplished performers are to be found among
that great group of birds known as the Passeres, or perching birds,
wherein the number of these muscles is never less than five pairs,
and generally rises to seven. This association of musculature with
performance is exactly what we should expect. In Nature, however,
it is always the unexpected that happens. In the first place, the
females are, so far as the dissecting-knife and the microscope can
show, as well provided as the males, yet they do not sing. In the
second, the Nightingale and the Crow are equally endowed, so far as
we can discover, yet it is unnecessary to state that the talents
which the Crow possesses are never used! More disconcerting still
is the reflection that the Parrot, which is far less generously
endowed by Nature in so far as singing muscles are concerned, is
a much more skilful performer, inasmuch as it will reproduce with
equal fidelity the human voice and the song of the Canary! The latter
feat, at any rate, has been accomplished with amazing accuracy both
by the little Budgerigar (_Melopsittacus undulatus_) and the Quaker
Parrot (_Myopsittacus monachus_). In their wild state the Parrot
family are notorious for their discordant cries. It is therefore the
more remarkable that such feats should be capable of attainment. But
wherefore the elaborate syrinx of the Nightingale, if the simple type
seen in the Parrot is capable of the same result, and why the elaborate
syrinx in the case of the Crow, which never attains to a greater
perfection of vocal effort than the wild Parrot?
One speaks of the syrinx of the Parrot as of a simpler type because of
its feebler musculature and the lesser complexity of its framework, but
it is nevertheless a more efficient instrument, since it is capable
of reproducing both the human voice and songs such as that of the
Canary. This fact becomes still more remarkable when we reflect that
the natural voice of the Parrot, as we have just remarked, attains to
no more than a harsh screech. How is it that, capable of so much, it
has achieved so little? The same question may be asked in the case of
the Raven. This bird has a syrinx indistinguishable from that of the
Nightingale, save in point of size; yet the Raven’s voice is never
musical, nor can it be trained to such an achievement. Like the Parrot,
however, it can be taught to speak, though its vocabulary is never
so extensive. One would have imagined that when the syrinx of, say,
the Raven, or any of the Crow tribe, was compared with that of the
Nightingale or the Skylark, some structural differences, commensurate
with the difference in performance, would be discovered; but such is
not the case.
What interpretation are we to place on these paradoxical facts? One
cannot help asking why seven pairs of muscles should have been produced
by one group of birds to perform what can as easily be achieved in
another by two? It is true that the more generously endowed species
are musicians by birth, the others only by training. But one cannot
make a silk purse out of a sow’s ear. In like manner one asks why male
and female, possessing precisely similar voice-organs, should not sing
equally well, but they do not. Evidently mere mechanism does not alone
answer these questions.
Some, perhaps, may see in them instances of what is known as
“Hypertely,” wherein the bounds of mere utility seem to be transcended.
Hypertely, however, implies something more than this: it implies a
shooting beyond the mark, the overdoing of a feature, where the
momentum gained, from some obscure cause, keeps on being increased by
cumulative inheritance: and not being checked by Natural Selection,
causes the species in respect of such characters to pass beyond its
congeners. Professor Lloyd Morgan’s theory of “over-production” would
seem better to apply here, though in a somewhat different sense from
that used by him. For in the instances just quoted there is a latent
potentiality for response to new demands which the struggle for
existence may make, but a potentiality varying in degree, and here
selection finds its _métier_.
Yet further illustrations of secondary sexual characters, such as are
concerned with vocal music, must now be considered. The discussion of
these has been designedly deferred. They embrace instances of voice
production more singular than any yet referred to, and if possible more
difficult to interpret.
The facts first to be reviewed concern the syrinx of certain of the
Anatidæ. It is noteworthy that each of the three divisions of this
group—the Swans, Geese and Ducks—contains species in which either
the syrinx or the windpipe has acquired some singular feature. In
the surface-feeding Ducks, modifications of the syrinx are most
frequently found. Commonly, as in the Mallard, this takes the form
of a spherical bony case; in the diving Ducks this bony chamber
has enormously increased in size. Furthermore it has conspicuously
changed both in form and character: for it is now roughly trihedral in
form, and its walls present large _fenestræ_ closed only by delicate
membrane, suggesting that the increased size of the chamber has not
been accompanied by a corresponding increase of bony tissue for its
construction. Hence all that is available is used for the construction
of girders to form supports for the now membranous chamber walls.
Some species seem to show that this fenestration has been pushed to
excess, leaving only vestiges of this singular chamber, as is shown in
PI. 21. In some species the bronchi are much swollen, and the syringeal
chamber has entirely disappeared: in others, as in the Merganser and
Goosander, a large syringeal chamber is supplemented by dilatations of
the windpipe.
[Illustration: Plate 21.
GRADES OF EVOLUTION IN THE SYRINX OR ORGAN OF VOICE IN THE MALES OF
SURFACE FEEDING AND DIVING-DUCKS.
1. Wigeon. 2. Common Sheldrake. 3 and 4. Red-crested Pochard. 5.
Red-crested Merganser. 6 and 7. Long-tailed Duck. 8. Steller’s Eider.
9. Common Scoter.
Face Page 126.]
Save in the case of the Goosander, these peculiar structures are found
only in the male, but in the species first named the male, in addition
to the syringeal chamber, has two fusiform swellings in the windpipe,
one above the other: in the female one of these swellings is present,
but there is no syringeal box.
This box is generally, and probably correctly, regarded as a sort of
musical instrument. Nevertheless the males are far less vociferous than
the females which have no such voice resonator. One has only to listen
to, and compare the notes of the Mallard drake and duck to discover
this fact. Here, then, we seem indeed to have a case of “Hypertely.”
Before, however, we build too much on this we must discover whether the
sibilant sounds uttered by the males do, or do not, play an important
part in arousing the sexual passions of the females.
Certain of the Swans and Cranes afford illustrations of musical
instruments of an even more remarkable kind. Herein the windpipe at the
base of the neck enters a large chamber formed by the absorption of the
diploe sandwiched between the outer walls of the keel of the breastbone
and the enlargement of the space so created until it can accommodate
the tubular windpipe. This, entering the cavity in the form of a
loop, runs the whole length of the keel, the upper limb of the loop
finally running to the lungs. That we have here an indubitable musical
instrument there can be no question, for its possessor is enabled
thereby to utter loud, trumpet-like, if harsh, sounds. Here again only
the males are so provided.
The profound interest of this really extraordinary association of
unrelated structures has never attracted the attention it deserves.
Originally, no doubt, one would have met with nothing more than a
loop of the windpipe impinging against the anterior border of a
normal, blade-like keel: later there would have been formed a broad
shallow surface on the keel at the point of contact with the loop, and
gradually the depression must have deepened till the bony chamber came
into being. By what nexus of sympathy were these reciprocal responses
made?
Another very singular type of looped windpipe is that wherein the
trachea forms a series of coils between the body and the skin. It
is surely somewhat surprising to find that precisely similar coils
are met with in widely different groups of birds. Among the Passeres
they occur in the Manucode: among the Plovers in the Painted Snipe
(_Rhynchea rostratula_): among the game-birds in some of the Curassows,
and among the Anatidæ in the aberrant Australian Black-and-White Goose
(_Anseranas_).
Very little is really known of the part played by these musical
instruments of the Anatidæ, nor, for the matter of that, of most of
the “musicians” among birds. Of some of the game-birds more has been
gleaned, and among these surely the most interesting is the love-song
or “lek” of the Capercaillie. With the advent of April the cock, just
before dawn, repairs to some favourite tree—used year after year—and
there performs a most astonishing if unmusical serenade; with
outstretched neck, drooping wings and spreading tail he gives forth a
weird, uncouth kind of song, more or less divisible into three parts.
He begins with a series of notes which remind one of nothing so much as
the sound made by two sticks knocked together at intervals of ten to
fifteen seconds, getting quicker and quicker, and changing in key till
at last they become bell-like. Then follows a series of sounds like
the drawing of a cork out of a bottle, and these end with bird-like
twitterings. By this time, however, the singer has worked himself up to
an ecstasy of fervour and passion so intense as to deaden him to all
that may be passing in the outer world. During these moments no sound
disturbs him, partly, apparently, because the excitement of the “song”
causes a turgid condition of the blood-vessels which for the time
effectually deafens him. “Sportsmen,” in Swedish and other European
forests, knowing this, select such performances as affording the most
favourable time for Capercaillie shooting, only cocks being selected.
A survey must now be made of some of the more remarkable cases whereby
more or less musical, or rhythmical, sounds are made by instruments
of percussion; or by rapid vibrations. These are in almost every
instance formed by varying grades of modification in the feathers of
the wings or tail. Their presence, and their use, seem natural enough
until we recall the fact that many other birds without any apparatus
whatever, make sounds in no way less remarkable or less penetrating.
Pigeons, Nightjars and Owls, for example, can produce at will curious
snapping sounds by bringing the wings smartly together over the back.
The White, and Shoebilled Storks make castanets of the beak, throwing
the head backwards till the point of the beak touches the back, when
the jaws are set rapidly clashing one against another, producing a
sound comparable to the “bones” of negro minstrels, but without the
varying rhythm. As this performance is proceeding, the head and neck
are slowly moved through half a circle, till the tip of the beak
touches the ground, when the music ceases. As with the wing-snapping
just referred to, both sexes are equally skilful performers; but while
they seem to indulge in such exercises much more frequently, and with
more vim during the breeding season, they will break out after this
demonstrative fashion at all times of the year. But why, then, the need
for the yet more elaborate contrivances which are to be met with among
the Snipe, the Game-birds, and certain of the Passeres?
However, be this as it may, in a large number of species a special
mechanism has been evolved to produce sounds which, as has been
remarked, in other species are no less effectually made without that
mechanism.
One of the simplest of the cases is that furnished by the remarkable
“bleating” or “drumming” performances of many species of Snipe,
generally, if not only, when sexually excited, and especially of
the Common Snipe (_Gallinago cœlestis_) during its love-flights.
Mounting to a great height, this bird, at such times, suddenly turns,
and descends with prodigious speed, meanwhile holding the tail fully
expanded. The outermost pair of feathers are, however, specially
modified so that, in the first place, during this descent they stand
at right angles to the long axis of the body and well apart from the
rest of the tail-feathers. This alone, however, would not produce these
weird sounds, which owe their origin to the fact that these particular
feathers have their shafts conspicuously thickened and peculiarly
curved, while the vane or web of the inner side of the feather is
of great width and structurally differs from the vanes of the other
feathers, whereby the vane becomes more resistant to the rush of air
caused by the wings during the descent.
But in the case of these Snipe it is to be noted this curious form
of musical instrument is found in both sexes, and there is little
difference in the quality of the sounds produced, but the bleating of
the male is said to be the more resonant.
The Common Snipe is the best performer among several different species,
and it is to be noted presents, to a casual examination, no remarkable
or peculiar feature whatever—the structural differences just described
are only to be discovered by very patient scrutiny. But in the
Pin-tailed Snipe (_Gallinago stenura_) the number of the feathers has
been greatly increased, while at the same time their webs have been
so reduced that the outspread tail seems to consist of little more
than spines. With such a transformation one expects to find a quite
exceptional performance, far surpassing that of the Common Snipe. Yet
so far as observation and experiment go they effect absolutely nothing!
Here again we have a case where modification of structure has passed
the bounds of need and passed so far as to make the whole tail useless
as a sound-producing organ!
A contrast and a parallel are afforded by some of the gallinaceous
birds of South America. The Black Penelope (_Penelopina nigra_) of
Guatemala, while on the wing, will, during its “love-flights,” pitch
suddenly earthwards with outstretched wings, and at such times a
crashing, rushing sound is produced, which has been likened to the
sound of a falling tree. Yet there is nothing in the shape of the wing
which will account for this. On the other hand, a near relation of
this bird, the Black-wattled Guan, _Aburria_ (_Penelope_) _aburri_ has
the four outermost primaries deeply incised along their inner vanes,
reducing the outermost portion of the feathers to mere spines. Yet, so
far as is known, this wing makes no especial noise. However, the males
of certain little South American Perching-birds known as Manakins have
the shafts of the secondary quills thickened to an extraordinary degree
so as to form solid, horny lumps, and these, when the wings are brought
together smartly over the back, produce a noise not unlike the crack of
a whip, so that here again structure and function are found together.
In the contradictory cases just cited where specialized parts are found
which are apparently functionless, we must suppose that the habit of
using them has been supplanted by some new stimulant.
The part played by musical instruments of percussion would seem to
be a variable one. In some cases, and possibly in all, it may serve
as an excitant, or stimulant, to the rousing of a “sex-storm”; in
many, at any rate, such sounds serve as calls to the sexes when
separated. This much seems to be demonstrated in the case of certain
of the Woodpeckers, which in this matter differ conspicuously from
any other species yet referred to, in that they have developed no
special sound-producing mechanism, but make use of hollow trees which
serve them as drums, the beak being used as the drumstick. This is a
very noteworthy fact, for one would have supposed that here at any
rate, where the production of loud and far-reaching sounds is of
vital importance, the means would have been provided by some such
modification of the wing-feathers as we have already seen to obtain in
the case, for example, of the Manakins. More closely examined, however,
this apparent failure of the organism to produce its own mechanism
becomes less remarkable, for Woodpeckers are forest-dwellers and but
indifferent fliers; loud sounds produced by the rapid vibration of
the wings or tail, as in the case of the Snipe, in mid-air, are thus
impracticable, if not impossible, and sounds produced after the fashion
of the Manakins would not have sufficient carrying power.
One of the most skilled performers among the Woodpeckers is the Great
Spotted Woodpecker (_Dendrocofus major_), whose weird drumming once
heard will never be forgotten. These sounds are produced by blows
of the beak on a branch, delivered so rapidly that the bird’s head
presents but a blurred appearance. The sounds thus made vary with the
resonance of the wood and can be heard at a distance of half a mile.
These strange vibrating notes are most frequently heard during the
courting season, and they will commonly beget a speedy response from
some more or less distant part of the wood, so that their purpose is
clear. They attain the same end as the bellowing of the stag or the
“lek” of the Capercaillie. They are, however, to be heard at other
times, as when the birds are greatly alarmed or when the nest is being
robbed.
CHAPTER VII
THE SEXUAL SELECTION THEORY AS APPLIED TO BIRDS
Where the Rôle of the Sexes is reversed—Polygamy and how it is
brought about—Coloration and Courtship—Instinctive Actions—The
Importance of Landed Possessions—The Meaning of “Display”—The Springs
of “Behaviour”—A New Light on the Wild-duck—The “Display” of the
Great-crested Grebe—Some Neglected Factors.
The significance of the varied behaviour of birds—more especially of
the males—during the period of reproductive activity must now be more
minutely analysed. But before this analysis can be profitably begun, it
will be necessary to recall the fact that there are several cases known
wherein the rôle of the sexes is largely reversed. Herein the females
do the “courting,” and fight one another as rivals for the males; while
the males perform the duties of incubation and brooding, and feeding
the young. This is really very remarkable, and demands more attention
than it has yet received.
What factors have brought about this curious reversal? In any search
for an explanation it must be borne in mind that in all such cases
polyandry is the rule, and in all such cases the female is larger and
more vividly coloured than the male. Here, then, we have exactly the
opposite to what obtains in cases of polygamy. What is the reason
for this preponderance of males? Why is it that when the males are
in excess of the females the latter should be the more brilliantly
coloured and the more amorous? These questions at present are
unanswerable. When polygamy obtains it seems always to be assumed that
it is explained by the excessive pugnacity of the males, which, after
fierce contests for the mastery, take forcible possession of as many
females as may be captured and held in durance; the same argument seems
never to have been applied when polyandry obtains. There can be no
doubt but that it applies in neither case.
When polygamy obtains, as we have already pointed out, the females
are not seized and captured by the males, they are not victims of a
lecherous lord. On the contrary, they seek the males, and the intensity
of the desire to satisfy their natural cravings extinguishes any
feeling of jealousy.
The same interpretation must obtain where the numerical values of the
sexes is reversed. Failure to appreciate this accounts for one of the
many futile suggestions made for the suppression of the rabbit plague
in Australia, which was that large hauls of these pests should be
made by netting, and that the females should be slain and the males
released. This, it was held, would lead to the speedy reduction of the
latter, which would kill one another in their fights for the remaining
females. The plan was impracticable, but the suggestion demonstrated
the prevalent belief as to the attitude of the male in this respect.
Had it been well founded, surely polyandrous species, whether of birds
or beasts, would never have existed; for, by the reduction of the
males, monogamy would speedily have been restored. How, then, are we to
explain polyandry? How are we to explain the fact, as it seems to be
the fact, that the excess of males has brought about such a complete
reversal in behaviour—the males, instead of the females, requiring
the aphrodisiac? The solution of this problem probably lies with the
physiologist. We now know that the problem of sex does not rest merely
in the complete development of the primary sexual organs; we know that
fertile unions do not depend merely on the act of pairing, but on the
functional activity of those ancillary glands already referred to. And
it may well be that some change in the character of the secretions
has not only altered the numerical values of the sexes, but reversed
the normal rôle of coloration and behaviour. That is to say, neither
polygamy nor polyandry among the lower animals, at any rate, has been
brought about or is maintained by the excessive death-rate due to
combats for possession of mates, but must be explained as demonstrating
inherent changes in the germ-plasm, disturbing the relative proportions
of the sexes and correlated with a profound transformation, not only in
the behaviour of the sexes during the period of reproductive activity,
but also in their physical characteristics.
The action of the primary sexual glands and of the ancillary glands
has, then, to be allowed for in all attempts to interpret behaviour
in sexual matters. No less so must this be the case in regard to the
development of coloration and other forms of ornament, and the genesis
of weapons of offence. But at present we are, in this direction,
dealing with an unknown quantity. The recognition of this, however,
should not deter us from attempting to solve the riddle of sex from the
phenomena which have so far been surveyed.
To-day the interpretation which holds the field is Darwin’s theory
of “Sexual Selection.” But this was framed rather to account for the
existence of conspicuous secondary sexual characters—the antlers of
Deer, the train of the Peacock, and so on; it did not take cognizance
of the unarmed, and the soberly-clad individuals. But whatever
shortcomings we may discover, real or imaginary, in this theory, we
must never forget that he had not only to analyse and present his
facts, but he had first to collect them. This, in his case, was a more
laborious task than most people seem to suppose. Our criticisms to-day
are based, not so much on the revelations of new facts, as on the
harvests of his gleaning. Yet when all is said and done, the theory of
“Sexual Selection” remains, though perhaps in a new setting.
To attempt to epitomize this theory is to essay a very difficult task.
But, in a condensed form, it may be said to be a theory which accounts
for the development of secondary sexual characters, on the one hand
through the agency of conquest by battle, whereby rival males strive
for the possession of one or more females, who have no choice in the
matter, or who may deliberately elect to follow the victor: and on
the other by display of conspicuous ornamentation, or of more or less
grotesque antics, or of some form of music, using this term in a very
wide sense. Wherever display is the agent, however, its purpose seems
to be to win the affections of the female to whom such attentions are
addressed. She is supposed to elect to mate with the finest performers
of a number of suitors. In this way, it is assumed, the intensity of
the display, whatever its nature, has been gradually increased.
Wallace strongly opposed this, contending that it assumed too much,
that it assumed a common and uniform standard of perfection shared by
all the females concerned in the selection, which is indeed assuming
too much. But his own theory was no more satisfactory. Indeed it was
very much less so, for he contended that these various exaggerations
of colour and form are to be regarded simply as evidences of a
superabundant vitality, though there is no evidence that “superabundant
vitality,” if it exists, is a transmissible character.
The revised version of the Sexual Selection theory advanced in these
pages is largely inspired by the work of Mr. H. Eliot Howard who,
in his Monograph on the British Warblers, has not only added very
materially to our knowledge of the life-histories of these birds,
during the reproductive period, but has also done much—both in the
direction of destructive, and constructive criticism, of generally
accepted conceptions on this head—to set us on the right track for
further research.
A study of his work leaves one with the conviction that, while these
birds exhibit what we may call a nascent intelligence, their actions,
on the whole, may be described as instinctive, or congenitally
definite. That is to say, they follow one another in definite
sequence. Hence we must regard each new phase in the chain of events
appertaining to the reproductive cycle, as following one another in
a definite sequence, so that any break therein throws the orderly
performance of the necessary acts out of gear. There is no realization
of what reproduction means, no deliberate striving to achieve that
end. Each new phase brings its own set of associations and sets a new
train of actions in motion, which are performed mechanically. For
instance, these Warblers, like hosts of other species under similar
circumstances, are scrupulously careful to remove the fæces of their
young from the nest; thereby preserving it in a sanitary condition. It
is certain that any neglect to do this would speedily end in the death
of the young. This act is “instinctive”; it is not performed because
the parents have evolved any views on sanitation, and any strain in
whom this instinct was defective would speedily become eliminated.
Mr. Howard has demonstrated the mechanical character of this sanitary
measure by placing leaves in nests of young. The parents, having fed
their offspring, at once seized upon the leaf and commenced to dispose
of it after their usual fashion, first by trying to swallow it and then
by carrying it away. They did not, evidently, realize the difference
between the texture of the leaf and the milk-white, jelly-like envelope
which always encloses the fæcal matter of the nestling. We shall
probably never know how this most vitally important instinct came into
being; nor can we hope to discover what chain of happenings begot the
instinct, which each parent displays, to gently stimulate the cloacal
lips of their offspring in order to induce the discharge of the fæces
when this does not immediately follow the stimulus of swallowing food.
We cannot credit these birds with notions on the importance of the
regular discharge of the evacuations. Equally mysterious is the
development of the envelope enclosing the fæcal matter. This is
jelly-like in substance, and of considerable thickness, and is enclosed
within a very delicate skin or pellicle, enabling one to lift the whole
in the fingers without soiling them. How and where it is formed should
not long evade discovery. But how it has come to be is another matter.
We can, at any rate, vaguely account for responses of the organism to
internal stimuli reacting directly on the individual, but here is an
elaborate mechanism evolved in response to extra-personal needs: and
which cannot be regarded as of exactly the same configuration as the
instinct to feed the young.
A return must be made to the nature of the early phases in the
procession of the reproductive instincts. Mr. Howard’s study of
the Warblers seems to show conclusively that these first manifest
themselves in an overmastering desire to seize upon territory large
enough to ensure an abundance of food for the offspring that are yet
to be. To this end the males arrive from their far-distant winter
quarters at least a week in advance of the females. Since each returns
approximately to the scene of last year’s nursery, the arrivals are
fairly distributed at the first; but nevertheless this distribution
inevitably brings a conflict of interests between one or more males,
perchance young birds about to start in life, and having therefore no
definite objective. But whatever the reason, the competition is there.
The strongest male remains in possession, and immediately commences
to express the ecstasy of feeling which possesses him in continuous
outbursts of song. Such, doubtless, answer to the bellowing of the
male stag. They advertise the presence of a male to the female, who,
as she arrives, would seem to be already stirred by the rising storm
of sexual desire, for having once discovered a male in possession of
the all-necessary site for the nest, and the equally necessary domain,
each settles down to conjugal bliss: within twenty-four hours the task
of building has begun. There is evidently here no sexual selection
in Darwin’s sense: no choice from among a number of males of the
individual which most excites desire within her; but the mating of
the most mettlesome, most virile males has been determined before her
arrival and by a double sieve. In the first place, the duller-witted
birds fail to secure suitable territory, and in the second, the
territory, having been taken, must be held by force, so that only the
strongest males remain to mate when the females eventually arrive.
So far as one can see, selection is less exacting in the case of the
females, which apparently need do little more than respond to the
advances of the males.
[Illustration: Plate 22.
From a drawing by H. Grönvold.
FIGHTING FOR TERRITORY.
Two Black-caps are here seen fighting for their annual breeding
territory. A Chiff-chaff has been unable to resist the excitement of
conflict.
Face page 140.]
With the advent of the females the amorous instincts of the male
speedily gather force; but for their satisfaction it is imperative that
the female should be possessed by a like desire. To provoke this, for
it is essential to the well-being of the race that offspring should be
produced as early as possible, some form of aphrodisiac seems to be
necessary. This fact has never been properly realized, though it is
implied in Darwin’s theory of “Sexual Selection.” Here, however, it was
used to account for the evolution of resplendent coloration, eccentric
postures, and dances which, it was assumed, enabled or induced the
female to choose the most mettlesome males. What obtained among
sombre-clad species, appears to have excited no curiosity among the
students of the evolution theory. Hence it comes somewhat as a surprise
to find that the soberly-clad Warblers behave exactly as though they
too wore coats of many colours. After what has been said in the last
chapter on this head it will be unnecessary to describe these displays
among the Warblers in detail, more especially as my friend Mr. Howard
has kindly allowed me to use some of the illustrations from his book.
These show convincingly enough that the wings and tail are made to
play the same part as though they bore all the hues of the rainbow. To
bring this fact home compare the figures of some of these small birds
clad in sober russet and black with that of the Sun Bittern (_Eurypyga
helias_) in like mood, whose wings and tail when spread, and only then,
display bands of vivid chestnut-red, contrasting with bands of black,
on a background of grey and buff, variegated with delicate mottlings
and vermiculations of black and brown, and streaks of white. In the
case of the Warblers, it is to be remarked, the male, in these ecstatic
moods, will commonly hold a leaf, or a piece of stick, in his beak, as
if suggesting the work of nest-building and its delightful sequence.
This, or its equivalent, is a common phase, for the Great Crested
Grebe, for example, in these paroxysms will dive and bring up weed,
the nest material of the species, as an offering to his mate, or as a
stimulant to her yet slumbering passion.
It seems clear, then, that the evolution of colour is not the
stimulant to display, for this is present where conspicuous colours
are wanting. Yet it can readily be understood how the association of
ideas in regard to colour and display arose, for there are cases where
this interpretation seems inevitable. Such are afforded by certain
sea-birds like the Kittiwake, Guillemot, Fulmar and Cormorant, wherein
the inside of the mouth is of a lurid orange-red in the case of the
first-mentioned, and of flaming gamboge yellow in that of the others.
During moments of sexual ecstasy the mouth is widely opened, as if
to charm the beholder with its gaudy hue. Both sexes have the same
colouring, and both behave alike. But it is doubtful whether either
is conscious that its own mouth is like that exposed to its gaze: the
action is sympathetic. No doubt it may play its part in stimulating
desire, but we cannot contend from this that it has been evolved
by sexual selection, that is to say, that the hues have undergone
a process of gradual intensification owing to the deliberate
rejection of the less gaily-coloured suitors. The tendency to develop
colour in the mouth would appear to be latent in all birds.
[Illustration: Plate 23.
_From a drawing by H. Grönvold._
THE DISPLAY OF THE GRASSHOPPER WARBLER.
The behaviour of this bird under the stimulus of sexual excitement is
precisely similar to that of the Sun-bittern and the Kagu, yet it has
no brilliant colours to exhibit by such actions.
Face page 142.]
[Illustration: Plate 24.
THE DISPLAY OF THE SUN-BITTERN.
Quite inconspicuous in repose, this bird, in its moments of exaltation,
becomes banded and blotched with vivid colours, revealed by spreading
the wings and tail.]
[Illustration: _Photos copyright, D. Seth-Smith._
THE KAGU IN DISPLAY.
What is true of the Sun-Bittern is true also of the Kagu.]
It is significant that whenever bright colours appear, they do so first
in the males, the females and young retaining the dress common, up to
this time, to the species at all ages. In the majority of instances,
at any rate, it would seem that this accession of colour appears with
the seasonal re-awakening of the reproductive activities: it forms a
“nuptial” dress, and is discarded after the breeding season is over for
a livery indistinguishable from that of the female, this forming the
so-called “winter plumage.” But if all the available facts are taken
into consideration there seems good reason to believe that the nuptial
plumage tends to be assumed earlier and to be retained later, as this
disposition to develop ornament gathers force, till finally only the
head and neck go into “eclipse,” as in the case of the Black-cock,
Jungle-fowl and Partridge.
In the Pheasant we have an instance—one of hundreds—where the
resplendent dress is worn throughout the year. The next phase in the
direction of the growth of colour occurs when the female, towards old
age, develops a more or less well marked tendency to assume the hues
of her lord, and this accession of colour makes its appearance earlier
and earlier in succeeding generations, till finally the adults of both
sexes are coloured alike, save that, as a rule, the female lacks the
intensity of coloration which her mate displays. The original sombre
dress is now only worn by the young. In due course the resplendent
dress is assumed also by the young, as witness the numerous instances
among the Kingfishers and among the Parrots, where adults and young
are all habited in the same vivid hues. There are infinite variations
of these changes which cannot be discussed here, for obvious reasons.
All that matters now is the fact of such sequences, which inevitably
raise the questions: Why, in so many cases, do the females show no
disposition to assume resplendent colours? And to what factors can such
coloration, when it occurs, be attributed? The second only of these
questions is germane to the present discussion, and to this no very
satisfactory answer can be returned.
To say that the development of brilliance in species hitherto sombrely
clad is due to “changes in the metabolism” is only an affectation of
wisdom. What we want to know is what induces the changes? Time was
when no more than a guess could be hazarded as to this: a suggestion
that ornament, of whatever kind, was one of the many modes of the
expression of that instability of the organism which is characteristic
of living things: that it was one of the outward and visible signs of
that inward, intangible tendency to vary which is so familiar. Later
research seemed to show, fairly conclusively, that ornament was one
of those “secondary sexual characters” which was dependent on the
stimulating juices, or “hormones,” emanating from the primary sexual
glands. To-day it is manifest that this is only partly true, for it is
certain that these glands are not alone concerned and they may only
participate indirectly. It seems to have been clearly demonstrated that
the thyroid and pituitary glands, or the “hormones” therefrom, play a
large part in this matter of the “secondary sexual characters.”
Castration, it is true, profoundly affects these characters. In the
case of Deer it inhibits the growth of antlers, in Cattle the horns
are increased in length but reduced in thickness—they are longer than
those of the female, but resemble them in appearance, and further,
the whole stature is greatly increased, but it is at the same time
conspicuously less massive, particularly at the neck and fore-quarters.
In eunuchs it results in immense stature and the loss of the more
characteristic male features, such as the beard and the bass voice. The
removal of the testes in birds is always a difficult operation and is
rarely successfully performed. Hence the accounts of changes in plumage
consequent on this operation are inconclusive. It has generally been
supposed that whenever, either by removal or by disease, the testes
are rendered inoperative the plumage, when normally of a resplendent
type, assumes the coloration of the female. This is probably an
erroneous supposition, but what happens is a failure to secrete the
more intense pigments and the more specialized forms of feathers, so
that the resultant dress answers to the juvenile male dress. It is
not a case of “reversion” to this livery, but a failure to assume the
latest acquirements of the species. These, as has already been shown,
are only very gradually developed. The intensity of pigmentation, or
concentration of pigmentation, which results in sharply defined areas
of colour, is a cumulative process. As it loses in intensity at any
given moult, so the individual tends to reproduce the phases of the
earlier and vanishing livery. Sooner or later, however, this earlier
livery disappears more or less completely: is eliminated from the
system, so to speak: and what is commonly called lack of “vigour”
results, not in a return to the earlier, sombre dress, but in the
later-acquired, resplendent plumage lacking intensity. The seasonal,
temporary secondary sexual character has become, as some say, a
“somatic” character. Highly probable as this view appears, it ought,
it may be argued, to receive support from nestling plumages. Young
gulls, for example, should occasionally revert from the mottled to the
earlier striped livery. But we have no evidence of this; and it does
not follow that this sequence of events should occur. The conditions of
control are different.
What exactly are the factors which govern the evolution of resplendent
plumage is not known. But they would seem to be more complex than
was supposed. That the primary sexual glands play an important part,
through the juices or “hormones” which they liberate, there can
be no doubt but these are only partial factors. The “hormones” of
the pituitary and thyroid glands are also necessary contributors,
controlling as they do both fertility and the more superficial
characters, such as colour and ornament. Evidence, indeed, is slowly
accumulating to show that the problem of the behaviour of animals
during the period of sexual activity, as well as the peculiarities
of structure and coloration which they develop at this time, are all
largely governed by the action of these secretions.
These, in their turn, are undoubtedly inhibited, or increased, by
the control of the nervous system, though this control is of course
involuntary. This much seems clear from the fact that birds will
display when under the excitement of fear, though the character of that
display is never the same as that in moments of sexual exaltation. If
the nervous system, through the eye, by “suggestion,” played no part,
there could be no use for display, but it is equally certain that for
the realization of the sexual activities a number of other factors have
to contribute.
The existence of this nexus of conditions is commonly overlooked, but
it is extremely important. Normally, not only among birds, but other
animals higher and lower in the scale of life, “suggestion” does not
suggest until the “hormones” concerned with the sexual activities have,
as it were, saturated the system and rendered it, so to speak, highly
inflammable. Even then it commonly happens that, with the male at any
rate, this inflammable state bursts into flame of its own accord. But
for this, indeed, how could the consummation—of the period of sexual
activity ever be realized? In many cases the sexes are sundered far
apart. What, but the merest accident, could bring them together if
it were not for this consuming fire of desire which impels each sex
to seek out the other? This stage is manifested in the case of the
Deer, where, we have seen, the stag wanders far and wide bellowing to
advertise his errand and listening for a response to his call. He is
possessed by a “male-hunger” which eventually attains to a state of
frenzy. Here no “suggestion” is needed, but the necessity for this
stimulus, for some form of aphrodisiac, occurs with him after the
first relief of his pent-up state has been attained. This stimulus is
applied, both through the eye and the sense of smell, by the females of
his herd. The same conditions apply in the case of the birds. But it is
to be noted that with the females, as in the case of mammals, sexual
desire is commonly less intense than in the males, and hence, in their
case the need for “suggestion” by display of some sort. But apart from
this, a “display” of some kind is necessary. How else can desire be
indicated? And here is “sexual selection.” For males, mate-hungry as
they might be, which resorted to no means of expressing their condition
would go mateless: and the same is true, though perhaps in less
extent, with the females; hence, then, it is clear display is a product
of sexual selection.
