| By Author | [ A B C D E F G H I J K L M N O P Q R S T U V W X Y Z | Other Symbols ] |
| By Title | [ A B C D E F G H I J K L M N O P Q R S T U V W X Y Z | Other Symbols ] |
| By Language |
|
Download this book: [ ASCII ] Look for this book on Amazon Tweet |
Title: Insect life: Souvenirs of a naturalist
Author: Fabre, Jean-Henri
Language: English
As this book started as an ASCII text book there are no pictures available.
*** Start of this LibraryBlog Digital Book "Insect life: Souvenirs of a naturalist" ***
INSECT LIFE
SOUVENIRS OF A NATURALIST
J.-H. FABRE
DOCTEUR ÈS SCIENCES
‘that inimitable observer.’—Charles Darwin
TRANSLATED FROM THE FRENCH
BY THE
AUTHOR OF ‘MADEMOISELLE MORI’
WITH A PREFACE BY
DAVID SHARP, M.A., F.R.S.
AND EDITED BY
F. MERRIFIELD
WITH ILLUSTRATIONS BY
M. PRENDERGAST PARKER
MACMILLAN AND CO., LIMITED
ST. MARTIN’S STREET, LONDON
1913
To the attentive eye the sight of industrial insects exhibiting
the most refined art in their labours is a spectacle both strange
and sublime. Human Reason is confounded by Instinct thus raised to
the highest pitch of which Nature can offer an example, and the
perturbation of intelligence increases on observing, patiently and
minutely, the details of the life of those creatures most highly
endowed with instinct.
E. Blanchard.
First Edition 1901. Reprinted 1913
PREFACE
This little volume introduces the work of a great French naturalist to
the reader of English. Réaumur, another Frenchman, is the greatest
naturalist devoting himself to the observation of insects the world has
yet seen. His six quarto volumes—Mémoires pour servir à l’histoire des
insectes—were published between 1734 and 1742. J.-H. Fabre, who happily
is still with us, is second only to Réaumur in this part of the great
field of Natural History.
Though compatriots the two men are remarkably different in the nature
of their genius. Réaumur, stately and slow, both discursive and
diffuse. Fabre,—styled by Charles Darwin the immortal Fabre,—a most
patient, indefatigable observer, ready to sacrifice everything to the
carrying on of his work, but making deductions too rapidly from his
observations, and taking a philosophical position from which he refuses
to budge, even though he stand alone among the naturalists of this
generation.
Fabre’s great merit is his graphic portraiture of the living insect as
it really is. This proves to be very different from insect life as it
is usually supposed to be by the uninstructed, and as it is only too
frequently represented to be in books. In the volume now offered to the
reader he is almost entirely concerned with the instinct of
Hymenoptera, the highest of the insect world in this respect. His
studies of this subject have been continued in several other volumes,
and he has also included in the series the results of many years of
observation of the habits of other and very different insects.
His philosophical position may be briefly stated to be a determined
refusal to recognise evolution as a legitimate idea. In this we may
think him wrong; but it must be admitted that his views form a valuable
antithesis to those of the many evolutionists who take the position
that all that remains for the naturalist to do is to repeat the words
Natural Selection and variation, and declare that thereby we understand
the Cosmos.
Fabre is a difficult writer to translate. Probably no one has ever
written on this subject with equal brilliancy and vivacity. But he is
the most Gallic of Frenchmen. If his words are literally translated,
they scarcely make English; if freely translated, the charm of his
diction is too easily missed.
We hope that this volume may induce the student to read Fabre’s
subsequent volumes. [1] Taken altogether they are, if not superior, at
least not inferior to this one—preferred simply because it is the first
of the series.
In his works there is a good deal of delightful autobiography. Starting
as a child amidst the direst poverty, he has become a highly
accomplished man, a great naturalist, a brilliant writer; and he has
done this with a complete contempt for money, and a great indifference
to the other rewards that Society is ready to bestow for such work.
D. SHARP.
Cambridge, 20th August 1901.
CONTENTS
PAGE
I. The Sacred Beetle 1
II. The Enclosure 27
III. Cerceris Bupresticida 40
IV. Cerceris Tuberculata 51
V. One Skilful to Slay 67
VI. The Yellow-winged Sphex 80
VII. Three Strokes of a Dagger 93
VIII. Larva and Nymph 101
IX. Advanced Theories 116
X. The Sphex of Languedoc 132
XI. The Science of Instinct 146
XII. The Ignorance of Instinct 164
XIII. An Ascent of Mont Ventoux 179
XIV. The Emigrants 193
XV. The Ammophila 205
XVI. The Bembex 219
XVII. Hunting Diptera 233
XVIII. A Parasite—The Cocoon 243
XIX. The Return to the Nest 258
XX. Mason Bees 271
XXI. Experiments 289
XXII. An Exchange of Nests 306
Descriptive Notes 317
LIST OF ILLUSTRATIONS
The Sacred Beetle Frontispiece
Dung Beetles gathering Provender Facing page 6
Geotrupes stercorarius fighting for the Pellet 12
Cerceris bupresticida and its Prey; Bupresticis micans and
Buprestis flavomaculata 46
Cerceris tuberculata dragging Weevil to its Burrow 54
Cerceris ferreri and its Prey, the Weevil; Rhynchites betulæ
on Birch Leaves, showing two leaves rolled up by the Weevil 58
Sphex flavipennis about to seize Grasshopper 120
Sphex occitanica taking a Sun Bath 136
The Sphex of Languedoc dragging to its Burrow an Ephippiger
of the Vine 156
The Sphex of Languedoc and its enemy, the Praying Mantis 166
Ammophila hirsuta attacking a Grub 194
Ammophila sabulosa taking stone to cover its Burrow;
A. argentata Mining 207
Ammophila hirsuta hunting for Caterpillars; Ammophila
sabulosa on the Wing 208
Bembex rostrata taking Gadfly to its Nest; Bembex rostrata
Mining 240
Mason Bees—Chalicodoma muraria on Old Nest 272
Mason Bees—Chalicodoma sicula and Nest 280
I
THE SACRED BEETLE
This was how it came about. We were five or six, I the oldest and their
professor, still more their comrade and friend; they, young fellows
with warm hearts and lively imaginations, overflowing with that
youthful vitality which makes one so open to impressions and so eager
for knowledge.
Talking of one thing and another we followed a path bordered with elder
and hawthorn, where already the Rose Beetle was revelling in the
overwhelming scent of the clustering blossoms. We were going to see if
the Sacred Scarabæus had yet appeared on the sandy plateau of Les
Angles, rolling the ball of dung which ancient Egypt looked on as
emblematic of the world; we wanted to discover whether the running
stream at the bottom of the hill might not hide young newts under the
net of water weeds—newts whose branchiæ look like tiny sprays of coral;
to see if that elegant little fish of the rivulet, the stickleback, had
donned his wedding cravat of azure and purple; if the new-come swallows
were dipping on pointed wings over the meadows chasing the midges which
scatter their eggs in their airy dance; to see if the Eyed Lizard was
sunning his blue-spotted body at the mouth of a hole made in the
sandstone; or if the flocks of Laughing Gulls, come up from the sea
after the legions of fish which ascend the Rhône to spawn, were
hovering over the river, and now and again uttering their cry like the
laugh of a maniac. But enough; suffice it to say that, like simple folk
who find much pleasure in living with the brute creation, we were
intending to spend a morning in enjoying the ineffable awakening of
life in springtime.
We were not disappointed. The stickleback was in full dress, his scales
would have made silver look dim; his throat was of the brightest
vermilion. On the approach of a great horse-leech with no good
intentions, up rose the spines on back and side as if moved by a
spring. Thus bravely encountered, the bandit beat an ignominious
retreat down among the water-plants. The dull race of molluscs,
Planorbinæ, and water-snails were sucking in air on the surface of the
water, and the great Water Beetle, with its hideous larva, went by
wringing the neck now of one, now of another, without the stupid band
seeming to notice it. But let us leave the waters of the plain and
climb the steep cliff dividing us from the tableland where sheep are
feeding and horses are being exercised for the approaching races, one
and all bestowing largesse on the rejoicing dung beetles.
For here at work are the scavenger beetles to whom is entrusted the
high office of clearing the ground of impurities. It is impossible to
admire sufficiently the variety of tools with which they are furnished,
both to stir the dung with, to divide and shape it, and to hollow the
deep retreats into which they shut themselves with their booty. These
tools form a kind of technological museum, where there is a specimen of
every kind of digging instrument. Some might be copied from those
devised by human industry, others are of an original type, and might
serve as models for new tools for man. Copris hispanica wears a strong
horn on its head, forked and bent back, like the long spike of a
pickaxe. To a similar horn C. lunaris adds two strong points, shaped
liked a ploughshare, projecting from the thorax, and between them a
sharp-edged protuberance, serving as a wide rake. Bubas bubalus and B.
bison, both exclusively Mediterranean species, have foreheads armed
with two stout, diverging horns, between which projects a horizontal
share from the corslet. Geotrupes typhæus carries three points on the
front of its thorax, parallel and standing straight out, the middle one
shorter than the others. Onthophagus taurus owns as implements two long
curving appendages like the horns of a bull, while the furcate
Onthophagus has a two-pronged fork on its flat head. Even those least
well off have on one part or other hard tubercules—tools blunt indeed,
but which the patient insect knows very well how to utilise. All are
furnished with a shovel, i.e. a large, flat, sharp-edged head; all use
a rake—in other words, they collect materials with their toothed front
legs.
As compensation for their unpleasant work, more than one gives out a
strong scent of musk, and its ventral parts gleam like polished metal.
Geotrupes hypocrita has the under part of its body bright with metallic
lights of copper and gold, and G. stercorarius with amethystine violet.
But the usual colour is black. It is in tropical regions that we find
dung beetles in gorgeous array—absolutely living jewels. Under camel
droppings in Upper Egypt is found a beetle rivalling the dazzling green
of an emerald; Guiana, Brazil, Senegal, can show Copridæ of a metallic
red, rich as the red of copper, bright as that of a ruby. If such a
jewelled race be wanting to our country, still its dung beetles are not
less remarkable for their habits.
What eagerness is displayed around a dropping! Never did adventurers
from the four corners of the world show such eagerness in working a
Californian claim! Before the sun grows too hot there they are by
hundreds, large and small, pell-mell, of every kind and form and shape,
hastening to secure a slice of the cake! Some work in the open air and
rake the surface, some open galleries in the thickest part, seeking
choice morsels, others toil in the under part and bury their treasure
as soon as possible in the adjacent ground, and the smallest crumble
some scrap fallen from the excavations of their strong fellow-workers.
Some again—newcomers, and doubtless the hungriest—eat then and there,
but the aim of the greater number is to lay up a store which will allow
them to pass long days of plenty down in some sure retreat. A fresh
dropping is not to be found just when wanted in a plain where no thyme
grows; such a gift is indeed a piece of good fortune, and only comes to
the lucky. So when found, the wealth is prudently stored. The smell has
carried the good news a couple of miles round, and all have rushed to
gather up provender. Some laggards are still coming in on the wing or
on foot.
What is the one now trotting towards the heap, fearing to arrive too
late? His long legs work with a brusque, awkward action, as if moved by
some machine inside him; his little red antennæ spread their fans—sure
sign of anxious greediness. He is coming, has arrived, not without
upsetting some of the guests. It is the Sacred Beetle, all in black,
the largest and most celebrated of our dung beetles.
Here he is at table, beside his fellow-guests, who are giving last
touches to their balls with the flat of their large front legs, or
enriching them with a last layer before retiring to enjoy the fruit of
their labours in peace. Let us follow this famous ball in each stage of
construction.
The edge of the beetle’s head is large and flat, and armed with six
angular teeth arranged in a semicircle. It is the tool for digging and
dividing, the rake to lift or reject such vegetable fibres as are not
nutritious, to seek out what is best and rake it together. A choice is
thus made, for these keen connoisseurs like one thing better than
another—a somewhat careless choice, indeed, if the beetle alone be
concerned, but one which is rigorously scrupulous if the maternal ball
be in question, with its central hollow where the egg will hatch. Then
every scrap of fibre is rejected, and only the quintessence of the
stercorous matter is used to build the inner layer of the cell. Then,
as soon as it is hatched, the young larva finds in the walls of its
dwelling a dainty food which strengthens digestion and enables it later
to attack the coarse outer layers. For its own needs the beetle is less
fastidious, contenting itself with a general selection. The toothed
head hollows and seeks, rejects and gathers, somewhat at haphazard. The
forelegs aid mightily. They are flattened, bent into the arc of a
circle, are furnished with strong nerves and armed with five stout
teeth. If an effort has to be made, an obstacle overthrown, a path
forced through the thickest part of the heap, the dung beetle elbows
its way; in other words, throws its toothed legs right and left, and
clears a half circle with a vigorous sweep of its rake. Room being
made, these same feet have a new task; they collect bundles of the
material raked up by the head, and pass it under the insect to the four
hind-feet. These are planned for the turner’s trade. The legs,
especially the last pair, are long and slender, slightly bent in an
arc, and ending in a very sharp spur or talon. A glance shows that they
form a spherical compass, capable of holding a globe in the bent legs
to verify and correct its shape. In fact, their mission is to shape the
ball. Bundle after bundle the material accumulates under the insect,
held between the four legs which by a slight pressure lend it their own
curve and something of shape. Then from time to time the rough hewn
ball is set in motion between the legs of the double spherical compass,
turned underneath the beetle, and rolled into a perfect sphere. Should
the outer layer fail in plasticity and threaten to scale off, or if
some part be too fibrous, and refuse to be shaped by rotation, the
faulty part is retouched by the forefeet; little taps of their broad
surface give consistency to the new layer and imbed the recalcitrant
fibre in the general mass. When the sun shines and work is urgent, one
is amazed by the feverish activity with which the turner labours. Work
goes on fast; first there was a pellet, now it is as large as a nut, by
and by it will be of the size of an apple. I have seen some greedy
beetles make up a ball as large as an apple. Assuredly there is food in
the larder for some days to come!
Provender being gathered, the next thing is to retire from the mêlée,
and carry it to a fitting place. Now we see some of the most
characteristic habits of the Scarabæus. He sets out at once, embracing
the ball with the long hind legs, whose talons, planted in the mass,
serve as pivots—leans on the intermediary legs as pivots, and using as
levers the flat of the toothed forefeet, which press the ground
alternately, journeys backward with his load, the body bent, the head
low, and the hinder part upraised. The hind feet, which are the chief
organs in the mechanism, move continually, going and coming and
changing the place where the talons are stuck in, to alter the axis of
rotation, to keep the load balanced and advance by an alternate push
right and left. Thus the ball comes in contact with the ground in every
part of it, which gives it a perfect shape and lends consistency to the
outer layer by a uniform pressure. Courage! it moves, it rolls, and the
journey’s end will be reached, though not without trouble. Here is a
first difficulty. The beetle has to cross a slope, and the heavy ball
would naturally follow the incline, but for reasons best known to
itself, the insect prefers to cross this natural slope—an audacious
plan, which one false step or a grain of sand to upset the balance will
defeat. The false step is made, the ball rolls to the bottom of the
valley, and the insect, upset by the impetus of its load, staggers,
gets again on its legs, and hastens to harness itself afresh. The
mechanism works capitally. But look out, scatterbrain! follow the
hollow of the valley, it will spare labour and misadventure. The road
is good and quite level, and your ball will roll along with no
exertion. Not a bit of it. The insect has made up its mind to remount
the slope already so fatal to it. Perhaps it suits it to return to the
heights. Against that I have nothing to say, the Scarabæus knows better
than I do whether it be advisable to dwell in lofty regions. At all
events, take this path which will lead you up by a gentle incline. Not
at all. If there be near at hand some very stiff slope impossible to
climb, then that slope this wrong-headed insect prefers. Then begins
the labour of Sisyphus. With endless precautions the monstrous load is
painfully hoisted, step by step to a certain height, the beetle always
going tail first. One asks one’s self by what miracle of statics such a
mass can be kept on the slope. Ah! a clumsy movement brings all this
toil to naught. Down goes the ball, dragging the beetle with it. The
escalade is repeated, soon followed by a fresh fall. The attempt is
renewed, and better managed at the difficult points; a nasty
grass-root, which occasioned the previous tumbles, is prudently turned;
we have almost got to the top. But gently! gently! the ascent is
perilous, and a mere nothing may ruin all. A leg slips on a bit of
smooth gravel, and ball and scavenger roll down together. The beetle
begins all over again, with tireless obstinacy. Ten times, twenty
times, will it attempt that further ascent, until persistency
vanquishes all obstacles, or until, better advised, it takes the level
road.
The scavenger does not always roll his ball single-handed, but
frequently takes a partner, or rather, a partner takes him. The affair
is usually managed thus: the ball being prepared, a beetle comes out of
the throng, pushing it backwards. One of the newcomers, whose own work
is hardly begun, leaves its task and runs to the ball, now in motion,
to lend a hand to the lucky proprietor, who appears to accept the
proffered aid in an amiable spirit. The two work as partners, each
doing its best to convey the ball to a place of safety. Was a treaty
made in the workshop, a tacit agreement to share the cake? While one
kneaded and shaped, was the other tapping rich veins whence to extract
choice material for their common use? I have never observed such
collaboration, but have always seen every beetle exclusively occupied
by his own affairs on the field of labour, so that the last comer has
no acquired rights.
Is it, then, an association of the two sexes, a couple about to set up
house? For a time I thought so. The two scavengers pushing a ball, one
before and one behind, with equal zeal, used to remind me of certain
couplets once on a time popular on barrel-organs—
Pour monter notre ménage, hélas comment ferons-nous?
Toi devant, moi derrière, nous pousserons le tonneau.
But the evidence of the scalpel forces me to give up this family idyll.
There is no outward sign of sex in the Scarabæus, but on dissecting a
couple employed on one and the same ball they often turned out to be of
the same sex. In fact, there is neither community of family nor
community of labour. What, then, is the reason of the apparent
partnership? Merely an attempt at filching. The eager fellow-worker,
under pretence of giving a helping hand, cherishes the project of
carrying off the ball at the earliest opportunity. To make one for
itself at the heap demands labour and patience; to abstract a
ready-made one, or at least to foist one’s self in as a sharer of the
feast, is much more convenient. If the owner’s watchfulness should
slacken, one will flee with the treasure; if too closely looked after,
one can at least sit down at table on the pretext of services rendered.