That sexual desire is less intense in the case of the females is to
be regarded as another result of this form of selection. If they
displayed the same intensity of passion the males would speedily become
exhausted, for it is well known that the gratification of the sexual
emotions is far more enervating in the case of the male. It may well
be that polyandry has arisen from this transference to the females, or
development by the females, of increased sexual hunger.
The fact that birds will repeat, albeit imperfectly, the phases of
the sexual display under the stimulus of fear, or anger, and when no
females are present, must be regarded as an indication, for we can
scarcely call it a proof, that exaggerated movements have become the
normal concomitants of great excitement, at any rate during the season
of reproductive activity. They are purely nervous responses to external
conditions. It must not be forgotten that, at this time, fear begets
other movements, equally striking, such as feigning lameness, and
death, which have no part in the sexual display.
Interpreted in this light one can understand that to the female not as
yet sexually “ripe” or sexually “hungry,” these movements, when not
interpreted as signs of fear or anger, fail to produce any response.
So soon, however, as this period of “ripeness” arrives, the stimulus
through the nervous system produces the desired response, begetting a
complementary stimulus through the secretions of the sexual glands,
by what we may call the flow of the hormones; just as the sight of
food stimulates the flow of saliva, or “makes the mouth water” before
we are conscious of feeling hungry. In due time hunger will assert
itself without the stimulus of the nervous system through the senses.
But there must in any case be some form of display, some form of
communicating and stimulating desire between the sexes, to secure the
consummation of the reproductive acts. How else could intimation of sex
hunger be indicated and satisfied?
That the desire for sexual congress is inherently more avid, more
intense, in the male than in the female is often called in question;
and more especially so by those who imagine that they have a mission
to carry on “social reforms” and to regulate the relations between
the sexes of the human race. Such aims and ambitions are commonly
those of the arrogantly ignorant. There are few people who possess a
sufficiently wide knowledge of this theme, or of the factors which
underlie it, to qualify them to become the mentors of their fellow-men
in these matters. However much we may choose to seek refuge in
sophistry, the fact remains that man is still an animal, and if the
human race is to continue he must always remain so.
A lurid light has just been shed on the fierceness of the sexual
passion in the male by Mr. Julian Huxley, who relates some facts
pregnant with meaning to all who have understanding, in regard to what
obtains among birds. These facts are primarily concerned with the
Mallard (_Anas boscas_). This bird is ostensibly monogamous, and, on
the whole, seems to be a fairly considerate mate. The normal period of
pairing having passed, and the duties of incubation having begun, the
female ceases to harbour any further desire for sexual intimacy. Her
whole energies are devoted to nursing her embryonic young into life.
Not so the male. He is yet far from satiated; in him the sexual fever
still burns fiercely, but somehow he seems never to make any attempt to
provoke in his mate a like condition, as in the days before brooding
began. On the other hand, he does not scruple to savagely pursue
every other female who ventures abroad in his neighbourhood. So soon
as a duck takes wing for a brief relaxation from the arduous work of
brooding she is pursued by ten or a dozen already mated males, till
at last she is obliged to descend on the water, and with her descend
her pursuers, now to mob her without mercy. Commonly at least half of
these infuriated males will eventually succeed in treading her; leaving
their victim only after she has become completely exhausted or killed
outright. This is no unusual occurrence. On the reservoirs at Tring,
where every spring from one thousand to one thousand two hundred pairs
congregate to breed, from seven per cent, to ten per cent, of females
are annually killed in this way.
It is just possible, however, that an error may have crept into these
observations. One cannot help asking, may it not be possible that these
pursuing males were actually unmated birds? The chief argument against
this is the fact that there is no sort of attempt to “display” apparent
with these birds, simply an overmastering, ravenous desire to satisfy
the craving which possesses them.
Evidence is not wanting that the evolution of pigment intensification
and the consequent development of vividly coloured liveries, or
the equivalent development of ornament, has been accompanied by an
intensification of the reproductive instincts. For there can be no
doubt but that the display of species which are conspicuous for
their ornamentation is more animated than those of duller hues. As an
argument in favour of this view the case of the display of the Great
Crested Grebe may be cited, wherein each sex has developed both colour
and ornament to a high degree, and are distinguishable only to the
expert.
The latest and the best exponent of the behaviour of this species
under the spell of sexual exaltation is Mr. Julian Huxley, whose
observations, in a condensed form, are now to be surveyed. The most
conspicuous features in this bird are the great Elizabethan ruff of
bright chestnut and dark Vandyke brown, and the long dark-brown tufts
of feathers, or “ears,” which surmount the head. But the satin-like
sheen of the white breast and the fore part of the neck and face add
not a little to the general effect. These ornaments are worn only
during the breeding season. So soon as the fires within begin to burn,
the parade of this finery commences, and it would seem that a somewhat
protracted dalliance takes place before any actual pairing. During
the early phases of these performances much play is made with ruffs
and “ears.” The courting pair will frequently face one another on the
water, and go through a strange ceremony of head-shaking. To this is
soon added a sort of ghost dance, wherein the male suddenly dives,
leaving his mate swinging excitedly from side to side. In a moment or
two, however, he appears, not suddenly, as usual, but arising gradually
out of the water. He seems to “grow” out of the water. First his head
appears, with ears and ruff extended, and beak pointed downwards; then
his neck, and finally the body arises into view, till only the extreme
tail end remains submerged, so that he looks more like a penguin than
a grebe! All the while he is turning on his long axis, as it were,
till he gradually displays before his mate the dazzling white sheen
of his breast and neck, set off by the rich red chestnut and brown of
his face and frills. A moment more and both subside into their normal
attitude, shake their heads at one another, and then proceed to feed as
if nothing had happened.
But these quaint antics are only the preliminaries to still stranger. A
pair of birds, engaged, apparently, solely in fishing and feeding, will
suddenly approach one another and begin head-shaking, each striving
to outdo the other. Then the ears, till now erect, are thrust out
laterally, and the ruff is still further erected till it forms, with
the ears, a common disc. Then the hen dives: immediately after down
goes the cock. After some fifteen seconds or so she appears at the
surface again, speedily followed by the cock, who breaks out about
five-and-twenty yards off. Each crouches low over the water, and
each will be seen bearing a tuft of weed in the beak. As each sights
the other a tremendous rush is made, as if they intend to charge.
But when about a yard apart each springs up and assumes the penguin
position, save that the beak, instead of pointing downwards, is now
held horizontally and bears its burden of weed. Still approaching,
they eventually touch one another, treading the water and swaying in a
sort of ecstasy, all the while shaking their heads from side to side.
Then they gradually settle down into the normal swimming pose, though
still keeping up the head-shaking; then this, too, subsides, the weed
is dropped, and the performers drift apart and begin feeding. But no
actual pairing accompanies these strange performances. This final rite
is associated with a quite different ceremonial, and was witnessed
more than once by Mr. Huxley. On the particular occasion which he
describes he was watching a male swimming along near the reeds,
apparently on the look-out for something, and turning his eyes in the
direction of the course, he saw, at some distance off, what he supposed
was a dead grebe lying hunched up in the water, with outstretched neck,
and ruff and ears depressed. Presently the male swam alongside the
body and bent down his head as if to examine it. Then he swam to the
tail end, and suddenly scrambled out of the water on to the body; and
there, with bowed head and depressed ears and crest, he seemed to stand
a moment. Then he waddled forward over its head and into the water.
Instantly the supposed corpse raised its head and neck, gave a sort of
jump, and was swimming by the side of its mate. They had been pairing
on a half-made nest, whose surface lay level with the water.
[Illustration: Plate 25.
_From a drawing by H. Grönvold._
A MALE-SAVI’S WARBLER
—in one of his “courtship” attitudes. Note the leaf held in the beak.
[Face page 152.]
Mr. Edmund Selous seems to have witnessed some almost incredible
behaviour on the part of the owners of a nest he had under observation,
inasmuch as, on more than one occasion, he declares the male lay prone
upon the nest and the female assumed the position of the male. After
this pantomime both would leave the nest, but commonly the female would
speedily return and pairing would be duly performed.
This brief summary of Mr. Huxley’s observations, which he was generous
enough to give me the privilege of seeing in manuscript, taken in
conjunction with many other facts of a like kind given in these pages,
seems to lend support to the view that an excessive amorousness is
commonly associated with conspicuous ornamentation, as if these stood
in the relation of cause and effect.
Finally, it is contended, the facts garnered during recent years
show that the theory of Sexual Selection, as Darwin propounded it,
especially in so far as birds are concerned, is no longer tenable:
but it is not an exploded theory, it has only undergone modification.
So far as the evidence goes, it would seem that the first of the
series of events in the sexual cycle is performed by the already avid
male, when he proceeds to secure a “territory” large enough for his
needs. In insectivorous and carnivorous species this area is fairly
extensive. No other male will be allowed within its confines. The
perfection of this instinct is vitally important, if sufficient food
for the offspring that are to be is to be assured. Where the food is
inexhaustible, as with the Auk-tribe, only a ledge large enough to
hold the egg is required. Only avid males will develop and respond to
this stimulus. The second stage occurs with the arrival of a female in
the area. She does not at once proceed to “select” her mate, passing
on if he fails to provoke her admiration. Her sexual condition is
apparently as yet but half awakened: to rouse this, the male supplies
an aphrodisiac in some form of display to which, in the normal course
of things, she responds, often also with some form of display, or
indication of the desire which has been aroused. The intensity of
the performance seems to vary with the intensity of the sexual
passion, which appears to be greater in some species than others, and
especially so with such as have conspicuously ornamental plumage. There
is, indeed, a variation in the sexual appetite as there is in the
ornamentation. The two are reciprocal, and are determined in degree by
the stimulatory qualities of the hormones of the sexual glands. Where
these have been developed in like intensity by the females, they also
display. Diminution in the quality and quantity of the stimulating
secretions of the ancillary sexual glands, the hormones of the
pituitary and thyroid, or the primary glands—testis and ovary—decreases
fertility, or induces sterility. Where these stimulants are lacking
there will be no desire, no display, and no pairing, and consequently
an end to this defective strain. Here then is Sexual Selection.
[Illustration: Plate 26.
Photo copyright by D. Seth-Smith.
ANOTHER ASPECT OF THE KAGU’S “DISPLAY.”
Herein two birds are seen facing one another with the great head-crest
fully erected. While in this mood these birds will strut up and down
with mincing gait and drooping wings. This is a posture commonly
assumed during momentary excitement, whereas the posture shown in plate
24 is apparently only assumed during moments of sexual excitement.
Face page 154.]
Instances of such impotency on the part of either sex are wanting,
and we can only speculate as to how such cases would be met. Would
a female who had chanced to settle in the territory of a male whose
sexual impulses carried him no further than seizing territory remain
with him throughout the mating season, held by an imperfectly roused,
ill-defined, sexual instinct? Or, eventually becoming mate-hungry, and
failing to stimulate him to perform his part, would she desert him and
seek another mate? On the other hand, would a male, failing to arouse
response in the female he had secured, drive her away and supplant her?
In other words, are we then justified in postulating differential
effects in regard to display: a minimum of intensity to ensure mating?
A display of some sort is essential. It may be feeble as compared with
that of another species—that of the Sparrow, for instance, compared
with that of the Peacock—but it must be sufficiently good of its kind
to effect its purpose, which is to “hustle” up the production of
offspring. A phlegmatic but virile male, or a too feeble performer,
is almost as certainly doomed to extinction as an impotent male; for
his offspring will probably be eliminated by the adverse conditions of
existence to which their late appearance exposed them. Where a female
settles down with a male which does not attain to the standard of
display characteristic of his race, it is conceivable she may sooner
or later seek a mate elsewhere, deserting the phlegmatic bird as if
under the impression that she had made the mistake of settling down
with one of her own sex. There is no need that the female should have
to “select” the best performer of a number of males displaying at the
same time and place as a number of rivals.
Finally, the ornamental crests and frills, and the vivid hues which
so many birds display have not arisen, as is generally supposed, as a
direct result of the selection, by the females, of the most vividly
coloured, or ornamented, from among a number of suitors presenting
varying degrees of intensity in ornamentation. Such “frills and
furbelows” are to be regarded as “expression points” of internal
variations in the germ-plasm, which have been free to develop along
their own lines because they have not proved in disharmony with the
conditions of the birds’ environment. Their development is to be
traced to the stimulating action of the “hormones” which control
both pigmentation and structure, as is shown by the fact that both
are modified by any interference with the glands in question. Such
ornamental features then are the concomitants not the results of Sexual
selection.
The development of ornament, whether of colour or structure, may be
taken then as an index of specialization, and as one of the many
manifestations of that variation which is going on in every part of
every living organism.
So long as the continued increments in the development of these
characters do not hamper their possessors in the struggle for
existence, they are free to go on developing. Sexual selection, other
things being equal, operates by according the greatest number of
descendants to the most amorous, and not necessarily to those of the
brightest hues.
[Illustration: Plate 27.
_Photos copyright, G. Herring._
SOME STRANGE ACCOMPANIMENTS OF COURTSHIP.
THE WHITE-HEADED BELL-BIRD.
This species is remarkable for the enormous, erectile wattles which
arise from the base of the beak of the male at the courting season.
THE UMBRELLA-BIRD
The crest which adorns the crown of the head has many counterparts, but
the long-feather clad wattle which depends from the fore-part of the
breast is unique.
[Face page 156.]
Plate 28.
SKULL OF THE AMERICAN WHITE BEAKED PELICAN.
The beak of this bird develops at each breeding season an irregular
horny plate which falls off at the end of this period, It is difficult
to regard this as a sexual “ornament,” yet it comes under this category.
_Photos copyright, H.G. Herring._
HEAD OF A PUFFIN, SHOWING THE MOULTING OF THE BEAK SHEATH.
At the breeding season, in both sexes, a triangular horny plate is
developed over the eye, an oblong plate below it, while the sides of
the beak become deepened by means of larger triangular horny plates.
All these embellishments are highly coloured, and they are shed at the
end of the breeding season. A further ornament is developed at the
gape, in the shape of a fleshy rosette of a bright orange colour.
Face page 156.]
But Sexual selection does not begin, and end, with the evolution of
frills and furbelows. “Behaviour” counts for more than is generally
supposed. This is as specific as “structure,” that is to say, it is
as constant for each species as is its coloration, and it is also as
variable. That Evolution may be determined by variation in behaviour,
no less than through structural variations, is a possibility which has
received but little consideration at the hands of students of Evolution.
The singular history of the Australian Bower-birds lends additional
support to this view, and at the same time provides an additional
argument against the generally accepted opinion that bright colours
have been evolved by reason of the preference shown by the females
for the most vividly coloured of their suitors. For while the males
affect all the tricks and turns which are the common accompaniment of
courtship, they, in addition, introduce very extraordinary features in
the shape of “bowers” cunningly constructed and often gaily decorated,
as will be seen presently. Eight of the total number of species of this
group exhibit this behaviour, and while they differ very conspicuously
in coloration among themselves, they agree very closely in the type
of the bower they build. If the coloration is determined by the
female, then in this they display very different standards, and if
they do select, each according to the standard of the species, then we
must suppose that they also must exercise a choice in regard to the
character of the bower, the favoured male being the best builder. But
why, in this case, is there not as much diversity in the form of the
bowers as in the coloration of the feathers? A survey of the facts will
perhaps make this point clear.
One of the best known of these bowers is that of the Satin Bower-bird
(_Ptilonorhynchus violaceus_). On either side of a platform of small
twigs a fence of similar twigs is reared, sloping inwards to form a
more or less complete tunnel. At the entrance to this is placed a
platform of sticks, which is strewn with a miscellaneous assortment of
brightly coloured feathers, bleached bones, and occasionally flowers.
The work of construction is almost entirely performed by the male: it
is indeed a little curious, having regard to the circumstances, that
the female should bear any share in its construction at all.
Really this is a more wonderful piece of architecture than would appear
from the mere description of its main features: for it represents
psychical activities which are difficult to fathom. It does not take
the place of display, but is an extension of this. During his amorous
moments the cock becomes greatly excited, chasing his mate in and out
of the bower, carrying the while, in his beak, a brightly coloured
feather or a leaf.
At the same time he sets all his feathers on end and every now and then
drops first one wing, then the other, accompanying these actions with
curious whistling notes and pretences of picking up food.
The Regent-bird (_Sericulus melinus_) differs conspicuously from the
Satin Bower-bird, for while this is of a uniform, deep, metallic
steel-blue, the Regent-bird is jet black, with a golden yellow crown
and hind-neck and a great blaze of golden yellow on the wing. Yet
the bowers of the two species—which belong to different genera—are
practically identical, save that brightly coloured berries are used
more frequently by the Regent-bird.
[Illustration: Plate 29.
Photo by W. P. Dando.
THE SATIN BOWER-BIRD AND ITS BOWER.
The “Bowers” of the “Bower-builders” are the most remarkable variants
on “Secondary Sexual Characters” yet brought to light.]
[Illustration:
Photo by L. Medland.
THE “BOWER” OF THE BOWER-BIRD.
The “Bower” must not be confused with the nest, which is placed in a
tree and bears no sort of likeness to the bower.
Face page 156.]
The Spotted Bower-birds (_Chlamydodera maculata_ and _C. nuchalis_)
are quite dull-coloured species save for a vivid semicircular crest of
pink and mauve feathers which arise from the nape of the neck. Their
bowers differ from those just described in having a longer run and for
the immense quantities of shells which are deposited at each end of the
run. Some of them are brought from long distances, as is shown by the
large number of sea shells which are to be found in the collections
made by birds living far from the sea.
By far the most remarkable of all are the bowers of Newton’s Bower-bird
(_Prionodura newtoni_) and the Gardener Bower-bird (_Amblyornis
inornata_). The first of these, a native of the Mountains of
Queensland, is somewhat strikingly coloured, at any rate so far as the
male is concerned, for he is of an oil green above and has a small
yellow crest, while his breast is of a bright yellow; the female, on
the other hand, is brown above and grey below.
The Gardener Bower-bird, on the other hand, is of a sombre olive-brown,
but the male boasts an enormous crest of a flaming orange yellow. Yet,
widely dissimilar as are these two species, in the matter of their
bowers they display much in common.
That of the Gardener Bower-bird takes the form of a hut-like structure
of twigs, arranged around a central support, commonly a very young
sapling. As a rule the thin stems of an orchid (_Dendrobium_) are used
in the construction of this curious hut, whose diameter is about three
feet. Before the entrance is a carpet of moss, which is kept clear of
leaves or debris of any sort, and on this the most vividly coloured
fruit, seed-pods, fungi, and flowers are laid, being constantly
replaced as they wither. Newton’s Bower-bird, in like manner, forms
a hut around a central column: a hut which may attain to a height of
as much as six or even eight feet, and the walls of the pyramid thus
raised are generally gaily decorated with flowers and fruit. Around
the central a number of subsidiary huts are not infrequently found,
and in and out of these the birds pursue one another in ecstasies of
excitement.
We have in these facts some extremely puzzling features, which at
present, at any rate, permit of no more than a very rough analysis.
Probably the whole of these bower-building instincts have their origin
in the habit, which the males of so many birds exhibit, of carrying
a leaf in the beak when under the excitement of love-making. This is
suggestive of nest-building, and in many species this is actually
begun before the arrival of a female in the breeding territory, while
others build what are known as “cock-nests” which are never used.
Among the Bower-birds these “cock-nests” have taken a new and more
elaborate form, and are placed on the ground instead of in the trees,
the normal site for the nest in all these birds. Furthermore, stages
in the evolution of such strange fabrications can be found. These are
furnished by the Tooth-billed Bower-bird (_Scenopaeetes dentirostris_),
the Cat-bird (_Aeluredus viridus_) and the gorgeous Lawe’s Bird of
Paradise (_Parotid lawesi_)—which is not perhaps a Bird of Paradise.
These build no bowers, but are content with clearing a patch of ground,
of about ten feet in diameter, on which to disport themselves. But
while the “displays” of these birds closely resemble one another, in
the matter of coloration and ornament they present the most striking
contrasts.
CHAPTER VIII
SOME “COLD-BLOODED” LOVERS
The Courtship of the Crocodile—Amorous Lizards—Horned Chamæleons—A
flagellating Terrapin—The Frog that would a-wooing go—Semo musical
Frogs—Some marvellous instincts in Newts.
The measure of the vitality of animals may be estimated by their
response to stimuli; and their behaviour increases in variety and
complexity as the nervous system develops. Our interpretation of
that behaviour commonly leaves out of account the character of this
responsiveness: we are apt to see proof of intelligence in acts which
should be read as instinctive. And instinct is to be regarded as a
co-ordinated response to stimulus, independent of prior experience.
The complexity of this response stands in very close relation to the
structural complexity of the organism in which it occurs, and this
because an ever-increasing number of mechanisms and actions must be
set in motion to carry out the fulfilment of any given stimulus, as
this is traced from the lower to the higher groups of animals: till at
last we have to distinguish between movements that are merely reflexes,
and those which are “instinctive.” The latter must be fulfilled by
the former—the reflex actions are the agents of the instinctive.
Indifferent performance in either, endangers the existence of the
individual, and in some directions of the race itself.
The sexual instincts, with which alone these pages are concerned, are
primarily stimulated and sustained by internal forces, generated, as we
have already seen, by the juices of certain glands whose relation to
the reproductive system has only recently been discovered. Though not
commonly realized, and though denied by some, the sexual instincts are
the dominant factors in the animal world. Even Man himself, the lord
of Creation, knowing good and evil, cannot escape their overmastering
rule. Commonly he is by no means inclined to rebel against this control
But there be some who, in their arrogance, imagine that its overthrow
is an end to be desired. Having scaled some slight intellectual
eminence they fondly imagine this feat was accomplished by virtue
of some spiritual grace of their own cultivation, and call to their
fellow-men to emulate their example. But such preceptors are labouring
under a strange delusion: they are suffering from a disease they wot
not of, a “Disharmony,” as Metschnikoff calls it, a disease which
blinds their perception of the motive power which has given them all
that they believe themselves to have created. For these same despised
instincts are the sacred fires of our being, and when they are quenched
all that makes us human, love, ambition, and life itself will be
extinguished. If the continuance of the race be a thing to be desired
it is well that the choice should not be left to us.
Truisms are sometimes trite, and while it is a truism to say that
no race can continue which does not reproduce its kind, it is more
exact to say that, other things being equal, the race depends for
its existence, primarily, on the efficient working of the sexual
instincts. In the higher animals, the phenomena which these present are
so complex that they often assume something more than a semblance of
intelligent, purposeful behaviour. It is therefore necessary, for their
right understanding, that they should be analysed in animals lower and
lower in the scale of life till at last we come to the very simplest
types of organisms wherein instinct can be said to play a part.
The lower we descend in the scale of animal life in our survey of
behaviour during the reproductive period, the more the evidence seems
to grow in favour of the interpretation of the Sexual selection theory
adopted in these pages—the view that neither the formal displays nor
the exaggerations of colour and ornament which so commonly accompany
them, are due to female choice; a choice not necessarily conscious,
but rather to be interpreted as the final abandonment to the finest
performer of a number of suitors. On the contrary, this ornamentation,
of whatever kind, is the expression of an intensification of the gland
secretions which is manifested by the process of pigment concentration
and a consequent intensification of coloration. Hand in hand with
these developments it would appear goes an exaggeration of the normal
movements which characterize the species when under the influence
of great excitement, whether of fear or pleasure. At any rate, the
displays of gaudily coloured and highly ornamental species are commonly
more striking than those of sober hue.
On this rendering, the behaviour of Reptiles, Amphibia and Fishes, is
much more readily interpreted, and this is even truer of the more lowly
groups of animals such as Spiders, Butterflies and Beetles.
Among the Reptiles, as among the birds and beasts, the desire to
obtain territory seems to be strong. But the information to be
gathered as to their behaviour in the search for mates, and after, is
exceedingly small.
Sluggish by nature, all become animated under the stimulus of
mate-hunger, and this is especially true of the males. As one
would have expected, from what has just been said, desire is most
demonstrative in brightly coloured and highly ornamented species. But
even the dullest hued and most phlegmatic display quite surprising
agility and animation under the fever of Love. Thus among the
Crocodiles fierce battles are fought by rival males for the possession
of some coveted female: and later the victor strives to dispel the
apathy of his mate by caperings most undignified in a Crocodile. He
will twist and turn, or rather twirl, round on the surface of his
chosen pool, with head and tail raised high in air, and his capacious
barrel of a body swollen out to bursting point. These antics are
performed to the accompaniment of loud bellowings and roars heard at no
other season of the year. But more than this, an appeal is made to the
nose as well as to the eyes of his apathetic mate, for during all this
parade of love he exudes from glands in the lower jaw, and tail, an
almost overpowering smell of musk. At last, however, these antics have
their reward, for sooner or later apathy awakens into interest, and
interest ends in desire.
The Crocodile is colourless, or at least is monochromatic; not so many
of the Lizards, which rival the birds in the vividness of their hues.
With the birds the colours undergo no changes save such as are due
to the incidence of light; with the Lizards, however, the bare skin
is exposed and this can, as it were, be made to blush with all the
colours of the rainbow. Having regard to what has been said already
as to the sources of this coloration it is not surprising to note
that here also the males are the more vividly coloured whenever the
sexes differ in this particular. And further, it is among the most
vividly coloured males that most animated displays take place when the
endeavour is being made to excite the amorous instincts of the females.
The males of the genus Sitana are very brightly garnished. They possess
a large throat pouch, coloured blue, black, and red when expanded, and
this occurs only during moments of excitement, whether this is due to
fear or pleasure. And at the same time the vividness of the coloration
is greatly increased. No such secondary sexual characters are present
in the female.
A variant on the throat pouch, of a much more striking character, is
displayed by the Frilled Lizard (_Chlamydosaurus kingi_), wherein
the tongue bones have become enormously elongated so as to project
backwards on each side of the body almost as far as the base of the
tail. With them they have carried a thin fold of skin, so that whenever
the mouth is opened these bones stand out at right angles to the head
and display a circular fold of skin stretched as it were on rods; or
they may be compared to the ribs of an umbrella. The great Elizabethan
frill thus formed, is displayed only during moments of great
excitement, and the open mouth, at such times, is flushed with a vivid
red, which, contrasting with the teeth, gives a very terrifying aspect
to prospective enemies, and doubtless also proves a valuable asset as a
“secondary sexual character.”
The display of a vividly coloured mouth during moments of sexual
excitement, it may be remembered, occurs in some birds. Among reptiles
it is a common feature. A good illustration of this is furnished
by the Moustached Lizard (_Phrynocephalus mystaceus_), a native of
Southern Russia. When violently excited it raises itself on its hind
legs, curls and uncurls its tail, and opens its mouth to its widest
extent, presenting, to our eyes, a quite fearsome aspect. This effect
is immensely increased by the fact that the corners of the mouth
are provided with flanges of skin, which at this time swell up into
crescentic plates, the inner borders of which pass gradually into the
rosy lining of the mouth, thereby causing it to appear much wider
than it really is. So far this display has been witnessed only when
the animal is under the influence of fear. But since we find that
birds will make similar displays, both when under the stimulus of fear
and that of sex, we may assume, with no little degree of certitude,
that the same applies in the case of the reptiles, for the origin of
the ornaments is almost certainly to be attributed to the same gland
secretions which produce the secondary sexual characters of birds and
beasts.
This, however, is no mere assumption, for we have some positive
evidence as to the association of bright coloration with “courtship,”
which has been furnished by Mr. Annandale, a naturalist of long
experience and having a first-hand acquaintance with tropical life.
He has given us a lively description of the courtship of the Malayan
Lizard (_Calotes emma_). “The males,” he says, “are very pugnacious,
and change colour as they fight. At the time of courtship a curious
performance is gone through by the male, the female remaining concealed
in the foliage hard by. He chooses some convenient station, such as a
banana-leaf, or the top of a fence, and advances slowly towards the
female. His colour is then pale yellowish flesh colour, with a
conspicuous dark spot on each of the gular pouches, which are extended
to their utmost. He stands upright, raising the fore-part of the body
as high as possible, and nodding his head up and down. As he does so
the mouth is rapidly opened and shut, but no sound is emitted. When he
is driven away, caught, or killed, the dark spot disappears entirely
from the neck.”
[Illustration: Plate 30.
Photo by W. Saville-Kent.
THE BEARDED LIZARD.
Paring moments of excitement the Bearded Lizard opens the mouth widely
displaying a vividly coloured interior.
Face page 166]
Normally sluggish, the Lizards display, it will have been remarked, a
quite surprising degree of animation when maddened by mate-hunger. Some
exhibit a considerable degree of pugnacity. In _Anolis carolinensis_,
for example, when two males meet they face one another, bob the head up
and down two or three times, expand the throat pouch, lash their tails
from side to side, and then, worked up to the requisite degree of fury,
rush at one another, rolling over and over and holding firmly with the
teeth. The conflict generally ends in one of the combatants losing his
tail, which is eaten by the victor.
The Chamæleons include among their number species which have developed
quite formidable horns, recalling those of the Rhinoceros or, better,
of the extinct Arsinoetherium, since they are placed side by side
instead of one behind the other. In Owen’s Chamæleon there are three
such horns, two on the forehead and a median horn on the snout, and
these are borne only by the males.
The marvellous play of colour which many Lizards display is commonly
attributed indifferently to “protective coloration” and to “sexual
selection.” It is unlikely that both have played equally important
parts in their development. If the case of certain of the Geckoes alone
is taken, then there would seem to be no doubt but that “Natural
Selection” was the agent which had determined their elaborations
for protective purposes, and in such and similar cases this may be
largely true. But the material which “Natural Selection” has worked
upon has been furnished by the secretions of the sexual glands to
which reference has so frequently been made already. These seem to
possess a very marked tendency to contain an excitant which promotes
the formation of intense pigmentation, or an excess of tissue which
may assume the form of weapons of offence, or of excrescences in the
form of spines, or other ornamental features. Animals in whom this
tendency to pigmentation and ornament has developed must, so to speak,
obtain a licence from “Natural Selection” if they are to retain it.
That is to say, if such ornament whenever it appears makes the wearer
conspicuous to its enemies, or hampers it in escaping therefrom, or in
fulfilling the ordinary avocations of life, then its further progress
will be inhibited, or the wearer will be exterminated. But the tendency
to produce colour, a by-product of the sexual gland secretions, may
incidentally serve to afford it a protective garb, and in this event
its further elaboration in the required direction is assured.
In certain abnormal, sexually poisoned individuals among the human race
it is well known pleasure is derived from flagellation. There is but
one instance known to me where this obtains as a normal accompaniment
of desire among the lower animals, and this occurs in one of the
Painted Terrapins (_Chrysemys picta_), whose finger-nails are produced
into long, whip-like ends. I had the good fortune to witness their use
one day when in the Reptile House at the Zoological Gardens in London.
The unusual activity of a male of this species was the first thing to
attract attention to his movements. Watched more closely, he was found
to be dodging a female and making frantic efforts to swim round so as
to oppose her path. This done, he closed up and immediately commenced
to apply the bastinado to her head. The movements were so rapid that
nothing more than a blurred image of these strange whips was visible.
As soon as she escaped his attentions, he set about circumventing her
again, and again succeeded: and this most extraordinary performance was
repeated many times during my watch.
Turning to the Amphibia, the descendants of that stock which must be
regarded as the ancestors of the Reptiles, the version of the sexual
rôle which is adopted in these pages, that “Sexual Selection” in the
older, Darwinian sense, does not exist, finds further support.
Among the tailless Batrachians—the Frogs and their kind—there is no
“display” immediately preceding the act of pairing. The males seize
upon the females and hold them in a close embrace which lasts for a
very prolonged period, covering many days or even weeks, until the
extrusion of the eggs, which he impregnates by successive emissions
of the fertilizing element. What controls the orgasm no one has yet
succeeded in discovering, but this is an important point, for it is
essential that the seminal fluid should not be emitted until the moment
the eggs are set free. The pairing act is here purely instinctive, as
is shown by the fact that if a Frog in embrace be removed and replaced
on some inanimate body, this will be treated as though it were a female.
With the tailed Batrachians—the Newts and Salamanders—the male
commonly executes a very animated display which is followed by
behaviour of a quite remarkable character. The display, which is always
associated with vivid coloration, or the development of fin-like
frills along the back, takes the form of amorous writhings and other
gesticulations. At times he will hit his mate with his snout, and
at others he will simply rub sides with her, as if to entice her
to respond to his advances. These evolutions may be followed by an
amplexus, an embrace. In some species, however, these performances are
followed by behaviour which leaves one gasping with astonishment.
To begin with, there is no act of pairing, no coitus, but the male
discharges a number of conical or bell-shaped “spermatophores,” each of
which is crowned by a bunch of spermatozoa, the male germs necessary
to ensure fertilization of the ova. These spermatophores adhere to
the bottom of the stream, and are gathered up by the female, either
directly, by placing herself in such a position that they can be seized
by the lips of the genital opening, or by seizing the spermatophore,
with its fertilizing germs, between her hind legs and pressing it
home! The more one contemplates this extraordinary proceeding the more
one marvels at the evolution of a departure from the normal sexual
relations so inconceivably strange. Here one sees the purpose of the
aphrodisiac in its true light. But for these facts it would have seemed
certain that its primary object was to enable the male to relieve
desire and at the same time to accomplish its end—the fertilization of
ova—without undue waste. And this, in all the cases so far discussed,
is possible only when the female has become inflamed with a like
desire for coitus. But here the male finds relief, without more ado,
by depositing the precious germs upon the ground. The display then is
indeed to serve as an aphrodisiac. For the continuation of the race now
rests entirely on the female. Any defect in the orderly working of her
sexual appetite means the waste of the spermatozoa and the failure to
effect fertilization. We cannot suppose that there is any realization
of these facts, or any deliberate action on her part, but rather that
she derives pleasurable feelings from the necessary passage of the
spermatophore, which, probably, she recognizes by its smell.
The statement that the Frogs and their kind dispense with a display
requires some qualification. For in the first place they, like their
tailed relatives the Newts, develop secondary sexual characters, but
these are of a quite peculiar kind. Among the Newt tribe, as has been
mentioned, these characters take the form of frills and crests and
vivid colours. They are intended to stimulate through the sense of
sight, and arouse emotion, as a city is beflagged to welcome those it
may delight to honour. The Frog tribe appeal to the musical sense, even
though that music be of a barbaric kind. But, it would seem, when once
the errant females have been drawn to the spot chosen by the males, no
further aphrodisiac is used, the male simply seizing upon the female
nearest at hand and, having once embraced her, she is not released
again until the eggs have been extruded and fertilized. To maintain
his hold, the forearm is often excessively muscular, while one or more
of the fingers may be armed with pads. In some cases, as with the
Himalayan _Rana liebigi_, the inner side of the arm and each side of
the breast are studded with small conical spines. But the absence of
ornament in these cases, as with such of the Newts where there is no
amorous display before embrace, is significant.
And now, as touching the musical performances of these troubadours.
These commence in the early spring. With many species, as with our
Common Frog (_Rana temporaria_) nothing more than loud croakings are
attained. But with others this “music” is enormously increased in
volume by resonators in the form of air-sacs or wind-bags. We may
surely, with some show of certainty, liken this “music” to the song
of birds, and assign its primary purpose to the same cause—a device
to advertise their presence to wandering females seeking mates. That
birds sing after mates have been found, and later, is no doubt due
to a general feeling of “fitness,” which finds expression in what
has become the usual mode for such emotional states. Most people
must have heard the spring concerts of our Common Frog; but these
are incomparably surpassed in volume by the Edible Frog and the Bull
Frog, which are provided with large, globular, inflatable, air-sacs in
the throat, serving as voice-resonators. Such performances, however,
are mere bawlings compared with some other species, which mew like
cats, or bark like dogs. The most famous of all is the Brazilian
“Ferreiro” or “Smith” (_Hylodes faber_), whose voice is one of the
most characteristic sounds to be heard in Tropical South America.
“Fancy,” says Dr. Gadow, “the noise of a mallet, slowly and regularly
beaten upon a copper plate, and you will have a pretty good idea of
the concert given generally by several individuals at the same time
and with slight variations of tone and intensity.” When seized, the
performer utters a “loud and shrill, most startling cry, somewhat
similar to that of a wounded cat.” Another, a Paraguayan species,
_Phryniaxus nigricans_, at the breeding season, utters a call note
which consists of two clear, musical “rings,” followed by a long
descending “trill” like that of our British Greenfinch. But, it is to
be noted, both sexes in this case perform.
The period of sexual activity with perhaps the majority of animals
is intermittent and extends over but a short period annually; with
others potency is continuous, at least with the males, though desire
becomes clamant only when aroused by external stimuli. But whenever
this condition be aroused it invariably finds expression in exaggerated
movements or vocal demonstrativeness. It uses the normal channels of
expression, in short, but intensifies them. Now this period of sexual
activity represents the maximum of “fitness” in animals, and it is not
surprising, therefore, to find that when the barometer of vitality
stands high some approach to the maximum of activity is indicated. In
many birds this is revealed in song, though the earlier stimulating
cause is absent. Among the cold-blooded frogs the same obtains. In the
Edible Frog (_Rana esculenta_), for example, the males, which “are
great musicians,” remarks Dr. Gadow, “go on singing for sheer enjoyment
not only during the pairing time, but throughout the months of June and
July. Warm, moonlight nights are the favourite times for the concert,
which takes place in the water, beginning at sunset and continuing till
early dawn. A few individuals utter a single note, ‘gwarr-oo-arr’ or
‘coarx’ but these are only preliminaries. The precentor ... begins with
a sharp-sounding ‘brekeke’ and this is the signal for all the others
to chime in with the same note, varied with all sorts of other sounds,
bass, tenor and alto, each performer filling its resounding vocal sacs
to bursting size, and these bags then look as if they acted as floats.
When there are several hundred of these sociable creatures the din is
continuous, and may be heard more than a mile off.”
From what has been said of the Amphibia, and especially of the
Newts, it would seem that, among the land vertebrates at any rate,
the sexual instincts in this lowest or simplest form are satisfied
with the discharge of the germinal products. Many, however, have
advanced a stage further and reveal the rudiments of that instinctive
care for offspring which develops to higher and higher grades as we
ascend in the animal kingdom, till at last, in the human race, where
the offspring is desired for its own sake, we ascend to the highest
plane of all. The varied means of expression which these rudimentary
instincts take in the Amphibia have already been discussed in “The
Infancy of Animals,” which preceded this present volume, and hence no
more need be said on this head in these pages.
CHAPTER IX
LOVE-MAKING AMONG FISHES
Germinal Variations—Fishes and mate—hunting—Some remarkable Sexual
differences displayed by the Teeth of Rays—The Double-eyed Fish—The
Coloration of the Dragonet—Some curious facts about Salmon—The strange
use of the kidneys in the Stickle-back—The Stickle-back and parental
duties—Siamese Fighting-fish.
Mammals, Birds, Reptiles and Amphibia, as has already been shown,
all exhibit practically the same line of conduct in regard to their
mate-hunting instincts; all use like modes of expression. And this is a
very significant fact. It becomes more so when we turn to the fishes,
for here again we meet with the same behaviour, and here again we meet
with the same rules in “secondary sexual characters.”
An instance or two of the latter distinction between the sexes should
suffice. As a rule, among fishes, the males are smaller than the
females: commonly there is no other external distinguishing feature
between them. In many cases, however, the males are more or less
strikingly different, thereby showing a departure in the nature of a
higher degree of complexity, or “specialization,” just as obtains among
the birds. And the same sequence to this also obtains. That is to
say, as has already been remarked in the case of the Mammals and the
Birds, the new features first appear in the males, leaving the females
and young of both sexes unmodified. A singular illustration of this is
afforded by some of the Rays, or Skates, as they are often called. In
the Thorn-backed Ray (_Raia clavata_) the teeth of the adult male are
sharp-pointed and directed backwards, while those of the female are
broad and flat, forming a sort of mosaic or pavement. The young male
agrees with the female in this respect. In the Common Blue Skate (_Raia
batis_) the teeth are pointed in both sexes, though more so in the
adult male. In the Spotted Skate (_Raia maculata_) the teeth are fully
pointed in both sexes. Here, then, the normal course in the evolution
of new characters is followed, but it is remarkable that the teeth,
which are so intimately related to the capture of food, should be thus
affected. Whether the change of teeth is associated with a change of
food, or whether neither pointed nor pavement teeth affect the feeding,
is unknown.
Still more remarkable is the case of the Double-eyed Fish (_Anableps_).
In this fish there is an intromittent organ in the shape of a tube
which is formed by a continuation of the urinogenital ducts down the
front of the anal fin. In the hinder half of this organ a bend is made
either to the right or left. Out of seventeen males, this bend was to
the right in eleven, to the left in six. Further, there is a small
fleshy tubercle at the side of the anal fin-ray, at the middle of its
length. When this prominence is on the left side, the organ bends to
the right; when it is on the right, the bend is to the left. In the
females the genital opening is covered by a special scale, which is
free on one side, left or right, and not on the other. Thus copulation
is possible only from the side, and a left-sided male can only
conjugate with a right-sided female, and vice versa. Here is one of the
most extraordinary cases of specialized secondary sexual characters
known. How do the sexes distinguish their complemental mates? It is
important that they should, for unions are otherwise impossible.
In the Dragonet (_Callionymus lyra_) the male differs conspicuously
from the female in being much the larger—an exception to the rule—and
in having the fin-rays enormously elongated. Further he wears a
conspicuously resplendent livery, but this is strictly a “nuptial”
livery, the colours waning as soon as the period of sexual activity is
past. That these colours play the same part as with the birds is clear
from the observations of the late Saville Kent. “The male,” he says,
“resplendent in his bridal livery, swims leisurely round the female,
who is reclining quietly on the sand, his opercula distended, his
glittering dorsal fins erect and his every effort being concentrated
upon the endeavour to attract the attention of his mate.... The
female, at first indifferent, becomes at length evidently dazzled by
his resplendent attire and the persistency of his wooing. She rises
to meet him, the pair so—far as is practicable with fishes—rush into
each other’s arms, and with their ventral areas closely applied, ascend
perpendicularly towards the surface of the water.” In the course of
this ascent the ova and sperms are shed, and fertilization takes place.
The difficulties in the way of the study of the behaviour of fishes
during the critical period of mate-hunting are many and obvious.
Something may be inferred from the nature of the secondary sexual
characters which they exhibit, and more definite information can be
obtained from such species as can be kept in aquariums. From these
two sources enough has been gleaned to show that these cold-blooded
creatures, in many cases, exhibit the same emotions and the same means
for their fulfilment as the higher vertebrates. And it is significant
that wherever anything approaching what may be called “Courtship”
obtains, the males commonly exhibit secondary sexual characters,
whether in the form of ornament or of armature; while among species
which consort in shoals during the breeding season no such distinctions
are present. The ova and milt are shed and fertilization takes place as
they escape.
Comment is frequently made in works on Natural History on the fact that
among fishes the males are commonly smaller, often conspicuously so,
than the females. Among mammals the males are the larger; but among
birds this is by no means always the case. It is somewhat surprising to
find this discrepancy among the birds of prey, where, as in the case
of the Sparrow-hawk, the male is little more than half the size of his
mate; commonly, however, there is little or no difference. Among the
fishes the differences are often much more marked, as for example in
the Conger-eel, wherein the male never exceeds a length of two feet
six inches or a weight of one pound; females, on the other hand, may
exceed eight feet in length and attain a weight of one hundred and
twenty-eight pounds, though such giantesses are rare, but specimens
of fifty pounds and upwards are frequently met with. The explanation
of this may lie in the fact that among fishes it is no uncommon thing
to and males becoming sexually mature long before they have attained
their full stature. With the Salmon, for instance, ripe spermatozoa
have been found in individuals of not more than a few inches in length,
and in this species also the male is the smaller. Ova take longer
to attain maturity, for in addition to the germ-plasm they must be
provided with a more or less extensive amount of food-material in the
shape of yolk. The formation of this is inhibited until the demands
on the system for the building up of the body have begun at least to
lessen.
Mate-hunger among the fishes seems generally to find peaceable modes
of expression, either in “display” or in consorting in vast shoals,
though, so far, the factors which govern their conduct in this matter
are as yet unknown. But here, as with the higher vertebrates, there
are some species which adopt more violent methods. A good illustration
of such conduct is furnished by the Salmon, which, during the period
of sexual activity, develops a curious modification of the lower jaw,
which is produced forwards and upwards to form a hook-shaped projection
of fibrous tissue. When the mouth is closed this hook is received
into a cavity formed within the fore-part of the roof of the mouth.
It has been described as a weapon of offence. But this it can hardly
be. On the other hand it has been suggested that it serves to protect
the jaws when charging a rival, for the shock on such occasions is
considerable. It answers, in short, like to the fibrous mass of tissue
which protects the fore-part of the head in Whales like the Black Whale
(_Globicephalus_) and the Bottle-nose Whale (_Hyperoodon_), serving as
a battering-ram. In the Pacific Salmon (_Onchorhynchus_) both jaws are
hooked, so that when the mouth is closed the hooks cross one another
as in the beak of the Crossbill. In this Salmon, too, the front
teeth attain a considerable length, while the body becomes laterally
compressed and a hump forms at the shoulders. Little, however, seems to
be known as to the nature of their battles.
The combats of the Salmon of our own islands, however, are evidently
severe, and this has long been known, for Darwin speaks of as many
as three hundred, all with one exception males, being found dead in
the Tyne during the month of June, killed by fighting. Such battles
are fought, it is to be noticed, not so much for the possession of
females—for it is a polygamous fish—as for the privilege of fertilizing
the eggs as they are shed. The absence of a “display” here is a
noticeable feature, and it is on this account, probably, that the
reproductive period is not associated with the appearance of any form
of resplendent livery. On the contrary, the marvellous silvery sheen
which adorned both sexes on their arrival at the spawning ground from
the sea has entirely vanished by the time that the consummation of the
journey has been attained, and in its place is naught but a slimy,
dingy copper-coloured hue. But no sooner has the reproductive period
passed than the silver lustre makes its appearance once more.
These facts are the more interesting when contrasted with what obtains
among other fighting species which must woo the females. Take the
case of the common freshwater Stickle-back. In this species the body
is invested with an armature of bony plates and spines in place of
scales, while the males are arrayed in vivid hues of red and blue. Any
survey, however, of the reproductive activities of this little fish
must take into account certain quite remarkable prenuptial actions
and instincts. Briefly, before the male commences his search for a
mate he constructs a nest of fine fragments of aquatic weeds, which
are held together, not by interweaving as with birds’ nests, but by
a sticky and copious secretion from the kidneys. According to some
authorities, this secretion is to be regarded as a pathological product
caused by the undue pressure of the ripening testes. It is difficult
to accept this interpretation, for it might with as much reason be
argued that the copious secretions of the salivary glands of the edible
Swift—which builds a nest constructed entirely of hardened saliva—are
also pathological in character. But be this as it may, the nest
completed, the male seeks a mate, or mates, for polygamy is the rule of
his tribe. In his search for these he has constantly to do battle with
other males, whom he endeavours to disembowl by swift rushes contrived
to t rip open his rival as he passes, by means of one or other of
the erectile spines which project from his back and belly. With the
females whom he desires he uses the arts of peaceful persuasion,
swimming backwards and forwards before her in his endeavour to excite
her amorous instincts. At last he persuades her to enter his bower and
deposit a few eggs, fertilizing them immediately they are laid. The
first to enter leaves by forcing a passage through the opposite wall
of the nest, a happy contrivance, for thereby a current of water can
be constantly driven through, leaving fresh oxygen to the developing
eggs. One female after another is inveigled into the bower, until the
complement of eggs is complete. These, singularly enough, are now taken
charge of by the male. He it is who creates life-sustaining currents
which bathe the eggs, by the rapid vibrations of his breast-fins, and
he it is who protects them from their most persistent enemies—the
females who laid them. As soon as the fry appear the duties of the male
are still further increased. He must guard them from their mothers,
and other foes, and he must prevent their too extensive wanderings.
Such as stray too far afield are sucked into the mouth and brought
back again to the nursery, where they are set at liberty by a reversal
of the sucking action. That the male of a polygamous species, and
with all the attributes of a polygamous species—pugnacity and vivid
coloration—should take upon himself the duties which under like
circumstances among the higher vertebrates are undertaken by the female
is a very remarkable and puzzling feature. In this species, in short
the male plays successively a polygamous and a polyandrous rôle.
Strange as these facts are, they are not apparently without parallel
among fishes, for certain of the labyrinth-gilled fish present many
features in common, though as yet proof seems to be wanting. Thus
the small Siamese “Fighting Fish” (_Betta pugnax_) is endowed with
so ferocious a nature that it is kept, as the Malays keep fighting
cocks, for the amusement of native sportsmen, two fish being pitted
against one another and large bets being made on the result. In a
state of quiescence it presents no very remarkable coloration, but if
two be brought together, or if one sees its image in a looking-glass,
it becomes thrown into a paroxysm of rage, the fins are raised and
the whole body becomes irradiated with metallic colours of dazzling
beauty. There can be no doubt but that a like play of colour occurs
during moments of sexual excitement; it is highly probable that it is
polygamous. Of its breeding habits, however, little or nothing seems to
be known. Not so, however, in the case of a closely-related species,
less pugnacious in disposition, but almost as vividly coloured, in so
far as the male is concerned. Now in this species a nest of froth is
made and the eggs, after deposition therein, are jealously guarded by
the male. Hence, on these facts, we may assume with a fair amount of
certainty that the closely-related “Fighting Fish” displays like habits.
That the Reptiles, Amphibia and Fishes have much in common with one
another, and with the higher vertebrates, in the manner of their
love-making is indisputable. We find no evidence anywhere that the
first faint throbbings of the sexual pulse in the female are quickened
to fever beats after the efforts of several successive wooers, each
more demonstrative than the last, to arouse this state—the conditions
required by the Sexual Selection theory. But successful mating depends,
in each year, on the sexual fitness of the male himself, and the mate,
or mates, which for that year he has taken “for better or worse.” It
is possible, of course, that a male, ambitious but impotent, will
be forsaken by his mate; it is possible that a female of low sexual
vitality may fail to respond to the most impassioned displays; in
either case no offspring result, and thus the failures are eliminated.
It is possible that here, as with the higher vertebrates, coition
may by no means always be immediately preceded by display. But the
“display” has done its work. It has stimulated the sexual appetite, as
the sight of tempting food stimulated the bodily appetite.
But both the Amphibia and the Fishes reveal a lower plane of the sexual
instincts, when the sexes, dominated by some imperious instinct,
gather in hordes, commingling to shed their precious germs into the
surrounding water, there to effect the work of fertilization and the
achievement of new birth. The all-important union of these germs is
no mere work of chance, as it might seem, but the sperms seek the ova
with unerring surety, guided, in this case, by that very efficient
substitute for instinct, chemotaxis, or the attraction which certain
chemical substances have for lowly organized living bodies. In
this case the allurement is furnished by the ova. It is surely no
unreasonable surmise that here we have the beginnings of the complex
phenomena which the earlier chapters have revealed. On this lower plane
we are probably confronted by instinct alone, but from this level
upwards intelligence plays an increasingly important part.
CHAPTER X
SOME OF THE “LOWER ORDERS”
Butterflies and Moths, and the Coloration of their Wings—Female
Choice and “Fine Feathers”—When Male Butterflies are Dominant—Sexual
Selection among Butterflies—Abortive Experiments—Wallace and the Sexual
Selection Theory—The Sense of Smell in Butterflies and Moths—Fragrant
Butterflies—Wingless Moths and their Lures to Lovers—Methods of Pairing
among Butterflies and Moths—More Experiments.
Not the least impressive feature met with in the study of animal
behaviour under the spell of the Sexual Instincts is its uniformity.
This fact becomes the more apparent as one turns to the lower grades
of life. Whether one starts with the vertebrates and works downwards,
or vice versa, the same problems arise and the same interpretation is
demanded. That is to say, the theory of “Sexual Selection” leads one to
the same conclusions whether it be tested by the evidence afforded by
the Butterflies and Moths, or that furnished by Birds or Mammals.
The accessory phenomena, the vehicles which give expression to these
internal fires, are in like manner curiously similar. These “vehicles”
are the “secondary sexual characters”—colour, and armature, and scent.
These very tangible signs are the phenomena in the Mystery Play of Sex
which first catch the attention of the investigator. To account for
these the theory of “Sexual Selection” was first devised.
After the birds, probably the group most conspicuous for its splendour
is that which contains the Scale-winged Insects or Lepidoptera, and it
has always been allowed that any explanation of the one must apply also
to the other. It seems impossible to avoid this conclusion. But before
going further it would be well to take note of one or two interesting
features in regard to coloration that have so far not been touched upon
in these pages.
The Coloration of Animals is generally regarded as a by no means
fortuitous feature, but one, on the contrary, controlled and
determined by various factors. Hence are recognized various kinds
of coloration: Obliterative or Protective-resemblance Coloration;
Warning Coloration; Mimetic Coloration; and Epigamic Coloration, or
the colours associated with courtship. These various types have been
subdivided and accorded technical labels by Professor E. B. Poulton,
in his “Colours of Animals,” but these need not be enlarged upon
here. Suffice it to say that it is generally held that all forms of
coloration can be explained, and all can be labelled, as to their
origin, with more or less certainty. There are those who doubt the
warranty for this classification. Commonly, it must be admitted, the
arguments of these sceptics are not impressive; they are sometimes even
stupid. That such coloration, however it be labelled, is subjected to
some control seems to be shown in the case of the Lepidoptera, for,
generally, in the Butterflies, the upper surface of the wings is much
more vividly coloured than the under surface, and this, apparently,
because when the creature is at rest the wings are brought up over
the back like the leaves of a book, so that the brightly-tinted, and
therefore conspicuous, area is concealed, as, for example, in the “Red
Admiral.” With the Moths the wings, while the creature is at rest, are
held horizontally, and it is the upper instead of the under surface
which is exposed, but the hind-wing is covered by the fore-wing. The
coloration is here very different; for while the exposed surfaces
of the fore-wings are commonly soberly tinted, the hind-wings may
be quite glaringly coloured. These bright colours are exposed only
during flight, or during moments of unusual excitement, as in the
case of the Eyed Hawk-moth. According to Weismann, this insect when
alarmed raises the fore-wings so as to expose the “eye-spots “on the
hind-wings, which, with the increased area of the wings, impart a
terrifying appearance to the body to would-be assailants. This is
as it may be, but for the moment the feature to be insisted upon is
that the bright colours are almost invariably hidden when the insect
is at rest, and by quite different means, determined, apparently, by
the different carriage of the wings. Now, according to some, bright
colours are begotten by strong light, but in the Moth and Butterfly the
surface area of the wing which is most exposed is the surface turned
to the light during rest, and this is the least coloured. The curious
relation between this coloration and the resting position is strikingly
illustrated by the case of one of the “small Blues” (_Lyccenæ_), cited
by Weismann. Herein the male, which has the upper surface of the wings
of a bright blue, rests in the position common to Butterflies—with the
wings raised and concealing the bright colour—while the female, which
has the upper surface of a dull brown, rests with the wings expanded.
As, however, the concealed under surface is not brightly coloured, it
is difficult to believe that these different postures and conspicuously
different colours can have been brought into existence solely by the
action of Natural Selection, which, it is generally contended, has
brought about the extinction of those individuals which neglected,
when resting, and therefore liable to be “caught napping,” to conceal
their arresting colours. There is, indeed, no apparent reason why the
female, which has nothing to conceal, should depart from the custom
common to Butterflies, of resting with the wings closed and raised,
this position effectively protecting the male. The facts seem to show
that the coloration of the exposed surfaces of the wings is determined
primarily by some physiological factor rather than by the incidence
of Natural Selection directly through external agencies. Thus, for
example, the action of light on the surface of the wings when in the
resting posture may well inhibit the production of vivid pigment owing
to some inherent physiological idiosyncrasy. But any individuals which
lack this inhibiting factor—as some species which, though resting, are
brightly coloured, appear to do—will be eliminated, if they live in an
environment harbouring eliminating factors, which the exceptions to the
rule we must suppose do not. But on this interpretation the fundamental
factor in the determination of the coloration is the action of light.
Selection imposes a bar only to certain types of coloration.
Some Butterflies and Moths, it has just been hinted, when resting
exhibit bright colours. Our “Swallow-tail” the under surface of the
wings is as brightly tinted as the upper. Among the Moths may be cited
many of the gorgeous Atlas Moths, the Hawk Moths, the beautiful Indian
_Dysphania militaris_—wherein the whole of the exposed surface is of a
beautiful and vivid violet and yellow—and the tropical members of the
Burnet Moths, belonging to the family Syntomidæ. In all these cases it
is not the under but the upper surface of the fore-wings which has thus
departed from the usual rule of the tribe. Not the least remarkable
feature of these insects is the fact that while the Atlas
and Hawk Moths are crepuscular in habits, the Dysphanias and Syntomids
and Burnet Moths are diurnal, and revel in the sunlight.
To revert for a moment to the factors to which these and other bright
and often conspicuous hues are due. That all highly-coloured animals
are descendants of dull-coloured ancestors there can be no room for
doubt. The vivid tints they now display are to be regarded as due to
some change in the metabolism, some clarifying process of the organism
whereby the various pigments became segregated, concentrated and
intensified. But many of the most vivid hues are not due to pigment at
all, but to changes in the surface structure of the coloured areas.
Such are the wonderful metallic colours which all kinds of animals
display. The iridescence is due to the breaking up of the light by
reflection from finely-grooved surfaces.
Whatever their nature, one still asks what is their origin, what
brought them into being. They cannot be regarded simply as adaptations
which have arisen to meet the demands of the environment, as are the
structural peculiarities of the skeleton for example; for in this
case both sexes, and all stages of growth, should display the same
hues, and this is rarely the case. Furthermore, we should not in this
case be left with a vast assemblage of forms which certainly cannot
be “pigeon-holed” as to the nature of their coloration. Such, for
example, as the marine types of birds.
The metallic and iridescent tints to which reference has just been
made, occur among animals to which they can be of but doubtful value,
as in the Golden Mole, for example, or the inside of the Oyster shell.
Their existence in such places well illustrates what we may call the
fortuitous, or apparently fortuitous, beginning of colour of whatever
kind, regarded from an analytical point of view. That is to say, we
are not concerned with the fact that animals are coloured—that is
inseparable from their existence; but with why this coloration should,
in some cases, assume so conspicuous a brilliancy and vividness—a
coloration varying in its character with every species, but apparently
unchanging among the individuals of that species.
No answer to this, likely to find general acceptance, seems to be
forthcoming at present. But it is significant to remark that all
coloration of the kind now under consideration has its origin, as
have most other structural characters, in the male. It is as true of
coloration as of, say, skeletal characters. One turns to the male
for what is new in the history of a species, to the female and young
for indications of past history. It is equally true that in their
coloration one finds the same sequence of development—the male first,
then the female, then the young, till both sexes, and all stages, are
once more alike in hue. And this rule seems to apply to coloration of
all kinds—Protective—Warning—Epigamic.
The tendency to develop brilliant colours is associated with some
physiological diathesis with which we are not yet acquainted. But
once having started, this tendency gathers force with each succeeding
generation and continues to exhibit an almost kaleidoscopic capacity
for change, unless, and until, checked by Natural Selection, whereby
its further progress in any given direction may be barred, or some
other element or aspect of the coloration may be introduced.
Given this controlling factor, all the various types of coloration
would seem to be interpretable. By almost common consent, however,
the resplendent coloration of the males among many species of birds,
a coloration often apparent only during the reproductive period, and
the more conspicuous ornamentation of the males of many other groups,
higher and lower in the scale of organization, are supposed to be
governed by an entirely different factor—female choice, or preference.
The exercise of this, it is contended, has gone on for countless
generations, and the tendency has ever been to heighten the intensity
of the ornament by the rejection of the less favoured suitors in favour
of their more resplendent rivals. Birds and Butterflies alike are
supposed to be swayed by the same irresistible desire to mate, and mate
only with what we may call the smartest and best—groomed of their many
suitors; and these, of course, being the most vigorous, most virile,
sustain the stamina of the race and so attain Nature’s end.
So long as attention was focused alone, or mainly, on birds conspicuous
for the highly ornamental character of their plumage, this theory
seemed reasonable and probable enough, for one may admit in their
courtships an element, at least, of intelligence and keenness of
perception. But it has now been abundantly demonstrated that the
animated displays so characteristic of these gaily-bedecked gallants,
are enacted with no less persistence and vim by species which exhibit
a Quaker-like soberness of dress. Thus, then, the champions of the
Sexual Selection theory have been dazzled by the tinsel, and have
missed the essential elements—the physical and psychological side of
the display—the contortions, prancings, and so on, and they have missed
the even more important element, the preliminary struggle for territory.
In this new light, the gaily-bedizened individuals of the Insect world
may be surveyed afresh. The explanation of such of their features as
are commonly attributed to Sexual Selection in terms of female choice,
whereby only the most favoured from among a crowd of suitors could
hope to succeed, may now be replaced by that which obtains also in
the case of the higher animals. It seems to fit the facts better. One
cannot understand, for example, how, on the interpretation of Sexual
Selection, the extraordinary disparity in numbers between the sexes
of some species of Butterflies came about. Thus in that marvellously
beautiful genus Ornithoptera there is one species (_O. brookiana_) in
which the females are excessively rare; so much so that the collector
Kunstler could only obtain fifteen females to one thousand males.
Though the males, among the Butterflies, are commonly much more
numerous than the females, the disparity is rarely so great as with
this species; but there are many in which the proportion of males to
females is as fifty to one. As with the higher vertebrates selection
affords no explanation of this curious disproportion. Though according
to Weismann it fulfills “the first postulate in ‘Sexual Selection’
namely, that there be an unequal number of individuals in the two
sexes.” But Sexual Selection here has a little over-reached itself,
for surely one hundred suitors seems an embarrassing number for an
inexperienced female to have to choose from! To say nothing of the
ninety-nine males doomed to perish without leaving offspring.
That the beauty of colour and form which the Lepidoptera, and
especially the diurnal Lepidoptera, or Butterflies, exhibit is due to
the choice by the females—albeit an unconscious choice—of the most
resplendent of her suitors, that is, in other words, that she yields at
last to the most ravishing member of the crowd—there is no evidence to
show. There would seem to be no possibility of a differential selection
from among a number of males, for there is no “display” comparable to
that, say, of birds. And what is more, it is unlikely that, if there
were, she would find anything to choose between them, for the range
of variation in, say, one hundred males of any given species is very
slight. Finally we have no trustworthy evidence to show that the eyes
of Butterflies and Moths are sufficiently good to enable them to make
nice distinctions between slightly different males. We have no evidence
that the eyes of Insects are capable of discriminating the details of
the often intricate patterns which their own wings, and those of their
suitors, exhibit.
In the matter of “Secondary Sexual Characters,” indeed, the Lepidoptera
exhibit very little difference between the sexes. As a rule the females
are larger, often strikingly so, but in the matter of coloration they
show far less disparity. But there are exceptions to every rule. A
striking illustration of this is afforded by the genus Ornithoptera.
The butterflies of this superb group are of huge size, and the females
are larger than their consorts, and commonly are extremely different
therefrom both in coloration and habits. In _Ornithoptera paradisea_
this disparity attains its maximum. The female, remarks Mr. David
Sharp, “is a large, sombre creature of black, white and grey colours,
but the male is brilliant with gold and green, and is made additionally
remarkable by a long tail of unusual form on each wing.” But a glance
at the two sexes will show that the female, though less gorgeously
arrayed, still disports a livery which is of a highly specialized
or elaborated character. How are we to account for her differences
in shape, size and coloration on the older interpretation of Sexual
Selection? The perceptual powers, the mentality, of a Butterfly are
surely of a far lower grade than those of a bird, or even a fish. Here,
therefore, we cannot attribute the same possibilities of response to
form and colour which we can ascribe with tolerable safety to the
vertebrates. Yet the Sexual Selection theory as generally understood
demands this.
So far so good. And now as to the part played by Sexual Selection among
the Lepidoptera. Darwin, in formulating this, found its application
to the Lepidoptera a very disconcerting problem, being naturally
disposed to regard the extraordinary wealth of colour which these
insects exhibit as the outcome of a process of female selection, in
every way comparable to that which he held to obtain among the birds.
He did not postulate a conscious, deliberate, selection; but a final
abandonment on the part of the female to the male which, by his beauty
and demonstrativeness, pleased her most. He assumed that at this
critical time she would always be surrounded by rival suitors, offering
varying if slight degrees of difference: and, indeed, in many cases she
is thus surrounded. He remarks, in discussing the case of Butterflies:
“The males sometimes fight together in rivalry, and many may be seen
pursuing or crowding round the same female.” But in the case of the
Silk-moths—and here is another illustration of the merciless criticism
to which he submitted his own theories—he remarks: “The females appear
not to evince the least choice in regard to their partners.” This fact,
which is certainly true in the case of both Butterflies and Moths, and
these gorgeous hues, disconcerted him, as is shown in the passage:
“Unless the female prefer one male to another, the pairing must be left
to mere chance, and this does not appear probable.”
The facts which have come to light in regard to the “Courtship” of
Butterflies since Darwin wrote are meagre enough, but such as have been
recorded give no support to the supposition that the females are really
influenced by, or even perceive the colours of, their mates. Just on
five-and-twenty years ago the naturalist Skertchly published some
observations on the Courtship of that magnificent Bornean Butterfly
_Ornithoptera brookiana_. He one day came on a male sipping honey from
the flowers of a tree, vibrating its wings with the rapidity of a
Hawk-moth, and the vivid green of the wings flashing in the sunlight,
though the crimson areas thereof were invisible. The female came “and
did all the wooing.” They circled about in flight with the female
above and somewhat behind, so that she could see, we are told, the
emerald markings; but there was no real evidence here that she was
really influenced by his coloration, and if this really were the case
then the coloration of the female equally demands an explanation,
for this, though less gorgeous than that of the male, is far from a
primitive type; on the contrary, it is of a highly differentiated
character. Furthermore, in this genus, as has already been remarked,
the males outnumber the females by, roughly, one hundred to one. Again,
Moseley, the naturalist on the Memorable Voyage of the Challenger in
1872, when in the Aru Islands, was once “lucky enough to find a flock
of about a dozen males fluttering round and mobbing a single female.
They were then hovering slowly, quite close to the ground, and were
easily caught.” But he was by no means convinced that any choice was
exerted. And he suggests “a series of experiments, in which, in the
case of highly-coloured and decorated Butterflies, the colours should
be rubbed off the wings of a few among a number of males, or painted
over of a black or brown colour. It might be tested whether the females
would always prefer the highly-coloured ones.” Such experiments are
foredoomed to failure, for the removal of the scales would remove the
only source of communication between the sexes.
Wallace, always a strenuous opponent of the Sexual Selection theory,
found in the behaviour of Butterflies and Moths when mate-hunting a
particularly powerful countervailing weapon. He assumes that Darwin
postulated a conscious selection on the part of the female, and with
some show of reason, though it is probable that Wallace was mistaken
in this. “The weakness of the evidence for conscious selection among
these insects,” he remarks, “is so palpable, that Mr. Darwin is obliged
to supplement it by the singularly inconclusive argument, ‘Unless
the female prefer one male to another the pairing must be left to
mere chance, and this does not appear probable’ But he has just said,
‘The males sometimes fight together in rivalry, and many may be seen
pursuing or crowding round the same female’ While in the case of the
Silk-moths—‘the females appear not to evince the least choice in
regard to their partners.’ Surely the plain inference from all this
is, that the males fight and struggle for the almost passive female,
and that the most vigorous and energetic, the strongest-winged or the
most persevering wins her. How can there be chance in this? Natural
Selection would here act, as in birds, in perpetuating the strongest
and most vigorous males; and as these would usually be the more highly
coloured of their race, the same results would be produced as regards
the intensification and variation of colour in the one case as the
other.”