With such tactics all turns to profit, so that pillage is carried on as
one of the most lucrative of trades. Some, as I have just said, play an
underhand game, hastening to the aid of some comrade who has not the
least need of them, and under the cloak of charitable assistance
conceal a highly indelicate greed. Others, bolder or more confident in
their strength, go straight to the goal and rob by main force. Every
moment some such scene as this will take place. A beetle departs alone,
rolling his ball, his own property, acquired by conscientious labour;
another comes flying, whence I know not, drops heavily, folds his smoky
wings under their elytra, and with the back of his toothed feet
oversets the proprietor, which, being hindside before, cannot defend
itself. While the latter struggles to its feet the aggressor stations
itself on the top of the ball, as a point of vantage whence to repel
attack, folds its feet under its breast, ready for action, and awaits
events. The bereaved owner moves round the ball, seeking a favourable
point whence to attempt an assault; the thief revolves on the top of
the citadel, constantly facing him. If the former raises itself for an
escalade, the latter gives it a cuff which stretches it flat on its
back. Secure on the top of the fortress, the besieged would bring to
nought for all time the efforts of its adversary to recover its lost
property if the besieger did not alter his tactics. Sapping threatens
to bring down both citadel and garrison. The ball being undermined,
staggers and rolls, carrying with it the robber, struggling his hardest
to keep at the top, which he generally succeeds in doing, thanks to the
hurried gymnastics that enable him to regain the altitude lost by the
rotation of his standing place. If a false movement should bring him to
the ground, the chances become equal, and the contest turns to a
wrestling match. Robber and robbed grapple body to body, breast to
breast. Their feet twist and untwist, their joints intertwine, their
horny armour clashes and grinds with the harsh sound of filed metal.
Then one will succeed in throwing its adversary on the back, and,
freeing itself, hastily takes up a position on the top of the ball, and
the siege is recommenced, now by the robber, now by the robbed, as the
chances of the fight may have decided. The former, no doubt a hardy
brigand and adventurer, often gets the best of it. After two or three
defeats the ex-owner wearies of the contest and returns philosophically
to the heap and makes a new ball. As for the other, when all fear of a
surprise is over, he harnesses himself to the conquered ball and pushes
it whither it seems good to him. I have occasionally seen a third thief
rob the robber. And upon my word I was not sorry.
Vainly do I ask myself what Prudhon introduced into Scarabæus-morality
the audacious paradox that “Property spells theft,” or what diplomatist
taught the dung-beetle that “they may take who have the power, and they
may keep who can.” I have not the evidence required to lead me to the
origin of these spoliations which have become a habit, or of this abuse
of strength in order to seize a ball of dirt. All that I can affirm is
that among beetles theft is universal. These dung rollers pillage one
another with a cool effrontery really matchless. I leave it to future
observers to elucidate this curious problem in the psychology of
animals, and return to the couple rolling their balls in partnership.
But first let us dissipate an error current in books. In the
magnificent work of M. Emile Blanchard, Metamorphoses, Habits, and
Instincts of Animals, I find the following passage: “Sometimes our
insect is stopped by an insurmountable obstacle: the ball has fallen
into a hole. At such a time the Ateuchus [2] displays a really
astonishing grasp of the situation, and a yet more astonishing power of
communication between individuals of the same species. Recognising the
impossibility of getting the ball over the obstacle, the Ateuchus
seemingly abandons it, and flies away. If you are sufficiently endowed
with that great and noble virtue called Patience, remain near this
forsaken ball. After a while the Ateuchus will return, and not alone;
it will be followed by two, three, or four companions who, alighting at
the appointed spot, will join in trying to lift up the load. The
Ateuchus has been to seek reinforcements, and this explains why several
beetles uniting to transport a single ball is such a common sight in
dry fields.” I also read in Illiger’s Entomological Magazine: “A
Gymnopleurus pilularius, [3] while constructing the ball of dung
destined to contain its eggs, let it roll into a hole, whence the
insect tried long and vainly to extract it. Finding this only waste of
time, he hastened to a neighbouring heap of manure to seek three of his
kind, which, uniting their efforts to his, succeeded in getting out the
ball, and then went back to their own work.”
I humbly beg pardon of my illustrious master, M. Blanchard, but
assuredly things do not happen thus. First, the two accounts are so
much alike that they must have had a common origin. After observations
not followed up closely enough to merit blind confidence, Illiger put
forward the story of his Gymnopleurus, and the same fact has been
attributed to the Scarabæus because it really is a common thing to find
two of these insects busy rolling a ball, or getting it out of some
difficult position. But the partnership does not at all prove that one
went to ask help from the other in some difficulty. I have had a large
measure of the patience recommended by M. Blanchard; I may claim to
have spent long days in the intimacy of Scarabæus sacer; I have tried
every means to comprehend its manners and customs, and to study them
from life, and never did I see anything which suggested that one had
called its companions to its aid. As I shall presently relate, I have
put the dung-beetle to proofs far more serious than that of a ball
fallen into a hole, and into far graver difficulties than having to
climb a slope—a thing which is mere sport for the obstinate Sisyphus,
who seems to enjoy the rough gymnastics required by steep places, as if
the ball grew thereby firmer, and therefore more valuable. I have
invented situations where the insect had extreme need of help, and
never could I detect any proof of good offices between comrades. I have
seen pillaged and pillagers, and nothing else. If a number of beetles
surrounded the same ball, it meant battle. My humble opinion is that
several Scarabæi gathered round a pellet with intent to thieve was what
gave rise to these stories of comrades called in to give a helping
hand. Incomplete observations have turned an audacious robber into a
serviceable companion who put his own work aside to do a friendly turn.
It is no slight thing to admit that an insect has a truly surprising
grasp of the situation and a facility of communication between
individuals more surprising still; therefore I insist on this point,
Are we to suppose that a Scarabæus in distress conceives the idea of
begging for help?—flies off, explores the country round to find
comrades at work on a dropping, and having found them, by some
pantomime, especially by movements of the antennæ, addresses them more
or less thus: “Hullo, you there! My load is upset in a hole yonder;
come and help me to get it out. I will do as much for you another
time.” And are we to suppose too that his colleagues understand him?
And, more wonderful still, that they leave their work, their ball newly
begun, their beloved ball, exposed to the greed of others, and certain
to be filched during their absence, in order to help the supplicant! I
am profoundly incredulous of so much self-sacrifice, and my incredulity
is borne out by all which I have seen during many long years, not in
collection boxes, but on the spots where the Scarabæi work. Outside of
the cares of maternity—cares in which it almost always shows itself
admirable, the Insect—unless, indeed, it lives in society like bees and
ants and some others—thinks and cares for nothing but itself.
Let us drop this discussion, excused by the importance of the subject.
I have already said that a Scarabæus, owner of a ball which it is
pushing backwards, is often joined by another which hastens to its aid
with interested views, ready to rob if it gets the chance. Let us call
the pair associates, though that is hardly the name for them, since one
forces itself on the other, who perhaps only accepts help for fear of
worse. The meeting is, however, perfectly peaceable. The arrival of the
assistant does not distract the proprietor for an instant from his
labours; the newcomer seems animated by the best intentions, and
instantly sets to work. The way they harness themselves is different
for each. The owner of the ball occupies the chief position, the place
of honour; he pushes behind the load, his hind feet upraised, his head
downward. The helper is in front, in a reverse position, head raised,
toothed arms on the ball, long hind legs on the ground. Between the two
moves the ball, pushed before it by the one, dragged towards it by the
other. The efforts of the couple are not always harmonious, especially
as the assistant turns his back to the road to be traversed, and the
view of the owner is bounded by his load. Hence repeated accidents and
ludicrous tumbles, taken cheerfully, each hastening to pick himself up
and resume his former position. On level ground this style of draught
does not answer to the expenditure of energy, for want of precision in
combined movements; the Scarabæus behind would do as well or better
alone, and the assistant, having proved his goodwill at the risk of
disturbing the mechanism, decides to keep quiet of course without
abandoning the precious globe, which he looks on as already his. A ball
touched is a ball acquired. He will not be so imprudent as to let go;
the other would instantly take advantage of it. So he folds his legs
under him, flattens himself, incrusts himself, as it were, on the ball,
and becomes part of it. Ball and beetle roll together, pushed along by
the lawful owner. Whether it should go over the body of the other,
whether he be above, below, or on one side of the rolling load, matters
not—the intruder lies low. A singular helper this, who lets himself be
run over for the sake of a share in the provender! But let them come to
a steep incline, and he gets a chance of displaying his usefulness. On
the steep slope he takes the lead, holding up the heavy load with his
toothed feet while his comrade steadies himself to hoist the load a
little higher. Thus, by a combination of judicious efforts, I have seen
them mount ascents, the one above holding up, the lower one pushing,
where all the obstinate efforts of a single beetle must have failed.
All, however, have not the same zeal in difficult moments; some, just
when their assistance is most wanted on a slope, do not appear in the
least aware that there is anything to overcome. While the unhappy
Sisyphus is exhausting himself in efforts to surmount his difficulties,
the other remains passive, incrusted on the ball, rolling down with it,
and forthwith hoisted up again.
I have often tried the following experiment on two associates in order
to judge of their inventive faculties in a serious predicament. Let us
suppose them on level ground, the assistant firmly seated on the ball,
the other pushing. Without disturbing the latter, I nail the ball to
the ground with a long, strong pin; it comes to a sudden stop. The
beetle, unaware of my treachery, doubtless believes in some rut, some
dandelion root or pebble stopping the way. He redoubles his efforts,
struggles his hardest, but nothing moves. What has happened? Let us go
and see. Twice or thrice he walks round his pellet. Discovering nothing
which can explain its immovableness, he goes behind and pushes again.
The ball remains motionless. Let us look above. He climbs up to find
nothing but his motionless colleague, for I have taken care to drive
the head of the pin in deep enough to hide the head in the mass of the
ball. He examines the summit and again descends; fresh thrusts are
vigorously applied in front and on either side with the same want of
success. Certainly no scavenger beetle ever yet found himself
confronted by such a problem of inertia. It is the very moment for
claiming assistance, a thing all the more easy that the colleague is
close at hand, squatted on the top of the dome. Will the Scarabæus give
him a shake, or address him somewhat thus: What are you about, lazy
bones? Come and look here; something has broken down. Nothing proves
that he does so, for the beetle long persists in trying to move the
immovable, examining now on this side, now on that, now above, now
below, while his friend still remains quiescent. In the end, however,
the latter becomes aware that something unusual is going on; it is
brought home to him by the uneasy comings and goings of his companion
and by the immobility of the ball, so in his turn he comes down to look
into the matter. Double harness does not prove more effectual than
single, and matters grow complicated. The little fans of their antennæ
open and shut, open again, quiver and betray their lively anxiety. Then
a stroke of genius ends their perplexities. Who knows what may be
underneath? They explore below the ball, and a slight excavation
reveals the pin. They recognise at once that the crux is there. Had I a
voice in the matter I should have said, “An excavation must be made,
and the stake which holds the ball must be got out.” This very
elementary proceeding, and one so easy to such expert excavators, was
not adopted nor even attempted. The scavenger beetle was cleverer than
the man. The two colleagues, one on this side, one on that, insinuated
themselves under the ball, which slipped up along the pin in proportion
as the living wedges raised it, the softness of the material allowing
of this clever manœuvre. Soon the ball was suspended at a height equal
to that of the beetles’ bodies. What remained to do was more difficult.
From lying flat they gradually got on their legs and pushed upward with
their backs. It was hard to accomplish, the feet losing strength the
more they stretched upward, but they did it. Then came a moment when
they could no longer use their backs to push, the highest point
possible being reached. There was a last resource, but one much less
favourable to the development of strength. Now in one of the postures
in which it drags a ball, now in the other,—that is to say, either head
downward or the reverse,—the insect pushes with hind or fore feet.
Finally, unless the pin be too long, the ball drops to the ground. The
perforation is repaired as best it can be, and the ball is at once
dragged onward.
But if the pin should be too long, the ball remains suspended at a
height which the insect cannot increase by rearing itself up. In this
case, after vain evolutions around the inaccessible maypole, the
beetles give up the struggle, unless you are kind-hearted enough to
complete the work yourself, and restore their treasure, or unless you
aid them by raising the floor with a little flat stone, a pedestal from
whence the insect can continue its work. Its use does not seem to be
immediately understood, for neither beetle shows any readiness to
profit by it. However, by chance or otherwise, one gets on the stone.
Oh, joy! as it passed it felt the ball touch its back. Thereupon
courage returns, and the struggle begins again. Standing on its
platform the beetle stretches its joints, rounds its back, and hoists
the pellet. When that no longer avails, it manœuvres with its feet, now
upright, now head downward. There is a new pause and new signs of
uneasiness when the limit of extension is reached. Without disturbing
the creature let us put another little stone on the first. By the help
of the new step, which gives a support for its levers, the insect
pursues its task. Adding one step to another as required, I have seen
the Scarabæus, perched on a shaky pile of three or four fingers’
breadth, persisting in its labour until the ball was completely freed.
Had it some vague consciousness of the services rendered by the
elevation of its point of leverage? I cannot believe it, although the
beetle profited very cleverly by my platform of little stones, for if
the very elementary idea of using a higher base to reach something too
elevated was not beyond it, how was it that neither beetle bethought
him of offering his back to the other, thus rendering the task
possible? One assisting the other, they might have doubled the height
attained. They are far indeed from any such combinations. Here, each
pushes the ball with all its might, but pushes as if alone, without
seeming to suspect the happy result which would be brought about by a
combined effort. When the ball is fastened to the ground by a pin, they
behave as they would when the ball is stopped by a loop of dandelion,
or held by some slender bit of stalk which has got into the soft,
rolling mass. My artifice brought about a stoppage not unlike those
which occur when the ball is rolling amid the many inequalities of the
ground, and the insect acts as it would have acted in some
circumstances where I had not interfered. It uses its back as a wedge
and lever and pushes with its feet without at all varying its means of
action, even when it might call a comrade to its help.
If it has to face the difficulties of a ball nailed to the ground with
no assistant, its dynamic manœuvres are exactly the same, and it
succeeds, so long as we give the indispensable help of a platform
gradually built up. Should this help be refused, the Scarabæus, no
longer stimulated by the touch of its beloved ball, loses hope, and
sooner or later, no doubt with bitter regret, flies off, whither I know
not. What I do know is, that it does not return with a squadron of
companions whom it has implored to help it. What could it do with them,
since it cannot utilise even the single comrade when one shares the
ball? Perhaps, however, an experiment which suspends the pellet at a
height inaccessible to the insect when its means of action are
exhausted may be too much outside of ordinary conditions. Let us try a
miniature ditch, deep enough and steep enough to prevent a beetle when
placed at the bottom with its load from rolling it up. These are the
exact conditions named by Blanchard and Illiger. What happens? When
persistent yet fruitless efforts show the beetle that it can do
nothing, it spreads its wings and flies off. Long, very long have I
waited, on the faith of what these learned men say, expecting it to
return with its friends, but I have always waited in vain. Often, too,
many days later I have found the ball just where I tried the
experiment, either at the top of the pin or at the bottom of the hole,
proving that nothing fresh had happened. A pellet abandoned from
necessity is abandoned for good and all, without salvage by the help of
other beetles. Dexterous use of wedge and lever to move the arrested
ball is the highest intellectual effort I have ever seen in the
Scarabæus sacer. As a counterpoise to what experiment refutes, namely,
an appeal for help to brother beetles, I very willingly chronicle this
feat of mechanics for the glorification of the Scarabæus. Straying over
sandy plains thickset with thyme, ruts, and slopes, the ball is rolled
for a while by the two partners, the material thus acquiring a firmness
which they probably find palatable. By and by a favourable spot is
selected. The proprietor, who has always kept the place of honour
behind the ball and is the one who performs almost the whole work of
draught, begins to hollow out the dining-room. Beside him is the ball,
to which his associate clings, motionless. Head and toothed legs attack
the sand, flinging quantities backward, and the excavation advances
rapidly. Soon the insect disappears therein. Each time that he brings a
load to upper air he never fails to glance at the ball to make sure
that all is going on well. Now and again he brings it nearer to the
edge of the cavity, feels it, and seems to gain new zeal from its
contact. The other beetle, hypocrite that he is, continues to inspire
confidence by his motionless attitude on the ball. Meanwhile, the
underground hall grows larger and deeper, and the excavator appears
more rarely, hindered by the extent of his labours. The moment is
favourable, the sleeper rouses up. The crafty partner decamps with the
ball, dragging it behind him with the haste of a thief fearing to be
caught in the act. This abuse of trust rouses my ire, but I let it pass
in the interest of the story—time enough to interfere on behalf of
morality if the upshot threaten to turn out ill.
Already the thief is some yards away. The robbed beetle comes up from
his hole, looks, and finds nothing. No doubt he has himself had a hand
in like proceedings. Scent and sight soon put him on the track and he
hurriedly comes up with the robber, whereupon this sly dog promptly
changes his position, gets on his hind legs and clasps the ball with
his toothed arms as he does when acting helper. Ah, you rascal! I see
through you! you would excuse yourself by declaring that the ball
rolled down the slope, and that you are trying to stop it and take it
home. I, however, who am an impartial witness, assert that the ball,
being well balanced at the mouth of the hole, did not move of its own
accord. Besides, the ground is level. I affirm that I saw you set it in
motion and make off with unequivocal intentions. It was an attempt at
larceny or I know nothing about it. My evidence not being taken into
consideration, the owner listens mildly to his companion’s excuses, and
the two roll the ball back as if nothing had happened.
But if the thief can get far enough away, or can conceal his track by
adroitly doubling back, the loss is irreparable. To have collected
provisions under a fiery sun, to have conveyed them a weary way, to
have hollowed out a comfortable banqueting hall in the sand, and then,
just when all is ready, and appetite whetted by toil lends charms to
the prospect of the approaching feast, to find one’s self suddenly
robbed by a companion is certainly a reverse of fortune that would try
most people’s courage. But the dung beetle does not allow itself to be
cast down by this malicious blow of fate; it rubs its cheeks, spreads
its antennæ, sniffs the air, and flies to the nearest heap to begin
again. This is a trait of character which I admire and envy.
Let us suppose the Scarabæus lucky enough to have met with a reliable
partner, or, better still, that he has no self-invited associate. The
hole is ready, made in friable earth, usually in sand, rather shallow,
about the size of one’s fist, communicating with the outer air by a
short passage, just wide enough to let the ball pass. As soon as the
provender is introduced, the Scarabæus shuts itself in, stopping up the
mouth of the passage with fragments kept in reserve in a corner. Once
the door is closed, nothing outside betrays the banqueting hall. And
now hurrah! all is for the best, in the best of all possible worlds.
The table is sumptuously laid, the ceiling tempers the heat of the sun,
only allowing a gentle moist heat to penetrate; the calm, the darkness,
the concert given by the field-cricket overhead, all favour digestion.
Carried away by my interest, I have caught myself listening at the
door, believing that I heard sung at table the famous
Ah! how sweet ’tis nought to do
When all around is endless stir.
from the opera of Galathea.
Who would dare disturb the beatitude of such a banquet? Alas! the
desire for knowledge makes one capable of anything, and I have not
shrunk from even this. I now give the result of thus violating the
sanctity of home-life. The ball filled almost the whole space, the
magnificent store of victuals rising from floor to ceiling, a narrow
passage separated it from the walls. In this sat the banqueters, two at
most, often but one, their faces to the table, their backs to the wall.