Commenting on Darwin’s interpretation of those cases wherein the
females are more brilliantly coloured than the males, he insists that
on his (Darwin’s) theory “throughout the whole animal kingdom the males
are usually so ardent that they will accept any female, while the
females are coy, and choose the handsomest males, whence it is believed
the general brilliancy of males as compared with females has arisen.”
“Mr. Darwin admits,” he continues, “that these bright colours have
been acquired for protection [because they resemble those of species
which from their disagreeable taste are avoided by birds and other
insect-eating enemies]; but as there is no apparent cause for the
strict limitation of the colour to the female, he believes that it
has been kept down in the male by its being unattractive to her. This
appears to me to be a supposition opposed to the whole theory of
Sexual Selection itself. For this theory is, that minute variations
of colour in the male are attractive to the female, have always been
selected, and that thus the brilliant male colours have been produced.
But in this case he thinks that the female Butterfly had a constant
aversion to every trace of colour, even when we must suppose it was
constantly recurring during the successive variations which resulted
in such a marvellous change in herself. But the case admits of a
much more simple interpretation. For if we consider the fact that
the females frequent the forests where the Heliconidæ abound [the
distasteful species already referred to] while the males fly much in
the open and assemble in great numbers with other white and yellow
Butterflies on the banks of rivers, may it not be possible that the
appearance of orange-stripes or patches would be as injurious to the
male as it was useful to the female, by making him a more easy mark
for insectivorous birds among his white companions? This seems a more
probable supposition than the altogether hypothetical choice of the
female, sometimes exercised in favour of, and sometimes against, every
new variety of colour in her partner.”
Wallace’s arguments are not so crushing as he supposed them to be,
and they contribute nothing towards the solution of the problem to be
faced. But if colour played the part which Darwin believed, and colour
alone be concerned, it is curious that the males should recognize
their mates in a guise so unlike their own. How is it that they do not
pass them by as members of the totally different distasteful species?
Whenever, indeed, the female is more or less brightly liveried than
the male, how do the sexes recognize one another, and how, when they
live in environments so different as those referred to by Wallace,
do they find one another when possessed by the insistent demands of
the “sex-hunger” which is the all-essential stimulant to secure the
continuation of the race?
The factors which assure the satisfaction of this hunger differ in
some important features from those which obtain among the higher
animals—birds, for example. In the first place there is no necessity to
find and hold territory, which is an imperative necessity where there
are eggs to be brooded and young to be fed. In the second, the males,
as has just been remarked, must search for the females, often indeed,
in the case of many Moths, because they are wingless.
This search is conducted by the sense of smell. This fact, familiar
enough to-day to the entomologist and the student of Evolution,
was unknown to the earlier naturalists. Neither Darwin nor Wallace
suspected it. It would have been wonderful if they had, for there is
nothing in the general appearance of these insects which suggests an
organ of smell, nor is there anything in the structure of the nervous
system which would indicate this subtle sense. During recent years,
however, the number of workers engaged on the investigation of the
senses of animals has increased immensely, and great strides have been
made in perfecting instruments of research. To the efforts of these
workers we owe the discovery of the seat of the scent-detecting organs
and the source of the scent. The former are furnished by the antennæ,
which lodge also the senses of taste and touch.
Among the Lepidoptera these constitute important secondary sexual
characters, the antennæ, among the Moths at any rate, presenting
striking differences in male and female. The scent-producing organs
are very elusive structures, and so far have been definitely traced,
among Butterflies, only in the males, where they are formed by certain
peculiarly modified scales known as “androconia.” They may be either
irregularly scattered over the wing, or may form complex structures.
Sometimes they are arranged in the form of brightly-coloured,
bristle-like tufts on the hind-wings, sometimes in a fringe along the
edge of the hind-wing. In some of the Moths they are arranged to form
a thick, glistening white felt, which fills a folded-over portion
of the edge of the hind-wing, and in many cases “the perfume can be
retained,” Weismann remarks, “and then, by a sudden turning out of the
wing-fold, be allowed to stream forth.” In the Ghost-moth (_Hepialus
humuli_), the hind-legs of the male have become pressed into service
and have become transformed into scent-bottles, since they are swollen
and filled with glands for the manufacture of odorous matter.
The naturalist Fritz Müller discovered the fact that some of the
Butterflies which haunted his Brazilian garden exhaled a flower-like
fragrance. Anyone can test this curious trait for himself who will take
the trouble to brush his finger over the wing of a newly-caught male
Garden-White Butterfly (_Pieris napi_). The white powder which will
adhere to the finger will be found to be made up of the wing-scales,
which will exhale a delicate perfume of lemon or balsam! Among the
Moths the strong odour of musk is exhaled by the Convolvulus Hawk-moth
(_Sphinx convolvuli_).
It is, however, only in the males that these odours can be detected,
and, though palpable enough to human nostrils, their power of
diffusion is apparently extremely limited. They would seem to serve as
aphrodisiacs for the stimulation of the female, and, as a consequence,
there is no need that they should start into activity until the male
has arrived at the immediate neighbourhood of his prospective mate.
[Illustration: Plate 31.
BRIGHT COLOURS WHICH CANNOT UK ATTRIBUTED TO “SEXUAL SELECTION.”
1. Eyed Hawk-moth, under the influence of excitement.
2, A Butterfly, Zeuxidia horsfieldi, Feld, showing tufts of
scent-diffusing scales on the hind-wings.
Face page 200.]
With the females of the Moths, however, matters are otherwise. For the
most part Moths are nocturnal, and hence could not distinguish one
another when on the search for mates, and in many species the females
are wingless, and consequently are unable to move from the immediate
neighbourhood in which they emerged from the pupal stage. In either
case some means of informing the males of the presence of females is
an imperative necessity for the continuation of the race. This is
provided by means of a subtle odour exhaled by the females which,
though imperceptible to human nostrils, must possess an extraordinarily
penetrating power. Weismann gives an instance of this in the case of
the nocturnal Eyed Hawk-moth (_Smerinthus ocellatus_). He placed some
females, without any special intention, in a covered vessel near an
open window. “The very next morning several males had gathered, and
were sitting on the window-sill, or on the wall of the room close to
the vessel, and by continuing the experiment I caught, in the course of
nine nights, no fewer than forty-two males of this species, which I had
never believed to be so numerous in the gardens of the town....” To
this power of exhaling odours we may attribute the wingless condition
of many Moths, for otherwise the loss of flight would have brought
about extinction long before any perceptible reduction in the wings had
taken place. The odour which such prisoners emit seems to possess an
irresistible attractiveness, and this fact is commonly taken advantage
of by entomologists. The Common Vapourer Moth (_Orgyia antiqua_)
affords a good illustration of this. The female is wingless, and little
more than a pouch for eggs, but in certain seasons it is very abundant,
even in the midst of London. That experienced entomologist Prof. Selwyn
Image, in a letter to my friend Mr. John Cooke, remarks, on this theme,
that the Caterpillars may be seen crawling by hundreds in and around
the squares, while the males may be seen flying up and down New Oxford
Street or Tottenham Court Road. If a virgin female be put in a box
placed outside the window, within a very short space of time, often not
more than a few minutes, several males will be fluttering round her.
This device for attracting males is commonly known as “assembling.”
More striking is the case of the Oak-eggar Moth (_Lasiocampa quercus_).
Mr. Richard South, in his most useful “Moths of the British Isles,”
relates that on one occasion he had a number of pupæ in a cage in
a cottage on the edge of a moor near Lynton, North Devon, and these
attracted quite a number of males into the room containing the precious
casket, and he was enabled to capture several. The next day he placed a
female which had meanwhile emerged, in a “roomy chip-box, and carried
it, in a satchel, to the moor, where it was placed on the ground; the
males began to arrive soon afterwards, and some fine examples were
secured.” But the sequel is even more remarkable; for, he remarks:
“Although the female was taken on the moor only on one occasion, that
satchel continued to be an object of interest to the male Eggars
for several days afterwards.” That this scent is capable of being
transferred to foreign objects, and of retaining its power for several
days, is a striking proof of its pungency, yet it is quite impalpable
to human nostrils! The Kentish Glory Moth (_Endromis versicolor_)
affords yet another instance of this curious attraction by scent, the
effectiveness of which is not even lessened by exhalations of the
human body, for if a virgin female be placed in a box, and this be
placed in one’s pocket, the males will often swarm round one and even
endeavour to gain access to the box. In all such cases the females,
even when capable of flight—the female Vapourer is wingless—never fly
until after impregnation has taken place. Hence males with defective
scent—detecting powers inevitably fail to leave offspring.
Selection, then, here lies between males of the most active
scent-detecting powers, and not between those of the most brilliant
colours. Nevertheless, both males and females—where the females
are winged—exhibit a remarkably beautiful coloration, and this is
especially true of the Kentish Glory, wherein both sexes wear a
resplendent dress. That of the male—which is much smaller than the
female—differs in that the fore-wings are darker, but bear the same
pattern as in the female, while the hind-wings are chestnut-red instead
of cream colour as in the female. If this scent-factor has replaced
colour as an inciting agent to pairing, then these Moths should be of
sombre hues. That such is not the case seems sufficient to show that
the colour is not due to Sexual Selection, for it is highly improbable
that scent and colour are both of equal importance, and this being so,
one would expect to find the negligible factor eliminated.
The existence, then, of bright colours in this and other species
in like case, seems to show that it has nothing to do with Sexual
Selection, directly at any rate. The males having assembled, their
presence is probably communicated to the female by the characteristic
male odour, which is never of the same penetrating quality as that
of the female. There is no need that it should possess this, for the
females never seek their mates. The successful male, where several
rivals are competing, is probably not simply the strongest, but he
who also disperses the right odour necessary to provoke the pairing
response. These illustrations furnished by the scent-hunting,
scent-dispersing males and females are of the highest importance
to students of the Sexual Selection theory, for they seem to show
conclusively that coloration plays at any rate but a minor part
therein. The importance of the scent-detecting organs is shown in
the very different types of antennæ which obtain between male and
female Moths, those of the male taking the form of huge feather-like
structures, as in some Saturniidæ, and far exceeding those of the
female in size.
The methods of pairing which obtain among Butterflies and Moths, it is
not surprising to find, are very different; for whereas in the former
it takes place on the wing, in the latter the female is always in a
resting position. Where the females are winged, long flights are often
taken for the purpose of depositing and distributing the eggs: the
flightless forms make no such excursions. A few, as in the case of some
of the _Psychidæ_ are not only wingless, but limbless and maggot-like.
They never leave the chrysalis case, but deposit their eggs inside it.
Though there is undoubtedly much that is wonderful about the mating
of these scent-distributing species, the history of the Moths of the
genus Acentrophus is more wonderful and more mysterious still. For
the females are aquatic. The males may sometimes be found in crowds
fluttering over the surface of large but shallow sheets of water. The
females, which are wingless, come to the surface and, like sirens, draw
the males under water, where coupling takes place; after which they
probably immediately die. But how do they discover their submerged
mates? The escape from the water of any odour which the females may
possess seems well nigh impossible.
Whether display, such as birds appear to delight in ever takes place
among the Lepidoptera seems doubtful Nevertheless, something closely
akin thereto seems to have been found in the case of certain species
of Butterflies (_Heliconius melpomene_ and _H. rhea_), which have been
seen dancing in the air like gnats, and when some of them withdrew
others took their places. Again, having regard to the fact that birds,
when alarmed or excited, will perform the display which is more or less
characteristic of periods of sexual excitement, it is possible that the
position of alarm assumed by some of the Hawk Moths may also be used in
Courtship (Fig. 1, Plate 31). But we have no evidence on this point,
and from the part played by scent in the mating of Butterflies it seems
improbable that such displays take place.
A serious attempt to test the Sexual Selection theory by experiment—to
test the extent, if any, of female choice in mating—was made some
years ago by Mayer, an American naturalist, on the large Bombycid Moth
(_Callosamia promethea_). This species exhibits striking dissimilarity
between the sexes in regard to colour and pattern. “The females,”
remarks Professor Kellog, “are reddish brown in ground colour, while
the males are blackish, and in the two sexes the pattern is distinctly
different....” Mayer took four hundred and forty-nine pupæ, in
cocoons, of this moth and endeavoured to discover, first of all,
whether the males found the females by sight or smell. Enclosing
females in jars, some of which were covered and some of which were
uncovered, he found that males paid no attention to females enclosed in
transparent jars so closed as to prevent the escape of odours, while
such as were enclosed in boxes or wrapped in cotton-wool, so as to be
invisible, but yet capable of exhaling odour, were besieged by males.
To locate the organs of scent in the female he cut off the abdomen of
several and placed the abdomens and their late owners at some distance
apart. Males came to the abdomens and not to the thorax and wings.
Males whose antennæ were covered with shellac, photographic paste,
glue, paraffin, etc., showed no response to the female exhalations,
until the covering medium was removed.
Mayer next tested the selective action of the females. He began by
removing their wings and affixing to the stumps the wings of males.
The males mated with the females quite as readily as under normal
conditions, though the most conspicuous female characters had been
exchanged for those of the male. After this he affixed female wings
upon the males, but mating took place as usual. The females did not
seem to detect anything unusual in their suitors, nor did normal
males attempt to pair with males bearing female wings. Later he tried
the experiment of dyeing the wings of three hundred males scarlet
or green, and matched these against three hundred which were left
untouched. The disguised, dyed males succeeded in pairing as easily
as their normally-coloured brethren. The females exhibited no choice
whatever. Hence, then, we have further reason to believe that with
the Lepidoptera scent, not sight, is the channel by which mates are
found. So far as the evidence goes, it seems to show conclusively that
in all that concerns sexual relationships, scent is the guiding and
determining factor. By scent the females attract the males, and by
scent of another kind the males sharpen the procreative appetites of
the females.
If the interpretation adopted in these pages is correct, these
manifestations and emanations of colour and scent are readily
accounted for; for they are manifestations of inherent growth changes
which, having started, are free to go on increasing in amplitude
unless, and until, checked by natural selection. There is nothing
unreasonable or improbable in this interpretation; on the contrary,
it embraces also many other features hitherto ignored, but no less
demanding an explanation. Such, for example, as the infinite variety
of form and sculpture which the scales of the wings and the eggs
display. These are details visible only by the aid of the microscope,
but they demand explanation as much as the more obvious characters.
Moreover they have the advantage of belonging to a set of characters
which cannot in any way influence the choice, if choice there be, in
the selection of mates, nor are they of a nature likely to affect the
results of the struggle for existence. Of these characters, then—the
sculpturing of the egg-shell and of the scales, the “nervation” of
the wings, and coloration—we can say no more than that they are
idiosyncrasies of growth, free to develop in any direction unless, and
until, checked by natural selection, which will speedily eliminate
disharmonies with the environment.
CHAPTER XI
BEETLES THAT “BLUFF”
The Coloration, and other Forms of Ornament in Beetles, and the
Significance thereof in regard to the Sexual Selection Theory—The
Courtship of Grasshoppers and their Kin—The Remarkable Ears of Locusts
and Grasshoppers—The Field-cricket and the Katydid as Troubadours—The
Wonderful Performances of the Cicadas—The Duels of Long-horned
Locusts—Dragon-flies—The May-flies’ “Dance of Death”—The Jaws of
the Giant Alder-fly and their Strange Use—Some Curious Facts about
Stone-flies.
In these pages it is contended that neither brilliant coloration nor
any other form of ornamentation is to be ascribed to the direct action
of “Sexual Selection.” That is to say, such conspicuous features have
not been dependent on the action of female choice for their survival
and development, but are rather the “expression points” of the
internal, inherent growth variations, which, not being inimical to the
welfare of the species, have been free to pursue their development in
any direction which apparent chance may dictate.
The Butterflies and Moths well illustrate this in regard to coloration,
for scent, not colour, would seem to be their principal source of
information as to the outer world. The Beetles are no less instructive;
for these creatures, though they contain numerous highly-coloured
and some exquisitely beautiful species, are more remarkable for
their bizarre shapes, and it seems impossible to regard these as the
products of sexual selection. Yet this is the interpretation of their
origin which, in the judgment of Darwin, we must adopt. He evidently
had misgivings as to the correctness of this view; but it must be
remembered that in reviewing the facts relating to these lower orders
of Creation he was biased by the evidence which he had brought together
in regard to the behaviour of the higher groups under the stimulus of
sexual emotion. Convinced that female choice obtained here, he was
but following the logical result of such conclusions in postulating
the same factor wherever it could conceivably be applied. The most
formidable critic of the Darwinian theory of Sexual Selection was
Darwin himself. The dominant ambition in all his work was to explain
his facts, not to establish his theory; and he was convinced that his
theory of Sexual Selection did achieve that end; though there were
cases where the evidence he was analysing seemed less clear than in
others. That the Beetles presented difficulties is evident from his
comments thereon. He was puzzled by the vivid coloration which some
species present. “They may serve,” he remarks, “as a warning or means
of recognition ... as with Beetles the colours of the two sexes are
generally alike, we have no evidence that they have been gained through
sexual selection; but this is at least possible, for they may have been
developed in one sex and then transferred to the other; and this view
is even in some degree probable in those groups which possess other
well-marked secondary sexual characters....
“Some Longicorns, especially certain Prionidæ, offer an exception to
the rule that the sexes of Beetles do not differ in colour. Most of
these insects are large and splendidly coloured. The males of the genus
Pyrodes ... are generally redder but rather duller than the females,
the latter being coloured of a more or less splendid golden-green. On
the other hand, in one species the male is golden-green, the female
being tinted with red and purple. In the genus Esmeralda the sexes
differ so greatly in colour that they have been ranked as distinct
species: in one species both are of a beautiful shining green, but
the male has a red thorax. On the whole, as far as I could judge, the
females of those Prionidæ in which the sexes differ are coloured more
richly than the males, and this does not accord with the common rule in
regard to colour when acquired through sexual selection.”
While there is nothing very remarkable in the two sexes being coloured
alike, it is certainly strange to find the female more brilliantly
coloured than the male. And this because among the higher vertebrates,
as among the birds, the female exceeds in brilliance only where she
also plays the rôle of wooer instead of wooed; leaving to the male the
whole responsibility of rearing the family. With the Beetles the family
has to rear itself, parental care being limited to the right disposal
of the eggs. By some change in the character of the germ-plasm the
females may have, in these cases, acquired more “maleness,” more of the
qualities which are answerable for the secondary sexual characters of
the male, or, what seems rather to be the case here, a result like that
which has been reached in certain of the Pigeons and Parrots has been
arrived at. That is to say, the tendency to intensification of pigment
in the female struck out a new line, instead of following that of the
male. This rather rare form of sexual dimorphism is also met with, it
will be remembered, among the Butterflies and Moths.
While brilliant colour is the more usual form of ornament among the
Beetles, there are many species wherein the males have developed
enormous horns, or have greatly exaggerated the length of the jaws;
and these outgrowths give the impression of a formidable armature,
but so far as the evidence goes this is by no means the case. They
must therefore be relegated to the category of “ornaments,” though the
term “excrescences” would more fittingly apply to them, for they are
“ornaments” only from a human standpoint. At any rate, there is no
evidence whatever that they serve to enhance their possessors in the
eyes of the females.
In relation to the Sexual Selection theory these excrescences are
of quite exceptional interest, for they throw a strong light on the
meaning of ornament, such as obtains among birds, which seem to show a
consciousness of its existence and effectiveness. Darwin argued from
the birds to the Beetles. Convinced that the gorgeous crests and trains
and vivid colours were appreciated by the females of the former, he was
impelled to believe that the ornaments of the latter had developed in
like case by the fostering influences of the females. Similarly, from
the evidence as to the use of horns in the case of mammals, and spurs
in the case of birds, he was induced to believe that the horn-like
outgrowths of Beetles had been attained by like influences. But in
both kinds of cases, he could only infer their action, for he could
discover no really decisive instances of conquest either by display or
by battle, such as he was able to produce in the case of the higher
animals. Had chance directed his attention in the beginning either
to the Warblers among the birds, or the beetles among the insects,
his interpretation of the action of sexual selection, it is more than
probable, would have been materially different from that developed in
the “Descent of Man.” No additions of any importance have been added to
the facts he so laboriously collected.
As touching the “horns” it should be remarked that these may arise
either from the head or from the thorax, or from both, and sometimes
even from the under surface of the body.
One of the most remarkable instances of these singular outgrowths is
that of the Hercules Beetle (_Dynastes hercules_) of the West Indies
and tropical America. Herein the roof of the head is prolonged into
a great upturned beam bearing tooth-like prominences, and the top
of this is opposed to a still more massive beam, whose base covers
the whole roof of the thorax, and whose tip extends far beyond that
projecting from the head. A pair of “teeth” point downwards from the
middle of this beam, whose under surface is thickly covered with short
chestnut-coloured hairs forming a brush-like surface. In another,
_Copris isidis_, the head bears two short, rhinoceros-like horns,
and the thorax a short, triangular overhanging ledge: in _Phanœus
jaunus_ there is a single horn on the head, and the thorax bears
two short, forwardly-projecting blades, one on each side; while in
_Onthophagus rangifer_—the Reindeer Beetle—the head bears a pair of
horns curiously like the antlers of a deer. One might cite many such
instances, all varying in detail, but these will suffice.
Darwin, in commenting on these structures, remarked: “The
extraordinary size of the horns and their widely different structure
in closely-allied forms indicate that they have been formed for
some purpose; but their excessive variability in the males of the
same species leads to the inference that this purpose cannot be of a
definite nature. The horns do not show marks of friction, as if used
for any ordinary work. Some authors suppose that as the males wander
about much more than the females, they require horns as a defence
against their enemies; but as the horns are often blunt, they do not
seem well adapted for defence. The most obvious conjecture is that
they are used by the males for fighting together, but the males have
never been observed to fight, nor could Mr. Bates, after a careful
examination of numerous species, find any sufficient evidence, in their
mutilated or broken condition, of their having been thus used. If
the males had been habitual fighters, the size of their bodies would
probably have been increased through sexual selection, so as to have
exceeded that of the females; but Mr. Bates, after comparing the two
sexes in above a hundred species of the Copridæ, did not find any
marked difference in this respect amongst well-developed individuals.
In Lethrus, moreover, a Beetle belonging to the same great division of
the Lamellicorns, the males are known to fight, but are not provided
with horns, though their mandibles are much larger than those of the
female.
“The conclusion that horns have been acquired as ornaments is that
which best agrees with the fact of their having been so immensely,
yet not fixedly, developed—as shown by their extreme variability in
the same species This view will at first appear extremely improbable,
but we shall ... find with many animals standing much higher in the
scale, namely, fishes, amphibians, reptiles and birds, that various
kinds of crests, knobs, horns and combs have been developed apparently
for this sole purpose.”
The assumption that these “animals standing much higher in the scale”
owe their weapons to the selective action of the females forms the crux
of the whole Sexual Selection theory in regard to the significance
of ornament. The evidence that the intensification of pigment and
the eccentricities of growth in the shape of crests and frills have
a fascinating effect on the female is more than under suspicion; it
is discredited by the facts which have come to light in regard to
behaviour during the periods of sexual exaltation. And there is a
growing conviction that this is so. No better proof could be found that
“ornaments” can, and do, exist in spite of, rather than because of, the
action of “sexual selection.” They are the accidents of this selection,
not a part of its machinery.
Incipient horns are found in not a few cases among the females of
these insects, while in others, as in the case of the Reindeer Beetle,
they are almost as well developed as in the males. This is what one
would expect to find if these outgrowths were the result of inherent
variations restrained as to their size by natural selection, which
eliminates only when this growth penalizes, by increasing the struggle
for existence.
As to the actual behaviour of Beetles when sexually excited but very
little information is obtainable; but there are records of species the
males of which fight with rivals for the possession of females. Wallace
saw two males of _Leptorhynchus augustatus_, a Beetle with no name in
common speech and a long beak, “fighting for a female, who stood close
by busy at her boring. They pushed at each other with their rostra, and
clawed and thumped in the greatest rage.” The smaller male, however,
“soon ran away, acknowledging himself vanquished.” In this case, it
is to be noted, the combatants lacked weapons. With the Stag Beetle it
is otherwise, and this species is said to engage in fierce conflicts.
Darwin cites an instance where two males were enclosed with one female
in a box, when the larger severely pinched the smaller one, until he
resigned his pretensions. This being so, it is curious to find that the
female, which makes no display of pugnacity, has the stronger jaws.
The fact that there are so few records of fighting among male Beetles,
and the absence of injury to the highly-polished surfaces of the horns
or jaws where these are conspicuously large, seem to indicate that at
most no more than a semblance of fighting ever takes place. In a North
American Stag Beetle (_Lucanus elaphus_) the jaws, which are greatly
developed, are used, Darwin tells us, for seizing the female, but they
do not appear to be employed for this purpose in any other species.
It might be held that they play the part of terrifying agents, as the
eye-spots of Caterpillars and adult Lepidoptera are believed to do.
At any rate, they seem to be so used in the case of a Beetle of South
Chile (_Chiasmognathus grantii_) wherein the jaws are of great size
and have their inner edges toothed. When threatened “he faces round,
opens his great jaws, and at the same time stridulates freely.” But
this parade of force is evidently no more than “bluffing,” for Darwin,
who describes this behaviour, remarks, “the mandibles were not strong
enough to pinch my finger so as to cause actual pain.” In the female,
it may be remarked, the jaws are quite small.
That too much stress has been laid upon the significance of the
enlarged jaws and other hypertrophied developments in the Beetles
seems to be shown by the case of certain carnivorous Beetles, of which
one species (_Taphroderes distortus_) may serve as an example. Herein
the left jaw takes the form of a long, crooked strap-shaped outgrowth,
whose purpose cannot even be conjectured. And in this connection one
may cite the case of certain species of Homoptera—Bugs—which occur in
tropical South America. Here, in both sexes, as may be seen in Plate
40, Fig. 4, the neck-shield is produced backwards far beyond the body,
to form a most elaborate superstructure which appears to confound the
most ingenious attempts at interpretation.
It is to be noted that wherever special structures are necessary for
the performance of specific acts such as are of vital importance to
the well-being of the race, they are developed to perfection: there
is little or no variation in their size, and no doubt as to their
purpose. Thus in many species means are necessary to enable the male
to seize and hold the female during the sexual embrace. In the Water
Beetle of our ponds and ditches (_Dytiscus marginalis_) the male bears
a very remarkable sucker on each fore-leg, the adhesive surface of
which, under the microscope, reveals an extraordinary complexity and
wondrous beauty. This sucker forms a very conspicuous “secondary sexual
character,” and is used in embracing his mate, whose back is deeply
grooved to enhance the hold of the suckers. In some species punctures
take the place of grooves. Suckers, like those of _Dytiscus_ are met with
again in a Wasp (_Crabro cribrarius_). In another genus of Beetles
(_Penthe_) cited by Darwin, the antennæ of the male have a few of the
middle joints dilated and their under surfaces furnished with a cushion
of hairs to aid in the sexual embrace.
Beetles are creatures of solitary habits; how, then, do they find their
mates when, by the insistence of the reproductive desires, they are
driven forth to begin the search? Though we have no direct evidence, it
seems more than probable that, as with the Butterflies and Moths, scent
furnishes their most reliable guide. At any rate, in a large number
of species, as among the Lamellicornia, the antennæ bear leaf-like
plates, which are much more developed in the males, in which they
probably serve as scent-detecting organs.
In some species stridulating organs occur such as are met with in even
greater perfection among the Crickets and Grasshoppers, and among the
Spiders and Scorpions. That these “musical-boxes” provide a means of
communication between the sexes there can be no doubt, even if, as
some contend, they are commonly used only to frighten enemies. This
purpose may well be the explanation of their presence in the larval
Stag Beetle, for it cannot be claimed that they have any relation to
the acts of courtship at this stage of development.
Stridulating organs, wherever they are met with, are fashioned on
the same principle. The mechanism for sound-production differs
conspicuously from that which produces the voice in the vertebrates.
For where there are no lungs or breathing apparatus, comparable to
that of birds and beasts, there can be no internal voice-mechanism.
Instead, the skeleton which in these creatures forms the external
surface of the body—that is to say, it encloses the muscles, whereas
in the vertebrates it is internal and overlain by the muscles—produces
the necessary sounds. And this by means of rubbing two opposed surfaces
against one another, one of which is ridged, the other toothed. In
the details both of position and structure a wonderful variety will be
discovered when all the known types are surveyed, and it is possible
that they perform different functions in different groups.
The Locusts and Grasshoppers are among the finest performers of
these “harpists,” and it would seem that in this group, at any
rate, the music they make is of an erotic character. In one of our
native Grasshoppers (_Stenobothrus melanopterus_) these high-pitched
and somewhat strident notes are produced by rubbing the roughened
inner surface of the hindmost thigh, which forms the base of the
great leaping leg, against one of the libs of the wing-case which
is specially enlarged and has a sharp edge. Thereby the wing is
thrown into a state of vibration and the musical sound produced. The
roughening of the inner surface of the thigh just referred to is
produced by a row of bead-like projections whose appearance under the
microscope is depicted in the adjoining illustration. This apparatus
is well developed in the males, and but feebly, or not at all, in the
females. That the music it produces is appreciated by the performers
and their mates there can be no doubt, for they are provided with
a special apparatus which fulfils the purpose of an ear. In the
short-horned Grasshoppers (_Acridiidæ_) this is placed in the middle
of the body just above the base of the great thigh. It differs in the
details of its construction. In some cases it is formed by a delicate
sheet of membrane surrounded by a rim, in others the membrane may be
slightly depressed, and in some very much so, the rim closing up to
form a broad slit. Such ears, it is to be noted, exist in both sexes,
while the stridulating organs do not. That such sound-producing organs
serve as stimulants to the sexual passions of the females is but a
natural inference. Some authorities, however, regard this as doubtful,
since there are species which appear to lack these stridulating
instruments, though possessing ears. But closer observation will
probably show that these apparently dumb species are not really so, as
Dr. David Sharp, commenting on this fact remarks: “It is well known
that sounds inaudible to some human ears are perfectly distinct to
others. Tyndall, in his work on Sound, has illustrated this by a fact
that is of special interest from our present point of view. ‘Crossing
the Wengern Alp with a friend’ he says, ‘the grass on each side of the
path swarmed with insects which, to me, rent the air with their shrill
chirruping. My friend heard nothing of this, the Insect world lying
beyond his limit of audition!’ If human ears are so different in their
capacity for perceiving vibrations, it of course becomes more than
probable that auditory organs so differently constituted as are those
of insects from our own may hear sounds when the best human ear can
detect nothing audible. On the whole, therefore, it would appear most
probable that the Orthoptera provided with acoustic organs, and which
we consider dumb, are not really so, but produce sounds which we cannot
hear, and do so in some manner unknown to us. If this be the case, it
is probable that these ears are special organs for hearing particular
sounds.”
[Illustration: Plate 32.
STRIDULATING ORGANS. ETC.
1. The stridulating mechanism of the Red Ocypode Crab.
2. The stridulating apparatus of a Grasshopper—highly magnified.
3. The head of a Gnat with the compound eyes split up.
4. The “ear” of a Grasshopper.
[Face page 218.]
Certain of the Grasshoppers of Africa, known to entomologists as
Pneumorides, have undergone a most extraordinary transformation
of their bodily shape, as if in response to the demands of these
musical performances. They have entirely lost the power of leaping,
and the abdomen, in the male, has become transformed into a huge,
pellucid, inflated bag or bladder, apparently to serve the purpose
of a resonator, increasing the volume of the sound produced by the
stridulating organ, which consists of a series of ridges placed on
each side. The noise which this mechanism produces is, as might be
supposed, considerable. It is curious to remark that in this group
the females are more vividly coloured than the males. In the case of
one South African species—_Pneumora scutellaris_—this coloration is
so extravagant that she has been said to look as if “got up” for a
fancy-dress ball (Plate 33, Fig. 1). Her ground colour is of a light
green, with pearly-white markings, surrounded by an edging of magenta;
the white areas are very numerous. The face has magenta patches, and
numerous, tiny, pearly-white tubercles, each of which, when placed on a
green part, is surrounded by a ring of mauve. This scheme of coloration
distinguishes her as one of the most remarkably coloured of insects.
But to what are we to attribute these hues? Sexual Selection will
not explain them, and it seems unreasonable to regard them either as
affording a protective or a warning coloration. They may then, perhaps,
be allowed to rank as another instance of unchecked variation in the
direction of vivid colouring, such as has been already described as
occurring both among birds and other animals lower in the scale.
[Illustration: Plate 33.
CRICKETS AND MAY FLIES.
1 and 2 afford illustrations of the excessive development of “ornament
“; fig. 3 of devices for seizing the female; figs. 4 and 5 of
unaccountable differences in the development of wings.
1. The Pneumatic Cricket (_Pneumora scutellaris_), showing the strange
markings on the female.
2. The Cleft-footed Burrowing Cricket (_Schizodactylus monstrosus_).
3. The Giant Alder-fly (_Corydalis crassicornis_), with its huge jaws
for grasping the female.
4. The Stone-fly (_Perla maxima_), the large-winged Continental form.
5. Loch Tanna Stone-fly (_Isogenus nubecula_), male, with vistigial
wings.
[Face page 220.]
In the Locustidæ the ear is placed on the side of the front leg and
the rim surrounding it may either take an oval shape or close up to
form a slit. The air necessary for the efficient action of the acoustic
apparatus is admitted through a gaping hole in the side of the body,
above the base of the leg, an arrangement not met with among any other
insects. The musical apparatus of these insects differs from that of
the Acridiidæ, for it is formed only by the wing-cases, and not by
the wing case and the leg. One of the wings bears a file on its
inner surface, the other, the right wing, is furnished with a sharp
edge placed on a prominent part of its inner margin. By slightly
tilting the fore-wings, or wing-cases, and vibrating them rapidly,
the edge passes under the file and a musical sound is produced. By
this means one of our native long-horned Grasshoppers (_Locusta
viridissima_) produces a shrill, but not unpleasant, sound, capable of
being sustained continuously for a quarter of an hour. But a species
encountered by Bates during his travels in the Amazons is a much more
efficient performer. Known by the name of Tanana by the natives, it
is so much admired by them for its singing powers that it is kept in
little cages as we keep Canaries. That these organs are of importance
to the species may be gathered from the case of a Bulgarian long-horned
or Green Grasshopper (_Poecilimon affinis_), wherein the wings have so
degenerated as to be useless in flight, but in the male they have been
retained solely as musical instruments. In some species both sexes have
a music-producing apparatus, but as a rule this is present only in the
male.