When once they have taken their places nobody stirs, all their vital
powers are absorbed by the digestive faculties. No little movement
which might cause the loss of a mouthful, no daintiness which might
waste the food—everything must be done decently and in order. To see
them thus absorbed round a lump of dung, one would say that they were
aware of their rôle as earth-cleansers, and consciously devoted
themselves to that marvellous chemistry which out of impurity brings
the flower that gladdens the eye, and the wing-cases of the Scarabæus
which adorn the turf in springtime. To fit it for this all-important
work, which turns into living matter the residue that horse and sheep
cannot utilise, in spite of the perfection of their digestive organs,
the dung beetle needs special tools. Accordingly anatomy shows the
immense length of its intestine, which, folded repeatedly on itself,
slowly deals with the material in its manifold circuits, and exhausts
the very last atom capable of being used. Where the stomach of the
herbivorous animal can extract nothing, this powerful alembic draws
riches which under its influence become the ebony mail of the Scarabæus
sacer, and a cuirass of gold and rubies for other species. Sanitary
principles require that this marvellous change be made as rapidly as
possible; therefore the Scarabæus is endowed with a matchless power of
digestion. Once shut up with food, it never ceases to eat and digest
until the whole store is devoured. Proof of this is easily come by.
Open the cell where it has retired from the world at any hour and you
find the insect eating, and behind it, still attached to the creature,
is a continuous cord, rolled carelessly like a bundle of cables.
Without going into particulars, we can guess what this cord represents.
Mouthful by mouthful the great ball passes into the digestive organs,
yielding up its nutritive principle, and reappearing spun into a rope.
Now this unbroken cord, often without a joint and always hanging from
the orifice, proves, with absolute certainty, how continuous is the
action of digestion. By the time that the food is nearly eaten, the
rope is astonishingly long. Where else could one find another stomach,
that, to avoid any loss in the debit and credit ledger of life, can
feast for a week or a fortnight on such miserable cheer? When the whole
mass has been digested, the hermit returns to daylight, seeks, finds,
and shapes a new ball, and begins all over again. This royal life lasts
one or two months, from June to July; then, with the coming of the
fierce heat, which the grasshoppers love, the Scarabæi take up summer
quarters and bury themselves in the cool earth. With the first rains
they reappear, less numerous and less active than in spring, but
apparently taken up by the all-important task of continuing their race.
II
THE ENCLOSURE
If you seek among writers for information as to the habits of Scarabæus
sacer in particular, and on the dung robbers in general, you find that
science has not got beyond some of the beliefs current in the time of
the Pharaohs. We are told that the ball which is dragged along contains
an egg, and is a cradle where the larva will find board and lodging.
The parents roll it over rough ground to make it round, and when shocks
and shakes and tumbles all along the slopes have shaped it properly,
they bury it and abandon it to mother earth.
So rough a start in life always seemed to me unlikely. How could a
beetle’s egg, so tender and fragile as it is, endure the rocking of its
rolling cradle? There exists in the germ a spark of life which the
slightest touch, the merest trifle, can extinguish, and is it likely
that the parents should take it into their heads to lug it about over
hill and dale for hours? Not they; maternal tenderness does not subject
its progeny to the martyrdom of Regulus.
However, something more than logical reasoning was required to sweep
away received opinions. I therefore opened hundreds of balls rolled by
the dung beetles and others out of holes dug under my eyes, and never,
never did I find either a central niche or an egg in the pellets. They
are invariably rough heaps of food, hastily shaped, with no particular
structure inside them, merely provender with which the beetles shut
themselves up to enjoy an orgy in peace for some days. They covet and
steal them with an energy which they certainly would not show if it
implied new family cares. It would be absurd for one Scarabæus to steal
the eggs of another, each having enough to do in securing the future of
its own. So on that point no more doubt can exist; the balls rolled by
beetles never contain eggs.
My first attempt to resolve the thorny question as to the bringing up
of the larva was by constructing an ample enclosure with an artificial
soil of sand and soil constantly renewed. Some twenty Scarabæus sacer
were introduced, together with Copris, Gymnopleurus, and Onthophagus,
and never did entomological experiment cost me so many mortifications.
The main difficulty was to renew the food. My landlord owned a stable
and a horse. I gained the confidence of his servant, who first laughed
at my plans, and then allowed himself to be gained over by a silver
coin. Every breakfast for my beetles cost twopence halfpenny; never
before did the budget of a scavenger beetle amount to such a sum, I can
still see and shall always see Joseph, as, when after grooming his
horse of a morning, he would raise his head a little above the wall
between the two gardens and call “Heigh! heigh!” on which I would hurry
to receive a pot of manure. Discretion on both sides was necessary, as
will be seen. One day his master appeared at the moment of transfer,
and made up his mind that all his manure went over the wall, and that
what he wanted for his cabbages went to grow my verbenas and narcissus.
Vainly did I try to explain; my explanations seemed to him mere jests.
Joseph got a sound scolding, was called this and that, and threatened
with dismissal if it happened again. It did not.
I still had the resource of going bashfully along the road with a twist
of paper to gather up stealthily provisions for my pupils. I did so,
and do not blush for it. Sometimes fate was kind. A donkey carrying the
produce of the market-gardens of Château-Renard and Barbentane to
Avignon would depose an offering as he passed my door. Such a gift,
instantly collected, enriched me for several days. In short, by hook or
by crook, by watching for a dropping, or turning diplomatist to get
one, I succeeded in feeding my captives. If success is earned by an
experiment conducted with a fervour that nothing can discourage, my
experiment deserved to prosper. It did not. After some time my
Scarabæi, consumed by home-sickness in a space which deprived them of
their wider movements, let themselves die miserably without revealing
their secret. Gymnopleurus and Onthophagus responded better to my
expectations. In due time I shall use the information furnished by
them.
Along with my attempts at education in an enclosed space, I carried on
direct researches, the results of which were far from what I desired. I
felt that I must have assistants. Just then a joyous band of children
were crossing the high land. It was a Thursday, and oblivious of school
and hated lessons, an apple in one hand and a piece of bread in the
other, they were coming from the neighbouring village of Les Angles and
wending their way to search on the bare hill where the bullets drop
when the garrison is shooting at a mark. A few bits of lead, worth
about a halfpenny, were the object of this early morning expedition.
The tiny rosy flowers of wild geranium enamelled the turf which for a
brief moment beautified this Arabia Petrea; the water wagtail, half
black, half white, uttered its scornful cry as it fluttered from one
point of rock to another; on the threshold of burrows, dug at the foot
of tufts of thyme, the field-crickets filled the air with their
monotonous symphony. And the children were happy in this festival of
spring—happier still at their prospective riches—that halfpenny which
they would get in return for the bullets they would find, that
halfpenny which would enable them next Sunday to buy at the stall set
up before the church two peppermint bull’s-eyes—two great bull’s-eyes
at a farthing apiece!
I accosted the tallest, whose wide-awake air gave me hopes of him; the
little ones formed a circle, each munching his apple; I explained the
matter and showed them Scarabæus sacer rolling his ball, and told them
that in a like ball, buried somewhere, I knew not where, a hollow is
sometimes found, and in this hollow a grub. The thing to be done was to
search about and watch the beetles in order to find such a ball. Those
with no maggot would not count. To stimulate the children by a fabulous
sum which would henceforward secure to me the time hitherto devoted to
some farthing’s worth of lead, I promised a franc, a lovely new coin
worth twenty halfpennies, for each inhabited ball. At the mention of
this sum eyes opened wide with delightful naïveté. I had quite upset
their ideas on the subject of money by naming this exorbitant price as
the value of a piece of dirt. Then, to show I was in good earnest, I
distributed some halfpence to clinch the bargain. The following week at
the same day and hour I was to appear at the same place and faithfully
perform the conditions of our compact towards all who should have made
the precious discovery. Having thoroughly posted up all the party, I
dismissed the children. “He really means it!” they said as they went
away; “he really means it! If we could only get one apiece!” and with
hearts swelling with sweet hope, they clinked their pence in the hollow
of the hand. The flattened bullets were forgotten. I saw the children
scatter over the plain and hunt about.
On the appointed day the week after I returned to the tableland
confident of success. My young helpers would no doubt have mentioned
this lucrative trade in beetle-balls to their comrades and shown their
handsels to convince the incredulous. Accordingly I found a larger
party assembled than the first time. On seeing me they ran up, but
there was no eagerness, no shout of joy. I saw that things had gone
ill. Many times on coming out of school had they sought for what I had
described, but in vain. Some balls, found underground with the
Scarabæus, were brought, but they were mere heaps of food, and there
was no grub. Fresh explanations were given and a new appointment was
made for the following Thursday. Again the same want of success. The
seekers, discouraged, were now few. I made a last appeal, but nothing
came of it. Finally, I paid the most zealous, those who had been
faithful to the last, and we dissolved partnership. I could count on no
one but myself for researches, which seemed simple enough, but really
were exceedingly difficult. Even up to the present time, after many
years, excavations made in favourable spots and hopeful opportunities
have not yet given any clear, consistent result. I am reduced to
combining incomplete observations and to filling up gaps by analogy.
[4] The little which I have seen, together with observations on other
dung beetles—Gymnopleurus, Copris, and Onthophagus—in my enclosure is
summed up in the following statement.
The ball destined for the egg is not fashioned in public, in the
hurry-scurry of the general workshop. It is a work of art and much
patience, demanding minute care impossible amid a crowd. One must
retire to meditate one’s plans and set to work, so the mother makes a
hollow from four to eight inches deep in the sand. It is a rather
spacious hall, communicating with the outside by a much narrower
gallery. The insect carries down choice materials, no doubt first
rolled into pellets. She must make many journeys, for the contents of
the hole are out of all proportion with the door, and could not be
carried in at once. I recollect a Spanish Copris which, at the moment I
came upon it, was finishing a ball as large as an orange at the bottom
of a burrow only communicating with the outside world by means of a
gallery where I could but just insert my finger. It is true that the
Copris do not roll balls or make long journeys to fetch food. They dig
a hole immediately under the dung, and crawl backward with successive
loads to the bottom of their cavity. The facility for provisioning and
the security offered by working under the manure favour a taste for
luxury not to be expected in the same degree among beetles belonging to
the rude trade of ball-rollers; but should it return two or three
times, Scarabæus sacer can amass wealth of which Copris hispanica might
well be jealous.
So far the insect has only raw material, put together anyhow. The first
thing to do is to select very carefully, taking what is most delicate
for the inner layers, upon which the larva will feed, and the coarser
for the outer ones which merely serve as a protecting shell. Then
around a central hollow which receives the egg the materials must be
arranged layer after layer, according to their decreasing fineness and
nutritive value; the strata must be made consistent and adhere one to
another; and finally, the bits of fibre in the outside crust, which has
to protect the whole thing, must be felted together. How can the
Scarabæus, clumsy and stiff as it seems, accomplish such a work in
complete darkness, at the bottom of a hole so full of provisions that
there is barely room to move? When I think how delicate is the work
done and how rude the tools of the workman,—of the angular feet fitted
to hollow the ground, and, if need be, even tufa,—I am reminded of an
elephant trying to make lace. Explain who can this miracle of maternal
industry; I give it up, especially as it has not been my good fortune
to see the artist at work. Let us restrict ourselves to describing this
masterpiece.
The ball which contains the egg is generally as large as a middle-sized
apple. In the midst is an oval cavity about a centimetre in diameter.
At the bottom is the egg, fixed vertically; it is cylindrical, rounded
at each end, yellowish-white, about as large as a grain of wheat, but
shorter. The wall of the hollow is washed over with a greenish-brown,
semi-fluid matter, manure cream, destined as the first food of the
larva. Does the mother collect the quintessence of the dung to make
this delicate food? The look of it tells me that it is a pap prepared
in the maternal stomach. The pigeon softens grain in its crop, and
turns it into a kind of milk food which it disgorges for its nestlings.
It would seem that the beetle shows the same tender care. It half
digests the choice food, and disgorges it in the shape of a delicate
film to line the walls of the cavity where the egg is laid. Thus, when
first hatched, the larva finds food easy of digestion, which rapidly
strengthens its stomach and allows it to attack the under layers which
lack the same refinement of preparation. Under the semi-fluid paste is
a choice pulp, compact and homogeneous, whence every particle of fibre
is banished. Beyond are the coarser strata where vegetable fibres
abound, and finally the outside of the ball is composed of the coarsest
materials felted together into a resistant shell. Manifestly there is a
progressive change of diet. On issuing from the egg the feeble grub
licks the fine paste on the walls of its dwelling. There is but little
of it, still it is strengthening and of high nutritious value. To the
bottle of early infancy succeeds the pap of the weanling, intermediate
between the dainty fare of the start and the coarse nourishment at the
end. This layer is thick enough and abundant enough to make the maggot
into a robust grub. Then, strong food for the strong, barley bread with
its husks, raw dung full of sharp bits of hay. The larva is
superabundantly provisioned with it, and, having attained its growth,
comes to the imprisoning outer layer. The capacity of the dwelling has
increased with that of its inhabitant. The small original cavity with
its excessively thick walls is now a large cell with sides only a few
lines thick. The inner layers have turned into larva, nymph, or
Scarabæus, as the case may be. In short, the ball is now a shell,
hiding within its spacious interior the mysteries of metamorphosis.
My observations go no further; my certificates of the birth and
condition of the Scarabæus do not go beyond the egg; I have not
actually seen the larva which, however, is known and described by
various authors. Neither have I seen the perfect insect while yet
enclosed in the cell, previous to exercising its functions as
ball-roller and excavator, and that is exactly what I should most have
desired to see. I should have liked to find the creature in its
birthplace, recently transformed, new to all labour, so that I might
have examined the worker’s hand before it set to its tasks, and for the
following reason.
Insects have each foot terminated by a kind of finger or tarsus,
composed of a series of delicate portions which may be compared to the
joints of our fingers. They end in a crooked nail. One claw to each
foot is the rule, and this claw, at least in the case of the superior
Coleoptera, especially the scavenger beetles, contains five joints. Now
by a strange exception, the Scarabæus has no tarsi on its forefeet,
while possessing well-shaped ones with five joints on the two other
pairs. They are imperfect, maimed, wanting in their front limbs in that
which represents, roughly indeed, our hand in an insect. A like anomaly
is found in the Onitis and Bubas, also of the scavenger family.
Entomology has long noted this curious fact without being able to give
a satisfactory explanation. Is it a birth imperfection? Does the beetle
come into the world without fingers on its front limbs, or does it lose
them as soon as it enters on its toilsome labours?
One might easily suppose such mutilation a consequence of the insect’s
hard work. To grope, to excavate, to rake, to divide now among the
gravel in the soil, now in the fibrous mass of manure, is not a work in
which organs so delicate as the tarsi can be used without danger. Yet
graver is it that when the insect is rolling its ball backward, head
downward, it is with the end of the forefeet that it grips the ground.
What becomes of the weak feet, no thicker than a thread, in this
perpetual contact with all the inequalities of the soil? They are
useless—merely in the way, and sooner or later they are bound to
disappear, crushed, torn off, worn out. Our workmen, alas! are too
often maimed by handling heavy tools, and lifting great weights, and
the same may be the case with the Scarabæus which rolls a ball that to
it is a huge load. In that case the maimed arms would be a noble
certificate of a life of toil.
But serious doubts at once suggest themselves. If these mutilations be
accidental, and the result of laborious work, they should be the
exception, not the rule. Because a workman or several workmen have had
a hand crushed in machinery, it does not follow that all others should
be maimed. If the Scarabæus often, or even very often, loses the
fore-claws in its trade of ball-roller, there must be some which,
cleverer or more fortunate, have preserved their tarsi. Let us then
consult facts. I have observed a very large number of the species of
Scarabæus which inhabit France, the S. sacer, common in Provence; S.
semipunctatus, which is seldom found far from the sea, and frequents
the sandy shores of Cette, Palavas, and of the Gulf of Juan; also S.
longicollis, which is much more widely spread than the two others, and
found at least as far up the Rhône Valley as Lyons. Finally, I have
observed an African kind, S. cicatricosus, found in the environs of
Constantine, and the want of tarsi on the forefeet has proved
invariable in all four species, at all events as far as my observations
go. Therefore the Scarabæus is maimed from birth, and it must be no
accident but a natural peculiarity.
Moreover, we have further proof in another reason. Were the absence of
fore-claws accidental, and the consequence of rough labour, there are
other insects, especially among the scavenger beetles, which undertake
excavations yet more difficult than those of the Scarabæus, and which
ought therefore to be still more liable to lose their front claws, as
these are useless and in the way when the foot has to serve as a strong
tool for excavation. For instance, the Geotrupes, who deserve their
name of Earth-piercer so well, make hollows in the hard and beaten soil
of paths among pebbles cemented by clay—vertical pits so deep that to
reach the lowest cell one has to use powerful digging tools, and even
then one does not always succeed. Now these miners par excellence, who
easily open long galleries in surroundings whose surface the Scarabæus
sacer could hardly disturb, have their front tarsi intact, as if to
perforate tufa were a work calling for delicacy rather than strength.
Everything then points to the belief that, if observed in its natal
cell, the baby Scarabæus would be found mutilated like the veteran who
has travelled the world and grown worn with labour.
On this absence of fingers might be based an argument in favour of the
theories now in fashion—the struggle for life and the evolution of the
species. One might say that the Scarabæus had originally tarsi on all
its feet in conformity with the general laws of insect organisation.
One way or another, some have lost these embarrassing appendages on
their forefeet, they being hurtful rather than useful. Finding
themselves the better for this mutilation, which proved favourable to
their work, little by little they gained a superiority over the less
favoured ones, founded a race by transmitting their fingerless stumps
to their descendants, and finally, the primitively fingered insect
became the fingerless Scarabæus of our time. I am willing to agree to
this reasoning if it could first be demonstrated why, with like
labours,—labours even far harder,—the Geotrupes has preserved his
tarsi. Meantime let us continue to believe that the first Scarabæus who
rolled a ball, perhaps on the shores of some lake where bathed the
Palæotherium, was as much without tarsi as him of our own day.
III
CERCERIS BUPRESTICIDA
Every one has met with books which, according to his turn of mind, have
been epoch-making, opening to him horizons whose very existence he had
never guessed. They throw wide open the gates of a new world where
henceforward he will use his mental powers; they are the spark which,
falling on a hearth, kindles into flame materials otherwise never
utilised. And very often it is mere chance which puts into our hands
some book which makes a new starting-point in the evolution of our
ideas. The most casual circumstance, a few lines which happen to come
under our eye, decide our future and impel us into the path which
thenceforward we shall follow. One winter evening, beside a stove where
the ashes were yet warm, while my family slept, I was forgetting, while
I read, all the cares of the morrow—the black cares of the professor of
physics, who, after having piled one university diploma on another and
rendered for a quarter of a century services whose merit was not
denied, earns for himself and family 1600 francs—less than a groom in a
well-to-do household. Such was the shameful parsimony of that day in
educational matters; thus did Red tape will it. I was a free-lance, son
of my solitary studies. Thus, amid my books I was putting aside acute
professorial worries when I chanced to light on an entomological
pamphlet which had come into my hands I forget how. It was by the
patriarch of entomology of that day, the venerable savant Léon Dufour,
on the habits of a Hymenopteron whose prey was the Buprestis. Certainly
long ere this I had felt a great interest in insects; from childhood I
had delighted in beetles, bees, and butterflies; as far back as I can
recollect I see myself enraptured by the splendours of a beetle’s
elytra, or the wings of the great Swallowtail butterfly. The materials
lay ready on the hearth, but the spark to kindle them had been lacking.
The accidental perusal of Léon Dufour’s pamphlet was that spark. I had
a mental revelation. So then to arrange lovely beetles in a cork box,
to name and classify was not the whole of science; there was something
far superior, namely, the close study of the structure, and still more
of the faculties of insects. Thrilled by emotion I read of a grand
instance of this. A little later, aided by those fortunate
circumstances which always befriend the ardent seeker, I published my
first entomological work, the complement of Léon Dufour’s. It gained
the honours of the Institute of France, a prize for experimental
physiology being adjudged to it, and—far sweeter reward!—shortly after
I received a most flattering and encouraging letter from the very man
who had inspired me. From far away in the Landes the venerated master
sent me the cordial expression of his enthusiasm, and urged me to
continue my studies. At that recollection my old eyes still grow wet
with a holy emotion. Oh, bright days of illusion, of faith in the
future, what has become of you!
I hope that the reader will not be sorry to meet with an extract from
the pamphlet which was the starting-point of my own researches, the
more so that it is necessary for the understanding of what follows. So
I will let my Master speak, only abridging slightly:—
In all insect history I know of no fact more curious and
extraordinary than that which I am about to relate. It concerns a
species of Cerceris which feeds its progeny on the most splendid
kinds of Buprestis. Let me share with you, my friend, the vivid
impressions gained by studying the habits of this Hymenopteron. In
July 1839 a friend, who lives in the country, sent me two Buprestis
bifasciata, an insect new to my collection, telling me that a kind
of wasp which was carrying one of these pretty beetles had dropped
it on his coat, and that a few minutes later a similar wasp had let
fall another on the ground. In July 1840, having been called in as
physician by my friend, I reminded him of his capture of the
preceding year, and asked about the circumstances. Season and place
corresponding with it, I hoped to do as much myself, but that
particular day was dark and chilly, unfavourable therefore to the
flight of Hymenoptera. Nevertheless, we made a tour of inspection
in the garden walks, and seeing no insects I bethought myself of
seeking in the ground for the homes of burrowing Hymenoptera. A
tiny heap of sand recently thrown up, like a miniature mole-hill,
attracted my attention. Scratching it away, I saw that it masked
the orifice of a gallery descending far down. We carefully dug up
the ground with a spade, and soon caught sight of the shining
elytra of the coveted Buprestis. Soon I not only found wing-cases
but a whole Buprestis, nay, three and four displayed their gold and
emerald. I could not believe my eyes. But that was only the prelude
to my feast. In the chaos caused by my own exhumations a
Hymenopteron appeared and was taken by me; it was the captor of the
Buprestis, trying to escape from amid her victims. I recognised an
old acquaintance, a Cerceris which I have found some two hundred
times in Spain and around Saint Sever.
But my ambition was far from satisfied. It was not enough to know
ravisher and prey: I wanted the larva for which all this rich store
was laid up. After exhausting the first vein of Buprestis I
hastened to make new excavations. Digging down more carefully I
finally discovered two larvæ, which completed the good fortune of
this campaign. In less than an hour I turned over three haunts of
the Cerceris, and my booty was some fifteen whole Buprestids with
fragments of a yet greater number. I calculated, and I believe it
fell far short of the truth, that there were twenty-five nests in
this garden, a fact representing an immense number of buried
Buprestids. What must it be, I said to myself, in localities where
in a few hours I have caught as many as sixty Cerceris on
blossoming garlic, with nests most probably near, and no doubt
provisioned quite as abundantly! Imagination, backed by
probability, showed me underground, within a small space, B.
bifasciata by thousands, although I who have observed the
entomology of our parts for over thirty years have never noticed a
single one. Once only, perhaps twenty years ago, did I see,
sticking in a hole of an ancient oak, the abdomen and elytra of
this insect. This fact was a ray of light, for it told me that the
larva of B. bifasciata must live in the wood of the oak, and
entirely explained the abundance of this beetle in a district where
the forests consist chiefly of that tree. As Cerceris bupresticida
is rare on the clayey hills of the latter stretch of country
compared to the sandy plains where grows Pinus maritima, it became
an interesting question whether this Hymenopteron when it inhabits
the pine region provisions its nest as it does in the oak district.
I had good reason to believe that it did not, and you will soon see
with some surprise how exquisite is the entomological tact of our
Cerceris in her choice of the numerous kind of Buprestids.
Let us hasten to the pine region to taste new pleasures. The spot
to be explored is a garden belonging to a property in the midst of
forests of the maritime pines. The haunts of the Cerceris were soon
recognised; they were exclusively found in the main paths, where
the beaten and compact soil offered the burrowing Hymenoptera
sufficient solidity for the construction of their subterranean
dwellings. I visited some twenty, and I did it, I may say, by the
sweat of my brow. It is a very laborious kind of exploration, for
the nests and provisions are only found at the depth of one foot,
so that it is necessary to invest the place by a line of square
trenches seven or eight inches from the mouth of the hole, first
inserting a stalk of grass in the gallery by way of clue. One must
sap with a garden spade, so that the central clod, thoroughly
detached all round, may be raised in one piece, then reversed on
the ground and broken up carefully. Such is the manœuvre which I
found successful. You would have shared our enthusiasm at the sight
of the beautiful species of Buprestis which this new style of
research revealed to our eager gaze. You ought to have heard our
exclamations as each time the clod was reversed, new treasures were
revealed rendered yet more brilliant by the hot sun, or when we
discovered the larvæ of every age attached to their prey, or the
cocoons of these larvæ incrusted with copper, bronze, and emerald.
I who had been for three or four times ten years, alas! a practical
entomologist had never beheld such an enchanting sight or had had
such good fortune. We only wanted you to double our enjoyment. With
ever increasing admiration we dwelt now on the brilliant Coleoptera
and now on the marvellous sagacity of the Cerceris which had buried
and laid them up for food. Can you believe it? Out of more than 400
beetles dug up, there was not one which did not belong to the old
genus Buprestis! Our Hymenopteron had not committed the smallest
error. How much there is to learn from this intelligent industry in
so small an insect! What value Latreille would have attached to the
vote of this Cerceris in favour of the natural system! [5]
Let us pass on to the various contrivances of the Cerceris in
making and provisioning her nest. I have already said that she
chooses ground whose surface is beaten, compact, and solid. I
should add that this ground must be dry and in full sunshine. This
choice shows an intelligence, or, if you like, an instinct, which
one is tempted to believe is the result of experience. Crumbly
earth or mere sand would of course be easier to work, but then how
construct an orifice which will remain wide open for ingress and
exit, and a gallery whose walls will not constantly fall in, yield,
and become blocked by the least rain? The choice is therefore both
reasonable and perfectly well calculated.
Our burrowing Hymenopteron hollows her gallery with her mandibles
and front tarsi, which accordingly are furnished with stiff points
to act as rakes. The orifice must not only have the diameter of the
miner’s body, but be able to admit a prey of larger bulk. This
shows admirable forethought. As the Cerceris digs deeper she brings
out the rubbish, and this makes the heap which I compared to a tiny
molehill. The gallery is not vertical, as this would have exposed
it to be filled up by wind or other causes. Not far from the
starting-point it makes an angle; its length is from seven to eight
inches. At the far end the industrious mother establishes the
cradle of her progeny. Five cells, separate and independent of one
another, are hollowed in the shape and nearly of the size of an
olive; within they are solid and polished. Each can contain three
Buprestids, the ordinary allowance for a larva. The Cerceris lays
an egg amid the three victims, and then stops up the gallery with
earth, so that when once the provisions for the brood are laid in,
the cells have no communication with the outside.
Cerceris bupresticida must be an indefatigable, daring, and skilful
huntress. The cleanness, the freshness of the beetles which she
buries in her den testify that they are seized just as they emerge
from the wooden galleries where their final metamorphosis takes
place. But what inconceivable instinct urges a creature that lives
solely on the nectar of flowers to seek amid a thousand
difficulties animal food for carnivorous offspring, which it will
never see, and to post itself on trees quite unlike one another,
which hide deep in their trunks the insects which are to fall her
victims? What entomological tact, yet more inconceivable, makes her
lay down a strict law to select them in a single generic group, and
to catch species differing very considerably in size, shape, and
colour? You observe how unlike are Buprestis biguttata, with its
slender long body and dark colour; B. octoguttata, oval-oblong,
with great stains of a beautiful yellow on a blue or green ground;
and B. micans, three or four times the size of B. biguttata, with a
splendid metallic greeny gold.
There is another very singular fact in the manœuvres of our
assassin of Buprestids. The buried ones, like those which I have
seized in the grasp of their murderers, give no sign of life, and
are unquestionably quite dead, yet, as I observed with surprise, no
matter when they are dug up, not only do they keep all their
freshness of colour, but every bit of them—feet, antennæ, palpi,
and the membranes which unite the various parts of their bodies—is
perfectly supple and flexible. At first one supposes the
explanation, as far as concerns the buried ones, to be in the
coolness of the ground, and absence of air and light, and for those
taken from their murderers, in the very recent date of death. But
observe that after my explorations, having isolated in cones of
paper the numerous Buprestids dug up, I have often left them over
thirty-six hours before pinning them out. And yet, notwithstanding
the dryness and great heat of July, I have always found the same
flexibility in the joints. More than this, after that lapse of
time, I have dissected several, and their visceræ were as perfectly
preserved as if I had used my scalpel on the live insect. Now, long
experience has taught me that even in a beetle of this size, when
twelve hours have passed in summer after its death, the interior
organs are either dried up or corrupted so that it is impossible to
be sure of form or structure. There is some peculiarity about
Buprestids put to death by the Cerceris which prevents corruption
or desiccation for a week, or perhaps two. But what is this
peculiarity?
To explain this wonderful preservation which makes an insect dead for
several weeks into a piece of game not even high, but, on the contrary,
as fresh as when first caught, and that during the greatest heat of
summer, the skilful historian of Cerceris bupresticida supposes that
there must be an antiseptic liquid acting as do the preparations used
in preserving anatomical specimens. This liquid can only be the poison
injected by the Hymenopteron into the body of the victim. A minute
globule of the venomous humour accompanying the dart or lancet,
destined for this purpose, acts as a kind of pickle or antiseptic fluid
to preserve the flesh on which the larva is to feed. But then how
superior to our processes are those of the Cerceris with regard to
preserved food! We salt or smoke or enclose in tins hermetically sealed
provisions which remain eatable, to be sure, but which are far, very
far from having the qualities of fresh meat. Sardines drowned in oil,
Dutch smoked herrings, cod hardened into slabs by salt and sun,—can any
of these sustain comparison with the same fish brought alive to the
kitchen? For meat properly so-called it is still worse. Beyond salting
and drying we have nothing which even for a short period can keep meat
eatable. At the present time, after innumerable fruitless attempts of
the most varied kind, special ships are equipped at great cost, which,
furnished with powerful freezing apparatus, convey to us the flesh of
sheep and oxen slaughtered in the Pampas of South America, frozen and
kept from corruption by intense cold. How far superior is the method of
the Cerceris, so rapid, so cheap, so expeditious! What lessons we
should have to learn from such transcendental chemistry when an
imperceptible drop of liquid poison renders in an instant the prey
incorruptible! What am I saying?—incorruptible?—that is far from being
all; the game is put into a condition which prevents desiccation,
leaves their suppleness to the limbs, and maintains all the organs in
pristine freshness, both the internal and external. In short, the
Cerceris puts the insect into a state differing only from life by a
corpse-like immobility.
Such is the conclusion arrived at by Léon Dufour before this
incomprehensible marvel of the dead Buprestis untouched by corruption.
An antiseptic fluid, incomparably superior to anything that human
science could produce, would explain the mystery. He, the Master,
skilful of the skilful, thoroughly used to most delicate anatomy; he
who with magnifying glass and scalpel has scrutinised the whole circuit
of entomology, leaving no corner unexplored; he, in short, for whom the
organisation of insects has no secrets,—can advance no better
conjecture than an antiseptic liquid to give at least a kind of
explanation of a fact which leaves him confounded. Let me insist on
this comparison between the instinct of the animal and the reason of
the sage in order the better to demonstrate in due time the
overwhelming superiority of the former.
I will add but a few words to the history of the C. bupresticida. This
Hymenopteron, common in the Landes, as we have heard, seems to be rare
in the department of Vaucluse. It is only at long intervals that I have
met with it, in autumn, and always isolated specimens, on the spiny
heads of Eryngium campestre, in the environs of Avignon or round Orange
and Carpentras. In the latter spot, so favourable to burrowing
hymenoptera, from its sandy soil of Mollasse, I had the good fortune,
not indeed of being present at the exhumation of such entomological
riches as Léon Dufour describes, but of finding some old nests which I
feel certain belonged to Cerceris bupresticida, from the shape of the
cocoons, the kind of provender stored up, and the existence of the
Hymenopteron in the neighbourhood. These nests, hollowed in a very
friable sandstone, called safre in those parts, were filled with
remains of beetles, easily recognised, and consisting of detached
wing-cases, empty corslets, and whole feet. Now these remains of the
larva’s feast all belonged to one species, and this was a Buprestis,
Sphænoptera geminata. Thus from the west to the east of France, from
the department of the Landes to Vaucluse, the Cerceris remains faithful
to its favourite prey; longitude does not affect its predilections, a
hunter of Buprestids among the maritime pines of the ocean sand-hills,
it is equally so amid the evergreen oaks and olives of Provence. The
species is changed according to place, climate, and vegetation—causes
influencing greatly the insect population, but the Cerceris keeps to
its chosen genus, the Buprestis. For what strange reason? That is what
I shall try to demonstrate.
IV
CERCERIS TUBERCULATA
With my mind full of the great deeds of the Buprestis hunter, I watched
for an opportunity of observing in my turn the labours of the Cerceris,
and I watched so closely that finally I got my chance. True, it was not
the Hymenopteron celebrated by Dufour, with such sumptuous provisions
that when dug up they made one think of the powder from a nugget broken
by the miner’s pickaxe in some gold field: it was a closely related
species, a giant brigand which contents itself with more modest prey—in
short, Cerceris tuberculata or C. major, the largest and strongest of
the genus.
The last fortnight in September is the time when our Hymenopteron makes
its burrows, and buries in the depths the prey destined for its brood.
The position of the domicile, always sagaciously chosen, is governed by
those mysterious laws varying with the species, but unchangeable for
any one of them. The Cerceris of Léon Dufour requires a horizontal,
beaten, compact soil, like that of a path, to avoid landslips and
changes which would ruin its gallery with the first rain. Ours, on the
contrary, selects vertical ground. By this slight architectural
modification she avoids most of the dangers which might threaten her
tunnel; therefore she is not particular as to the nature of the soil,
and hollows her gallery either in friable earth with a little clay, or
in the crumbling soil of the Mollasse, which makes the labour of
excavation much easier. The only indispensable condition seems to be
that the soil should be dry, and exposed to the sun for the greater
part of the day. It is therefore in the steep bank along a road, and in
the sides of hollows made by rain in the sandy Mollasse, that our
Hymenopteron makes its abode. Such conditions are frequent near
Carpentras in what is known as the hollow way, and it is there that I
have found C. tuberculata in the greatest abundance, and have collected
most of the facts relating to its history.
It is not enough to choose this vertical situation; other precautions
are taken to guard against the already advanced season. If some bit of
hard sandstone project like a shelf, or if a hole the size of one’s
fist should have been hollowed naturally in the ground, it will be
under this shelter or in this cavity that the gallery is made, a
natural vestibule being thus added by the Cerceris to its own edifice.
Although there is no kind of community among them, these insects like
to associate in small parties, and I have always found their nests in
groups of about ten, with orifices, though usually far apart, sometimes
touching.
When the sun shines it is wonderful to see the ways of these
hard-working miners. Some patiently extract bits of gravel from the
bottom of a hole with their mandibles, and push out the heavy mass;
others scratch the walls of their tunnel with the sharp rakes of their
tarsi, forming a heap of rubbish which they sweep out backward, and
send sliding down the steep incline in long dusty streams. It was these
periodical sand waves thrown out of galleries in process of
construction which betrayed my first Cerceris, and led to the discovery
of the nests. Others, either weary, or having completed their hard
task, rested and polished their antennæ and wings under the natural
caves which usually protect their dwelling, or else sat motionless at
the mouth of their holes, only displaying their wide, square faces,
barred with yellow and black. Others again were flying with a deep hum
on the bushes near the cochineal oak, where the males, always on the
watch near the burrows in process of construction, speedily join them.
Couples form, often troubled by the arrival of a second male, which
tries to supplant the happy possessor. The humming grows menacing,
quarrels begin, and often both males roll in the dust until one
acknowledges the superiority of his rival. Not far off the female waits
with indifference the upshot of the struggle, accepting finally the
male bestowed on her by the chances of the fight, and the pair fly out
of sight to seek peace in some distant thicket. Here the part of the
male ends. One half smaller than the females, they prowl about the
burrows but never enter, and never take any part in the hard work of
excavation, or that perhaps yet harder of provisioning the cells.
In a few days the galleries are ready, especially as after some repairs
those of the preceding year are used again. Other Cerceris, as far as I
know, have no fixed home, transmitted from one generation to another.
True Bohemians, they establish themselves wherever the chances of their
vagabond life may lead them, so long as the soil suits them. But C.
tuberculata is faithful to her penates. The projecting shelf of
sandstone used by its predecessors is used again; it hollows out the
same layer of sand hollowed by its forbears, and, adding its own labour
to theirs, obtains deep-seated retreats sometimes only visited with
difficulty. The diameter of the galleries would admit a thumb, and the
insect can move about easily, even when laden with the prey which we
shall see it capture. Their direction is horizontal, from four to eight
inches, then makes a sudden turn downward more or less obliquely, now
in one direction, now in another. Except the horizontal part, and the
angle of the tunnel, the direction seems to depend on the difficulties
of the ground, as is proved by the windings and changes in the farthest
part of this kind of canal, which is half a yard in length. At the far
end are the cells, not numerous, and provisioned with five or six dead
beetles. But let us leave the details of how a Cerceris builds, and
turn to more wonderful facts.