That these curious and complex stridulating organs do indeed primarily
act as aphrodisiacs seems to have been clearly demonstrated by the
naturalist Bates, who, in speaking of the European Field Cricket
remarks: “The male has been observed to place himself at the entrance
to his burrow, and stridulate until a female approaches, when the
louder notes are succeeded by a more subdued tone, whilst the
successful musician caresses with his antennæ the mate he has won.”
Among the most efficient and most celebrated performers of all on these
instruments of percussion are the “Katydids” of North America. The
sounds they produce are said to form the words “Katy-did, O-she-did,
Katy-did-she-did.” The first of these extraordinary concerts is heard
about mid-July; by mid-August they are in full song. By others the
sounds have been likened to those produced by the slow turning of a
child’s rattle, ending in a sudden jerk; and this prolonged rattling,
which is peculiar to the male, is always answered by a single, sharp
“chirp” or “tschick” from one or more females, who produce the sound by
a sudden upward jerk of the wings.
Pride of place, however, among insect performances of this kind must
surely be awarded to the Cicadas, which are notoriously the noisiest
members of the Insect world, far eclipsing the shrill calls of the
Grasshoppers and even of the Crickets. Darwin remarks that the noise
they made could “be plainly heard on board the _Beagle_ when anchored
off Brazil at a quarter of a mile from the shore; and Captain Hancock
says it can be heard at a distance of a mile. The Greeks formerly kept,
and the Chinese now keep, these insects in cages for the sake of their
song, so that it must be pleasing to the ears of some men.” Only the
males sing, the females being completely dumb, and this prompted the
Greek poet Xenarchus to make the now famous remark, “Happy the Cicadas’
lives, for they have voiceless wives.” Another naturalist, Riley, says:
“The general noise, on approaching the infested woods, is a combination
of that of a distant threshing-machine and a distant frog-pond.”
Another species, _Tympanoterpes gigas_, also Brazilian, is said to make
a noise equal to the whistle of a locomotive: recalling that of a nest
of young snakes, or young birds, when disturbed—a sort of scream. They
can also produce a chirp like that of a Cricket and a very loud, shrill
screech prolonged for fifteen or twenty seconds, gradually increasing
and decreasing in force.
Curiously enough, no special auditory organs have yet been discovered,
and it has been suggested that these insects do not hear in our sense
of the word, but feel rhythmical vibrations. But whether the males
“sing in rivalry,” as Dr. David Sharp suggests, is another matter.
The purpose of the “song” in the first place is no doubt intended as
a guide to the females seeking mates. But it is quite conceivable
that the call of one male may stimulate every other male in the
neighbourhood. Darwin, commenting on this aspect of the music, gives a
quotation from Dr. Hertman, who says: “The drums are now ... heard
in all directions. This I believe to be the marital summons from the
males. Standing in thick chestnut sprouts about as high as my head,
where hundreds were around me, I observed the females coming around the
drumming males.... This season a dwarf pear-tree in my garden produced
about fifty larvæ of _Cicada pruinosa_; and I several times noticed
the females alight near a male while he was uttering his clanging
notes.”
The structures, he remarks, from which these sounds proceed, “must be
ranked amongst the most remarkable voice-organs in the animal kingdom.
They are totally different from the stridulating organs that are found
in many other insects.... Some difference of opinion has existed as to
the manner in which the structures act, but the account given by Carlet
... will, we believe, be found to be essentially correct.” They are
partly thoracic and partly abdominal. On examining a male Cicada there
will be seen, on the under surface, two plates, meeting in the middle
line of the body and overlapping the base of the abdomen. They can
be slightly moved away from the abdomen, and thereby a wide fissure
will be produced, displaying the mechanism beneath. If the whole
operculum be removed, three membranes will be seen, an external, called
the “timbal,” an anterior folded and soft membrane, and a posterior
“mirror.” This last is a very beautiful object, tensely stretched and
pellucid, yet reflecting all the hues of the rainbow. The sound is
primarily produced by the vibrations of the timbal, to which a muscle
is attached; the other membranes are probably also set vibrating, and
the whole skeleton helps to increase or modify the sound, which is
probably also influenced by the position of the operculum, which varies
in different species. A further control of the tension of the air is
exerted by “stigmata” or pores, and certain air-chambers connected
therewith.
Throughout these pages comment has been made on the apparently
“fortuitous” character of complex patterns and structures. The
“musical-box” of the Cicada affords yet another instance. Nevertheless
there is an impressive harmony between the several parts; an
interdependence which is not fortuitous. There is obviously a nexus of
growth-controlling factors preserving harmony between each separate
part which as yet has escaped all endeavour to discover.
While it is difficult to picture the initial stages of growth of so
complex an organ as that of the Cicada, the beginnings of simpler
structures such as the stridulating organs of Beetles and Grasshoppers
are more easily discernible. “It is probable,” remarks Darwin, “that
the two sexes of many kinds of Beetles were at first enabled to find
each other by the slight shuffling noise produced by the rubbing
together of the adjoining hard parts of their bodies; and that as
those males or females which made the greatest noise succeeded best
in finding partners, rugosities on various parts of their bodies were
gradually developed by means of sexual selection into true stridulating
organs.”
Structures to which we can ascribe a use are commonly supposed to have
been evolved for the purpose which we assign to them. The “horns”
of Beetles afford a case in point; but there are many other equally
remarkable and extravagant developments among the insects which seem to
defy explanation. And they will continue to do so until it is realized
that they are but exaggerations of the normal processes of growth,
which is not limited to definite areas but may produce extensions
and excrescences of an almost infinitely varied character. The only
controlling factor is that imposed by Natural Selection when these
growth-changes tend to impair the well-being of the organism as a
whole. Often such changes confer benefits, giving rise to new organs,
and in this case Natural Selection encourages the new departure.
Nothing, indeed, “succeeds like success.” New departures in one
direction may be promptly suppressed, in another they spell fortune:
there is no “Socialism” in Nature. Often these “new departures” neither
help nor hinder, and instances of this kind are commonly afforded
by “ornaments.” One of the most singular illustrations of this kind
is furnished by that extraordinary Long-horned Grasshopper of India
(_Schizodactylus monstrosus_), wherein the wings, when at rest, have
their tips coiled up like a watch-spring, while the appendages to the
legs are scarcely less remarkable. It is a burrower, driving long
tunnels in the banks of rivers. But little is known of its habits,
save that it does not emerge from its burrow till night, when it takes
long flights. This being so, the bizarre character of its wings and
legs is the more difficult to explain on any Sexual Selection theory.
But regarded as spontaneous variations which have not fallen under the
ban of Natural Selection, they are somewhat less puzzling, though,
having regard to the extraordinary transformation which the burrowing
Mole-cricket and the allied Cylindrodes have undergone, in adaptation
to fossorial habits, the legs of this insect are remarkable indeed.
While there can be no doubt that the musical performances of the
Crickets and Locusts play an important part in courtship, in some of
the Long-horned Locusts, at any rate, the males fight furiously when
mate-hunting, and to this end the head and jaws are greatly enlarged.
During the progress of the duel the wings are extended and held erect,
which is hardly what one would have expected, since in this position
they would seem to be more exposed to danger.
All the insects so far surveyed have been more or less conspicuous
for their vivid hues, yet in none of these have elaborate “displays”
been recorded. To find demonstrativeness of this kind one must turn
apparently to a group of minute, lowly organized, dull-coloured,
wingless insects with ugly misshapen heads and bodies. The sexes do
not differ in appearance, but they are interesting on account of the
sedulous court which the males pay to the females. The late Lord
Avebury, in a Communication to the Linnean Society, remarked of them:
“It is very amusing to see these little creatures (_Smynthurus luteus_)
coquetting together. The male, which is much smaller than the female,
runs round her, and they butt one another, standing face to face
and moving backwards and forwards like two playful lambs. Then the
female pretends to run away and the male runs after her. With a queer
appearance of anger, he gets in front and stands facing her again; then
she turns coyly round, but he, quicker and more active, scuttles round
too, and seems to whip her with his antennæ; then for a bit they stand
face to face, play with their antennas and seem to be all in all to one
another.”
The Dragon-flies are among the most beautiful of insects; they are
also relatively long-lived, and they are conspicuous. Yet this beauty
must be attributed to some inherent inward grace rather than to the
æsthetic instincts of the female. Moreover, in the matter of size
and beauty there is little to choose between the sexes; where any
difference occurs the males have the advantage. Though the mode of
copulation is well known, nothing has been discovered as to the means
whereby male and female discover one another. It is doubtful whether
this can be done by sight, for with all the beauty of their shimmering
suits of mail and gauzy wings, their vision is limited to a field
of a few inches. Possibly scent is their guide; at any rate, dead
Dragon-flies have a vile odour.
It is worth noting that there are no wingless Dragon-flies, and that
none have developed unnecessary ornament in the form of spines, horns,
or frills of any kind, such as are so commonly met with among groups of
more sedentary habits like the Phasmidæ and the Beetles, for example.
In other words, there is clearly a direct relation between ornament
and the mode of life. It is also clear that some modes of subsistence
are very inelastic, allowing of no more than very slight structural
variations, for the Dragon-flies are an extremely ancient group. Fossil
species of large size are known from the Lower Lias, and the remains
of a giant measuring two feet in expanse of wings has been found in
the Carboniferous. This species, however, seems to have stood near the
parting of the ways between the May-flies and the Dragon-flies. But
be this as it may, undoubtedly Dragon-flies hovered over the backs of
sleeping Ichthyosaurs and furnished food for Pterodactyles millions of
years ago, as they now hover over lazy kine for the sake of the flies
forgathered there, or dodge to avoid the stoop of the Hobby, and in all
this vast space of time they have not appreciably changed.
And what is true of the Dragon-fly is true also of the May-fly, for it
is clear that they are of the same stock. It is true at any rate in so
far as the conformation of the body is concerned. The possibility that
it may be equally true in regard to the details of their life-history
almost staggers one, because these are, in many respects, of a quite
remarkable character. As with the Dragon-fly, there is a prolonged
period of larval life, lasting from one to two years, which time is
passed in streams and pools where a luxuriant vegetation ensures a
plentiful supply of food. Some are carnivorous, but in the majority of
species minute plants only are eaten. More than forty species are to
be reckoned as natives of the British Islands, the commonest being the
“Green Drake” and “Grey Drake,” beloved by the fisherman. These names
are applied, it may be mentioned, to the phase known as the sub-imago
which precedes the fully-adult stage, of _Ephemera vulgata_ and _E.
danica_.
Save that it is curious that while the larvæ of some species are
carnivorous those of others are vegetarians, there is nothing very
remarkable about what may be called the infantile period. But when
this is ended the span of life remaining to them as adults is brief
indeed. Instinctively realizing that the time of transfiguration is at
hand, the erstwhile crawling grub rises to the surface of the stream,
and almost in the twinkling of an eye it mounts into the air on gauzy
wings, there for a brief space to execute an aerial dance which in its
every phase is amazing. Some species never see the sun. They emerge as
the sky begins to redden, and as its glory fades they, too, expire.
This brief space is all that Nature has allowed them in which to fulfil
her behest to all living things—to increase and multiply. And myriads
die without even a chance to effect this consummation of existence.
The dance is a Dance of Death, and it is performed by a host so vast
as to surpass the bounds of belief save to those who have had the good
fortune to witness a scene so amazing.
D’Albertis tells of a gathering which he witnessed on the Fly River,
New Guinea—for these insects have a world-wide distribution—wherein
countless myriads were assembled. “For miles the surface of the river,
from side to side, was white with them as they hung over it on gauzy
wings; at certain moments, obeying some mysterious signal, they would
rise in the air and then sink down anew like a fall of snow.” And in
this assemblage he estimated that there was but one female to every
five or six thousand males. It is during this flight that the act of
mating is performed. The fortunate male from the host of rivals, in
this mid-air embrace is aided by the foremost pair of legs, which are
especially curved to effect this purpose. The embrace is momentary.
Thereafter he dies; to the female a somewhat longer span of life
remains, for she has yet to deposit her eggs, and this being done _en
masse_, she, too, expires.
It is curious that these creatures, which in their winged state have
never seen the sun, should be attracted by light. But such is the
case. I well remember witnessing an instance of this years ago, while
staying, one August, at Bingen on the Rhine. Dinner was served in the
open air, and just as the soup was served May-flies in myriads swarmed
round the lamps and fell on the tables as thick as snow-flakes. Some
of these were in copula, and I succeeded in bottling a few specimens
for the British Museum, where they still remain to remind me of this
amazing scene.
About three hundred species of May-flies are known, and some enjoy a
somewhat longer span of life than others. In no case, however, do they
emerge till just before sunset; but in some species it is believed life
may be prolonged for as much as three or four days, or even longer, if
the weather be cold and wet, so as to keep them in a state of enforced
rest, which amounts to a state of coma.
That their hold on life during this final stage of existence is
brief there can be no gainsaying, for it is passed fasting. Jaws are
wanting, and the whole alimentary canal has been transformed into
one long air-chamber. Its walls are now of extreme tenuity, and by
changes in the interior of the tube, valves are formed which convert
the stomach into a capacious air-sac.” When movements,” remarks Dr.
David Sharp, “tend to increase the capacity of the body cavity then air
enters into the stomachic sac by the mouth orifice, but when muscular
contractions result in pressure on the sac they close the orifices of
its extremities by the valve-like structures just referred to; the
result is, that as the complex movements of the body are made the
stomach becomes more and more distended by air.” It was known even to
the old naturalists that the dancing May-fly is a sort of balloon,
but they were not acquainted with the exact mode of inflation. Palmen
says that in addition to the valve-like arrangements we have described,
the entry into the canal is controlled by a circular muscle with which
are connected radiating muscles attached to the walls of the head. The
canal thus strangely transformed performs the functions of a balloon,
and at the same time aids the functions of the reproductive organs.
Where vast numbers of individuals set out simultaneously to achieve
their nuptials there would seem to be no need for special devices
on the part of either sex to call attention to their whereabouts.
Nevertheless, it is highly probable that the female exhales some
distinctive odour; otherwise, having regard to the fact that she
is overwhelmingly outnumbered by suitors, her discovery in such a
crowd would be impossible, and it is of vital importance that no
time should be lost in effecting conjugation, for the time for its
accomplishment is perilously short. But there is another possible means
of discrimination—the males may distinguish the females by the very
different appearance of the head in the latter. At any rate, this may
be true of some species wherein the males have no less than seven eyes,
and these of three different kinds! The compound eyes, characteristic
of insects, are, in these, divided, one half being set upon the summit
of a pillar raised high above the level of the head, the other part
remaining in its normal place at the side of the head; and in front of
these, on what may be called the forehead, are three separate simple
eyes, or “ocelli.” A reference to Plate 32, Fig. 3, will make this
clear.
That the history of the later life of the May-fly is remarkable
no one will deny: in many respects it is unique. Yet for all its
strangeness it enables us to set our compasses, so to speak, in
regard to the phenomena of sex in other groups. The extraordinary
disparity in the proportions between male and female, for example, is
full of significance, for it shows, as has been suggested more than
once in these pages, that, in the case of polygamous species, we are
probably in error in supposing that the excess of females is due to
the reduction in the number of males by reason of the elimination
of males by fighting. The excess of males, or females, as the case
may be, is due to an inherent quality in the germ-plasm. The May-fly
might be regarded as an excessively polyandrous species if the number
of males in relation to females alone be regarded: but actually it
is monogamous. After a prosaic infancy they are suddenly transformed
into gay lovers, dancing a marriage-dance. But for them is no marriage
feast, nor any later sequence of domesticity. One in ten thousand
may find a mate, and only in this is he more fortunate than his
neighbours, for, like them, he too must die before the dawn. Theirs is
not even a sleep and a forgetting, but “one splendid hour of Life, and
then—oblivion.” It may be urged that even these which might seem to
have been fooled, have not really lived in vain, for hosts of animals
feast upon their bodies. Myriads, indeed, are snapped up by fishes even
before they have opened their wings, while birds rudely invade the
swarms as they dance in mid-air, feasting on these fasting ones. But
this is, after all, an inglorious end, and leaves us still asking _Cui
bono_?
Is this amazing life-history a thing of yesterday, a new phase, or an
order of things as old as the origin of the species, dating back some
millions of years?
So far as one can profitably speculate on such a theme it would seem
more likely to be a relatively recent innovation. The nearly-related
Alder-flies (_Sialidæ_), so well known to anglers, seem like to meet
with a similar fate, for the female lives but for a few days only
and the male has an even briefer existence as a winged insect. The
family to which the Alder-flies belong contains a few species which
attain gigantic proportions, as, for example, in the case of the North
American members of the genus _Corydalis_, which are giants. The males
thereof are remarkable for the fact that they are armed with enormous
jaws, which may be likened to a pair of callipers whose limbs have been
crossed. These weapons serve as claspers, enabling the males to seize
and hold the females during the act of mating. But even here the same
brief span of life has to suffice them, for death follows swiftly on
the fulfilment of the nuptial rites.
The Perlidæ, or Stone-flies, which, like the Sialidæ, are aquatic
Neuroptera, the larval stages being passed in streams, present very
puzzling features in regard to the adult males which, so far, have
baffled all attempts at solution; yet they seem to have a very
important bearing on the all-important work of reproduction. They
are among the earliest insects to appear in spring, and possess an
extraordinary power of resisting cold. One species, _Capina vernalis_,
common in the Albany River, in Canada, frequently comes up through
cracks in the ice and casts its skin there! Another, _Nemoura
glacialis_, which appears at about the same time, actually performs
the nuptial rites in crevices in the dissolving ice! Happily reason
is denied them, or they would find life a mockery indeed; for having
attained their final development, when the joyous and exhilarating
exercise of flight should be theirs, they are compelled forthwith
to fulfil their reproductive functions and die—in an ice-chamber!
The males have wings which are rarely or never unfurled; as a rule
they present nothing more than a crumpled mass of gauzy tissue, as if
glued together. Such species as attain to flight are most indifferent
performers, travelling but slowly, with laboured movements and settling
after a few yards have been traversed.
As a rule, among insects, where there is a difference in the power of
flight, it is the male which is superior. The case of _Nemoura_, just
referred to, affords an instance where the contrary is the case, and
Mr. J. J. Lister records the case of one of these flies—_Isogenus
nubecula_—taken at Loch Tanna in Arran, wherein the wings of the female
were greatly reduced, while those of the male were so much so as to be
mere useless vestiges. Similar facts have been recorded of more than
one species in Scotland, but in all such cases the phenomenon seems to
be associated with the appearance of the insect in very early spring.
In another species—_Nemoura trifasciata_—only the front wings are
reduced, the hind pair being large enough to cover the body. In male
specimens of _Perla maxima_ taken in Scotland, the wings are so short
as to be useless for the purposes of flight, yet, in the same species
taken in Central Europe, they are of ample proportions.
These facts are puzzling indeed, but they seem to show that flight is
not essential to attain the ends of reproduction. As to whether these
flies secure their mates by any kind of “courtship,” or how they find
one another, seems not to be known. But the female is remarkable for
the fact that she carries her eggs about with her, to the number of
five or six thousand, attached to the end of the abdomen.
Having regard to the fact that three thousand species of Perlidæ are
known, and that they have a wide distribution over the earth’s surface,
one might have expected that more would be known of their singular
life-history. They are, however, flies of very unattractive appearance
and great frailty, hence, save to anglers, by whom they are esteemed as
bait for trout, they attract but little attention.
CHAPTER XII
SCORPIONS, SPIDERS AND CRABS
Musical Lovers among Spiders and Scorpions—Colour among Spiders, and
its uses—The Spiders’ Dance of Death—Spiders and Conjugal Bliss—How
Pairing is accomplished—Scorpions in Love—Musical Crabs—Quarrelsome
Fiddler-crabs—Crabs and Courtship in the Deep Sea—Amazons among
Prawns—Brine-shrimps and Water-fleas—“Natural” _v._ “Sexual” Selection.
It is a curious and significant fact that in the most brilliantly
coloured of the Invertebrates—the Butterflies and Moths—” courtship”
in the sense of “wooing” is extremely rarely met with; and this is
quite contrary to what the Sexual Selection theory of Darwin demands,
for, according to this, the colours are the result of that selection.
On the other hand, Spiders, which are for the most part dull-coloured
creatures, and the Scorpions, which are also dull-coloured, are
commonly extraordinarily demonstrative during the early stages of
“mate-hunger.” Some practise the form of instrumental music known as
“stridulation,” others dance and indulge in other forms of posturing.
In the Spiders the stridulating apparatus is formed either between
the limb-bearing portions of the body, or “cephalothorax,” and the
abdomen; between the palps or leg-like feelers, and the jaws; or
between these feelers and the front legs. But the construction is
similar in all. In some Spiders the abdomen bears a horny collar, which
is toothed, and these teeth, as the abdomen is raised and depressed,
scrape against a number of delicate ridges on the thorax, or “chest,”
which form a surface recalling that of a file. The grating of these
opposing surfaces against one another produces shrill rasping or
chirping sounds, which, in some cases at any rate, seem to be designed
to inform the female of the presence of a suitor. Those who will,
may examine this strange instrument for themselves if they will take
the trouble to seek for it in one of our commonest English Spiders
(_Steatoda bipunctata_). That it serves as a sexual excitant, or as
an aid to mate-hunting, is indicated by the fact that it is found in
males only, or in a very rudimentary condition in the female. There is
a large Spider in Assam (_Chilobrachys stridulatus_) which produces
a sound like the drawing of the back of a knife along the edge of a
strong comb; and there are others which, by the friction of the feelers
against the jaws, produce sounds like the buzzing of bees. One of the
Wolf-spiders (_Lycosa kochy_) is known as the “purring” or “drumming”
Spider from its custom, at mating-time, of rapidly drumming on dead
leaves with its feelers. It is a wood-haunting species, and runs hither
and thither over the ground as if searching for something, and pausing
frequently to “purr.” This singular method of producing sound recalls
that of the drumming of Woodpeckers on the hollow branches of trees,
and similarly is produced without any special mechanism.
That the Scorpions should possess similar stridulating organs is only
what we should expect, having regard to their kinship with the Spiders.
In the great Rock scorpions of India and Africa the stridulating
apparatus lies between the basal segment of the pincers and that of
the first pair of legs, and consists of a set of tubercles and a
cluster of curved, hair-tipped spines. During moments of excitement the
pincers are waved up and down so that the spinules scrape against the
tubercles, emitting a rustling sound, which has been compared to that
produced by rubbing a stiff tooth-brush with one’s finger-nails. In
the South African _Opisthophthalmus_ the mechanism differs, consisting
of leaf-like hairs placed on the inner surface of the jaws. But since
both sexes possess these strange sound-producing mechanisms it has
been suggested that their main, if not their only purpose, is to serve
as a warning to enemies to keep their distance. Some of the great
bird-eating Spiders (_Aviculariidæ_) produce a kind of whistle; others,
sounds like the dropping of shot upon a plate.
These stridulating contrivances present some curious and puzzling
features. In the first place the sounds they produce are never loud
to human ears; therein they differ from the shrill piercing sounds
produced by like mechanism by the Crickets and Grasshoppers, though
even with some of these the notes are, to us, inaudible. In the second,
it has been suggested that where both sexes possess a stridulating
apparatus its purpose is solely to warn off enemies, and this because
the performers have no sense of hearing, and are thus, we presume,
unaware of the sounds they produce. There is something unsatisfactory
about this line of argument. There seems to be no evidence either that
the sounds produced are loud enough to terrify an enemy, or that the
performers are really deaf.
In cases where the males alone stridulate it is always supposed that
this “music” serves the purpose of a lure, or acts as an excitant, to
the female, even though inaudible to human ears. But there are many
people who are unable to hear the shrill squeal of our native bats. Yet
no one doubts but that all bats hear it. The argument as to the absence
of any sense of hearing in certain Spiders is based on their failure
to respond to the vibrations of a tuning-fork, but this evidence is
not conclusive. Neither is it safe to infer that the presence of
stridulating organs in the adult and immature stages of both sexes,
in some species, precludes their recognition as secondary sexual
characters. They may serve the double purpose of sexual excitants and
terrifying enemies, their motive being expressed by the quality of the
sound as certainly as the timbre of the human voice may express rage or
pleasure.
Neither Spiders nor Scorpions exhibit any very striking secondary
sexual characters. As a rule the female is the larger, often
strikingly so. Bright colours are rare, and are met with only among
the Spiders, wherein sometimes the male, sometimes the female, is the
more resplendent; where bright colours—apple-green, red and yellow—do
occur, they seem rather to be of the type known as Anti-cryptic,
or aggressive resemblance colours. That is to say, they are hues
developed to deceive prey by reason of the likeness they afford the
wearer to its surroundings. Thus, for example, one of our native
Spiders (_Tibellus oblongus_) is straw-coloured, and has an elongated
body, which is therefore seen with difficulty amid dry grass and
rushes which are the haunts of the species. _Misumena vatia_, one of
the Crab-spiders, resembles the flowers on which it is accustomed
to lurk for its prey. It is of a variable hue, commonly yellow or
pink, and a favoured lurking-place is near the blooms of the great
mullein (_Verbascum thapsus_), where it seizes upon bees coming for
honey. Exotic relatives of this species afford far more striking
illustrations of this kind. One has a pink, three-lobed body which
bears a striking likeness to a withered flower, and it exhales a sweet
odour of jasmine. Insects attracted by the smell are thus readily
pounced upon. Dr. Trimen, of Cape Town, describes a rose-red species
which exactly matches an oleander flower, and to complete the deception
the abdomen is marked with white. The same observer, approaching a
bush of the yellow-flowered _Senecio pubigera_, noticed that two of
the numerous butterflies settled upon it did not fly away with their
companions. Each of these he found to be in the clutches of a spider
whose remarkable resemblance to the flower lay not only in its colour,
but in the attitude it assumed. “Holding on to the flower-stalk by
the two hinder pairs of legs, it extended the two long front pairs
upwards and laterally. In this position it was scarcely possible to
believe that it was not a flower seen in profile, the rounded abdomen
representing the central mass of florets, and the extended legs the ray
florets; while to complete the illusion the femora of the front pair
of legs, addressed to the thorax, have each a longitudinal red stripe
which represents the ferruginous stripe on the sepals of the flower.”
But more remarkable still is the case cited by my friend Dr. H. O.
Forbes. This came under his notice while butterfly hunting in Java. The
butterflies of the family _Hesperidæ_ have a habit of settling on the
excreta of birds. Forbes noticed one on a leaf apparently enjoying a
feast. Creeping up, he seized hold of this victim of a depraved taste
and found it mysteriously held down. On further examination of this
“excreta” he found that it was really a spider! Later, when in Sumatra,
the same species once more in like manner deceived him. The deception
is more than usually remarkable, for it is not due to the coloration
of the body, but to what may almost be described as a diabolically
ingenious display of intelligence. For the creature weaves upon a leaf
a small white patch of web exactly resembling the fluid excrement of
a bird sliding down the smooth surface of the leaf. Having completed
this, the weaver lies on its back in the middle of the web holding on
by the spines with which the legs are furnished. It then awaits its
victim with the disengaged portions of the legs ready to close in a
deadly embrace the moment the lure has done its work. Though somewhat
in the nature of a digression, these facts show that colour often
plays a vital part in well-being; though in the matter of courtship
its rôle has probably been overestimated. Colour as an aid to “mate
hunting “probably nowhere plays so important a part as was at one time
believed. The Warblers among the birds, and the Spiders among more
lowly animals, seem to demonstrate this fact.
The actual mating of Spiders, the act of coition, is peculiar, and
demands notice, for the orgasm is not accomplished at the moment of the
ejection of the sexual products. The male discharges the seminal fluid
upon a small web woven for the purpose, and the liberated spermatozoa
are then sucked up into a tube—the _receptaculum seminis_—which lies
coiled up within a hollow bulb attached to the base of the last joint
of the leg-like feeler, or “pedipalp” at the base of the head. The
precious fluid is there stored and retained until the moment arrives
when these palps can be thrust into die genital aperture of the
female, and their contents discharged for the second and last time.
This is the critical moment of the Spider’s life, and it is noteworthy
that it should occur now, instead of at the moment of the discharge
from the body. The ejection from the palpal organ is effected by means
of a fibro-elastic bag, in its normal, collapsed, state spirally
disposed round the base of the bulb which contains the sperm tube.
Immediately preceding copulation this elastic bag or “hæmatodocha”
becomes turgid with blood, and it is probably the pressure thus exerted
on its base which affords the final fury of desire without which,
indeed, one might well imagine the necessary courage for copulation
would never be raised, at any rate, in the case of some species.
Strange as these facts are, the nice adjustment of the instincts for
their effectual performance is, by comparison, stranger still. By what
subtle sense is the male Spider informed of the importance of the
fertilizing fluid which escapes his body? What prompts him before its
escape to prepare a web for its reception? What prompts him after its
deposition to collect it within the palp till it shall be needed? The
least defect in the instincts appertaining to these vitally important
acts would mean the extinction of the race. We cannot suppose that the
nature of their performance is in any way realized by the performer,
and this makes their orderly execution the more wonderful.
[Illustration: Plate 34.
MALE ASTIA DISPLAYING BEFORE THE LESS BRILLIANT FEMALE.]
[Illustration:
From drawings, T. Carreras, in “Marvels of the Universe.”
MALE ICIUS DISPLAYING.
The “courtship” of the male spider takes the form of a “display”
recalling that of birds. He commonly ends in being eaten by his mate.
Face page 242.]
Our knowledge of Spiders under the afflatus of sexual desire has been
immensely increased by the long and patient observations of Mr. and
Mrs. Peckham. The fact that their investigations were carried on with
captive specimens, and therefore under artificial conditions both as
to environment and the number of individuals placed together at one
time, must not be lost sight of; nor must we forget that they worked
under the firm conviction that the Sexual Selection theory of choice
by the females was an indisputable fact. Wherever colour was present
they looked for, and saw, evidence that the female appreciated such
hues, though from their observations it would seem that dull-coloured
species behaved as though they were suffused with resplendent hues.
In the course of their studies the courtship of several species was
investigated, but a summary of their results is all that can be given
here. _Saitis pulex_ formed the subject of one of their experiments.
A male was placed in a box containing a mature female. “He saw her as
she stood perfectly still, twelve inches away; the glance seemed to
excite him and he moved towards her; when some four inches from her he
stood still, and then began the most remarkable performance that an
amorous male could offer to an admiring female. She eyed him eagerly,
changing her position from time to time so that he might be always in
view. He, raising his whole body on one side by straightening out the
legs, and lowering it on the other by folding the first two pairs of
legs up and under, leans so far over as to be in danger of losing his
balance, which he only maintains by sidling rapidly towards the lowered
side. The palpus, too, on this side was turned back to correspond to
the direction of the legs nearest to it. He moved in a semicircle for
about two inches, and then instantly reversed the position of the legs
and circled in the opposite direction, gradually approaching nearer and
nearer to the female. Now she dashes towards him, while he, raising his
first pair of legs, extends them upwards and forwards as if to hold her
off, but withal slowly retreats. Again and again he circles from side
to side, she gazing towards him in a softer mood, evidently admiring
the grace of his antics. This is repeated until we have counted one
hundred and eleven circles made by the ardent little male. Now he
approaches nearer and nearer, and when almost within reach whirls madly
around and around her, she joining and whirling with him in a giddy
maze. Again he falls back and resumes his semicircular motions with his
body tilted over; she, all excitement, lowers her head and raises her
body so that it is almost vertical; both draw nearer; she moves slowly
under him, he crawling over her head, and the mating is accomplished.
After they have paired once the preliminary courtship is not so long.
On one occasion a female was the more eager of the two, but this is
evidently very exceptional. The female always watches the antics of the
male intently, but often refuses him in the end, even after dancing
before her for a long time.”
Of another species—_Epiblemum scenicum_—they write: “The females seemed
to have some difficulty in choosing from among the males, but after a
decision has been reached and a male accepted, there appeared to be
complete agreement.” A species of the genus Iritis, which seems to have
baffled identification, was watched for hours under natural conditions
as well as in confinement.” A dozen or more males, and about half as
many females, were assembled together within the length of one of the
rails. The males were rushing hither and thither, dancing opposite now
one female, now another; often two males met each other, when a short
passage of arms followed. They waved their first legs, sidled back and
forth, and then rushed together and clinched, but quickly separated,
neither being hurt, only to run off in search of fairer foes.”
These most patient observers seem to have been convinced that whenever
Spiders possess vividly coloured areas on their bodies they are not
only conscious of this fact, but desire to make the most of such
splendour during the period of love-making. Thus they interpret the
behaviour of a curiously ant-like Spider—_Synageles picata_—which
has the first pair of legs especially thickened, flattened on the
anterior surface, and of a highly iridescent steel-blue colour. As
he approaches the female he pauses “every few moments to rock from
side to side, and to bend his brilliant legs so that she may look
full at them; ... he could not have chosen a better position than
the one he took to make a display.” And similarly they interpret the
movements of another species—_Dendryphantes capitatus_—which has a
bronze-brown face, rendered conspicuous by snow-white bands. The
attitude he assumes when sexually excited is one which seems, to them
at any rate, to serve admirably to expose this feature to the watchful
female. But he has other charms, and his “antics are repeated for a
very long time, often for hours; when at last, the female, either won
by his beauty or worn out by his persistence, accepts his addresses.”