The victim chosen to feed the larvæ is a large weevil (Cleonus
ophthalmicus). One sees the captor arrive, carrying the victim between
its feet, body to body, head to head. It alights heavily some way from
the hole to complete the journey without the aid of wings, and drags
the prey laboriously with its jaws, on ground if not vertical, at least
very steeply inclined, which often results in sending captor and
captive headlong to the bottom, but the indefatigable mother finally
darts into her burrow, covered with dust, but with the prey of which
she has never let go. If she does not find walking with such a burden
easy, it is otherwise with her flight, which is surprisingly powerful,
if one considers that the strong little creature is carrying a prey
nearly as large as and heavier than herself. I have had the curiosity
to weigh the Cerceris and her prey separately, and the first weighed
150 milligrammes, and the second about 250, almost double.
These weights speak eloquently for the vigorous huntress, and I never
wearied of watching how swiftly and easily she resumed her flight, and
rose out of sight with the game between her feet when approached too
closely. But she did not always fly away, and then, though it was
difficult to do so, and yet avoid hurting her, I would make her drop
the prey by worrying and upsetting her with a straw. Then I would take
possession of the victim, and the Cerceris, thus despoiled, would hunt
about, go into her hole for a moment, come out, and resume the chase.
In less than ten minutes the sharp-sighted insect would find a new
victim, murder it and carry it off, not seldom to my profit. Eight
times running have I stolen from the same individual; eight times did
the indefatigable Cerceris resume her fruitless journey. Her
perseverance tired out mine, and I let her keep the ninth capture.
By this means, and by breaking open cells already filled with
provisions, I got nearly a hundred weevils, and in spite of what I had
a right to expect from what Léon Dufour has told us of the habits of
the Cerceris bupresticida, I could not repress my astonishment at the
sight of the singular collection which I had made. His Cerceris, though
it limits itself to one genus, yet takes any species within that limit,
but the more exclusive C. tuberculata preys exclusively on Cleonus
ophthalmicus. On looking through my booty I met with but one single
exception, and that belonged to a closely allied species, C.
alternans—one which I never met with again in my frequent visits to the
Cerceris. Later researches furnished me with a second exception,
Bothynoderes albidus, and these are all. Can a specially succulent and
savoury prey explain this predilection for a single species? Do the
larvæ find in this unvaried diet juices which suit them peculiarly, and
which they would not find elsewhere? I do not think so, and if Léon
Dufour’s Cerceris hunted all the kinds of Buprestids, no doubt it was
because they all have the same nutritive properties. But this must
generally be the case with all the Curculionidæ; their alimentary
properties must be identical, and in that case this amazing choice can
only be one of size, and therefore of economy of labour and time. Our
Cerceris, the giant of its race, chooses C. ophthalmicus as the largest
in our district, and perhaps the commonest. But if this favourite prey
fail, it must fall back upon other species, even if smaller, as is
proved by the two exceptions above mentioned.
Moreover, it is by no means the only one to hunt the long-nosed class
of weevils. Many other Cerceris, according to their size, strength, and
the chances of the chase, capture Curculionidæ most various in genus,
species, shape, and size. It has long been known that Cerceris arenaria
feeds her young with similar food. I myself have found in its burrows
Sitona lineata, S. tibialis, Cneorhinus hispidus, Brachyderes gracilis,
Geonemus flabellipes, Otiorhynchus maleficus. Cerceris aurita is known
to prey on Otiorhynchus raucus and Phytonomus punctatus. In the larder
of Cerceris ferreri I saw Phytonomus murinus, P. punctatus, Sitona
lineata, Cneorhinus hispidus, Rhynchites betuleti. This weevil, which
rolls up vine leaves into the shape of cigars, is sometimes of a superb
metallic blue, but more usually of a splendid golden copper. I have
found as many as seven of these brilliant insects laid up in one cell,
and the gorgeous colours of the little heap might almost bear
comparison with the jewels buried by the huntress of the Buprestids.
Other species, especially the weaker, hunt smaller game, the lesser
size being compensated by numbers. Thus, Cerceris quadricincta heaps in
each cell some thirty Apion gravidum, but does not disdain on occasion
bigger weevils, such as Sitona lineata, Phytonomus murinus. Cerceris
labiata also lays up small species. Finally, the smallest Cerceris in
my part of France, C. julii, hunts the least weevils, Apion gravidum
and Bruchus granarius, game proportioned to its own size. To end this
list of provender, let us add that some Cerceris follow other
gastronomic laws, and bring up their families on Hymenoptera. Such is
C. ornata. These tastes being alien to our subject, let us pass on.
We see that out of eight species of Cerceris which lay up Coleoptera as
food, seven hunt weevils and one Buprestids. What singular reason
confines the chase of these Hymenoptera within such narrow limits? What
are the motives of such an exclusive selection? What internal likeness
is there between the Buprestids and the weevils, outwardly quite
dissimilar, that both should become food for carnivorous and nearly
related larvæ? No doubt between such and such a victim there are
differences as to taste and nutritive qualities which the larvæ
thoroughly appreciate, but there must be a far graver reason than these
gastronomic considerations to explain these strange predilections.
After all that has been so admirably said by Léon Dufour on the long
and marvellous preservation of the insects destined as food for the
carnivorous larvæ, it is needless to say that the weevils which I dug
up, as well as those taken from between the feet of their murderer,
were perfectly fresh, though permanently motionless. Freshness of
colour, suppleness of the membranes and smallest articulations, normal
condition of the viscera, all combine to make one doubt whether the
inert body under one’s eyes can really be a corpse, all the more that
even under the magnifying glass it is impossible to perceive the
smallest wound; and in spite of one’s self one expects every moment to
see the insect move and walk. Yet more, in weather so hot that insects
which had died naturally would in a few hours have become dried up and
crumbly, or again in damp weather which would with equal rapidity have
made them decay and grow mouldy. I have kept specimens in glass tubes
or cones of paper over a month with no precautions, and wonderful to
say, after all this length of time, the intestines were as fresh as
ever, and I found dissection as easy as if the creatures were alive.
No, in presence of such facts one cannot talk of an antiseptic, and
believe in real death; life is still there—life latent and
passive—vegetative life. It alone, struggling successfully for a time
against the destructive invasion of chemical forces, can thus preserve
the organism from decomposition. Life is still there, but without
motion, and we have under our eyes such a marvel as chloroform or ether
might produce—a marvel caused by the mysterious laws of the nervous
system.
The functions of this vegetative life are slackened and troubled no
doubt, but still they are feebly exercised. I have the proof of this in
that action of the viscera which takes place normally and at intervals
in the weevils during the first week of that deep slumber, which will
never be broken, and yet which is not death. It only ceases when the
intestine is empty, as is shown by autopsy. But the faint rays of life
which the creature manifests do not stop there; and though sensation
appears annihilated for ever, I have succeeded in reawakening some
vestige of them. Having placed weevils, recently exhumed and absolutely
motionless, in a bottle with sawdust moistened with benzine, I was not
a little surprised to see a quarter of an hour later moving antennæ and
feet. For a moment I thought I could recall them to life. Vain hope!
these movements, last trace of a sensitiveness about to cease, soon
stopped, and could not be excited a second time. I have repeated this
experiment from some hours to several days after the murder, and always
with the same success; only movement is tardy in appearing in
proportion as the date of the victim’s death is distant. The movements
are always from the forepart backward. First, the antennæ move, then
the front tarsi tremble and share in the oscillations; next, the second
pair do the same; and finally, the third. Once movement is excited, all
these members oscillate without any order until all become again
motionless, as they do sooner or later. Unless death has been quite
recent, movement does not go beyond the tarsi, and the legs remain
motionless.
Ten days after the murder I could not obtain the least sign of
irritability by the proceeding described, and I had recourse to the
Voltaic battery. This is more effective, and provokes muscular
contractions where the vapour of benzine fails. One or two elements of
Bunsen suffice, which are armed with the rheophores of slender needles.
Plunging the point of the one under the furthest ring of the abdomen,
and the point of the other under the neck, you obtain each time that
the current is established, not only the quivering of the tarsi, but a
strong flexion of the feet, which fold themselves under the body, and
relax when the current is interrupted. These movements, very energetic
during the first days, gradually lose intensity, and after a certain
time appear no more. On the tenth day I have still been able to obtain
visible motions, but on the fifteenth the pile was unable to provoke
them, notwithstanding the suppleness of the limbs and freshness of the
viscera. I have submitted also to the action of the pile Coleoptera
really dead, Blaps, Saperda, Lamia, asphyxiated by benzine or
sulphureous gas, and two hours later it was impossible to provoke the
movements obtained so easily from weevils lying already for several
days in the singular state, intermediate between life and death, into
which their redoubtable enemy plunges them.
All these facts contradict the supposition of an animal completely
dead, and the hypothesis of a real corpse rendered incorruptible by
some antiseptic liquid. One can only explain them by admitting that the
animal is struck in the principle of its movements, and that
sensitiveness, suddenly benumbed, dies slowly out, while the more
tenacious, vegetative functions die yet more slowly and preserve the
intestines during the time necessary for the larva.
The most important detail to show was how the murder is committed.
Evidently, the chief part must be played by the poisoned dart of the
Cerceris. But where and how does it penetrate the body of the weevil,
covered with a hard cuirass, with pieces so closely joined? Even under
the magnifying glass nothing told where the sting entered. Direct
examination, therefore, was required to discover the murderous ways of
the Cerceris—a problem before whose difficulties Léon Dufour had
already recoiled, and the solution of which seemed to me for a time
impossible. I tried, however, and had the satisfaction of succeeding,
though not without some groping about.
When they fly from their holes to the chase, the Cerceris go here and
there, sometimes on one side, sometimes on the other, and return from
all directions, loaded with prey, so that they must seek it on all
sides; but as they barely take ten minutes between going and returning,
the space worked over could not be very great, especially considering
the time necessary to discover the prey, to attack and render it an
inert mass. I, therefore, set myself to examine all the adjacent ground
with close attention, hoping to discover some Cerceris on the hunt. One
afternoon devoted to this weary work convinced me of the uselessness of
my researches, and of the little chance I had of surprising any of the
few Cerceris, scattered here and there, and soon lost to view by their
rapid flight; above all, in difficult ground, planted with olives, I
gave up the attempt. But by carrying live weevils to the neighbourhood
of the nests might I not tempt the Cerceris by a prey found without
trouble, and so observe the drama? The notion seemed good, and the very
next day I set out to find live Cleonus ophthalmicus. Vineyards,
wheat-fields, and crops of lucerne, and heaps of stones did I visit and
examine one and all, and after two days of close search I
possessed—dare I own it?—three weevils! bare, dusty, maimed of antennæ
or tarsi, shabby old creatures which, perhaps, the Cerceris would not
touch! Since the day of that fevered search, when, for a weevil’s sake,
I bathed myself in perspiration during my wild expedition, many a year
has passed, and yet, in spite of almost daily entomological researches,
I am still ignorant of the life and habits of this Cleonus, which I met
here and there, straying on the edge of paths. Wonderful powers of
instinct! in the same spots, and in a fraction of time, one
Hymenopteron would have found hundreds of these insects which man
cannot find, and found them fresh and shining, no doubt just emerged
from the cocoon!
No matter; let us experiment with my wretched victim. A Cerceris has
just gone into her gallery with her prey; before she comes out for a
new expedition I place a weevil a few inches from her hole. The weevil
moves about; when it strays too far I bring it back to its place. At
last the Cerceris shows her wide face at the mouth of her hole; my
heart beats fast. She walks for a few minutes near her dwelling, sees
the weevil, brushes against it, turns, passes several times over its
back, and flies off without even honouring my captive with a bite—my
captive which cost me so much labour! I was confounded—knocked over.
New attempts at other holes, new disappointments. Decidedly these
dainty hunters will have none of the game which I offer them. Perhaps
they find it too old, too tasteless; perhaps, in handling it, I
communicated some smell to it which displeases them. Foreign contact
disgusts these connoisseurs.
Should I be more fortunate if I obliged the Cerceris to defend herself?
I enclosed one with a Cleonus in a bottle, irritating them by shaking
it. The Hymenopteron, sensitive by nature, was more impressed than the
other prisoner, with its dull, heavy organisation; she thought of
escape, not attack. Their parts were exchanged; the weevil became the
aggressor, sometimes seizing with the end of its trunk a foot of its
mortal foe, who made no attempt at defence, so terrified was she. I
could devise nothing more; my desire to be present at the dénoûment had
only added to former difficulties. Well, let us try again.
A luminous idea flashed upon me, bringing hope, so naturally did it
touch the very heart of the question. Of course, it was the right thing
and must succeed. My disdained game must be offered to the Cerceris in
the heat of the chase—then, absorbed and preoccupied, she will not
discover its imperfections. I have already said that on returning from
the chase the Cerceris alights at the foot of the incline at some
distance from the hole, whither she laboriously drags the prey. What I
then had to do was to deprive her of her victim, drawing it away by one
foot with pincers, and instantly throwing her the living weevil in
exchange. This manœuvre succeeded perfectly. As soon as the Cerceris
felt the prey slip under her body and escape her, she stamped with
impatience, turned round, and perceiving the weevil which had replaced
hers, flung herself upon it and clasped it in order to carry it away.
But she promptly perceived that this prey was alive, and then the drama
began and ended with inconceivable rapidity. The Cerceris faced her
victim, seized its proboscis with her powerful jaws and grasped it
vigorously, and while the weevil reared itself up, pressed her forefeet
hard on its back as if to force open some ventral articulation. Then
the tail of the murderess slid under the Cleonus, curved and darted its
poisoned lancet swiftly two or three times at the joining of the
prothorax, between the first and second pair of feet. In a twinkling
all was over. Without one convulsive movement, with no motion of the
limbs such as accompany the death of an animal, the victim fell
motionless for ever, as if annihilated. It was at once wonderful and
terrible in its rapidity. Then the assassin turned the Weevil on its
back, placing herself body to body with it, her legs on either side of
it, and flew off. Three times I renewed the experiment with my three
Weevils, and the same scene was always enacted.
Of course, each time I gave the Cerceris back her first prey and
withdrew my Cleonus to examine it at greater leisure. This examination
only confirmed my opinion of the terrible skill of the assassin. It is
impossible to find the slightest trace of a wound, or the smallest flow
of vital liquids from the point which was struck. But the most striking
thing is the rapid, complete annihilation of all movement. Vainly did I
seek even immediately after the murder for any trace of sensibility in
the three Weevils done to death under my eyes—neither pinching nor
pricking provoked it; to do so required the artificial means already
mentioned. Thus these robust Cleonus, which, pierced alive with a pin
and fixed by a collector on his fatal sheet of cork, would have
struggled for days, weeks, nay, whole months, instantly lose all power
of motion from the effect of a little prick which inoculates them with
a minute drop of poison. Chemistry knows none so active in so small a
dose; scarcely could prussic acid produce such an effect, if, indeed,
it could do so at all. It is not then to toxology, but to physiology
and anatomy that we must turn to find the cause of such instantaneous
catalepsy; it is not so much the great virulence of the poison
injected, as the importance of the organ injured by it which we must
consider in order to explain these marvels. What, then, is found at the
point where the sting penetrates?
V
ONE SKILFUL TO SLAY
The Hymenopteron has partly revealed her secret by showing us where the
sting strikes. But does that explain the question? Not yet, by any
means. Let us retrace our steps, forget for a moment what the insect
has taught us, and consider the problem set before the Cerceris. The
problem is this: to lay up in an underground cell a certain number of
heads of game which may suffice to nourish the larva hatched from the
egg laid upon the heap of provender.
At first sight this storing of food appears simple enough, but
reflexion soon discovers graver difficulties. Our own game is brought
down by a shot and killed with horrible wounds. The Hymenopteron has
refinements unknown to us; she chooses to have her prey intact, with
all its elegance of form and colour. No broken limbs, no gaping wounds,
no hideous disembowelment. Her prey has all the freshness of the living
insect; she does not destroy an atom of the fine-coloured powder which
the mere contact of our fingers deflowers. If the insect were really
dead, really a corpse, how difficult it would be for us to obtain such
a result! Any one can slay an insect by stamping brutally on it, but to
kill it neatly leaving no sign is no easy operation, within every one’s
power. How many of us would be at our wits’ end if we had to kill on
the spot, without crushing it, a little creature so tenacious of life
that even beheaded it still goes on struggling! One must have been a
practical entomologist before thinking of asphyxiation, and here,
again, success would be doubtful with the primitive methods of vapour
of benzine or burnt sulphur. In this deleterious atmosphere the insect
struggles too long, and tarnishes its brightness. One must have
recourse to more heroic methods—for instance, to the terrible
exhalations of prussic acid slowly disengaging themselves from strips
of paper impregnated with cyanide of potassium, or better still, as
being without danger to the collector, to the thunderbolt of vapour of
bisulphide of carbon. It requires a real art, an art calling to its aid
the redoubtable arsenal of chemistry, to kill an insect neatly; to do
that is what the elegant method of the Cerceris brings about so
quickly, if we admit the stupid supposition that her prey really
becomes a dead body.
A dead body! But that is by no means the diet of the larvæ, little
ogres greedy for fresh meat, to whom game ever so slightly tainted
would inspire insurmountable disgust. They must have fresh meat with no
high taste—that first sign of decay. Yet the prey cannot be laid up
alive in the cell like animals destined to furnish fresh meat to the
crew and passengers of a vessel. What would become of a delicate egg
laid among living food? What would become of the feeble larva, a worm
bruised by the slightest thing among vigorous Coleoptera moving their
long spurred legs for whole weeks? It is absolutely necessary—and here
we seem caught in a blind alley—to obtain deathly immobility with the
freshness of life for the interior organs. Before such an alimentary
problem the best instructed man of the world would stand helpless—even
the practised entomologist would own himself at a loss. The larder of
the Cerceris would defy their reasoning powers.
Let us then imagine an academy of entomologists and physiologists, a
congress where the question should be discussed by Flourens, Majendies,
Claude Bernards. To obtain at once complete immobility and long
preservation of food, the first and most natural and simple idea would
be that of preserved meats. One would invoke some antiseptic liquid, as
the illustrious savant of the Landes did with regard to his Buprestids,
and attribute such virtue to the poisonous fluid of the Cerceris, but
this strange quality has yet to be proved. Gratuitous hypothesis
replacing the unknown quantity of the preserving liquid may perhaps be
the final verdict of the learned assembly, as it was that of the
naturalist of the Landes.
Should one insist and explain that the larvæ require not preserved food
which could never have the properties of flesh still palpitating, but
prey yet alive, so to say, in spite of complete absence of motion, the
learned Congress, after ripe consideration, will fall back upon
paralysis: “Yes, of course; the creature has to be paralysed without
being killed.” There is but one means of arriving at this result,
namely, to injure, cut, and destroy the nervous system of the insect in
one or more skilfully chosen points.
If the question be thus left in hands unfamiliar with the secrets of a
delicate anatomy it will not have advanced far. What is the arrangement
of this nervous system which must be paralysed without killing the
insect? First, where is it? In the head no doubt and along the back,
like the brain and spinal marrow in the superior animals. “A grave
mistake!” our congress would reply; the insect is so to say an animal
reversed, which walks on its back—that is, it has the spinal marrow
below instead of above, all along breast and stomach; therefore on the
lower surface alone can the operation to paralyse the insect be
performed.
This difficulty removed, a far graver one presents itself. Armed with
his scalpel, the anatomist can direct its point where he will in spite
of obstacles which he may have to set aside. The Hymenopteron has no
choice. Its victim is a solidly cuirassed beetle, its lancet a dart,
extremely delicate, which the horny mail would certainly turn aside.
Only certain points are vulnerable to the frail tool, namely, the
joints, protected simply by a membrane with no power of resistance. But
the joints of the limbs, although vulnerable, do not in the least
fulfil the necessary conditions, for through these the utmost that
could be obtained is local paralysis, not one affecting the whole
organism of motion. Without any prolonged struggle, without repeated
operations, which, if too numerous, might endanger the victim’s life,
the Hymenopteron has, if possible, to abolish all motive power at one
blow. Therefore she must direct her dart at the nervous centres, the
source of the power of motion whence radiate the nerves running up to
the various organs of movement. Now these sources of locomotion, these
nervous centres, consist of a certain number of ganglia, more numerous
in the larva, less so in the perfect insect, and arranged on the median
line of the under surface in a string of beads more or less distant and
connected by a double ribbon of nervous tissue. In all insects which
have reached the perfect state the ganglia called thoracic, i.e. those
furnishing nerves to wings and feet and governing their movements, are
three in number. Here are the points to be struck: if their action can
be in any way destroyed, the possibility of movement is destroyed also.
Two ways of reaching these motive centres offer themselves to the
feeble dart of the Hymenopteron; one, the joint between neck and
corslet; the other the spot where the latter joins the continuation of
the thorax, between the first and second pair of feet. The way through
the neck does not answer; it is too far from the ganglia, which lie
near the base of the feet which they animate. The blow must be dealt at
the other spot, and through that only. Thus would an academy decide
where Claude Bernards illuminated the question by their profound
science. And it is precisely there, between the first and second pairs
of feet on the median line of the under surface, that the Cerceris
plunges her lancet. By what learned intelligence must she be inspired!
To choose as the spot in which to plant her sting the one vulnerable
point, the point which only a physiologist versed in the anatomy of
insects could determine beforehand is by no means enough; the
Hymenopteron has a far greater difficulty to overcome, and she
overcomes it with a mastery which fills one with amazement. We said
that the nervous centres controlling the organs of motion in an insect
are three. These are more or less distant from each other, but
sometimes, though rarely, near together. They possess a certain
independence of action, so that an injury to one does not cause, at all
events immediately, more than paralysis of members connected with it,
while the other ganglia and their corresponding members are not
affected by it. To reach these three sources of motion one after the
other, the second farther off than the first, and the last farther
still, and by a single way, between the first and second pairs of feet,
seems impossible for the sting, which is too short, and besides, so
difficult to aim well in such conditions. True, certain Coleoptera have
the three ganglia of the thorax almost touching, and others have the
two last completely united, soldered, smelted together. It is also
recognised that in proportion as the different nervous centres combine
and centralise, the characteristic functions of animality become more
perfect, and also, alas, more vulnerable. Those Coleoptera with centres
of motion so near that they touch or even gather into one mass, and so
are made part of each other, would be instantly paralysed by one sting;
or if several were needed, at all events the ganglia to be paralysed
are all collected under the point of the dart.
Now which are the Coleoptera so specially easy to paralyse? That is the
question. The lofty science of a Claude Bernard, floating in the
fundamental generalities of organisation and life, is no longer enough
for us; it is unable to inform and guide us in this entomological
selection. I appeal to every physiologist under whose eye these lines
may fall. Without having recourse to his book-shelves, could he name
the Coleoptera where such a nervous centralisation is found, and even
with the help of his library, could he instantly lay his hand on the
information wanted? The truth is, we are entering on the minute details
of the specialist; the highway is quitted for a path known to few.
I find the necessary documents in the fine work of M. E. Blanchard
(Annales des Sciences Naturelles, 3me série, tome v.) on the nervous
system of Coleoptera. There I find that this centralisation of nerve
power belongs especially to the Scarabæus, but most of these are too
large; the Cerceris could neither attack nor carry them away; besides,
many live in filth, where the cleanly Hymenopteron could not go to seek
them. Motive centres very close together are also found among the
Histers, which live on impurity, amid the smell of decay, and again
that will not do; also in the Scolytus, which is too small, and finally
in Buprestids and Weevils.
What unexpected light amid the pristine obscurities of the problem!
Amid the immense number of the Coleoptera which the Cerceris seem able
to prey upon, two groups alone, Weevils and Buprestids, fulfil the
indispensable conditions. They live far from decay and dung, which
perhaps cause invincible repugnance in this dainty Cerceris; they are
of most varied size, proportioned to that of their different captors,
which may thus choose according to their convenience. They are far more
vulnerable than all the others at the one point where the sting of the
Hymenopteron can penetrate successfully, for at that point, all easily
accessible to the dart, crowd the motor centres of feet and wings. At
this point the three thoracic ganglia of Weevils lie very close, the
hind two are contiguous. At that same spot in the Buprestids the second
and third are welded in one large mass a little distance from the
first. And as it is precisely Buprestids and Weevils which are hunted,
to the absolute exclusion of all other game, by the eight species of
Cerceris, whose food stores of Coleoptera have been ascertained, a
certain internal likeness, namely, in centralisation of the nervous
system must be the explanation why there are heaped in the dens of
various Cerceris victims, outwardly so unlike.
In this choice, upon which even transcendent knowledge could not
improve, such an assembly of difficulties is splendidly resolved, that
one asks if one be not the dupe of some involuntary illusion, and if
preconceived theories have not obscured the reality of facts, in short,
whether the pen has not described imaginary marvels. A scientific
result is only solidly established when confirmed by experiments
repeated in every possible way. Now let us submit to experimental proof
the physiological operation taught us by Cerceris tuberculata. If it be
possible to obtain artificially what the Hymenopteron obtained by her
sting, i.e. abolition of movement, and long preservation of the victim
in a state of perfect freshness; if it be possible to bring about this
wonder with the Coleoptera hunted by the Cerceris, or with those
possessing a like nervous centralisation, while one fails with those
whose ganglia are far apart, one must admit, however exacting one may
be in the matter of proof, that the Hymenopteron possesses in the
unconscious inspirations of instinct the resources of sublime science.
Let us see then what experiment shows. The manner of operation is very
simple. With a needle, or, better still, with the point of a fine steel
pen, we must introduce a tiny drop of some corrosive liquid into the
thoracic motive centres, pricking the insect slightly at the jointing
of the prothorax behind the first pair of feet. The liquid which I use
is ammonia, but it is evident that any other liquid whose action is
equally strong would produce the same results. The metal pen being
charged with ammonia as it might be with a droplet of ink, I give the
prick. The effects thus obtained differ enormously, according to
whether the experiment be made upon species with thoracic ganglia near
together or upon those where these same ganglia are far apart. With
regard to the first category, my experiments were made on Scarabæus, S.
sacer and S. longicollis; on a bronze Buprestis; and on weevils,
especially that Cleonus hunted by the heroine of these observations. In
the second category I have experimented on Caraboidea, Carabus,
Procrustes, Chlœnius, Sphodrus, Nebria; Longicornia, Saperda, and
Lamia; on Melasomes; Blaps, Scaurus, and Asida.
Among the Scarabæus class, the Buprestids, and the Weevils, the effect
is instantaneous. Every movement stops suddenly, without any
convulsion, as soon as the fatal drop has touched the nerve centres.
The sting of the Cerceris does not produce prompter extinction. Nothing
can be more striking than this sudden immobility in a vigorous
Scarabæus sacer, but the likeness between the effects produced by the
dart of the Cerceris and the steel pen charged with ammonia does not
stop here. Scarabæids, Buprestids, and Weevils artificially stung, in
spite of their complete immobility, preserve for three weeks, one
month, or even two, the perfect flexibility of every joint and the
normal freshness of the interior organs. With them defecation takes
place on the first days as in the normal condition, and movement can be
excited by the Voltaic current. In a word, they behave exactly as do
Coleoptera sacrificed by the Cerceris. There is complete identity
between the state into which she plunges her victims and that produced
at will by injecting ammonia into the nerve centres of the thorax. Now,
as it is impossible to attribute the perfect preservation of the insect
during so long a time to the drop injected, one must altogether reject
the notion of an antiseptic fluid, and grant that in spite of utter
immobility the creature is not really dead. A spark of life exists,
keeping the organs for some time in normal freshness, but dying out by
degrees and leaving them at last subject to corruption. Moreover, the
ammonia in some cases produces extinction of movement in the feet only,
and then the deleterious action of the fluid having doubtless not
extended far enough, the antennæ preserve some mobility, and one sees
that the creature, even a month after inoculation, draws them back
quickly at the least touch—an evident proof that life has not
completely abandoned the inert body. This movement is not rare with
Weevils wounded by the Cerceris.
Injection of ammonia always stops motion at once in Buprestids,
Weevils, and Scarabæus, but it is not always possible to put the
creature into the state just described. If the wound be too deep, or
the little drop instilled be too strong, at the end of two or three
days the victim really dies, and after two or three days there is but a
decaying body. If, on the contrary, the prick be too slight, it
recovers the power of motion, at least partially, after being inanimate
for more or less time. The Cerceris herself may operate clumsily, just
like man, for I have seen this kind of resurrection in a victim struck
by the dart of a Hymenopteron. Sphex flavipennis, whose history will
presently occupy us, heaps in her dens young crickets struck by her
venomed lancet. From one of her holes I have taken three poor crickets
whose extreme flabbiness would, in any other circumstances, have
denoted death. But here, again, death was only apparent. Placed in a
bottle, these crickets kept quite fresh but motionless for nearly three
weeks, after which two grew mouldy, while the third came partly to
life—that is to say, it regained motion of the antennæ, mouth-parts,
and, which is more remarkable, of the first two pairs of feet. If even
the skill of the Hymenopteron sometimes fails to benumb a victim for
good and all, can one expect constant success with the rough
experiments of man?
In Coleoptera of the second category—those where the ganglia of the
thorax are distant one from another—the effect of ammonia is quite
different. Those which show themselves least vulnerable are the
Caraboidea. A puncture which would instantly have annihilated motion in
the large Scarabæus sacer, in the middle size Caraboidea only causes
violent, disordered convulsions. By degrees the creature quiets down,
and after some hours’ rest resumes its habitual movements as if nothing
had happened to it. If the experiment be repeated on it twice, thrice,
even four times, the results are the same, until the wound becomes too
serious, and it dies outright, as is proved by the drying up and
putrefaction which soon follow.
The Melasomes and the Longicorns are more sensitive to the action of
ammonia. The injection of a small corrosive drop quickly renders them
motionless, and after some twitching they seem dead. But the paralysis
which would have persisted in Weevils, Scarabids, and Buprestids is but
momentary. Before long motion reappears as energetic as before. It is
only when the dose of ammonia is of a certain strength that movement
does not reappear. But then the creature is really dead, and
putrefaction rapidly comes on. It is then impossible to cause complete
and persistent paralysis in Coleoptera with ganglia far apart by the
means so efficacious in those with ganglia near together. At the utmost
one can only obtain momentary paralysis, which passes quickly away. The
demonstration is decisive. Cerceris which prey on Coleoptera conform in
their choice to what the most learned physiology and finest anatomy
alone can teach. It would be vain to endeavour to see nothing here but
chance agreement; it is not chance which explains such harmony.
VI
THE YELLOW-WINGED SPHEX
In their impenetrable coat of mail the Coleoptera offer but one
vulnerable point to their dart-bearing foe. This defect in the cuirass
is known to the assassin, and the poisoned sting is there inserted,
striking at one blow the three centres of motion, the Weevil and
Buprestid, which alone have a nervous organisation sufficiently
centralised, being selected. But what happens when the insect wears no
armour and is soft-skinned, so that the Hymenopteron can pierce it
anywhere that the chances of the struggle may direct? Is there then a
choice as to where the blow is given? Like the assassin who strikes at
the heart to shorten the dangerous struggles of his victim, does the
Sphex follow the tactics of the Cerceris, and strike by preference at
the motor ganglia? If so, what happens when these are distant from one
another, acting so independently that paralysis of one does not affect
the others? These questions will be answered by the history of an
insect which hunts field crickets, Sphex flavipennis.
It is towards the end of July that this Sphex tears open the cocoon
which until then has protected it, and flies away from its subterranean
cradle. During the whole of August one constantly sees it seeking drops
of honey on the spiny heads of Eryngium campestre, the commonest of
such robust plants as brave the dog days. But this careless life is
brief, for in the earliest days of September the Sphex has begun the
hard existence of miner and hunter. It is usually on some small flat
spot on banks along a road that the dwelling is established, only there
must be two indispensable conditions—a sandy soil easy to work, and
sun. Beyond this no precaution is taken to shelter the domicile against
autumn rain and winter frost. A horizontal position, unsheltered,
beaten by rain and wind, suit the Sphex perfectly, so long as it is
exposed to the sun. But when the work is half-way through, if heavy
rain should come, it is sad to see next day galleries in course of
construction choked with sand and finally abandoned.
Rarely does the Sphex work in solitude; it is in small bands of ten,
twenty, or more excavators that the claim selected is worked. One must
have spent some days watching one of these colonies in order to form
any idea of the restless activity, the feverish haste, the abrupt
movements, of these hard-working miners. They rapidly attack the ground
with the rakes of their forefeet, canis instar, as Linnæus says. A
puppy does not show more energy in scratching up the ground in play. At
the same time each labourer hums a joyous song—shrill, high-pitched,
interrupted at short intervals, and modulated by vibrations of wings
and thorax. One would think they were a troop of merry comrades,
stimulating one another to work by a cadenced rhythm. Meanwhile, the
sand flies, falling in fine dust on their quivering wings, and the
heavier gravel, pulled out bit by bit, rolls far away. If a bit resist
too much, the insect goes at it with a high note, reminding one of the
cry with which a woodcutter accompanies the stroke of his axe. Under
the redoubled efforts of tarsi and mandibles the cavity is already
sketched out, and the Sphex can already dart into it. Then comes a
lively interchange of forward movements to detach material, and of
backward to brush out fragments. In this hurried coming and going the
Sphex does not so much walk as dart forward, as though impelled by a
spring. With panting abdomen, antennæ vibrating, the whole body moved
by a strong thrill, she springs forward and is out of sight. You still
hear the unwearied hum underground, and one sees from time to time hind
legs pushing backward a wave of sand to the mouth of the burrow. From
time to time labour underground is interrupted either that the Sphex
may dust herself in the sunlight, and get rid of grains of dust which
insinuate themselves into delicate joints and hamper the liberty of her
movements, or that she make a reconnaissance in the neighbourhood.
Notwithstanding these short interruptions, in a few hours the gallery
is hollowed out and the Sphex appears on her threshold, to voice her
triumph, and give the last touch to her labours by effacing some
inequality, or carrying away some particles of earth, the objection to
which only the eye of a Sphex could perceive.
Of the many tribes of Sphegidæ visited by me, there is one of which I
retain a specially lively recollection, on account of its singular
installation upon the edge of a high road, where were little heaps of
mud thrown up from side ditches by the cantonnier’s shovel. One, well
sun-dried, had a conical shape like a sugar-loaf over fifteen inches
high. The situation pleased the Sphegidæ, who had established a more
populous community than I have ever again met with. From base to summit
the cone of dried mud was pierced with burrows, giving it the
appearance of a huge sponge. In every story was feverish animation, and
a busy coming and going which brought to mind the scene in some great
workshop when orders are pressing. Crickets were being dragged by the
antennæ up the slopes of the conical city; there was storing of
provisions in the larders of the cells; dust was pouring from galleries
in process of construction; at intervals the grimy faces of the miners
appeared at mouths of passages—there was a constant going and coming.
Now and then, in a short interval of leisure, a Sphex ascended the top
of the cone, perhaps to take a general and well-satisfied view from
this belvedere. What a tempting sight!—one to make me long to carry
away the entire city with its inhabitants. It was useless to try; the
mass was too heavy. One cannot take up a village by the roots to plant
it elsewhere.
Let us look at the Sphex at work in flat ground, as is much more
frequently the case. As soon as the burrow is hollowed out, the chase
begins. Let us profit by the absence of the Hymenopteron in search of
game, and take a look at her dwelling. The spot chosen by a Sphex
colony is generally horizontal, though the ground is not so level but
that there are little mounds crowned by a tuft of grass or thrift, or
inequalities consolidated by the slender roots of the vegetation which
covers them. It is on the sides of such furrows that the Sphex places
her den. For two or three inches in depth the gallery is horizontal,
serving as an approach to the hidden shelter for the provender and the
larvæ. In this vestibule the Sphex takes refuge in bad weather, rests
there at night, and occasionally by day for a few instants, showing
only her expressive face and impudent eyes. Beyond the vestibule an
abrupt turn descends more or less obliquely to a depth of two or three
inches more, ending in an oval cell rather larger in diameter, whose
axis lies parallel with the horizontal gallery. The cell walls are not
covered with any particular cement, but in spite of their bareness they
have evidently been the object of most careful labour. The sand is
heaped and levelled on the floor, on the ceiling, and sides, so as to
do away with the risk of landslips, or any roughness which might injure
the delicate skin of the larva. This cell communicates with the passage
by a narrow entrance, just wide enough to allow the Sphex, burdened
with prey, to enter. When this first cell is furnished with an egg and
necessary provisions, the Sphex walls up the entrance, but does not yet
abandon her burrow. A second cell is hollowed beside the first, and
provisioned in the same manner; there is then a third made, and
sometimes a fourth. Only then does the Sphex cast back into the burrow
the rubbish heaped at the entrance, completely effacing all outward
trace of her work. Three cells are usually found in each burrow, rarely
two, and yet more rarely four. As one learns by dissecting the insect,
one may estimate the number of eggs laid at about thirty, which would
make the number of burrows needed ten. Now these are hardly begun
before September, and are finished before the end of the month.
Consequently the Sphex cannot devote more than two or three days at
most to each burrow and its stores. Evidently the active little
creature has not a minute to lose, when in so short a time she has to
hollow out the lair, procure a dozen crickets, sometimes brought from a
distance through endless difficulties, to store them, and finally to
stop up the burrow. Moreover, there are days when wind makes hunting
impossible; rainy days or overcast ones suspending all work. The Sphex
cannot give to her building the enduring solidity that Cerceris
tuberculata gives to its deep galleries. This species transmit their
solid abodes from one generation to another, each year hollowed more
deeply, so that I was often bathed in perspiration when I tried to
reach them, and frequently my efforts and my implements proved useless.