_Habrocestum splendens_—unhappily these creatures have no names in
common speech—possesses an abdomen of a magnificent purplish red, and
the attitude which he assumes at courtship they regard as one designed
to display this to the full. Another case of quite remarkable interest
is that of _Astia vittata_, because the males appear to be dimorphic.
That is to say, they appear under two quite distinct forms, the one
red, like the female; and the other black, with three tufts of hair
just behind the head. The attitudes and the movements of courtship, it
is significant to remark, are entirely different in the two varieties:
the black form, assumed to be the later development, “is much the more
lively of the two, and whenever the varieties were seen to compete for
a female, the black one was successful.”
Professor Poulton, commenting on this particular case, contends that
“it must be admitted that these facts afford the _strongest support_ to
the theory of Sexual Selection.” But do they? A further examination of
the facts will probably show that the red “form” is but an immature
example, and this being so, the difference in performance and the
invariable success of Othello is at once accounted for. The fact that
the “two forms pass into each other” and that the “tufts only occur in
the fully developed _niger_ form” is an additional reason for regarding
the red form as immature.
Professor Poulton remarks: “When the males possess any special
adornment they make a point of displaying them as fully as possible.”
If this be so it seems to be a very foolhardy proceeding, akin to
holding the proverbial “red rag” to a bull: for it is well known that
the male Spider seeking a mate carries his life in his hands, at any
rate in the case of many species. Mr. and Mrs. Peckham observed several
instances of this remarkable sequel to Love’s embraces. In describing
the female of _Phidippus morsitans_ they remark that she was “a savage
monster. The two males we provided for her had offered her only the
merest civilities, when she leaped upon them and killed them.” The
first pair of legs in the males of this species possess “special
adornments” in the shape of long white hairs, and it was “while one
of the males was waving these handsome legs over his head that he was
seized by his mate and devoured.” Again, in the case of a male of
_Phidippus rufus_, the display of his “ornaments” was his undoing,
for he was “caught and eaten when he insisted upon showing off his
fine points too persistently.” Thus the females seem to “select” the
more resplendent males as much for eating as for mating! The ogre-like
habits of the females in this regard, indeed, are almost without
parallel in the animal kingdom.
Anyone who cares to take the trouble to watch the web of the large
Garden Spider (_Epeira diademata_) may witness one of these connubial
tragedies. In this species, the males are conspicuously smaller than
the females, and it is possible that this disparity has been brought
about by Sexual Selection, the largest and least active males having
been exterminated. In some species the discrepancy in size is most
striking, as for example in _Nephila chrysogaster_, the female of which
measures two inches in length, the male not more than one-tenth of an
inch, and less than one one-thousand-three-hundredth part of her weight.
The males, apparently, fully realize the perils which their amours may
lead them into. They haunt the borders of the webs of unmated females,
but exhibit a hesitating, irresolute manner. For hours they will linger
near her, feeling the silken carpet cautiously with their legs, and
apparently trying to ascertain the nature of the welcome likely to be
extended to them. The odds are against them: for even if allowed to
mate, unless they are extraordinarily agile in slipping away the moment
they have attained their object, the chances are they will be slain and
eaten!
Among some species, however, matters are otherwise: for the males of
the genus _Linyphia_, for example, are generally to be found living
peacefully with their consorts.
More rarely the male weaves a small nuptial tent, into which he
partly leads and partly drives the female: though the “driving” would
appear to be merely for form’s sake! The habits of the Cellar Spider
(_Tegenaria parietina_), a long-legged species fairly common in the
South of England, affords a yet further interesting and instructive
contrast with the foregoing accounts. The pairing habits of this
species have been studied by many observers, but perhaps the best
account is that of Mr. F. M. Campbell. He found, to begin with, that in
this species the tender ties of mating are at any rate rarely violated
by the horrible aftermath of cannibalism so common a feature with so
many other Spiders.
One or two illustrations from Mr. Campbell’s work must suffice. On
one occasion he placed together a male and a female. For four days
they took no notice of one another; then the female cast what proved
to be her last skin, and within three hours after, the male began
to show signs of interest in her presence—which is a fact of some
significance, for not till then had she attained maturity. “After a
few convulsive twitchings of the legs, the male pressed forwards,
moving his palpi”—the leg like “feelers” on each side of the head
which form the genital organs (page 241)—“up and down, when, as they
touched the palpi of the female, the pair played with these organs
like two friendly bees with their antennæ. After a few minutes the
female raised herself, leaning a little on her left side, and the male
crept forward until his head was under the breast of his mate, while
his first pair of legs were resting upon hers. He now advanced his
right palpus, leaning a little to the left and using the left palpus
as part of his support. The right palpus was slightly twisted so as
to bring the surface (containing the fertilizing germs) opposite the
sexual organs of the female.... He now rapidly raised his palpus up and
down for four or more seconds, and with such energy as to compel her
to assume a vertical position. He then retired and again approached
her, repeating the movements ... occasionally pausing before he
withdrew his palpus.... At times he would leave the female for five
minutes, and strut with straightened legs round the vase, wagging his
abdomen. Now and then he would remain perfectly still with the palpus
withdrawn, or play with the palpi of the female, while she seemed in
a comatose state. He would then renew the union with undiminished
vigour, appearing on each occasion less desirous of changing his
position. I left them at 12-30 a.m. and returned at 7 a.m. The male
was still using his right palpus. I saw no application of the left
palpus, but have no doubt that it was employed during the night, as
in other cases. I have not observed the pairing ever interrupted by a
fresh collection of semen, although there is no reason to think this
may not occur. The duration of pairing is long; but I am inclined to
think it is more dependent on the difficulty in inserting the palpus
than on sexual endurance. The impregnation appeared to take place
when the male retained his palpi in front of the bursa copulatrices
for about thirty seconds, which was frequently the case.” There
are occasions, however, when a very different sequel attends this
dalliance. In one instance, for example, Mr. Campbell placed a pair
together, and at once the male began to pay his addresses. “Shortly
afterwards he rapidly applied one of his palpi to the female ...
apparently with her consent.” Five hours later “he charged her, tore
away two legs ... and began to suck one, using the mandibles to hold
the limb as a human being would a stick of asparagus.” It is not
surprising to find she died an hour afterwards. An examination of her
remains brought to light the fact that she was not mature. But this
does not apparently explain the ferocity of her partner, for this
investigator on two other occasions saw males similarly dismember
their spouses an hour or so after impregnation. This horrid feast
cannot have been prompted by hunger, for one of these males had, but
a few hours previously, eaten a daddy-long-legs and two blow-flies.
Only twice did this investigator see a female of this species drive
away a male, and in each case immediately after union. “On the other
hand,” he says, “I have kept an adult pair together from the 22nd of
August to the 28th of October, and they lived in perfect amity. The
male never ceased paying unrequited attentions except to feed.” It will
have been remarked that the behaviour of this species in regard to
mating differs conspicuously from the accounts of observations on other
species, wherein the aggressive instincts are displayed by the female.
Mr. Campbell, commenting on these facts, remarks that such conduct is
just what one would expect from creatures which lead solitary lives,
and must have “come to regard weaker forms of animal life as food, or
as an inconvenience, if we except its young or its mate when in the
act of pairing.” Instincts which are habitually practised throughout
the greater portion of the life of the species, and on which existence
depends, would scarcely be suspended for a longer period than necessary
for sexual union. Spiders frequently eat one another, and such an
occurrence after pairing is only curious if considered apart from their
habits. When the sexual desire is satisfied, their actions would again
be directed by the dominant instinct of destruction.
It is to be noticed that the attack, when made by a female, often
immediately follows the sexual union, while in the case where males
assume the aggressive it takes place some time afterwards. Mr. Campbell
explains this by the supposition that the action of the female, when
satiated, would be precipitated by the threatened and unacceptable
continued application of the hard, spiny palpus, while the more lasting
desire of the male would have to subside before he became directed by
another instinct. By that time, other attractions, if not his wandering
disposition, would take him away from the web.
The fact that male Spiders are comparatively rare is perhaps explained
by the fact that they are very short-lived; they probably die soon
after pairing—even if they are not eaten! The snares they spin, it is
to be noted, are very imperfect, though curiously enough, when young
they make perfect snares on a small scale.
It will have been noticed, in the course of the foregoing descriptions,
that Spiders display a more or less conspicuous wariness, a cool,
deliberate “counting on the cost” in their matrimonial ventures that is
often wanting in such matters in the human race. But, then, the risks
involved are more patent, more imminent. Mr. Campbell comments on this
intelligent behaviour in the case of the Cellar Spider, remarking that
they measure “each other’s strength when on the same web by the tension
and motion of the threads.”
A word as to the Scorpions. These creatures are near relations of the
Spiders, and in many things resemble them, notably in regard to their
ferocity. One does not meet here, however, with the same disparity in
size between the sexes, nor are vivid colours ever developed. This,
according to some, would be accounted for by the fact that though these
creatures possess numerous eyes they are practically blind, and depend
for their information as to what is going on around them by their sense
of touch, which is excessively delicate. They are morose in disposition
and always solitary. It has been said that if two are found under the
same stone—a favourite lurking-place—one is engaged in eating the
other! Nevertheless, they are of abstemious habits, for the naturalist
Fabre found that from October to March they last, though throughout
this time they remain alert, and always ready to resent disturbance. In
April they exhibit more activity, though even then they eat but little.
But now they begin to wander in search of mates.
Fabre’s observations on their mating habits are exceedingly
interesting, and they have brought to light some very extraordinary
phenomena. His notes were made on the species common in the South
of France—_Buthus occitans_. Mr. Cecil Warburton, referring to the
distinguished Frenchman’s work, quotes the following noteworthy passage
in the Cambridge Natural History: “After some very curious antics, in
which the animals stood face to face with raised tails, which they
intertwined ... they always indulged in what Fabre calls a ‘promenade
à deux’ hand in hand, so to speak, the male seizing the chelæ of the
female with his own and walking backwards, while the female followed,
usually without any reluctance. This promenade occupied an hour or
more, during which the animals turned several times. At length, if
in the neighbourhood of a suitable stone, the male would dig a hole,
without for a moment entirely quitting his hold of the female, and
presently both would disappear into the newly-formed retreat.”
[Illustration: Plate 35.
Photo by P. H. Fabre.
SCORPIONS.
The early stages in the courtship of the scorpions are full of romance.
The two prospective partners for life engaging in a kind of waltz,
holding each other’s “hands.”
Face page 252.]
After the mating, as with the Spiders, the male is often devoured by
the female. After any combat with an enemy, such as a _Lycosa_ or a
_Scolopendra_, it seems to be _de rigueur_ to eat the vanquished.
If the mating period in the case of the higher animals rouses the
males to the pitch of frenzy, that frenzy is dangerous only to
possible rivals. With the more lowly Spiders and Scorpions ferocity of
disposition is a normal feature, and one which can with difficulty be
held in check long enough to permit the all-important act of mating
to take place. In how far this is accounted for by the extremely
deficient senses of sight and hearing, which are such marked features
in these animals, it would be difficult to estimate. But that the
manner of their display is governed by these deficiencies there can be
no doubt. The Spider, having a more or less efficient vision at short
range, executes more or less elaborate antics in front of the female,
designed, as in the case of the birds, to serve as excitants to fan
sexual desire, already smouldering, to a flame. With the purblind
Scorpion the Spider-antics are useless; he must proclaim his desire
by a pressure of the hand, and by intertwining his tail with that
of his prospective mate as they “walk out” together. But Scorpions
at one time were credited with a very acute sense of hearing; later
investigations, however, fail to yield any evidence whatever that they
possess this sense, though experiment has proved that their sense of
touch is excessively delicate and seems to reside in the hairs which
are thickly distributed over the legs and body. Now, hearing and touch
are senses near akin, and the vibrations produced by stridulation may
be, and probably are, received by, and interpreted through, the medium
of these hairs. For though the Scorpion may not respond to sounds made
by curious investigators, it may be that they can perceive notes of a
low pitch imperceptible to our ears, such as are made by stridulating
organs, as in the case of the Spiders.
Perchance certain comb-like structures known as the “pectines” may
play a part in mate-hunting. These are placed on either side of the
under-surface of the body between the last two pairs of legs. The fact
that they are larger in the male, and sometimes strangely modified in
the female, seems to show that they have some function in relation to
sex. They also appear to serve as sources of information as to the
nature of the ground traversed by the animal, since they are long in
species which walk with the body raised high off the ground and short
in such as adopt a more grovelling posture. That the Scorpions possess
but a very limited means of gleaning information of the outer world
there can be no doubt. How, then, do they find one another when that
insistent desire to mate begins to make itself felt? Are the “pectines”
their informants through the sense of smell? Do the hairs scattered
over the body act as sound-collectors responding to the notes emitted
by the stridulating organs? These are points on which information is
much to be desired.
[Illustration: Plate 36.
Photo by P. H. Fabre.
DEATH OF THE MALE SCORPION.
But by the time the nuptial rites have been performed the female has
thrown off her “sweetness,” and ends by eating her lover!
Face page 254.]
[Illustration: Plate 37.
Photo by Paul H. Fabre.
THE FEMALE MANTIS DEVOURING HER MATE.
With these insects, as with the spiders and scorpions, the male is
often eaten by the female.]
Our survey of the “Arthropoda,” as those limb-bearing jointed animals
invested in a horny, or, more exactly, a “chitinous” external skeleton
are called has so far been confined to such as, during adult
life, at least, are land-dwellers. But the aquatic types known as the
“Crustacea” furnish some extremely interesting facts in regard to the
problems of sex. In the first place, they too possess a stridulating
apparatus. This is curious, but not surprising, because, although
the skeleton of such creatures is of a harder and almost stone-like
character, the development of roughened surfaces working in opposition
to one another might well have been foretold to occur, at least in
some individuals. Colonel Alcock—a naturalist who has contributed
largely to our knowledge of marine animals by his researches in the
Indian Ocean—in his most delightful book “A Naturalist in Indian Seas,”
describes what he calls a “musical crab.” This is the great-horned
Coromandel Strand Crab (_Ocypoda macrocera_). In both sexes of this
remarkable genus he says, “the nippers, or chelipeds, are singularly
unequal in size, and in all the species but one there is present on
the inner surface of the ‘hand’ of the larger cheliped a transverse
row of five teeth, which, when the cheliped is flexed, can be made to
play against a ridge or another row of teeth on its ‘arm’ ... much as a
man might rub one side of his chest with the palm of the corresponding
hand. The whole mechanism, except that it is on a larger scale and has
a more finished appearance, is very much like that by means of which
crickets and grasshoppers produce their shrill music, and no one has
ever doubted that it is used for the same purpose, though very few
people have actually heard it in action. I myself ... was beginning
to think that the structure must, after all, have some quite other
function, when one morning ... on the sandy wastes of the Godavari
delta, I at last, like Ancient Pistol, heard with ears that which I
had been so long waiting for. That is to say, I heard a noise very
much like that which an angry squirrel makes, and discovered that it
came from a red ocypode crab into whose burrow another individual had
trespassed.
“In order to understand the matter it should be known that these
crabs ... are gregarious, and that each one has a burrow of its own.
Though they may be seen marching in battalions across the sand, yet as
a rule they stay close to their burrows, methodically searching and
sifting the surrounding sand for any food that may have been thrown
up by the tide, and flying to their burrows with headlong speed when
alarmed. At first sight one does not understand the necessity for so
much wariness, and for such a deep system of entrenchment, for the
creatures seem to hold undisputed possession of the whole shore; but as
a matter of fact they are preyed upon all day long by Brahminy kites,
and when the jackals come out in the evening, by them. Now, although
each crab may on ordinary peaceful occasions know its own home, yet
when a crowd of them are running for their lives they may sometimes,
one would think, act on the devil take the hindmost principle and
try to squeeze into the nearest burrow. But as ancient philosophers
do report, things may be done upon occasion which it is inexpedient
to make a habit of doing, and this seems to be one of those things;
for if many Crabs made a practice of crowding into one small burrow
they would certainly run the risk of being suffocated, if not crushed
to death outright. It seems probable, therefore, that it would be
advantageous to the species as a whole if the rights of property in
burrows were rigidly respected, and if each individual member possessed
some means of giving notice that its burrow was occupied ... and
I think that this consideration gives us a clue to the use of the
stridulating mechanism. At any rate, I was often able, after my first
accidental discovery, to elicit the sound, by catching one of these
crabs and forcing it into a burrow which I knew was already occupied:
the intruder would never go far in, but would crouch just inside the
mouth of the burrow, and if it were made to travel deeper, then the
voice of the rightful owner would be heard in indignant remonstrance
from the depths.” Another species, the Grey Ocypode Crab (_Ocypoda
ceratophthalmus_), possesses a similar instrument, and makes therewith
a loud, croaking noise. But it does not often burrow deeply. Colonel
Alcock therefore suggests that in this case it may be used for scaring
enemies.
That these curious musical instruments may also be used in mate-hunting
seems highly probable. If the stridulation is produced on one occasion
to announce the fact that callers are not desired, it may on another
signify an equally emphatic invitation to enter, the mood of the
occupant being expressed by the character of the sounds emitted. It is
significant, at any rate, that there are no external sexual differences
in these species; hence the probability that it is by stridulation that
the sexes distinguish one another.
This view seems to obtain confirmation from the fact that the Crabs of
the genus _Gelasimus_, or “Fiddler-crabs,” which are near relations of
the ocypode Crabs, and, like them, live in burrows in large companies,
and are exposed to the same enemies, which they avoid in the same
way by burrowing, have no stridulating mechanism, but the sexes are
strikingly different. This is especially so in the case of the nippers,
or chelipeds. These, in the female, are slender and much shorter than
the legs, being used mainly for feeding. In the adult male one of these
“hands” is often twice as big as the body itself! “Many uses,” remarks
Colonel Alcock, “have been assigned to this enormous, lop-sided organ:
some say that it is used as a stopper to barricade the mouth of the
burrow, others that it is a sort of cradle or bridal-couch upon which
the female reclines—the male, in this case, literally bestowing his
hand upon the female; but from observations of _Gelasimus annulipes_, the
species which most frequents the Godavari mud-flats, I believe that it
primarily serves as a war-club, for the males indulge in interminable
tournaments for the hand of the female; and secondarily, for it is of a
most beautiful cherry-red colour, as an ornament to attract and delight
the latter capricious sex.
“Landing one afternoon in March upon a cheerful mud-flat of the
Godavari sea-face, I was bewildered by the sight of a multitude
of small pink objects twinkling in the sun, and always, like
will-o’-the-wisps, disappearing as I came near to them, but flashing
brightly on ahead as far as the eye could reach. It was not until I
stayed perfectly quiet that I discovered that these twinkling gems were
the brandished nippers of a host of the males of _Gelasimus annulipes_.
By long watching, I found out that the little creatures were waving
their nippers with a purpose—the purpose apparently being to attract
the attention of an occasional infrequent female, who, uncertain,
coy, and hard to please, might be seen unconcernedly sifting the sand
at the mouth of her burrow. If this demure little flirt happened
to creep near the burrow of one of the males, then that favoured
individual became frantic with excitement, dancing round his domain
on tip-toe and waving his great cherry hand as if demented. Then, if
another male, burning with jealousy, showed a desire to interfere, the
two puny little suitors would make savage back-handed swipes at one
another, wielding their cumbrous hands as if they had no weight at all.
Unfortunately, though I spent many a precious hour on the watch from
time to time, I could never see that these combats came to anything;
the males seemed always to be in a state of passionate excitement, and
the females to be always indifferent and unconcerned; and though the
dismembered chelipeds of vanquished males could often be seen lying
on the battle-field, I never had the satisfaction of beholding a good
stand-up fight, fought out to the sweet end, or a female rewarding a
successful champion with her heartless person.”
[Illustration: Plate 38.
THE “FIDDLER-CRAB” AMONG MANGOE ROOTS.
This species is remarkable for the enormous size of the right “arm,”
which exceeds that of the body.]
[Illustration: _Photos by W. Saville-Kent._
THE “FIDDLER-CRAB.”
This “strong right arm” is used in conflicts with rivals for the
possession of the females.
[Face page 258.]
The fascinating tale of Colonel Alcock’s observations does not end
here, however, for he has brought to light some extremely interesting
facts in regard to the sexual aspect of Crustacean life in the deep
sea; information gathered during his exploration work on board the
Investigatory much of which was done to enlarge our knowledge of the
abysses of the ocean where the light of day never penetrates. Here, he
remarks, the conditions of life might seem to be reduced to a minimum
of simplicity, yet evidences are not wanting that, among the higher
Crustacea, they are complicated, much as they are everywhere else, by
the play of the sexual instincts.
In these awful depths, where reigns eternal night, most of the
inhabitants, of whatever kind, from fishes downwards, are blind and
eyeless, or they possess enormous eyes and a purblind vision responding
to the only light these regions display, that of phosphorescence,
which is generated by so large a number of those creatures which are
condemned by Fate to live this sunless life.
“It is written,” he remarks, “that the male must exert himself to
find a mate, and where sight cannot help him in his search, a kind of
blind-man’s buff is the only alternative. In this serious game many
deep-sea Crustacea, especially those of the Shrimp-tribes, trust to the
sense of smell, as the greatly developed outer, or olfactory, branch of
the first pair of antennæ bears witness. These antennæ, again, seem
to be used by the males of some species for catching their partners,
and in _Parapeneus rectacutus_ ... they are turned into a sort of crook
for this purpose. This has long been thought to be their function in
the Prawns of the oceanic genus _Sergestes_.” In the male of certain
other deep-sea Prawns, the hind pair of foot-jaws are modified in a way
which can only mean that they are used for hooking on to a partner of
the opposite sex. In the deep-sea Hermit-lobsters of the genus _Munida_
the nippers are greatly enlarged, as in many Shore-crabs, for the
purpose of subjugating rivals and embracing the females; and in all
such cases these are much smaller in the female and immature male.
Mention of numerous cases has already been made where the female is
larger than the male, and is the more pugnacious, and in such cases
the females are generally more numerous than the males. Some of
the deep-sea Prawns exhibit the same peculiarity. And in these the
sword-like forward prolongation of the head-shield is far larger than
in the male. Now this rostrum is the most formidable weapon which the
Prawn possesses, so that we may, with tolerable certainty, conclude
that the females fight their rivals for the possession of the males,
which are, in these species, far less numerous than the females.
Among the lower Crustacea, such as the “Fairy-shrimps,”
“Brine-shrimps,” the “Water-fleas,” and the “Copepoda,” which play so
important a part in furnishing food for many of the fishes which in
turn feed us, secondary sexual characters of an extremely interesting
kind are met with. These, however, are never such as appeal to the eye,
for the vision in these creatures is but feebly developed. Scent, as
is usual where sight is defective, plays an important part in enabling
the sexes to discover one another. Selection here secures success only
to such as have the proper odour and the most sensitive organs of
smell. In these creatures, as with the butterflies and moths, the odour
emanating from the female is most powerful, while the sense of smell
is most developed in the male. One of the most striking illustrations
of these facts is furnished by that very beautiful species _Leptodora
hyalina_—a veritable giant among these small Crustacea—wherein the
antennæ of the male are produced into enormously elongated comb-like
structures, the teeth of the comb being formed by delicate olfactory
filaments. In the female these antennæ are extremely short and their
olfactory filaments are limited to a small terminal tuft to the
antennæ, answering to the larger tuft at the base of the comb of the
male.
To the majority of species, however, delicate odours seem to make
little or no appeal, since excessive development of the olfactory
apparatus, such as is seen in the aberrant Water-flea (_Leptodora_),
is rare. This is perhaps explained by the fact that Leptodora is a
species which does not herd together in vast numbers, hence, probably,
the need of some exceptional means whereby the males may discover
the whereabouts of the females, while in the case of the swarming
hosts formed by Water-fleas and Brine-shrimps, for example, no such
highly specialized aid is necessary. Instead, the males have developed
powerful arms for the capture and retention of the females. In the case
of the Brine-shrimp these arms are of quite formidable proportions. The
males of the Copepoda, remarks Weismann, “possess on their anterior
antennæ an arrangement which enables them to throw a long, whip-like
structure like a lasso round the head of the female as she rapidly
swims away. The antennæ of the male Daphnids, too, are in one genus
(_Moina_) developed into a grasping apparatus; ... the first antennæ
... are not only much longer and stronger than those of the female,
but they are also armed with claws at the end, so that the males can
catch their mates as with a fork, and hold them fast. And even that
was not enough, for, in addition, the males of most Daphnids possess a
sickle-shaped but blunt claw on the first pair of legs, which enables
them to cling to the smooth shell of the female, and to clamber up on
to it to get into the proper position for copulation.
[Illustration: Plate 40.
SOME REMARKABLE DEVICES.
1. A Water-flea (_Moina rectirostris_): male showing the claspers-the
front pair of “legs,” for grasping the female.
2. The female of the same, in which the “claspers” appear as mere
stumps.
3. The aberrant Water-flea (_Leptodora kindlii_): the male showing the
long comb-like antenna for the discovery of the female (the left only
is drawn), and the female, just beneath, lacking this olfactory organ.
4. An extraordinary species of Bug in which the upper surface of the
thorax has been produced backwards to form an overhanging pent-house,
of unknown function, and illustrating the theory of “Hypertely.”
Face page 262.]
“If we inquire into the manner of the origin of secondary sexual
characters of this kind, we shall find that both may have been
increased by sexual selection, for a male with a better sickle will
succeed more quickly in getting into the proper position for copulation
than one with a less perfect mechanism. This assumption does not rest
on mere theory, for I was once able ... to observe for a considerable
time, under the microscope, a female to whose shell two males were
clinging, each trying to push the other off. Nevertheless, it seems
to me very questionable whether the origin of this sickle-claw
can be referred to sexual selection, for without this clamping-organ
copulation in most Daphnids would not be possible. It was thus not as
an advantage which one male had over another that the clamping-sickle
evolved, but rather as a necessary acquisition of the whole family,
which must have developed in all the species at the same time as the
other peculiarities, and notably those of the shell. The competition of
the males among themselves is thus in this case simply an expression
of the struggle for existence on the part of the species as such, and
it is not a question merely of a character which makes it easier for
the males to gain possession of the females, but of one which had
necessarily to arise lest the species should become extinct. In other
words, in this case Natural Selection and Sexual Selection coincide.
“The case of the antennæ of _Moina_, which have been modified into
grasping organs is quite different; these owe their origin, not to
natural selection, but to sexual selection, for antennæ of that kind
are not indispensable to the existence of the species, as we can see
from the closely related genera, Daphnia and Simocephalus, where the
males have quite short, stump-like antennæ, furnished with olfactory
filaments not much more numerous than the females possess. Just as
these supernumerary olfactory filaments were produced by sexual
selection and not by the ordinary natural selection, because those
males with the more acute sense of smell had an advantage over those in
which it was blunted, so the males of the genus Moina which could grasp
most securely had an advantage over those that gripped less firmly, and
thus arose these two different kinds of male characteristics. Neither
of them is of advantage to the species as such, but only to the males
in their competition for the possession of the females.”
Much uncertainty would seem to exist in regard to two very
extraordinary marine species of Copepoda. In one, _Calocalanus pavo_
the male possesses enormous antennæ, and a remarkable development of
iridescent feather-like structures at the end of the body, arranged
in a sort of open fan-work; the female has what may be called “normal”
antennæ, and a brush-like tuft at the end of the body. In the other
species—_Calocalanus plumulosus_—of which the female only is known,
there is a similar arrangement of plume-like structures at the end of
the body, but all but one are extremely small; the single plume differs
from the rest in being of enormous length. Commonly these structures
are regarded as mechanisms to reduce the expenditure of energy
necessary to keep at the surface of the water, for these creatures
inhabit the surface-waters of the open ocean. Many larval Crustacea
inhabiting similar areas are in like manner kept afloat, or at any rate
aided in keeping afloat, by the excessive development of spines. But
if this be the purpose of these strange excrescences of _Calocalanus_
it seems curious that the female of C. pavo should not be similarly
provided. If they are to be regarded as secondary sexual characters it
is curious that the females of _C. pavo_ and _C. plumulosus_ should be
so utterly dissimilar. The male of _C. plumulosus_ is unknown. On the
whole, it seems more reasonable to regard these strange structures as
mechanical aids to swimming rather than as secondary sexual characters.
CHAPTER XIII
SOME STRANGE MARRIAGE-CUSTOMS: AND VIRGIN BIRTHS
The Courtship of the Cuttle-fish—The Sumptuous Cradle of the
Argonaut—The Love-darts of the Snail—Hermaphrodites and the Dangers
of Self-fertilization—Oysters and Beauty—Sex reduced to its Lowest
Terms—Parthenogenesis and Virgin Birth—The Story of the Hive-bee—The
Departure of the Queen—The New Queen and her Marriage-flight—The
Celebration of the Nuptials and its Surprising Sequel—The Widowed Queen
turns Executioner—The Queen as Mother—The Queen’s Daughters—Nursemaids’
Duties—Change of Work—The Drones and their Career—Food and Sex—The
Bumble-bee and its Life-story.
That the psychical emotions sway the goad of sexual instincts in the
higher animals there can be no doubt; and there can be as little
uncertainty that this stimulating and controlling factor gradually
loses force as we descend in the scale of animal life. Just where
it ceases it is impossible to say. A vague, nebulous intelligence
doubtless persists after these more subtle emotions have ceased, and
this, probably, in turn, gives place to purely instinctive behaviour.
These various phases of the sexual problem grade one into the other.
But they are all parts of a continuous sequence, beginning, apparently,
in relatively simple responses to chemical interactions of the kind
known as chemotaxis and ending with the passion which, in the human
race, may become a consuming fire, purifying and ennobling, or exactly
the reverse—according to the nature of the inflammable material. That
is to say, in the phenomena of sex one sees emotions in the making. The
begetting of children becomes the underlying goal of life, the hidden
heart and soul of animated nature.
This being so, one cannot but feel surprised at the discovery that,
in certain groups of the animal kingdom one meets with a strange
exception to this great rule. And this is furnished by the phenomenon
of parthenogenesis, wherein sexual desire has been dethroned.
Offspring result from Virgin births: parental care is non-existent.
This anomalous condition must be regarded as an offshoot of the
normal course of events traced in these pages, and not as a primitive
condition. This interpretation seems to be shown clearly enough in
that almost every case where parthenogenesis obtains, males, sooner
or later, make their appearance—periodically or sporadically. Every
stage between the normal, seasonal appearance of males and their entire
suppression can be traced, and an analysis of these cases demonstrates
unequivocally the uplifting character of the bi-sexual state, if only
by the fact that the uni-sexual condition makes no demands on the
parent, and does nothing to foster the growth of the higher emotions.
No attempt need now be made to discover the origin of parthenogenesis.
Let it be assumed, for the moment, that it is a condition derived from
hermaphroditism, wherein each individual is monœcious or bi-sexual.
In all diœcious or uni-sexual animals, that is to say, where the
individuals composing the species are either male or female, each
contains a leaven of the opposite sex, even when adult. It is still
a moot point whether, in the earlier stages of development, chance
decides whether the sex shall be male or female, or, at any rate,
whether the growing body is potentially male or female, till the die is
cast by some as yet undiscovered factor; or whether this is determined
from the very beginning of germinal life. In many of the lower animals,
as among the Mollusca and some of the insects, each individual is as
much male as female, and it is from a condition such as this that
parthenogenesis probably had its rise.
These two groups are selected here because they, more than any others
in like case, afford some extremely interesting gradations in this
strange phenomena of what is to be regarded as the degeneration of
sexual individuality, for each contains some members wherein the sexes
are separate, and in these cases sexual desire is present in varying
degrees. In some it is associated with very remarkable phenomena.
Among the Mollusca the Octopuses afford one of the most striking
illustrations of such phenomena. In these creatures one of the
sucker-bearing arms is more or less completely transformed to subserve
the ends of sexual congress. Without entering into the technical
details of the changes, it will suffice to remark that it is modified
in such a way as to allow the transference of the spermatozoa from
the body cavity wherein they are formed, to the arm near, or at, the
tip of which they are stored in a special sac or “spermatophore,” and
such modified arms are said to be “hectocotylized.” This extraordinary
modification attains its maximum development in the celebrated
Argonaut, and one or two of the more typical Octopuses. In the Argonaut
this arm does not make its appearance until sexual maturity has been
attained, when a large more or less globular swelling appears,
enclosing the third arm of the left side, coiled upon itself. Having
attained its full development the sac bursts and releases the arm. The
folds which formed the sac now bend back to form a new receptacle into
which the spermatophore is passed. But this is not all. The tip of the
newly released arm bears another sac, which sooner or later bursts,
forming a long, slender penis, and along the central tube of this the
spermatozoa pass from the spermatophore to their destination. Their
conveyance thereto forms the last and most amazing feature of this
strange history. The male, eager with pent-up desire, and glowing with
all the colours of the rainbow, gradually approaches the female of his
choice, who apparently awaits him with no little palpitation, and then,
with a sudden rush flings himself upon her, and apparently thrusts
the penis into her mantle cavity, when at once the whole arm breaks
off from his body and remains attached to her person, retaining its
vitality, strange as it may seem, for some considerable time, during
which, no doubt, the spermatozoa are slowly making their way out of
the spermatophore and along the channel prepared for their reception.
That the Cuttle-fish are polyandrous there seems to be little room for
doubt, inasmuch as no less than four such detached arms have been found
beneath the mantle of one female. With the majority of the Cuttle-fish
and Octopus tribe the arm is not detached, but when it is so, and this
occurs in all the species belonging to three different genera, a new
arm is grown.
[Illustration: Plate 41.
SOME REMARKABLE METHODS OF “COURTSHIP.”
1. The female Argonaut and her egg-casket.
2 and 3. The male Argonaut and his “hectocotylized” arm.
4. A Cuttle-fish (_Ocyhöe catenulata ♂_), showing the “hectocotylized”
arm described in the text, and the “spermatophore” at the base of the
long filament.
Face page 268.]
As a rule, among these animals the males are smaller than the females.