The Sphex inherits nothing, and must herself do everything, and that
rapidly. Her dwelling is but a tent, hastily erected and moved on the
morrow. In compensation the larvæ, covered but by a thin layer of sand,
know how to supply the shelter which their mother has not given them;
they can clothe themselves with a double and triple waterproof
covering, far superior to the thin cocoon of the Cerceris.
But here comes a Sphex with noisy hum, returning from the chase. She
pauses on a neighbouring bush, holding in her mandibles one of the
antennæ of a big cricket, weighing far more than herself. Tired out by
the weight, she rests a moment, then grasps her captive between her
feet, and with a supreme effort flies right across the ravine between
her and her abode. She alights heavily on the flat ground where I am
watching, in the very middle of a Sphex village. The rest of the
journey is made on foot, the Sphex, not in the least intimidated by my
presence, comes astride her victim, holding her head proudly aloft
while she drags along the cricket between her feet by one of its
antennæ held in her jaws. If the soil be bare there is no difficulty,
but should a network of grass spread its runners across the way, it is
curious to see the astonishment of the Sphex at finding her efforts
baffled by this little obstacle—curious to witness her marches and
countermarches and repeated attempts until the difficulty is surmounted
either by the aid of her wings or a well-planned détour. The cricket is
at last conveyed to its destination and placed so that its antennæ come
exactly to the mouth of the burrow. Then the Sphex abandons it and
descends in haste to the bottom of the cave. A few seconds later she
puts her head out with a little cry of joy. The antennæ of the cricket
are within reach; she seizes them and promptly conveys it down to her
den.
I still ask myself in vain why these complicated manœuvres at the
moment of conveying the cricket into the burrow. Why, instead of going
down alone and returning to resume the prey left on the threshold, does
not the Sphex drag it into the gallery, as she did in the open air,
since the space is wide enough, or take it with her while she enters
backwards? The various predatory Hymenoptera which I have been able to
observe all drag their prey at once to the bottom of their cells,
holding it underneath them by their mandibles and intermediary feet.
Léon Dufour’s Cerceris does indeed somewhat complicate her movements,
since after putting down her Buprestis for a moment at the door of her
underground abode, she instantly goes backward into the gallery, seizes
her victim with her mandibles and drags it down; but that is very
unlike the tactics adopted in a like case by the Sphex. Why this
domiciliary visit, which invariably precedes the introduction of the
prey? May it not be that before descending hampered by a load, the
Sphex thinks it prudent to give a look round the bottom of her dwelling
to make sure that all is in order and to drive out, if necessary, some
impertinent parasite which may have slipped in during her absence?
Several Diptera, predatory flies, especially Tachinidæ, watch at the
doors of all the hunting Hymenoptera, spying out the favourable moment
to lay their eggs on other people’s game, but none penetrate into the
dwelling, nor venture into the dark passages, where, if by ill-luck the
owner caught them, they might have to pay dearly for their audacity.
The Sphex, like others, pays her tribute to the predatory Tachinidæ,
but they never enter her burrow to commit their misdeeds. Besides, have
they not all the time they need to lay their eggs on the cricket? If
they look sharp, they may very well profit by the Sphex’s momentary
absence from her victim to confide their posterity to it. What yet
greater danger menaces the Sphex which renders this preliminary descent
to the bottom of the burrow such an imperious necessity?
The one observed fact which can throw any light on the problem is this.
Amid a colony of Sphegidæ in full activity, whence all other
Hymenoptera are habitually excluded, I one day surprised a sportsman of
a different kind, Tachytes nigra, carrying one by one, without any
haste and with the greatest composure, amid the crowd where he was but
an intruder, grains of sand, little bits of dry stalk, and other small
materials, to stop up a burrow of the same shape and size as the
neighbouring ones of the Sphegidæ. This labour was pursued too
conscientiously to admit of any doubt as to the presence of the
worker’s egg in the underground dwelling. A Sphex with anxious
movements, apparently the legitimate owner of the burrow, never failed
each time that the Tachytes entered the gallery to dart in pursuit, but
emerged swiftly, as if frightened, followed by the other, who continued
her task unmoved. I visited this burrow, the evident cause of strife
between them, and found a cell provisioned with four crickets.
Suspicion almost gave place to certainty, for this allowance far
exceeded the needs of a Tachytes’ larva, which is at least one-half
smaller than the Sphex. The calm insect whose care to stop up the
burrow at first suggested that it was the owner was really a usurper.
How comes it that the Sphex, larger and more robust than her adversary,
allows herself to be robbed with impunity, limiting herself to a
fruitless pursuit, and flying like a coward when the intruder, who
seems not even to perceive her, turns round to come out of the burrow?
Is it with insects as with men, the first quality needed for success is
audacity—audacity—audacity? Certainly the usurper had no lack of it. I
can still see that Tachytes, imperturbably calm, going and coming
before the meek Sphex, which stamped with impatience, but did not
venture to fall upon the thief.
Let us add that in other circumstances I have repeatedly found this
Hymenopteron, I suppose to be a parasite—this Tachytes nigra, dragging
a cricket by one of its antennæ. Was it a prey lawfully acquired? I
would fain think so, but the indecision of the insect which strayed
about the ruts in the paths as if seeking a convenient burrow always
left me suspicious. I have never been present when it burrowed, if
indeed it ever does undertake that labour, and what is more, I have
seen it abandon its game to decay, perhaps not knowing what to do with
it for want of a hole where to put it. Such wastefulness seems to
indicate goods ill-gotten, and I ask myself if the cricket were not
stolen when the Sphex left it on her threshold? I also suspect Tachytes
obsoleta, banded with white round the abdomen like Sphex albisecta,
which nourishes its larvæ with crickets such as are hunted by the
latter. I have never seen it digging galleries, but I have caught it
dragging crickets that the Sphex would not have disdained. This
similarity of food in species of different genera makes me doubtful
whether the booty were lawfully come by. Let me add, however, to atone
in some measure for the injury which my suspicions may do to the
character of the genus, that I have seen the perfectly lawful capture
of a little cricket yet wingless by Tachytes tarsina, and have also
seen it hollow cells and store them with prey bravely acquired. Thus I
have only suspicions to offer as to why the Sphex persists in
descending to the bottom of her hole before carrying in prey. Is there
some other end besides that of dislodging a parasite which may have got
in during the owner’s absence? I despair of finding out; who can
interpret the thousand manœuvres of instinct? Poor human reason which
cannot even explain the wisdom of a Sphex!
At all events, it is proved that these manœuvres are singularly
invariable, àpropos of which I will mention an experiment which greatly
interested me. At the moment when the Sphex makes her domiciliary
visit, I take the cricket and put it some way off. The Sphex comes up,
utters her usual cry, looks round with astonishment, and seeing the
game too far off, comes out to seize and put it in the right position.
Then she goes down again without the cricket. Same manœuvre on my part,
same disappointment when she reappears. Again the prey is brought to
the mouth of the hole, and again the Sphex goes down alone, and so on
as long as my patience holds out. Forty times on end have I tried the
experiment on the same individual; her persistence vanquished mine, and
her tactics never varied.
Having proved the inflexible pertinacity of all the Sphegidæ in one
colony on whom I cared to experiment, I could not but perplex myself
over it. “Does then the insect obey a fixed tendency which
circumstances cannot modify?” I asked myself. “Are its actions all done
by rule, and is it unable to acquire the least experience from its own
proceedings?” Later observations modified this too absolute judgment.
The following year, at the proper time, I visited the same spot. The
new generation had inherited for their burrows the place chosen by the
preceding ones; it had also faithfully inherited their tactics, for the
cricket experiment gave the same results. Such as were the Sphegidæ of
the past year such are those of the present one, equally persistent in
a fruitless attempt. My error grew confirmed until good luck brought me
to another colony in a different place. I renewed my experiments. After
two or three trials with the old, well-known result, the Sphex got
astride of the cricket, seized its antennæ with her mandibles, and
dragged it at once into the burrow. Who looked a fool then? The
experimenter baffled by the clever Hymenopteron. At the other holes her
neighbours, some sooner, some later, found me out, and went down with
their prey instead of persisting in leaving it on the threshold to
seize it later. What is the meaning of this? This colony, descended
from another stock, for sons return to the spot selected by their
forefathers, is cleverer than the one observed last year. Craft is
inherited; there are sharper-witted tribes and duller ones, apparently
according to the faculties of their forefathers. With Sphegidæ, as with
us, the kind of intellect changes with the province. Next day I tried
the cricket experiment in another locality, and it invariably
succeeded. I had come upon a dense-minded tribe, a true colony of
Bœotians, as in my earlier observations.
VII
THREE STROKES OF A DAGGER
There can be no doubt that the Sphex uses her greatest skill when
immolating a cricket; it is therefore very important to explain the
method by which the victim is sacrificed. Taught by my numerous
attempts to observe the war tactics of the Cerceris, I immediately used
on the Sphex the plan already successful with the former, i.e. taking
away the prey and replacing it by a living specimen. This exchange is
all the easier because, as we have seen, the Sphex leaves her victim
while she goes down her burrow, and the audacious tameness, which
actually allows her to take from your fingertips, or even off your
hand, the cricket stolen from her and now offered, conduces most
happily to a successful result of the experiment by allowing the
details of the drama to be closely observed.
It is easy enough to find living crickets; one has only to lift the
first stone, and you find them, crouched and sheltering from the sun.
These are the young ones of the current year, with only rudimentary
wings, and which, not having the industry of the perfect insect, do not
yet know how to dig deep retreats where they would be beyond the
investigations of the Sphex. In a few moments I find as many crickets
as I could wish, and all my preparations are made. I ascend to the top
of my observatory, establish myself on the flat ground in the midst of
the Sphex colony and wait.
A huntress comes, conveys her cricket to the mouth of her hole and goes
down alone. The cricket is speedily replaced by one of mine, but placed
at some distance from the hole. The Sphex returns, looks round, and
hurries to seize her too distant prey. I am all attention. Nothing on
earth would induce me to give up my part in the drama which I am about
to witness. The frightened cricket springs away. The Sphex follows
closely, reaches it, darts upon it. Then there is a struggle in the
dust when sometimes conqueror, sometimes conquered is uppermost or
undermost. Success, equal for a moment, finally crowns the aggressor.
In spite of vigorous kicks, in spite of bites from its pincer-like
jaws, the cricket is felled and stretched on its back.
The murderess soon makes her arrangements. She places herself body to
body with her adversary, but in a reverse position, seizes one of the
bands at the end of the cricket’s abdomen and masters with her forefeet
the convulsive efforts of its great hind-thighs. At the same moment her
intermediate feet squeeze the panting sides of the vanquished cricket,
and her hind ones press like two levers on its face, causing the
articulation of the neck to gape open. The Sphex then curves her
abdomen vertically, so as to offer a convex surface impossible for the
mandibles of the cricket to seize, and one beholds, not without
emotion, the poisoned lancet plunge once into the victim’s neck, next
into the jointing of the two front segments of the thorax, and then
again towards the abdomen. In less time than it takes to tell, the
murder is committed, and the Sphex, after setting her disordered
toilette to rights, prepares to carry off her victim, its limbs still
quivering in the death-throes. Let us reflect a moment on the admirable
tactics of which I have given a faint sketch. The Cerceris attacks a
passive adversary, incapable of flight, whose sole chance of safety is
found in a solid cuirass whose weak points the murderers know. But here
what a difference! The prey is armed with redoubtable mandibles,
capable of disembowelling the aggressor if they can seize her, and a
pair of strong feet, actual clubs, furnished with a double row of sharp
spines, which can be used alternatively to enable the cricket to bound
far away from an enemy or to overturn one by brutal kicks. Accordingly,
note what precautions on the part of the Sphex before using her dart.
The victim, lying on its back, cannot escape by using its hind levers,
for want of anything to spring from, as of course it would were it
attacked in its normal position, as are the big Weevils by Cerceris
tuberculata. Its spiny legs, mastered by the forefeet of the Sphex,
cannot be used as offensive weapons, and its mandibles, held at a
distance by the hind-feet of the Hymenopteron, open threateningly but
can seize nothing. But it is not enough for the Sphex to render it
impossible for her victim to hurt her: she must hold it so firmly
garrotted that no movement can turn the sting from the points where the
drop of poison must be instilled, and probably it is in order to hinder
any motion of the abdomen that one of the end segments is grasped. If a
fertile imagination had had free play to invent a plan of attack it
could not have devised anything better, and it is questionable whether
the athletes of the classic palestra when grappling an adversary would
have assumed attitudes more scientifically calculated.
I have just said that the dart is plunged several times into the
victim’s body, once under the neck, then behind the prothorax, lastly
near the top of the abdomen. It is in this triple blow that the
infallibility, the infused science of instinct, appear in all their
magnificence. First let us recall the chief conclusions to which the
preceding study of the Cerceris have led us. The victims of Hymenoptera
whose larva live on prey are not corpses, in spite of entire
immobility. There is merely total or partial paralysis, and more or
less annihilation of animal life, but vegetative life—that of the
nutritive organs—lasts a long while yet, and preserves from
decomposition the prey which the larvæ are not to devour for a
considerable time. To produce this paralysis the predatory Hymenoptera
use just those methods which the advanced science of our day might
suggest to the experimental physiologist—namely, wounding, by means of
a poisoned dart, those nervous centres which animate the organs of
locomotion. We know too that the various centres or ganglia of the
nervous chain in articulate animals act to a certain degree
independently, so that injury to one only causes, at all events
immediately, paralysis of the corresponding segment, and this in
proportion as the ganglia are more widely separated and distant from
each other. If, on the contrary, they are soldered together, injury to
the common centre causes paralysis of all the segments where its
ramifications spread. This is the case with Buprestids and Weevils,
which the Cerceris paralyses by a single sting, directed at the common
mass of the nerve centres in the thorax. But open a cricket, and what
do we find to animate the three pairs of feet? We find what the Sphex
knew long before the anatomist, three nerve centres far apart. Thence
the fine logic of the three stabs. Proud science! humble thyself.
Crickets sacrificed by Sphex flavipennis are no more dead, in spite of
all appearances, than are Weevils struck by a Cerceris. The flexibility
of the integuments displays the slightest internal movement, and thus
makes useless the artificial means used by me to show some remains of
life in the Cleonus of Cerceris tuberculata. If one closely observes a
cricket stretched on its back a week or even a fortnight or more after
the murder, one sees the abdomen heave strongly at long intervals. Very
often one can notice a quiver of the palpi and marked movements in the
antennæ and the bands of the abdomen, which separate and then come
suddenly together. By putting such crickets into glass tubes I have
kept them perfectly fresh for six weeks. Consequently, the Sphex larvæ,
which live less than a fortnight before enclosing themselves in their
cocoons, are sure of fresh food as long as they care to feast.
The chase is over; the three or four crickets needed to store a cell
are heaped methodically on their backs, their heads at the far end,
their feet toward the entrance. An egg is laid on each. Then the burrow
has to be closed. The sand from the excavation lying heaped before the
cell door is promptly swept out backward into the passage. From time to
time fair-sized bits of gravel are chosen singly, the Sphex scratching
in the fragments with her forefeet, and carrying them in her jaws to
consolidate the pulverised mass. If none suitable are at hand, she goes
to look for them in the neighbourhood, apparently choosing with such
scrupulous care as a mason would show in selecting the best stones for
a building. Vegetable remains and tiny bits of dead leaf are also
employed. In a moment every outward sign of the subterranean dwelling
is gone, and if one has not been careful to mark its position, it is
impossible for the most attentive eye to find it again. This done, a
new burrow is made, provisioned and walled up as soon as the Sphex has
eggs to house. Having finished laying, she returns to a careless and
vagabond life until the first cold weather ends her well-filled
existence.
The Sphex’s task is accomplished. I will finish mine by an examination
of her weapon. The organ destined for the elaboration of her poison is
composed of two elegantly branched tubes communicating separately with
a common reservoir or pear-shaped vial, whence proceeds a slender
channel leading to the axis of the sting and conducting to its end the
little poisoned drop. The dart is extremely small, and not such as one
would expect from the size of the Sphex, especially from the effect
which her sting produces on crickets. The point is quite smooth,
without the barbs found in the sting of the hive bee. The reason of
this is evident. The bee uses her sting to avenge an injury only at the
cost of life, the barbs preventing its withdrawal from the wound, and
thus causing mortal ruptures in the viscera at the end of the abdomen.
What could the Sphex have done with a weapon which would have been
fatal the first time it was used? Even supposing that the barbed dart
could have been withdrawn, I doubt if any Hymenopteron using its
weapon, especially to wound game destined for its progeny, would be
provided with one. For here the dart is not a fine gentleman’s weapon,
unsheathed for vengeance, which is said to be the pleasure of the gods,
but a very costly one, since the vindictive bee sometimes pays for it
with life. It is a worker’s tool, on which depends the future of the
larvæ, thus it should be one easily used in a struggle with captured
prey, plunging into and coming out of the flesh without any delay—a
condition much better fulfilled by a smooth blade than by a barbed one.
I wished to ascertain at my own expense if the Sphex’s sting be very
painful—that sting which knocks over robust victims with frightful
rapidity. Well, I own with great admiration that it is slight and
cannot be at all compared as to pain with those of the bee and the
irascible wasp. It hurts so little that, instead of using pincers, I
never hesitated to catch with my fingers any Sphegidæ which I wanted
for my researches. I may say the same of the various Cerceris,
Philanthides, Palares, and even of the huge Scoliides, whose very look
is terrifying, and in general of all predatory Hymenoptera which I have
been able to observe. I except, however, those that hunt spiders, the
Pompili, and even their sting is far less severe than that of a bee.
One last remark. We know how furiously Hymenoptera armed with a sting
used only for defence rush at the bold man who disturbs their nest, and
punish his temerity. Those on the contrary whose sting is used only for
hunting are very pacific, as if they guessed how important for their
family is the little poison drop in their vase. That droplet is the
safeguard of their race—I might really say their means of subsistence;
therefore they use it economically, in the serious business of the
chase, with no parade of vengeful courage. I was not once punished by a
sting when I established myself amid colonies of our various predatory
Hymenoptera, whose nests I overturned, carrying off larvæ and
provisions. To induce the creature to use its weapon, one must lay hold
of it, and even then the skin is not always pierced, unless one puts
within reach a part more delicate than the fingers, such as the wrist.
VIII
LARVA AND NYMPH
The egg of Sphex flavipennis is white, elongated, and cylindrical,
slightly curved, and measuring three to four millimetres in length.
Instead of being laid fortuitously on any part of the victim, it is
invariably placed on one spot, across the cricket’s breast—a little on
one side, between the first and second pairs of feet. The eggs of the
white bordered, and of the Languedocian Sphex occupy a like
position—the first on the breast of a cricket, the second on that of an
ephippiger. This chosen spot must possess some highly important
peculiarity for the security of the young larva, as I have never known
it vary.