In the case of the Argonaut there is a yet more striking difference,
for the female possesses a very beautiful shell in which she carries
her eggs. This remarkable cradle, translucent and beautifully
sculptured, she attaches to her person by means of a pair of arms which
are expanded to form great lobes, almost but not quite completely
covering the shell. The earlier naturalists believed that this shell
served as a boat, and that the lobated arms were spread as sails! This
supposed fact naturally caught the fancy of the poets, who seized upon
it to point a moral and adorn a tale. Byron celebrated these imaginary
feats of seamanship in the familiar lines:
The tender Nautilus who steers his prow,
The sea-born sailor of his shell-canoe.
and Pope bids us:
Learn of the little Nautilus to sail,
Spread the thin oar, and catch the driving gale.
Sir Richard Owen years ago, however, dispelled these pretty fancies,
though the facts are surely as wonderful as the fables they have
replaced. They afford, too, one of the most striking secondary sexual
characters to be met with among the Mollusca; nowhere else, indeed,
among the members of this group is so strange a cradle to be met with.
But little, unfortunately, is known of the behaviour of these animals,
which are by far the most active of the Mollusca, and which also
display no small degree of intelligence. Their eyes, which are of great
size and complex structure, are undoubtedly far more effective organs
of vision than are possessed by any other Molluscs. It is possible,
therefore, that the sexes discover one another by sight; and it is
certain that something in the nature of a “Courtship” takes place.
The majority of the species, also, possess the most extraordinary
powers of changing their coloration, especially during moments of great
excitement. The magnificence of the hues which succeed one another,
like a series of variegated blushes suffusing the whole body, may be
one of the weapons in the armoury of Cuttle-fish love-making. In how
far the “courtship” of the Cuttle-fish resembles that of terrestrial
animals, however, is a matter on which at present nothing is really
known. That even the comparatively sedentary species, like the Octopus,
seize upon and hold territory is very improbable, for there is no
need of such landed estates, inasmuch as the offspring are not tended
and fed by the parents—this would indeed be a laborious task in the
case of some of the “Squids” which lay between thirty thousand and
forty thousand eggs! Having regard to the fact that the records of
the reproductive habits of the Octopus tribe date back to the time of
Aristotle, more than two thousand two hundred years ago—for he first
drew attention to the hectocotylized arm—it is curious that so little
has been gleaned during this vast space of time.
There are facts in regard to the sexual relationships of some of the
Snails that are in nowise less remarkable than those just related of
the Octopus tribe. Unlike the Octopuses, the Snails are hermaphrodite,
nevertheless sexual congress takes place as with unisexual species:
the eggs of the one being fertilized by the spermatozoa of the other.
During this process the orgasm of the sexual act appears to be brought
about by stabbing one another by means of a little dart formed of
carbonate of lime, the dart burying itself in the flesh and apparently
promoting a pleasurable, tingling sensation in the course of its
journey. Speedily, no doubt, it becomes absorbed, the material being
then available for the formation of a new dart.
This remarkable instrument, which is known as a “Love-dart,” or
_Spiculum amoris_, assumes a different form in each species in which
it occurs. In some the shaft is ridged like a bayonet, as in the case
of the Garden Snail, in others the form assumed is that of an awl.
These darts are formed within a special receptacle, or “dart-sac,” but
so far no explanation as to the origin of these remarkable structures
has even been hinted at. They do not seem to have been derived by the
modification of some pre-existing organ serving a different function,
as wings, for example, are derived from walking limbs, or as lungs are
derived from air-sacs. Their origin is as mysterious as their use:
for they are not found in all Snails, though they occur in one or two
Slugs—which are degenerate Snails. But no other Molluscs save the
Snails and one or two of their immediate allies are so armed.
The hermaphrodite conditions of these animals, as with other Mollusca
in like case, present some knotty points for consideration, and
especially in regard to the problem of sex-attraction. Where each
individual is as much male as female, which is the dominating factor in
desire, the maleness or the femaleness? Though each individual contains
both ova and sperm cells, probably these ripen at different times, to
avoid danger of self-fertilization. In this case the sex impulses are
on the same footing as in the case of animals wherein the sexes are
not thus combined. That is to say, the individual which is for the
moment only potentially male mates with another for the moment only
potentially female. But this being so, how does each discover the
condition of the other?
Many of the Snails, like _Helix nemoralis_, are gaily coloured. Are
these hues, these bands of black and yellow, the product of “sexual
selection”—the outcome of a process of selection from among the most
conspicuously coloured individuals as postulated by the Darwinian
theory of Sexual Selection? If so, then this choice must be regarded
as a periodic recurrence coinciding with the period during which the
individual is dominated by its female attributes. In due course it
becomes, for the time, a male, and may find itself rejected, owing
to a lack of intensity in its coloration, or, on the other hand, it
may vanquish a rival by its very splendour. Each, in short, would
help materially in this process of beautification. If the choice of
mating for it is this rather than a choice of mates—proceeds on these
lines, the bright coloration of the members of this species becomes
easy to understand. But does it? It is more than doubtful whether the
eyes of Snails are sufficiently good to distinguish the coloration
of their neighbours’ shells, or for the matter of that of their own,
for their eyes being carried on long mobile stalks, they should have
no difficulty in contemplating their own charms. And what of Snails
of more sober hues? It seems highly probable that here, as in so
many cases, scent is the selecting factor, and the coloration is an
“accidental” feature. That the colour of the shell plays no such part
as that just postulated may be gathered from the evidence afforded by
many marine species, whose shells, though conspicuously marked, are,
during life, completely enveloped and concealed by the all-investing,
fleshy mantle. In like manner the exquisite beauty in the form and
sculpturing of the shell which so many species exhibit, are characters
which cannot be regarded as due to sexual selection.
As touching the danger of self-fertilization to which reference has
been made. That this is real is shown by the fact that the ova and
spermatozoa are rarely ripe in one individual at the same time.
However, among the pulmonata, or air-breathing gastropods, it seems to
have been established that self-fertilization can, and does, occur.
That in some species, at any rate, where cross-fertilization, for some
reason, is impossible, the individual thus isolated can store up its
own spermatozoa to be used in fertilizing its own eggs. But the fact
that this rarely happens is testimony enough that such occurrences are
inimical to well-being.
The Lamellibranch, or bivalve Mollusca, _e.g._, Oyster, Mussel, and
Cockle, afford valuable evidence as to excrescences and extravagances
of growth which appeal to our eyes as ornamental, and therefore likely
to be due to the influence of sexual selection. And this because such
ornamentation is a very conspicuous feature among these animals. Yet,
save in a few cases, locomotion is impossible, and sight is wanting.
Light-distinguishing organs, and therefore eyes, are possessed by some,
but in no case probably are they strong enough to appreciate form.
Even if they did, such revelations of beauty would play no part in
mate selection from among the most ornamental; for these creatures are
commonly fixed throughout life in one position, often, indeed, buried
in mud or sand. Some move laboriously: a few, like the Cockles and
Pectens, swim by rapidly opening and closing the shell. The Pectens
are brilliantly coloured, not only as regards the shell, which is also
beautifully sculptured, but the foot also is of a vivid scarlet, and
the Pecten have numerous minute eyes. But the Cockles and Mussels
possess like attributes as to colour and sculpture, yet they are
blind. More to the point is the fact that these animals do not mate
after the fashion of higher animals, but the males, where the sexes
are distinct, discharge immense quantities of spermatozoa into the
water, and these find their way to the ova of the female through the
action of the inhalent currents set up by the animal for the purpose of
drawing in fresh supplies of water containing food and oxygen. There
are no “secondary sexual characters,” that is to say, that even where
the sexes are separate, and many, like the Oysters, are hermaphrodite,
they are externally indistinguishable. Nevertheless, many, as has been
already remarked, have shells of great beauty. As, for example, the
giant Tridacna and the strangely spinous valves of the “Thorny Oysters”
(_Spondylidæ_).
The fact that the Lamellibranch, or bivalve molluscs, are far less
numerous in point of species than the univalve tribes is accounted for
by the fact that in the first place they are of necessity aquatic, and
in the second their means of locomotion is extremely limited. Some few
species swim spasmodically: some crawl: many are incapable of movement
when once the motile larva settles down and the shell-bearing adult
stage is attained. Such species can extend their range only by means
of larval wanderings. Enormous numbers, millions, of young have to be
produced and set adrift each year by every adult in the community, and
yet but a few of each brood can ever attain to maturity. Life, for such
species, must be a dull, monotonous business: the only opportunity for
excitement is that which is preliminary to being eaten, and the only
purpose in life is to be eaten. But happily Oysters don’t think. They
and their kind are simply semi-conscious living things, responding
mechanically to stimuli. Any approach, then, to beauty, either of form
or coloration, or both, must be regarded as due to innate, inherent
changes in the germ-plasm affecting the parts so made conspicuous:
the only form of selection to which such “ornaments” can be subjected
is Natural Selection. If, and when, such ornaments penalize their
possessor either by their cumbrousness or their conspicuous characters,
or by increasing the difficulty of feeding or distributing offspring,
then the further development of such excrescences is checked by the
death of all individuals which have passed the bounds of endurance in
this respect.
Sex, and all that appertains thereto, in short, is in these creatures
reduced to its lowest terms. There are not wanting, to-day, both men
and women, who affect to believe that all would be well for the human
race could a similar slowing-down, or strangulation, of the sexual
instincts be brought about. Such blind leaders might profitably
contemplate the Oyster: but such contemplation, to be profitable,
requires intelligence of a higher order than these protagonists of
folly appear to possess.
In justice to Darwin it should be remarked that he himself fully
realized, and carefully points out, the inconceivability of the
application of the Sexual Selection theory to the Mollusca. In
commenting on the beauty of colour and shape which many species
display, he remarks: “The colours do not appear in most cases, to be
of any use as a protection; they are probably the direct result, as in
the lowest classes, of _the nature of the tissues_[1]: the patterns and
the sculpture of the shell depending on the manner of growth.” Just
so: and this is surely the fundamental explanation of ornament, using
this term in its widest sense, everywhere in the Animal Kingdom. The
peculiarities and eccentricities of behaviour, which occur among the
higher groups, act as “aphrodisiacs” to hasten reproduction because
this confers an advantage, the earliest to produce offspring—so soon as
the conditions for their nurture are favourable—having the best chance
of survival. Premature sexual activity is checked by the death of the
offspring.
[1] Italics mine.
It has been contended that the hermaphrodite condition represents the
primitive mode of reproduction among the multicellular animals—that is
to say, all animals above the level of those whose bodies are composed
of but a single cell, or particle, of protoplasm—but this view is
probably erroneous, and the hermaphrodite state must be regarded as a
secondary condition, a later innovation.
More remarkable are the facts concerned with that singular form of
reproduction known as parthenogenesis, or the production of offspring
by virgin females. This is undoubtedly a degenerate sexual condition
occurring as a normal mode of reproduction, among the microscopic
“Rotifers,” _e.g._ the “Wheel-animalcule,” Crustacea, and Insects, and
in varying degrees of intensity.
The most familiar instances of Parthenogenesis are furnished by the
Hymenoptera, and notably by the Bees and the Aphides.
There are certain cases among the Rotifers where no males have ever
been found, and it is possible that they have become entirely
suppressed, but in every other case the periodical advent of males is
an absolute essential for the continuation of the race. Perhaps the
least degenerate of these types are the Bees, wherein we meet with
well-developed, highly-organized males and females, which, in their
sexual relationships, are perfectly normal. But in the fulfilment
of the mating instincts in these insects, a most amazing sequence
of events is revealed such as are without parallel in the rest of
the Animal Kingdom. The story has been charmingly told already by
Maeterlinck, in his delightful “Life of the Bee,” and it has been
told again by Tickner Edwardes, with less of poetry, perhaps, but
still fascinatingly: and it must be told again now, but in a condensed
fashion.
Briefly, a community of hive-bees harbours both male and female
individuals only for a very short space. During the greater part of the
year it consists only of a vast concourse of infertile females, the
daughters of one mother; the “queen” of the hive. The males of that
hive are the brothers, not the fathers, of the workers, as some have
supposed, and their sojourn there is brief. To gain a clear idea of the
facts in regard to the life-history of these insects it is necessary
to trace some of the incidents which lead up to the manner in which
the population of the hive is regulated, and its continuance ensured.
These may well begin with the time when the number of the inhabitants
consonant with the well-being of the hive has reached its limit. This
occurs during the early part of June, when the queen leaves the hive,
accompanied by several thousands of her daughters; they settle at
some distance from their late abode in a “swarm” for the purpose of
founding a new colony. Here we may leave them. The house just vacated
is, however, not entirely deserted. A few of the inhabitants, the
infertile sexless workers, degenerate females—degenerate so far as
the power of reproduction is concerned at any rate—are left behind,
and there remain also in their cradles a variable number of unhatched
queens, and drones or males. One of these potential queens and the
males now speedily emerge, and for a day or two remain within the
seclusion of the hive, feeding upon the honey stored in the combs.
The males are the first to leave, making daily excursions abroad in
the search for mates. They display in this a very leisurely behaviour,
rising late and not venturing out till the day is well aired. Returning
early in the afternoon with sharpened appetites, they feed to repletion
and soon fall asleep.
In about three days, however, the young queen ventures abroad, timidly
at first, to stretch her wings in the sunshine. She is preparing for
the great moment of her life, the nuptial flight. So far, though drones
may swarm on every side of her, no sign of recognition is given, nor do
the males evince any consciousness of her presence. She behaves warily
and demurely throughout. Her first excursions abroad are very brief;
they are not so much trial flights, apparently, as efforts to locate
the exact position of the hive in relation to the outer world. To this
end the flights are rapidly extended in ever-widening circles, till at
last, with lightning speed, she makes for the blue sky, to return to
the gloom of the hive almost immediately after. During all this time
the stimulus of sexual desire has been gathering force, and now, being
no longer controllable, she darts off, and up into the sky; almost
at once she is recognized by the swarms of males from neighbouring
hives, some thousands in number, which for days have been seeking this
event. Instantly they give eager chase, mounting after her higher and
ever higher. But as they ascend so their numbers decrease. Some, the
feeble, the ill-fed from impoverished hives, are speedily left behind;
many endure to the end, but only one secures the prize, and this great
moment of his life is also his last, for the fact of impregnation is
no sooner completed than Death claims him. He falls earthwards, as if
struck by lightning, and in his fall the intromittent organ is dragged
from his body, to be removed by the survivor of this mad flight, on her
descent.
She leaves a bride and returns a widow, filled with murderous
intentions. There are captive queens in the hive, and she can
tolerate no rivals. So soon as she has removed from her person the
embarrassing souvenir of her nuptial flight she makes for the Royal
cells. Accompanied by attendant workers she proceeds to tear off their
waxen coverings and put their occupants to death with a thrust of her
stiletto. No sooner is the work of execution over than the dead bodies
are seized by the workers and borne out of the hive. This awful task
is soon over, however, and henceforth for four or five long years she
remains a prisoner within the walls of her own palace. Craving neither
the air nor the light of the sun, she will die without once having
sipped the nectar from a flower. And during all this time, save during
the winter sleep, her sole duty is to produce sons and daughters. In
the prime of her maternity she may lay as many as three thousand eggs
a day. But strangely enough the number of eggs produced is determined
for her by the workers, who are the real rulers in this constitutional
state. By varying the amount and quality of the food they give her they
can increase or check the number of eggs produced; while even the sex
of the resultant larva is apparently also under their control.
During that brief, weird honeymoon in the clouds she received a store
of spermatozoa, the fertilizing male germs, sufficient for all the eggs
she can ever lay, and they may amount to nigh on a million. Incredible
as this may seem, their purpose is yet more so; for they are destined
to be expended solely in the production of female offspring doomed for
the most part to perpetual spinsterhood. One youngster in ten thousand
may attain to a higher state, may, if Fate wills, become a queen and
mother. And because of this need for mothers to carry on the race, this
extraordinary state of affairs has been brought about. All is under the
control of her daughters—the spinster-workers. As she proceeds on her
rounds of egg-laying an attendant crowd waits upon her, controlling
her actions by gentle caresses. As she passes from cell to cell, the
cradles of the young that are to be, she thrusts down her abdomen and
lays an egg in each. The cells destined to produce the workers are
the smallest, those for drones are larger, and those for queens are
largest of all, and the walls are formed of pure pollen, not of wax as
are those of the workers and drones. But it would seem that she never
lays an egg in any of the last named. The sight of a queen-cell rouses
her to fury. These cells, then, are filled by the workers, who remove
the requisite number of worker—eggs from the cells in which they were
laid and deposit them in the queen-cradles. The larvæ at hatching,
and for the first three days of life, differ in no wise from their
sisters around them. Their Royal state is determined solely by the food
which is administered to them. This consists of “bee-jelly,” which is
furnished in abundance: a white, shining liquid, regurgitated by the
ever-zealous nurse-bees. These superfed babies cease feeding at about
the fifth day, and each spins for herself a silken vestment in which to
undergo the pupal state. This done, the door of each cell is sealed up
with pollen. During the following sixteen days strange transformations
take place: the queen that is to be is taking shape. But the cradle now
becomes a prison, for at the end of the sixteenth day each of the four
or five young queens begins to clamour for release. But this cannot be,
for such as succeeded in emerging would immediately be slain by the
reigning queen. A small hole is bored through the roof of the cell, and
through this each is fed, and a close guard is kept night and day to
ensure that they shall not emerge till the moment is ripe. Soon each
captive begins to gnaw away the roof of her prison chamber, and as
rapidly more material is placed by her guards on the outer surface. Not
until the old queen leaves the hive with thousands of her daughters to
“swarm” and found a new colony will freedom be allowed; and then only
to one. The rest must remain till the new queen either also “swarms,”
or returns from her nuptial flight, and in this case all will be
slaughtered in their cramped quarters, unable to resist.
But what of the drone? He, as has already been mentioned, is reared
in a larger cradle than that of his sisters—save such as are destined
to be queens—and for the first three days of his life is fed on
“bee-milk” of a special kind and more generous quality than that of his
worker—sisters, the Cinderellas of the hive; but this generous diet
is diminished at the end of three days, when a mixture of honey and
pollen is given him. In about three weeks or rather more he emerges, a
great, lazy drone, and for a fortnight more he wanders about the hive
alternately soliciting bee-milk from his sisters and helping himself
to honey from the comb, and when full to repletion he seeks some
snug corner in which to sleep off his surfeit. In due time, however,
he ventures abroad, his hour is at hand. He takes his daily flights
abroad in search of a mate, returning home early in the afternoon for
his rations, being too indolent or too stupid to draw nectar from the
flowers for himself. Thus for many days he and his brothers disport
themselves in riotous living, till one or other of them attains the
end for which he was born; and after a few delirious moments drops
earthwards a mutilated corpse.
But so far only a part of the story of the drone’s life-history has
been told. Though the son of a queen, he has never had a father; and
should he ever attain to the dignity of fatherhood his posthumous
children are all daughters, most of whom die spinsters within six or
seven weeks of their birth, worn out by a life of ceaseless toil and
drudgery!
The queen, it will be remembered, cohabits with the male but once
in her life. The sperm-cells then received are stored in a special
receptacle and are released during the passage of the egg down the
oviduct. In this act of releasing the fertilizing germs a singular
economy is practised. In the case of most other creatures myriads of
sperm-cells are released for the fertilization of a single egg, and
of these but one can possibly attain its goal, the minute aperture or
“micropyle” which is the doorway to the germ liberated, in the form
of an egg, by the female. The rest die. In the case of the queen bee
but one of these precious sperm-cells is liberated at a time. Hence
her prolonged ability to produce fertilized eggs. But eggs destined
to produce males, or drones, are never thus fertilized: they are born
without the intervention of a father. A queen which has never mated
will lay only male-producing eggs. This is an astounding thing, but it
is true. No less remarkable is the fact that the sperm-cells should
survive in their encapsuled state for periods extending over several
years: it seems almost incredible, but it is nevertheless true.
One cannot suppose that the queen in coming to a drone cell
deliberately withholds the male germ as the egg passes down her
oviduct; some inhibitory factor preventing the release of the
sperm-cell must be brought into play which as yet we have not
discovered. This production of males from unfertilized eggs, or
“parthenogenesis” as it is called, is a common feature among the
hymenoptera, and some other groups of insects, and it occurs also among
other lowly creatures to be described later.
Having regard to the importance of the workers, a brief summary of
their life-history must be given. These, it has already been indicated,
are all, at any rate till three days old, potential queens. Their
development into, or degradation to, the lower grade is determined,
apparently, solely by the quality of the food, for the fact that
queens are reared only in specially constructed cells of large size
with walls of pollen instead of wax is explained by the larger size
of the queen and the need for a more porous, air-permeated cell-wall
on account of the longer time which must be spent in confinement.
The worker is certainly the most “intellectual” member of the hive,
but this superiority has been gained at a great price. Emerging from
the chrysalis skin at about three weeks from the time that the egg
from which she emerged was laid, she begins forthwith to gnaw her way
through the mass of wax and pollen which forms the door of her prison.
Rather, she eats her way through, for the material removed is swallowed
as it is detached, thus the young bee, as Mr. Tickner Edwardes remarks,
is caused to effect her own release by the promptings of her appetite.
Hunger-strikes in the bee community are unknown. Speedily the youngster
steps out, distinguishable from her elder sisters only by her weak,
grey-hued, flaccid appearance. Her first act on gaining freedom is to
groom herself down, after which she proceeds to explore the gloomy,
busy, crowded thoroughfares of the hive. A day or two is thus passed in
gathering strength. On the second appetite returns, and she proceeds
to help herself from the vats of honey and pollen bins scattered here
and there among the cradles of her sisters yet prisoners. But speedily
she is caught and thrust, so to speak, on to the treadmill of work
which is to know no cessation during her short span of life-some six
or seven weeks. Her first duties are those of nursemaid. Without
instruction, or previous experience, she begins to feed her younger
sisters and brothers yet in the larval stage. But besides, during her
first fortnight, before she is allowed to leave the hive she and her
sisters of the same age have to fulfil a variety of tasks. All the
indoor work of the house falls on these Cinderellas. Not only do they,
and they alone, feed the young, but they have to produce the wax and
build the combs and attend to the sanitary arrangements: “they are the
brewers of the honey and the keepers of the stores; they feed the queen
bee on her ceaseless rounds and give the drones, their brothers, their
daily rations of bee-milk”—what else these lazy creatures need they
take for themselves from the honey-vats. But this is not all. They have
to meet their older sisters returning from the fields and gardens laden
with nectar. This is regurgitated and transferred to the pouches of
the youngsters, by whom it is transformed into honey and stored in the
combs in the upper region of the hive. At the end of about a fortnight
these little drudges are allowed a brief respite, during the heat of
the day, to emerge into the outer air and gather ideas on the world
which is yet to be explored. Soon a measure of freedom is allowed, the
indoor work ceases, and each takes up the new and more agreeable task
of gathering pollen, and after a few days of this the more responsible
task of gathering nectar is undertaken, which is continued till death
ends one of the most crowded, surely, of existences. Such as are born
near “swarming-time” may have the good fortune to take part in the
exodus and the settling down in the new home, and some may taste yet
other moments of excitement, but they are moments only. The worker
bee knows no leisure for the improvement of her mind and morals. She
needs none, for she has neither: she is a creature of routine, a
living automaton apparently. Yet there are incidents in this wonderful
community which seem too complex to be merely the result of instinct
unaided, uninspired, by intelligence albeit of a nebulous kind.
The worker-bees, it has been remarked, are barren: their reproductive
organs are atrophied, and by the decree, not of the queen-mother of the
hive, nor of the males, but of their own caste. In spite of the fact
that they are incapable of producing offspring, they, and they alone,
determine who shall undertake this task; and they decree the fate that
awaits those thus appointed when they can no longer fulfil this purpose.
When the queen, waxing old, and waning in fecundity, lays fewer
and fewer eggs, and these only producing males, they take silent
note of the fact, and at the appointed time decree the death of
their Sovereign-mother. Yet they hesitate to lay violent hands on
her. She, as queen, claimed the right in her early youth to slay
her sister-queens, and sped them with a dagger-thrust; now her turn
comes to die. But it must be a bloodless death, carried out with due
ceremonial. So her daughters cluster about her, and in a mock embrace,
that tightens every moment, her breath is squeezed out of her body.
There are no State pensions for those who are past work, but a State
execution instead. This is vastly more economical, and it may yet
commend itself to some would-be social “reformers,” who will doubtless
contrive to make exceptions to the rule!
The execution of a queen is not an event of common occurrence; but
that of male members of the hive forms part of the ordinary routine,
though coming only within the larger cycle of the year. As the summer
wanes and the harvest of nectar grows perceptibly less, visions of a
possible famine, and its attendant horrors, seem to arise. So heads are
counted and occupations are scrutinized, when it is discovered that
the only members of the community who are contributing nothing to the
general well-being are the males, who are now but useless drains on
the hive. None of the neighbouring hives are now likely to send forth
a virgin queen to her nuptials, to which end each hive is obliged to
contribute—for no hive utilizes the services of its own drones; these
idle fellows, then, are “eating their heads off”—and males, too; perish
the thought! While they had anything to gain from him their motto
was “Feed the brute”; but now, on each, doom is pronounced. It must
be admitted that a live drone at the end of summer is one of life’s
failures. Notoriously unable to feed himself save upon the honey made
by his sisters, and having no function in life to perform save that of
mating, his very existence now is a damning witness against himself.
When the mother of the hive ceases to maintain the standard of
fertility set by her exacting daughters, she is put to death
stealthily, as if in an excess of devotion: she is smothered under
their embraces. Towards the drones now under sentence no such
consideration is to be shown. When the word goes forth, the slaughter
begins, and it gathers in ferocity. It begins in a massacre of the
innocents—every helpless larval drone is ruthlessly dragged from
its cot and thrown out of the hive to die: there is now no crime in
infanticide, nor in the most gruesome massacre that is presently to
follow. The drones, all unsuspecting, are to be tolerated a brief spell
longer. The cool, calculating spirit of these unsexed ones seems to
realize that there is even yet a remote possibility that the services
of these doomed ones may be wanted. No sooner, however, does it become
clear that this chance is past, than the decree of death is made
absolute, and the poor drones are suddenly and viciously attacked by
half a dozen frenzied spinsters at once. Each tries to bite through
the base of the victim’s wings, and succeeding in this, he is speedily
pushed towards the door of the hive and out into the open, whence
return is impossible, so that nothing is left but death by starvation.
Some of the victims will escape in the _mêlée_, but only for a brief
season. Such as find their way, unmaimed, to the open air, are still
faced by inevitable death. To remain out is to die of starvation or
cold, to return is to fall a prey to the now infuriated guards, who,
strongly reinforced, stand at the doorway of the hive to intercept
and dispatch these unlucky fugitives. It will be remarked that these
executioners make no use of their stings; these they might be unable to
withdraw from their victim’s body, in which case they, too, would die.
But there is no need to run this risk, for the males, their brothers,
whom they so cheerfully slay, are unarmed; they may be attacked without
risk. The dreadful work, however, is soon over, and the survivors, the
queen and her daughters, have the house to themselves to make the final
preparations for the winter sleep, which is apparently undisturbed by
qualms of conscience.
There are certain structural differences distinguishing the three types
in such a hive—the queen, the drone and the worker—which must now be
referred to. The queen is larger than the worker; she has a larger
and longer abdomen, a longer and much-curved sting, and her eyes have
fewer facets. Only vestiges remain of the wax-secreting organs, and no
trace is to be found of the wonderful pollen-baskets which perform so
important a function in the worker; and finally, her instincts are of a
very different kind.
The “pollen-basket” of the worker is a strange contrivance. The pollen
is mainly collected by the hairs which clothe the under surface of
the body, from which it is scraped by special brushes of hairs which
clothe the inner surface of the “metatarsus “—the big, flat joint to
which are attached a series of small triangular joints, the last of
which bears the claws. When the brushes are “clogged up,” the legs are
crossed and the pollen is combed out by specially stiff hairs on the
“tibia”—the joint immediately above the metatarsus—and the bolus thus
formed is then transferred to the outer surface of the tibia, which is
trough-shaped, forming the “corbiculum,” or pollen-basket. The next,
or middle, pair of legs are then employed to ram the pollen well into
the basket, for safe conveyance to the hive. On arrival at the combs,
the bee pushes its hind-legs into a cell, or “pollen-tub,” and with a
special spur dislodges the pellet of pollen and lets it fall into the
tub. These are complex movements, performed without instruction and, we
must suppose, without any intelligent conception of their purpose.
The drone is larger than either queen or worker, and has enormous
eyes, which meet one another over the top of the head; he has no
wax-secreting organs, no pollen-basket, no sting. His antennæ are
longer, his hum is deeper, his sole function is to fertilize a queen,
and this done, he promptly dies. Failing in his first flight, he may
make yet other ventures, but the chances are that he will die without
attaining the only purpose for which he exists.
The fact that he lives for some days in the hive with the queen,
before her nuptial flight, apparently unaware of her presence, would
seem to indicate some special “trigger” for the release of the sexual
instincts. But it must be remembered that he does not attain to
maturity until after his first flight, and this it is, probably, which
arouses the mate-hunger. More than this, however, it is probable that
coitus is possible only when on the wing, when the air-sacs become
inflated, and exert pressure on the genital organs. How he recognizes
the queen when on her wild flight heavenwards is unknown: possibly by
scent, but more probably by the very different vibrative note of her
wings, that of the male being much stronger and deeper. His continued
return to the hive is a proof of his failure to justify his existence,
for no drone ever experienced Love’s embrace and lived to tell the
tale: hence, when the time comes, he is slain without compunction.
These differences between the fully-developed male and female present
nothing very striking; but how are the singular peculiarities of
structure and instinct in the “workers” to be accounted for? They are
present in neither queen nor drone, yet by them they are transmitted
to their offspring from one generation to another! It is true that
every worker, for a time, is a potential queen, and every queen, but
for the grace of Chance, might have been a worker. All depends on the
food. It is remarkable, but apparently the fact, that a more generous
diet, or, rather, a more stimulating diet, should so profoundly modify
the organism, but, it is to be noted, this sleight-of-hand is only
successfully practised on a larva during its first three days of
existence. Thus the royal bee jelly stimulates the growth of the sexual
organs and inhibits the development of the structures peculiar to the
worker—the basket, and pollen-hairs, and so on. These structures are
not made by the food; they are simply nourished or inhibited, as the
case may be. Nevertheless, one cannot help being mystified by the fact
that the mere difference in the quality of the food, or, rather, in the
chemical constituents thereof, should cause the inhibition, or, rather,
the suppression, of relatively complex structures like the corbiculum
and the reduction of the number of the facets of the eye. To say that
the structures inhibited, in the case of the queen, are just those
which will be of no service when in her royal state, is by no means to
explain the mystery. And what is true of the physical side is no less
true of the psychical, for with this change of diet the behaviour of
the insect, throughout its whole life, is most profoundly changed. If
the pollen-basket is wanting, no less so are the instinctive actions
associated with its use; if the genital organs are atrophied, so also
are the instinctive acts associated therewith. This nexus between
instinct and structure is not to be lost sight of.
How—and the question has often been asked—are the experiences of the
infertile females, the workers, transmitted to the germ-plasm? For the
workers, it has been contended, being sterile, are incapable of handing
on such acquirements: this is so. These workers hold the same position
in regard to the species that structures essential to well-being hold
in regard to the individual. These last are not under the control of
the individual, but are determined by a plus or minus quality in its
germ-plasm. The worker-bees are products of the germ-plasm, committed
to the care of the queens. Any strain, so to speak, of that germ-plasm
which gives rise to defective workers brings about its own extinction,
or elimination, sooner or later. Any strain of germ-plasm which
contains, so to speak, a spark of that quality which in the individual
is expressed by intelligent behaviour, will gain advantages in the
struggle for existence.
The complex, the extraordinarily complex, behaviour of the worker-bees
on any interpretation is still mysterious. This interpretation can be
tested only by a reference to the life-history of other social-bees
which have attained to a less complexity. This shows us that the
sterile worker is not to be regarded as a newly-evolved type so much as
an arrested stage of a more complete ancestral condition, and the fact
that the worker is potentially a queen is further evidence of this.
A clue to many of the more puzzling features presented by the domestic
economy of the Hive-bee may be obtained by a study of the life-history
of other species of social-bees which have not attained to so high a
degree of specialization. The Bumble-bees afford illustrations of the
stages through which _Apis mellifica_, the Hive-bee, must have passed.
In the stone Bumble-bee (_Bombus lapidarius_), a queen, who has passed
the winter in blissful sleep, will lay the foundation for a new colony
on some bright May morning by collecting a small quantity of moss. This
done, she starts forth to gather pollen, with which, under cover of the
moss, she forms a waxen cell, mixing the newly-gathered pollen with the
wax so mysteriously formed within her body, as in the case of Hive-bees
of the worker type. Slowly and laboriously this waxen cradle grows.
Fashioned like a globe, its inner surface is lined with pollen soaked
in honey, and with the last pellet of this a number of eggs are laid
arid the nursery is sealed up. By the time these labours are completed
the queen is worn out; she therefore rests awhile, clinging to the
outer wall of this cunningly-wrought cradle. After a few days’ rest she
adds another and commonly yet a third cell to the first, joining each
to the other with wax. But before the third cradle is finished the eggs
in the first have hatched. The youngsters will have consumed the layer
of honey-soaked pollen placed there for this purpose. They therefore
require feeding, and thus the labours of this very industrious queen
are still further increased. Divining the needs of her imprisoned
first-born, she bites a small hole through the nursery wall and pours
in a quantity of honey for their sustenance. In due time they are
“full-fed,” and each spins for itself a silken vestment wherein to
undergo its transformation into a worker-bee. The careful mother,
during this period of transition, now scrapes away an opening through
which the young bees may creep when they awake. This event takes place
in the course of a few days, when her work is materially lightened, for
these newly-hatched workers at once take over the duties of building
nurseries and feeding the further batches of young which, for a time,
follow one another in quick succession. The queen, indeed, has now
nothing else to do but to lay eggs in the nurseries as they are ready.
So far all the children born to her are daughters. The earliest-born,
it is to be noted, were “workers”; those which follow and are tended by
the workers are also females, and supplement their mother’s labours by
producing fertile eggs, though they have never even seen the male of
their own species. Thus, if the queen-mother die her virgin daughters
carry on the colony. But it sometimes happens that she may have left
no descendants capable, for the time, of laying fertile eggs. In this
case, if there be larvæ still in the nursery, the workers feed them
assiduously as if in the hope that some may prove fertile. But if
there be no infants to be fed they apparently abandon work, become
despondent, and spend the greater part of their time sitting at home
by the empty cradles, till at last death comes to their rescue and the
colony is extinct.
Much that baffles one in the history of the Hive-bee becomes clear in
the light of the facts revealed by the life-story of the Bumble-bee.
In the first place it will be remembered her first eggs produced only
workers, which appeared at a time when her energies were severely
strained, and their food allowance was no more than barely sufficient
to sustain life. The females which appeared later produced fertile
eggs, having been more abundantly fed by their infertile elder sisters.
The number of fertile females which appear at this stage of the colony
seems again to be regulated by the abundance of food, which varies
in amount with fine, or cold, weather. Even among the worker broods
fertile females may appear. They owe their fertility apparently to good
luck, which afforded them the opportunity of securing more food than
their sisters. The birth of young from females about whose virginity
there can be no question is certainly remarkable, but it would seem
that this parthenogenetic state is one of limited endurance, for
towards the end of summer males appear, and these mating with some of
the later-born females, lead again to the appearance of a queen, who,
being fertilized, alone survives the winter to carry on the race with
the succeeding summer.
Thus, then, the mysterious existence of the workers among the
Hive-bees, displaying structural peculiarities and instincts so
different from those of the queen-mother, is explained. For the queen,
in this case, is evidently the product of a more intensified, more
perfected, social system, relieved, from the first, of the labours
of building and the care of her offspring, duties which the queen
Bumble-bee has at first to perform for herself, because all her
children die at the end of the summer. Among Hive-bees fertile workers
also occasionally occur; they are probably bees which in their larval
state received a more than usually abundant supply of food, or food
approximating to the “bee jelly” which produces young queens. The
difference, then, between the individuals of a colony of Hive-bees and
one of Bumble-bees lies in the greater abundance of fertile workers
and in the fact that the queen of the Hive-bees is relieved of all
work from the first, and so is enabled to devote her whole energies to
the duties of reproduction. She is the descendant of a race of queens
which in earlier times, like the Bumble-bee queen, had to perform
the duties now relegated to her daughters, who inherit not only her
house-building and child-nurturing instincts, but also her potentiality
for child-bearing, though this potentiality is commonly inhibited
by the starvation of the reproductive activities. Selection secures
survival of this state of affairs by the elimination of any tendency
to lose any of these qualities on the part of the queen. The workers
of the Hive-bee, in short, have not evolved their peculiarities of
structure and instinct by some mysterious process of natural selection
confined to the workers individually, for these, being infertile, could
not transmit any of their inherent qualities or tendencies to variation
in the direction of more efficient workers. On the contrary, all that
they possess they inherit from the queen-mother, who transmits to her
offspring the qualities and characteristics her forebears in the female
line possessed in their own person.
CHAPTER XIV
PARTHENOGENESIS AND ITS SEQUEL
Courtship among the Ants—The Great Renunciation—Maternity carried to
Extremes—Where Males are Superfluous—Degenerate Males—Keeping Death at
Bay—Where Females are Unknown.
The phenomenon of virgin birth is one of profound mystery. The
existence of so astonishing a mode of reproduction was an established
belief among the ancients, though they could have had no means of
demonstrating the faith that was in them. But these men saw no
difficulty in ascribing to the females of their own race this faculty
of producing offspring without the intervention of a male. One
suspects, indeed, that there was no solid foundation whatever for this
belief in these miraculous powers: they lived in credulous times, and
the recorded occurrences of these, even to them, irregular births are
to be regarded as devised to afford a convenient means of escape from
the consequences of lapses from the path of virtue. Yet, incredible
as it may appear, there are not wanting to-day both men and women who
affect to believe that this mode of reproduction obtains still among
the human race, in certain exceptional cases; and further, they profess
a conviction that in the future it may become the normal mode, males,
in consequence, becoming unnecessary! Such professions of faith are
made only by the ignorant, or by those who trade on human credulity.
Parthenogenesis not only does not occur in the human race, but it does
not even occur in any member of the great group of vertebrates of which
man himself stands at the head, and it never will occur.
Those near relations of the Bees, the Ants, afford a further insight
into this strange method of reproduction. Each community in the case
of these insects harbours not one, but many queens. The nuptial
flight, like that of the Bees, takes place in mid-air; but myriads
of both sexes participate therein, forming a filmy, ever-shifting
cloud, now rising, now falling, in the shimmering sunlight. At no time
do they seek to attain the altitude, or the privacy, so strenuously
striven for by the Bees. But in the case of the latter there is but
one female, and her life is precious. She must seek sanctuary for the
consummation of her marriage in the highest heavens, beyond the risk
of instant destruction by insect-eating birds; for though thousands of
suitors accompany her, she rises above them all, save one or two, and
hence would form an easy mark. With the Ants there are thousands of
queens, and the destruction of a few hundreds more or less is rather
an advantage to the species than otherwise. On their return to earth
the males die: their life’s work is accomplished. The females, or as we
must call them, the queens, on the other hand, have a long life before
them; far longer than that of the queen bee. But for them the joys of
flight are restricted to this one brief revel, for, no sooner have they
reached terra firma, than they renounce, as it were, the pleasures of
life to devote themselves entirely to the work of reproduction. And as
if to make all regrets vain, to stamp out all possible temptation to
desert their vows, they tear off their gauzy wings, and with them goes
all hope of fertile repentance: for the rest of this life their home is
underground.
Each queen, on her descent, departs a separate way, and hard is the
road before her. She left the parental nest well-fed, and in good
liking, her body well, stored with food in the shape of fat and the now
useless, bulky, wing-muscles, and with this, her only dowry, she starts
the formation of a new colony out of her own substance. Her first
task is to form a burrow, and at the end of this she fashions a small
chamber. This done, she closes the mouth of the burrow and cuts herself
off from the world. The labour of this burrowing is so severe that it
often wears away her teeth, her only tools, and the hairs from her
body. In this retreat she now waits patiently for the eggs within her
to ripen, which may take months to accomplish: she is still fasting,
or, rather, feeding upon herself. When at last the eggs are laid and
hatched, she feeds her children on saliva, the very juice of her body,
for she is still fasting. Nor is the strain relaxed till the larvæ
undergo their transformation into pupæ, and, after a brief sleep,
emerge as “worker” Ants, puny in stature owing to the poorness of their
food during larval life. In some species this fast may last for ten
long months. So soon, however, as these little workers emerge, like
dutiful daughters they make their way to the outer world, and go forth
in search of food, which they share with their now exhausted mother.
But, besides, they enlarge the original chamber, and drive galleries in
all directions to provide accommodation for the vast population that
is soon to crowd the thoroughfares. Meanwhile the queen resumes her
task of producing more and yet more daughters, in whom she now displays
not the slightest interest. Her elder children now bear away the eggs,
and feed the young as they hatch. In course of time, as with the Bees,
the task of wet-nurse falls on the youngest of the Ants, those who have
just attained to anthood. For ten or fifteen years this queen-mother
may continue her work of reproduction, a slave, indeed, to domesticity,
with monotonous regularity, checked only by the chill of autumn and the
sleep of winter.
Those among our own race who profess to hail the prospect of a time
when parthenogenesis shall be the normal mode of reproduction may
well take the Ant as an awful warning. Their ambitions may overreach
the mark. The poor queen becomes a slave to reproduction; children
in myriads are born to her; even if she would she could not sustain
her interest in them, she could not even recognize them as the fruit
of her body. Her daughters are born to a lifelong drudgery, her sons
are mere fertilizing agents: for their only purpose in life is to
perpetuate this awful thraldom, this appalling prolificness; and having
accomplished this, they die forthwith. If there be any joy in this life
it is drunk by the males alone. Thus does the female rule overreach
itself. It is well, indeed, that the participants of the joyous nuptial
flights dancing deliriously on gauzy wings in the glare of a summer
day, have no foreknowledge of the long night that is to follow.
Unlike the Bees, the Ants may produce as many as five grades of
workers, each of which have different duties towards the community. But
the nature of those duties and the manner of the evolution of these
types, are themes foreign to these pages: enough has been said already
to indicate the nature of the problems they present when discussing the
life-history of the Bees.
The subject of parthenogenesis need be pursued no further in this
volume than is sufficient to bring out its retrograde character. It
is a form of reproduction which may be limited to a small number of
generations, as with the Aphides, or to a single generation alternating
with normal sexual generations, as in many Cynipidæ or Gall-flies, or
it may be the only mode of reproduction, as in some other Gall-flies,
some Saw-flies and some Crustacea, wherein no males have ever been
seen. In some species this form of reproduction gives rise to females
only—the Thelyotokous parthenogenesis of scientific text-books—as in
the Saw-flies and Gall-flies, and the parasitic _Tomognatbous_. In
some other Saw-flies, unfertilized queens and workers of Ants, Bees,
and Wasps, which occasionally produce offspring, the progeny is always
male, and this is known as Arrhenotokous parthenogenesis. In one or two
species of Saw-fly, _e.g._ _Nematus curtispina_, both males and females
may be produced, when the species is said to be Deuterotokous.
In the case of the Aphides, winged males normally appear in large
numbers at the end of the summer, and these fertilize the females; but
if kept in a warm green-house, parthenogenetic reproduction may be
sustained for as long as four years. Under quite normal circumstances
these tiny insects show a singular range of variability, for egg-laying
and viviparous individuals are met with; while winged and wingless
generations appear sporadically, apparently according to the abundance
of food. The winged form is sometimes so abundant as to float about
in swarms that darken the air. There are at least three kinds of
males-winged males, wingless males with a functional mouth, and small
wingless males which have no mouth, and, one need hardly say, are
very short-lived. The Aphides are a feeble folk, individually, but
collectively a power in the land, causing at times incalculable loss
to the farmer and gardener; but on this head and on the subject of
their strange habits, and sometimes adventurous lives as slaves in the
service of Ants, no more than a hint may be dropped in these pages.
But some such aids to faith seem to be necessary when those who are
not tolerably familiar with these insects are told of their amazing
fertility. Linnæus long since estimated, in regard to one species,
that in the course of one year a single Aphis will give rise to a
quintillion of descendants—all produced without the aid of a male.
Every one of these females begins to reproduce within from ten to
twenty days of her birth, but even this statement does not bring home
the result of such an astounding fecundity like Huxley’s calculation
which was carefully worked out. He estimated that the produce of a
single female would, in the course of ten generations, supposing all
the individuals to survive—and possess the normal fertility of their
race—“contain more ponderable substance than five hundred millions of
stout men: that is, more than the whole population of China.”
To explain such a riot of reproduction one might almost suppose these
insects to be imbued with a dread of the impending dissolution of
their race, and endowed with the power to avert such a calamity by
these stupendous efforts; for it is evident that parthenogenesis
confers quite extraordinary powers of raising the birth-rate. But then
the normal mode of procreation is capable of achieving results quite
as remarkable. The queen Termite or White Ant, for instance—which,
by the way, is no Ant, but a near relation of the Stone-flies—when
in her prime will lay eggs at the rate of sixty a minute, or eighty
thousand and upwards in the course of a day of twenty-four hours. But
this unenviable mode of breaking the record is attended, surely, with
some little inconvenience; for to attain to such fertility her abdomen
increases until it attains something like two thousand times that of
the workers of the community in which she lives. That the history of
the queen Termite is unique of its kind is not surprising: indeed, such
an amazing story could only be told of creatures which enjoyed the
seclusion of a subterranean existence. Here, on a bare couch, with her
Royal spouse beside her, she lies, a bloated, heaving mass, incapable
of movement, depositing eggs with the rhythm of a machine, the mother
of offspring which she will never see. A more unsightly picture of
maternity it would be impossible to conceive: it is well, indeed, that
it is hidden from the light of day. No such state of affairs could ever
arise among creatures living an outdoor life, with enemies to avoid,
and food to find.
The instances just surveyed, these extremes of the potentiality of
procreation, are instructive in more ways than one. They are to be
regarded as “excrescences” of reproduction, comparable to those
“excrescences” of individual growth which we call “ornament,” for
example. Individuals on whom this fertility has settled, so to speak,
are the victims of the machinery of sex and reproduction. Their
amazing powers of multiplication are not of their own seeking, they
are inherent manifestations of variations of growth, uncontrollable
save by the machinery of Natural Selection. Incidentally such victims
serve a useful purpose, for their myriad hosts afford food for hordes
of other animals, which in turn are eaten. Little though we realize
it, the well-being of the human race would suffer if these prolific
creatures—the uncomplaining victims of that inexorable law which bids
all living things “increase and multiply” or die—should cease to be;
for with them would disappear a host of animals on whose existence
man’s comfort more or less depends.
During the millions of years that have rolled by since the first
appearance of life on the earth, who shall count the number of types
which have been exterminated without leaving the faintest trace of
their having ever existed? The survivors which have contrived to
maintain a place in the sun present an infinite range of variation
in colour, size, habit, and structure, as well as in emotions. These
varied aspects are all so many facets of the mysterious phenomenon
we call Life: and they are so many witnesses of the versatility of
Life. Not the least mysterious feature of this Life is its faculty
of reproduction, which expresses itself in an infinite variety of
ways, defying all but the crudest forms of analysis. The evolution of
sex has exercised the speculative ingenuity of some of the acutest
students of Nature from the earliest times, and we are still far from
a satisfactory solution of the problems it presents. Hermaphroditism
and Parthenogenesis are commonly regarded as degenerate forms of
reproduction, but it would probably be more correct to see in them
exceptional modes of adaptation enabling such individuals to occupy
niches in the world untenable to creatures of more conservative habit.
That the peculiar “strains” of animal life have turned into backwaters
which offer no opportunity or possibility of further advancement seems
clear enough, but they are nevertheless interesting and instructive.
The parthenogenetic Crustacea and the Rotifers afford some good
evidence of this adaptability—of the way in which creatures manage to
cling to the skirts of life by reason of their power to survive the
extremest tests of endurance. And this success has largely been due
to some mysterious property of the germ-plasm enabling reproduction
to take place through the female line alone, or in some cases with
an occasional fillip from the intervention of males. Of the many
marvellous things that could be related of these creatures but few
instances can be cited here.
The case of the Brine Shrimp (_Artemia salina_) will afford an
exceptionally good illustration because the facts can be tested by
anyone who will take the trouble to make a simple experiment for
himself. Those anxious to do this should dissolve eight ounces of
Tidman’s sea-salt in a glass jar containing five pints of water,
keeping the mixture well stirred till the salt is dissolved. It should
be allowed to stand and be carefully watched. In about three days, with
a pocket-lens, or even without, minute white specks will be seen moving
with a jerky motion up and down the water. These are larval Brine
Shrimps. Now they must be fed. Take a piece of lettuce-leaf or any
green stuff, and pound it up, or grind it up with a knife-blade on a
plate with a little water, till the whole is reduced to the consistency
of green paint; then empty this into the water. This must be done
daily, or at any rate frequently. Quickly these tiny specks will grow
into Brine Shrimps, translucent creatures nearly half an inch long,
swimming about back downwards with a marvellously rhythmical movement
of delicate feet. In all probability no males will be found, but, on
the other hand, both sexes in almost equal numbers may be present. The
males may readily be distinguished by their massive arms immediately
behind the head, for the purpose of embracing the females.
Whence came these wonderful animals? The mystery is easily explained.
The salt is genuine sea-salt, formed in brine-pans, chiefly in the
Mediterranean. As the water evaporated the Shrimps it contained
gradually died; but the eggs in the females became encapsuled in
the salt-crystals to hatch out long months after. In one of my own
experiments I succeeded with salt that I had kept for more than a
year. Of course, every sample of salt experimented with will not
yield successful results, but failures are not expensive. Now in
this brine-pan there were myriads of other animals which were killed
outright: the Brine Shrimp is at least able to pass on descendants by
reason of the vitality of its eggs. Some near relations of the Brine
Shrimps live in fresh water and possess similar powers of resistance to
adverse conditions. The Fairy Shrimp (_Chirocephalus_) is one of these.
Not unlike its cousin the Brine Shrimp in appearance, it lives in
shallow pools, such as have muddy bottoms and are constantly liable to
dry up. Birds hunting by the margins of the pool where the retreating
water has left a fringe of mud bear away more or less of this on
their feet and transport it to similar pools, or even puddles. Such
transplanted samples may easily contain numbers of eggs of this tiny
creature. Only a year or two ago Fairy Shrimps were found in abundance
in rain pools at Eton, and some, indeed, were discovered swimming gaily
about in a rain-filled cart-rut!
Another very singular Crustacean, known as _Apus_, bears a curious
superficial likeness to the King Crab (_Limulus_), having a large
back-shield and a long tail. This little creature, a giant compared
with his nearest relations, is an inhabitant of wayside ponds and
ditches. Thousands of females may be taken for years in succession
without the advent of a single male. Then, for some strange reason
which we cannot even guess at, males appear. Like its freshwater
cousin, the Fairy Shrimp, _Apus_ can withstand drought: its favourite
haunts may be transformed into sun-baked hollows, but with a heavy
fall of rain and a few hours’ soaking the eggs left by dead females
develop, and once more the pool and its inhabitants are established
again. Having regard to the extraordinary vitality of these small
creatures, it is curious that they should ever disappear from their
favoured haunts. But they do. Not many years ago _Apus_ could be
found in abundance in many parts of the South of England. It is now
extinct; its last resorts were the ponds at Hampstead: now one may
search in vain for them. “No British specimens,” remarks Dr. Caiman,
a great authority on the Crustacea, “had been recorded for over forty
years, and the species was believed to be extinct in this country,
when it was found in 1907 by Mr. F. Balfour Browne in a brackish marsh
near Southwick, in Kirkcudbrightshire.” These had probably developed
from eggs accidentally transported by some bird from the Continent.
The extinction of the race throughout the British Islands can only
be attributed to the too long absence of males, and the consequent
inability to restore vigour by the more normal method of reproduction
by sexual congress.
Among the Rotifers the little Wheel-animalcules exhibit an even greater
vitality, for not only can their eggs withstand prolonged desiccation,
but in some the body of the animal survives even harsher treatment. If
specimens be enclosed within a chamber containing a little sand or moss
the contents may be dried over sulphuric acid, or heated up to 200° F.,
or left to the neglected dust of years, and will yet revive if a little
fresh water be added to the sand. Males are rare, and when they do
occur are little more than animated receptacles for semen, for they are
incapable of feeding, the gullet and digestive tract being reduced to a
solid cord. A certain amount of nourishment, however, may be absorbed
through the delicate body wall.
The degeneration of the males in these parthenogenetic species
irresistibly reminds one of the smile of the Cheshire cat; they grow
smaller and smaller, and their functions less and less, till finally
nothing is left. The “complemental males” discovered years ago by
Darwin in the Barnacles well illustrate this process. In dissecting
adult specimens of the stalked Barnacle (_Scalpellum_) he found, just
inside the valves, in a pocket of the mantle, a varying number of
“complemental males,” tiny organisms which Mr. Geoffrey Smith describes
as “little more than bags of spermatozoa,” and they apparently serve
to fertilize the ripe ova of the larger animal—one cannot say of the
female, for Scalpellum, like most of the Barnacles, is hermaphrodite.
But it is believed that these complemental males are really arrested
hermaphrodites. At any rate, if it so be noted that with some of the
Barnacles, as with some other Crustacea, the larvæ are males, but
when adult life is attained female glands appear and hermaphroditism
is established. Such hermaphrodites have the singular distinction of
being males which have acquired female attributes, true females being
unknown among them!
In one of the parasitic Crustacea (_Chondracanthus_) infesting the
gills of Gurnard, Plaice, Skate and other fish, the adult female is
about half an inch long, and very unlike a Crustacean in appearance;
the male is an extremely minute maggot-like object—a few millimetres
in length—and lives permanently attached to the belly of his mate just
at the base of the egg masses. More remarkable still is the case of
another nearly related parasitic species—_Lernea_—which becomes sexually
mature in its childhood. The males perform their part and die; their
mates arrive at maturity and settle down to a comfortable life as
parasites on fish, reproducing without further mating.
That Parthenogenesis and Hermaphroditism are but specialized forms of
reproduction, leading sooner or later to degeneration and extinction,
there can be no doubt. They are, so to speak, failures in the evolution
of sex, demonstrating in a very forcible fashion the impossibility
of progress—as we understand it—where the sexual functions are thus
combined.
To the differentiation of sex, resulting in separate male and female
individuals, we must attribute the marvellous complexity of the pageant
of life which confronts us to-day. The story of the Courtship of
Animals is only one of an infinite number of incidents in this pageant,
and one which is by no means easy of interpretation.
In these pages an attempt has been made to show that this
differentiation of sex has, throughout, been accompanied by,
and largely moulded by, common instincts and behaviour, and this
interpretation is only to be reached by a study of the phenomena in
their simplest form among the lower grades of animal life. Colour and
the various sexual differences in form have been allowed to dominate
this investigation of the problem of sex, and have diverted attention
from more profitable and fruitful channels.
The lower we descend in the scale of animal life the less convincing
becomes the argument that the colour, ornament or armature of the
males is the result of sexual selection in the older, Darwinian sense.
The argument of Geddes and Thomson and others that the males are more
“katabolic,” the females more “anabolic,” seems no less unsatisfactory,
for in many cases the female is just as highly ornamented as the
male, and in others she is considerably large. Further, in their less
specialized species the sexes are almost or quite indistinguishable
externally, and are sombrely clad, just as at the opposite extreme we
find them equally ornamented and equally active.
We shall be nearer the truth if we regard these secondary sexual
characters as expression points of germinal variations. Though we
seem hopelessly ignorant as to the inciting cause of the variations,
at least we seem to be able to lay a finger on the agents by which
they are effected. And these are the hormones of the primary and
secondary sexual glands, whose functions affect more than the merely
sexual side of the organism. They profoundly affect the coloration of
animals, giving rise on the one hand to purely ornamental “secondary
sexual characters,” and on the other to changes of coloration which
achieve the ends of protective resemblance colours, or of “warning
coloration,” as circumstances may demand. There is nothing more
remarkable in this than the control which the pituitary body exercises
over stature, either when in a pathological condition, or when the
controlling action of the other gland secretions is removed, as by
castration.
Hitherto much has been made of trophic nerves, which control growth;
but it is probable we have overlooked the still more important
action of “trophic” glands, such as the thyroid. This apparently
controls growth in many directions. Adaptations to environment which
are effected by changes in bodily shape-as in the transformation of
land-dwelling mammals into Seals and Whales—are probably largely
controlled by these glands. Their activity is as great as their
manifestation is varied.
Why their action should be more stimulating in the case of the male,
why he should lead the way in all the new acquirements of the species,
both in non-sexual as well as in sexual characters, is by no means
plain. But the fact remains that this is so. Remove any one of these
glands and the machinery of growth is thrown out of gear; it is not
merely the secondary sexual characters which are affected.
But these glands are concerned no less intimately with the behaviour of
animals. This is most obvious in all that concerns sexual appetite as
the preceding chapters have already shown. Having regard to the immense
variety of animals concerned, this behaviour presents an underlying
uniformity of expression which must not be lost sight of: and the same
is no less true of what we may call the physical manifestations of
these glandular activities.
THE END
INDEX
Alcock, Colonel, on courtship of
crabs, 255
Alder-flies, claspers of, 233
Amorousness, a factor in evolution, 24
— power of, 6, 9
— where absent, 6
Andrews, Dr. C. W., on display
of Frigate-bird, 111
Antelopes, battles of, 64
— horns of, 63
— scent glands of, 67
Antennæ, sense of smell in, 199
Antlers, branching of, 61
— eaten when shed, 58
— in female deer, 62
— shedding of, 53
— types of, 60
— use of, 55
Ants, nuptial flight of, 297
— dismal fate of queen, 298
Apes, brilliant colours of, 45
— — — use of, 46
— family relations of, 43
— polygamy in, 48
— power of voice in, 42
— related to man, 41
Aphides, appalling fertility of, 301
— parthenogenesis in, 301
Argonaut, remarkable egg-cradle of, 269
Armature in birds, 117
Argus Pheasant, display of, 96
— — ocelli of, 97
Baboons, mane of, 44
Bailador, dances of, 121
Barrett Hamilton, Major, on Fur-seals, 85
Bee, Bumble, life of, 292
— drone, life of, 281, 289
— queen, as executioner, 279
— — execution of, 286
— — nuptial flight of, 279
— worker, evolution of, 290
Beetles, fighting between, 214
— stridulating organ of, 217
— vivid coloration in, 209
“Behaviour,” specific character of, 157
Birds, secondary sexual characters of, 94
Birds-of-Paradise, display of, 101
Bower-birds, coloration of, 158
— — origin of “bowers,” 160
— — singular behaviour of, 157
Brine-shrimp, vitality of, 304
Bug, extraordinary armature of, 216
Bustard, Australian, display of, 108
Bustard, Great, display of, 107
Butterflies, courtship of, 195
— excess of males in, 192
— experiments on, 205
— and female choice, 193
— females larger than males, 193
— fighting between, 194
— fragrance of, 200
— males mobbing females, 196
— methods of pairing, 204
— scent scales of, 199
Butterfly, Small-blue, method of folding wings of, 187
Caiman, Dr. W. T., on A pus, 306
Campbell on courtship of spiders, 247
Cassowary, roar of, 112
Castration, effects of, 144
Chamæleons, armature of, 167
Cicada, music of, 222
Cockles, blindness of, 274
Coloration, cause of iridescent, 189
— forms of, 186
Conger-eel, huge size of females in, 178
Cooke, Mr. John, and the behaviour of sheep, 69
Courtship, meaning of, 21
Crabs, courtship of, 258
— seizing mates, 260
— stridulating organs of, 255
Crane, dances of, 120
Crocodile, courtship of, 164
Cunningham, J. T., and secondary sexual characters, 14
Dancing in birds, 119
Darwin, his theory of Sexual Selection, 12
Darwin on coloration of beetles, 210, 211
— on coloration of mollusca, 275
— on “horns” of beetles, 212
— on mane of baboons, 44
— on sexual selection in butterflies, 194
Deer, antlers of, 53, 62
— courtship of, 53
— fatal encounters of, 55
“Diathetic” types, meaning of, 50
“Display,” function of, 183
— in birds, need of, 147, 149
Double-eyed fish, 176
Dragon-flies, antiquity of, 227
Dragonet, courtship of, 177
Eland, horns of, 65
— strange habits of, 68
Elephant, courtship of, 71
— remarkable scent glands of, 69
— use of tusks in, 70
Elephant-seal, courtship of, 87
Emotions and human evolution, 32
— and sexual selection, 17
Emu, air-sacs of, 112
Eunuchs, peculiar features of, 145
Extinction, causes of, 17
Fabre on courtship of scorpions, 252
Fashions among savages, 33 _et seq._
Fighting-fish, ferocity of, 182
Fish, disparity in size of sexes 178
Forbes, Dr. H. O., on deceptive coloration in a spider, 240
Frigate-bird, air-sacs in display of, III
Frilled-lizard, courtship of, 165
Frogs, concerts of, 171
— courtship of, 169
— singing like a Greenfinch, 173
Fur-seals, courtship of, 81
— polygamy of, 81
— precocious sexual instincts in, 86
Germ-plasm, nature of, 11
Giraffe, kick of, 73
— strong smell of, 68
Grasshopper, air-bladder of, 219
— stridulating organs of, 218, 221
Grebe, Great-crested, courtship of, 151
Groos, Professor, on emotions, 18
Hippopotamus, bloody sweat of, 69
— teeth of, 72
Hooded-seal, air-sac of, 88
Hormones, nature of, 16
— part played by, 146, 147
Horns, evolution of, 51
Hottentots, remarkable peculiarities of, 31
Howard, H. E., on importance of “territory” 140
— on play in warblers, 121
— on sexual selection, 138
Huxley, Mr. Julian, on the behaviour of Mallard, 149
— on the Great-crested Grebe, 151
Hypertely, meaning of, 125, 127
Image, Professor Selwyn, on Vapourer Moth, 201
Impotency, possible consequences of, 155
Ingram, Sir William, on display of King Bird-of-Paradise, 102
Insects and sexual selection, 192
Katydid, song of, 222
Kinetogenesis, meaning of, 80
Leptodora, olfactory sense of, 262
Life, lowest forms of, 3 _et seq._
Lion, mane of, 77
— polygamy in, 81
Lizards, courtship of, 165 _et seq._
— fighting among, 167
Locusts, ear of, 220
— remarkable ornaments of, 225
Lucas, Dr. F. A., on sea-lions, 86
Males, degenerate, 307
— first to acquire new features, 9
— lead in new departures, 190
— where superfluous, 307
Mallard, remarkable behaviour of, 149
Man, evolution of, 22 _et seq._
“Mate-hunger,” part played by, 147
— power, importance of, 5
Mating, preferential, 155
May-flies, dance of death of, 229, 232
— nuptial flight of, 232
— remarkable eyes of male, 231
May-flies, remarkable use of stomach in, 230
Mayer, Mr., experiments on moths, 205
Moina, claspers of, 262
Moose, peculiar habits of, 58
Morgan, Professor Lloyd, on emotions, 18
— on factors in selection, 19, 126
Moth, aquatic females in, 204
— Eyed-hawk, display of, 201
— Ghost, scent-bottle of, 200
— Kentish Glory, sexual differences in, 203
— Oak-eggar, remarkable sense of smell in, 202
— Vapourer, remarkable sense of smell in, 201
Moths, bright colours of, 188
— diurnal, 189
— males, sense of smell of, 199
— scent organs of, 200
Mouth, brilliant colour in birds, 142
Muller, Fritz, on fragrant butterflies, 200
Music in birds, 123 _et seq._
Narwhal, tusk of, 90
Newts, courtship of, 170
— remarkable pairing habits of, 170
Ocelli in birds, nature of, 98
Octopus, courtship of, 267
— remarkable mating habits of, 268
Ornament, controlling factors of, 168
Orthogenesis, nature of, 17
Osborne, Professor, on factors in evolution, 17
Ostrich, roar of, 112
Oysters, helpless condition of, 274
— and social reformers, 275
Painted Terrapin, remarkable courtship of, 168
Parthenogenesis in Crustacea, 304
— occurrence of, 276
— significance of, 308
— types of, 300
Peacock, display of, 95
Peckham, Mr., on courtship in spiders, 241
Pheasants, display of, 100
Pigment intensification, cause of, 150
Plovers, fatal conflicts among, 117
— dances of, 119
Plumage, evolution of, 143
Polyandry, human, 29
— in birds, 134
— interpretation of, 136
Polygamy, human, 27
— in birds, 115, 135
— in ungulates, 75
— interpretation of, 76, 115, 135, 136
Poulton, Professor E. B., on animal coloration, 186
— on courtship of spiders, 245
— on sexual selection in spiders, 245
Prairie-hen, air-sacs in display of, 109
Pugnacity in birds, 116
Rays, remarkable teeth of, 176
Reproduction, forms of, 10
Rhinoceros, horns of, 75
Ruff, amorous instincts of, 115
— display of, 113
— variability of, 114
Sabre-toothed tiger, huge canines of, 80
— jaw-flanges of, 80
Salmon, coloration of, 180
— courtship of, 179
Sandpiper, Pectoral, air-sacs in display of, 108
Scent glands, 67
Scorpions, courtship of, 242
Secondary Sexual Characters, meaning of, 13
Selection, forms of, 7
Selous, Mr. F. C., on habits of moose, 59
— on the mane of the lion, 78
Sex, beginnings of, 4
— birth of, 12
Sex-antagonism, 9
Sexual instincts, dominance of, 162
— grades of, 183
— importance of, 27
Sexual selection, definition of, 20
— and human evolution, 38
— in the human race, 32
— instance of working of, 147
Sexual Selection Theory, modification of, 154
Sharp, Dr. David, on stridulating organs, 219
Sheep, scent of, 69
Skull, human, malformation of, 35
Smith Woodward, Dr. A., on factors in evolution, 17
Smynthurus, remarkable courtship of, 26
Snail, hermaphrodite state of, 271
— “love-darts” of, 271
— significance of coloration of, 272
Somato-plasm, nature of, 11
South, Mr., on Oak-eggar moth, 202
Spiders, courtship of, 242 _et seq._
— dread sequel to nuptial rites, 246
— drumming of, 237
— nuptial rites in, 248
— remarkable coloration of, 239
— stridulating organs in, 237
Starling, Prof., on Hormones, 14, 16
State executions v. State pensions, 286
Stickle-back, paternal care in, 181
— remarkable nest of, 181
Stone-flies, degenerate wings in, 234
— nuptial rites performed in ice, 233
Stridulating organs of grass hoppers, 218
— nature of, 217
Sun-bittern, display of, 142
Syrinx in birds, 123
Termite, amazing fertility of queen, 302
“Territory,” importance of, 154
Thomson, Prof. J. A., on evolution of sex, 12, 309
Townsend, Mr., on sea-elephants, 87
Tragopans, display of, 100
Trimen, Dr., on deceptive coloration in a spider, 240
Turkey, display of, 99
Use, inherited effects of, 59
Virgin births, belief in, 296
Voice in birds, 123
Wallace, Alfred Russell, and Sexual Selection, 13, 137, 196
Warblers, play in, 121
Water-fleas, olfactory organs of, 261
Water-fleas, mating apparatus of, 226
Weismann, Professor, on coloration of butterflies, 187
Whales, armature of, 89
— battering-rams of, 179-89
Wheel-animalcule, vitality of, 307
Windpipes, where coiled, 128
Zebras, fighting among, 73
Printed at The Chapel River Press, Kingston, Surrey.
ERRATUM
For the first line of page 16, instead of “by certain glands of the
ductless glands,” read: “by certain of the ductless glands.”
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