Hatching takes place at the end of two or three days. A most delicate
covering splits, and one sees a feeble maggot, transparent as crystal,
somewhat attenuated and even compressed in front, slightly swelled out
behind, and adorned on either side by a narrow white band formed by the
chief trachea. The feeble creature occupies the same position as the
egg; its head is, as it were, engrafted on the same spot where the
front end of the egg was fixed, and the remainder of its body rests on
the victim without adhering to it. Its transparency allows us readily
to perceive rapid fluctuations within its body, undulations following
one another with mathematical regularity, and which, beginning in the
middle of the body, are impelled, some forward and some backward. These
are due to the digestive canal, which imbibes long draughts of the
juices drawn from the sides of the victim.
Let us pause a moment before a spectacle so calculated to arrest
attention. The prey is laid on its back, motionless. In the cell of
Sphex flavipennis it is a cricket, or three or four, piled up; in that
of the Languedocian Sphex there is a single victim, but proportionately
large, a plump-bodied ephippiger. The grub is a lost grub if torn from
the spot whence it draws nourishment. Should it fall, all is over, for
weak as it is, and without means of locomotion, how would it again find
the spot where it should quench its thirst? The merest trifle would
enable the victim to get rid of the animalcule gnawing at its entrails,
yet the gigantic prey gives itself up without the least sign of
protestation. I am well aware that it is paralysed, and has lost the
use of its feet from the sting of its assassin, but at this early stage
it preserves more or less power of movement and sensation in parts
unaffected by the dart. The abdomen palpitates, the mandibles open and
shut, the abdominal styles and the antennæ oscillate. What would happen
if the grub fixed on one of the spots yet sensitive near the mandibles,
or even on the stomach, which, being tenderer and more succulent, would
naturally suggest itself as fittest for the first mouthfuls of the
feeble grub? Bitten on the quick parts, cicada, cricket, and ephippiger
would display at least some shuddering of the skin, which would detach
and throw off the minute larva, for which probably all would be over,
since it would risk falling into the formidable, pincer-like jaws.
But there is a part of the body where no such peril is to be feared—the
thorax wounded by the sting. There and there only can the experimenter
on a recent victim dig down the point of a needle—nay, pierce through
and through without evoking any sign of pain. And there the egg is
invariably laid—there the young larva always attacks its prey. Gnawed
where pain is no longer felt, the cricket does not stir. Later, when
the wound has reached a sensitive spot, it will move of course as much
as it can; but then it is too late—its torpor will be too deep, and
besides, its enemy will have gained strength. That is why the egg is
always laid on the same spot, near the wounds caused by the sting on
the thorax, not in the middle, where the skin might be too thick for
the new-born grub, but on one side—toward the junction of the feet,
where the skin is much thinner. What a judicious choice! what reasoning
on the part of the mother when, underground, in complete darkness, she
perceives and utilises the one suitable spot for her egg!
I have brought up Sphex larvæ by giving them successively crickets
taken from cells, and have thus been able, day by day, to follow the
rapid progress of my nurslings. The first cricket—that on which the egg
is laid—is attacked, as I have already said, toward the point where the
dart first struck—between the first and second pairs of legs. At the
end of a few days the young larva has hollowed a hole big enough for
half its body in the victim’s breast. One may then sometimes see the
cricket, bitten to the quick, vainly move its antennæ and abdominal
styles, open and close its empty jaws, and even move a foot, but the
larva is safe and searches its vitals with impunity. What an awful
nightmare for the paralysed cricket! This first ration is consumed in
six or seven days; nothing is left but the outer integument, whose
every portion remains in place. The larva, whose length is then twelve
millimetres, comes out of the body of the cricket through the hole it
had made in the thorax. During this operation it moults, and the skin
remains caught in the opening. It rests, and then begins on a second
ration. Being stronger it has nothing to fear from the feeble movements
of the cricket, whose daily increasing torpor has extinguished the last
shred of resistance, more than a week having passed since it was
wounded; so it is attacked with no precautions, and usually at the
stomach, where the juices are richest. Soon comes the turn of the third
cricket, then that of the fourth, which is consumed in ten hours. Of
these three victims there remains only the horny integument, whose
various portions are dismembered one by one and carefully emptied. If a
fifth ration be offered, the larva disdains or hardly touches it, not
from moderation, but from an imperious necessity.
It should be observed that up to now the larva has ejected no
excrement, and that its intestine, in which four crickets have been
engulfed, is distended to bursting. Thus, a new ration cannot tempt its
gluttony, and henceforward it only thinks about making a silken
dwelling. Its repast has lasted from ten to twelve days without a
pause. Its length now measures from twenty-five to thirty millimetres,
and its greatest width from five to six. Its usual shape, somewhat
enlarged behind and narrowed in front, agrees with that general in
larvæ of Hymenoptera. It has fourteen segments, including the head,
which is very small, with weak mandibles seemingly incapable of the
part just played by them. Of these fourteen segments the intermediary
ones are provided with stigmata. Its livery is yellowish-white, with
countless chalky white dots.
We saw that the larva began on the stomach of the second cricket, this
being the most juicy and fattest part. Like a child who first licks off
the jam on his bread, and then bites the slice with contemptuous tooth,
it goes straight to what is best, the abdominal intestines, leaving the
flesh, which must be extracted from its horny sheath, until it can be
digested deliberately. But when first hatched it is not thus dainty: it
must take the bread first and the jam later, and it has no choice but
to bite its first mouthful from the middle of the victim’s chest,
exactly where its mother placed the egg. It is rather tougher, but the
spot is a secure one, on account of the deep inertia into which three
stabs have thrown the thorax. Elsewhere, there would be, generally, if
not always, spasmodic convulsions which would detach the feeble thing
and expose it to terrible risks amid a heap of victims whose hind legs,
toothed like a saw, might occasionally kick, and whose jaws could still
grip. Thus it is motives of security, and not the habits of the grub,
which determine the mother where to place its egg.
A suspicion suggests itself to me as to this. The first cricket, the
ration on which the egg is laid, exposes the grub to more risks than do
the others. First, the larva is still a weakly creature; next, the
victim was only recently stung, and therefore in the likeliest state
for displaying some remains of life. This first cricket has to be as
thoroughly paralysed as possible, and therefore it is stabbed three
times. But the others, whose torpor deepens as time passes,—the others
which the larvæ only attack when grown strong,—have they to be treated
as carefully? Might not a single stab, or two, suffice to bring on a
gradual paralysis while the grub devours its first allowance? The
poison is too precious to be squandered; it is powder and shot for the
Sphex, only to be used economically. At all events, if at one time I
have been able to see a victim stabbed thrice, at another I have only
seen two wounds given. It is true that the quivering point of the
Sphex’s abdomen seemed seeking a favourable spot for a third wound; but
if really given, it escaped my observation. I incline to believe that
the victim destined to be eaten first always is stabbed three times,
but that economy causes the others only to be struck twice. The study
of the caterpillar-hunting Ammophila will later confirm this suspicion.
The last cricket being finished, the larva sets to work to spin a
cocoon. In less than forty-eight hours the work is completed, and
henceforward the skilful worker may yield within an impenetrable
shelter to the overpowering lethargy which is stealing over it—a state
of being which is neither sleeping nor waking, death nor life, whence
it will issue transfigured ten months later. Few cocoons are so complex
as is this one. Besides a coarse outer network, there are three
distinct layers, forming three cocoons, one within another. Let us
examine in detail these various courses of the silken edifice. First
comes an open network, coarse and cobwebby, on which the larva places
itself and hangs as in a hammock to work more easily at the cocoon
properly so called. This incomplete net, hastily spun to serve as a
scaffolding, is made with threads carelessly placed and holding grains
of sand, bits of earth, and remains from the larva’s banquet—cricket’s
thighs, still banded with red, feet, and skull. The next covering,
which is the first of the real cocoon, is a felted wrapper, light red,
very fine, very supple, and somewhat crumpled. A few threads cast here
and there connect it with the preceding scaffolding and the following
covering. It forms a cylindrical purse, with no opening and too large
for what it contains, thus causing the surface to wrinkle. Then comes
an elastic case, markedly smaller than the purse which contains it,
almost cylindrical, and rounded at the upper end, toward which is
turned the head of the larva, while at the lower it makes a blunt cone.
Its colour is light red, except towards the lower end, where the shade
is darker. It is fairly firm, though it yields to a moderate pressure,
except in the conical part, which resists and seems to contain a hard
substance. On opening this sheath it is seen to be formed of two layers
closely pressed together, but easily separable. The outer is a silken
felt precisely like that of the preceding purse, the inner one, the
third of the cocoon, is a kind of lacquer—a brilliant violet-brown
varnish, fragile, very soft to the touch, and of quite a different
nature to the rest of the cocoon. The microscope shows that instead of
being a felt of silky filaments like the other coverings, it is a
homogeneous covering of a peculiar varnish, whose origin is, as we
shall see, sufficiently strange. As for the resistance of the conical
end of the cocoon, one finds it caused by a load of friable matter,
dark violet, and shining with numerous black particles. This load is
the dry mass of excrement, ejected once for all by the larva, inside
its cocoon, and to it is due the darker colour of the conical end. The
average length of this complex dwelling is twenty-seven millimetres,
and its greatest width nine.
Let us return to the purple varnish which covers the interior of the
cocoon. At first, I thought it should be attributed to the silk glands,
which, after serving to spin the double wrapper of silk and the
scaffolding, must finally have secreted it. To convince myself, I
opened larvæ which had just completed their task of weaving, and had
not yet begun to lay on the lacquer. At that period I found no trace of
violet fluid in their glands. It is only seen in the digestive canal,
which is swelled with a purple pulp, and later in the stercorous load
sent down to the lower end of the cocoon. Elsewhere all is white, or
faintly tinged with yellow. I am far from suggesting that the larva
plasters its cocoon with excrement, yet I am convinced that this wash
is produced by the digestive organs, and I suspect—though I cannot
positively assert it, having several times missed the moment to
ascertain it—that the larva disgorges and applies with its mouth the
quintessence of the purple pulp in its stomach to make the wash of
lacquer. Only after this last piece of work would it eject the remains
of digestion in a single mass, and thus is explained the disgusting
necessity of storing the excrement within the larva’s habitation.
At all events the usefulness of this layer is clear; its absolute
impermeability protects the larva from the damp which would certainly
penetrate the poor shelter hollowed for it by its mother. Recollect
that it is buried but a few inches deep in sandy, open ground. To judge
how far cocoons thus varnished are capable of resisting damp, I have
plunged them in water for several days, yet never found any trace of
moisture within them. Let us compare the Sphex cocoon, with manifold
coverings to protect the larva in a burrow itself unprotected, with
that of Cerceris tuberculata, sheltered by a layer of sandstone, more
than half a yard down in the ground. This cocoon has the form of a very
long pear, with the small end cut off. It is composed of a single
silken wrap, so fine that the larva is seen through it. In my many
entomological researches I have always found the labour of larva and
mother supplement each other. In a deep well-sheltered dwelling the
cocoon is of light materials; for a surface abode, exposed to wind and
weather, it is strongly constructed.
Nine months pass, during which a work is done which is quite hidden. I
pass over this period, occupied by the unknown mystery of
transformation, and to come to the nymph, go from the end of September
to the first days of the following July. The larva has thrown aside its
faded vestment, and the chrysalis, a transitory organisation, or
rather, a perfect insect in swaddling bands, awaits motionless the
awakening which is still a month off. Feet, antennæ, the visible
portions of the mouth, and the undeveloped wings, look like clearest
crystal, and are regularly spread out under the thorax and abdomen. The
rest of the body is of an opaque white, slightly tinged with yellow;
the four intermediary segments of the abdomen show on either side a
narrow, blunt prolongation; the last segment has above a blade-like
termination, shaped like the section of a circle, furnished below with
two conical protuberances, side by side, thus making in all eleven
appendages starring the contour of the abdomen. Such is the delicate
creature which, to become a Sphex, must assume a particoloured livery
of black and red, and throw off the fine skin which swaddles it so
closely.
I have been curious to follow day by day the progress and coloration of
the chrysalid, and to experiment whether sunlight—that rich palette
whence Nature draws her colours—could influence their progress. With
this aim I have taken chrysalids out of their cocoon and kept them in
glass tubes, where some, in complete darkness, realised natural
conditions, while others, hung up against a white wall, were all day
long in a strong light. These diametrically opposed conditions did not
affect the colouring, or if there were some slight difference, it was
to the disadvantage of those exposed to light. Quite unlike to what
occurs with plants, light does not influence insect-colouring, nor even
quicken it. It must be so, since in the species most gifted with
splendid colour—Buprestids and Carabids for instance—the wonderful hues
that would seem stolen from a sunbeam are really elaborated in
darkness, deep in the ground, or in the decayed trunk of some aged
tree.
The first indication of colour is in the eyes, whose horny facets pass
successively from white to tawny, then to a slaty hue, and lastly to
black. The simple ones at the top of the forehead share in their turn
in this coloration before the rest of the body has at all lost its
whitish tint. It should be noted that this precocity in the most
delicate of organs, the eye, is general in animals. Later a smoky line
appears in the furrow separating the mesothorax from the metathorax,
and four-and-twenty hours later the whole back of the mesothorax is
black. At the same time the division of the prothorax grows shaded, a
black dot appears in the central and upper part of the metathorax, and
the mandibles are covered with a rusty tint. Gradually a deeper and
deeper shade spreads over the last segments of the thorax, and finally
reaches the head and sides. One day suffices to turn the smoky tint of
the head and the furthest segments of the thorax into deep black. Then
the abdomen shares in the rapidly increasing coloration. The edge of
the anterior segments is tinted with daffodil, while the posterior
segments acquire a band of ashy black. Then the antennæ and feet take a
darker and darker tint, till they become black, all the base of the
abdomen turns orange-red, and the tip black. The livery would then be
complete, but that the tarsi and mouthpieces are transparent red and
the stumps of wings ashy black. Four-and-twenty hours later the
chrysalis will burst its bonds. It only takes six or seven days to
acquire its permanent tints; the eyes have done so a fortnight before
the rest of the body. From this sketch the law of chromatic evolution
is easily apprehended. We see that, omitting the eyes and ocelli, whose
early perfection recalls what takes place in the higher animals, the
starting-point of coloration is a central one, the mesothorax, whence
it invades progressively by centrifugal progression—first the rest of
the thorax, then the head and abdomen, and finally the various
appendages, antennæ, and feet. The tarsi and mouthpieces take colour
later still, and the wings only on coming out of their cases.
Now we have the Sphex in full costume, but she still has to free
herself from the chrysalis case. This is a very fine wrap, enfolding
every smallest detail of structure, and hardly veiling the shape and
colours of the perfect insect. As prelude to the last act of
metamorphosis, the Sphex, rousing suddenly from her torpor, begins to
shake herself violently, as if to call life into her long-benumbed
limbs. The abdomen is alternately lengthened and contracted, the feet
are suddenly spread, then bent, then spread again, and their various
joints are stiffened with effort. The creature, curved backwards on its
head and the point of the abdomen, with ventral surface upward,
distends by vigorous shakes the jointing of its neck and of the petiole
attaching the abdomen to the thorax. At last its efforts are crowned
with success, and after half an hour of these rough gymnastics the
sheath, pulled in every direction, ruptures at the neck, at the
insertion of the feet and petiole, and, in short, wherever the body has
been movable enough to allow of sufficiently violent displacement.
All these tears leave several irregular strips, the chief of which
envelops the abdomen and comes up the back of the thorax. To it belong
the wing sheaths. A second strip covers the head. Lastly, each foot has
its own sheath, more or less dilapidated toward the base. The biggest,
which forms the chief part of the whole covering, is got off by
alternate dilatations and contractions of the abdomen, which gradually
push it back into a little ball connected for some time with the animal
by tracheal filaments. Then the Sphex again becomes motionless, and the
operation is over, though head, antennæ, and feet are still more or
less covered. It is clear that the feet cannot be freed in one piece on
account of the roughnesses and thorns with which they are armed. These
rags of skin dry up and are got rid of later by rubbing the feet
together, and by brushing, smoothing, and combing the whole body with
the tarsi when the Sphex has acquired full vigour.
The way in which the wings come out of their sheaths is the most
remarkable feature in this casting of the skin. In their undeveloped
state they are folded lengthways and much contracted. A little while
before they acquire their normal appearance one can easily draw them
out of their sheaths; but then they do not expand, remaining always
crumpled, while, when the large piece of which the sheaths are a part
is pushed back by the movements of the abdomen, they may be seen
issuing gradually from the sheaths, and immediately they gain freedom,
assuming dimensions out of all proportion to the narrow prison from
which they emerge. They are then the seat of an abundant influx of
vital juices which swell and spread them out, and the turgescence thus
induced must be the chief cause of their coming out of their sheaths.
When freshly expanded the wings are heavy, full of moisture, and of a
very light straw colour. If the influx should take place in an
irregular manner, the point of the wing is seen to be weighed down by a
yellow droplet contained between its under and upper surface.
After denuding itself of the abdominal sheath, which draws away with it
the wing-cases, the Sphex again is motionless for about three days.
During this interval the wings assume their normal colouring, the tarsi
take colour also, and the mouth-parts, at first spread out, assume
their normal position. After twenty-four days as a nymph the insect
attains its perfect state, tears its imprisoning cocoon, opens a way
through the sand, and appears one fine morning in the light as yet
unknown to it. Bathed in sunshine, it brushes wings and antennæ, passes
its feet again and again over its abdomen, washes its eyes with its
forefeet moistened with saliva, like a cat, and, its toilette made,
flies joyfully away. Two months of life are before it.
Beauteous Sphegidæ, hatched under my eyes and brought up by my hand,
ration by ration, on a bed of sand, at the bottom of an old feather
box,—you whose transformations I have followed step by step, waking up
with a start at night for fear of missing the moment when the nymph
breaks through her swaddling bands and the wings issue from their
cases. You have taught me so many things, learning nothing yourselves,
knowing without teachers all that you need to know. Oh, my beautiful
Sphegidæ! fly away without fear of my tubes, my phials, and all my
boxes and cages, and all my prisons for you; fly through the warm
sunshine, beloved by the cicadas! Go, and beware of the Praying Mantis,
who meditates your destruction on the purple thistles; beware of the
lizard watching for you on the sunny slopes. Depart in peace, hollow
out your burrows, stab your crickets scientifically, and continue your
race, so as to afford to others what you have afforded to me—some of
the few moments of happiness in my life.
IX
ADVANCED THEORIES
There are many species of Sphex, but for the most part strangers to our
country. As far as I know, the French fauna contains but three—all
lovers of the hot sun in the olive region—namely, Sphex flavipennis, S.
albisecta, and S. occitanica. It is not without keen interest that an
observer notices in all three of these predatory insects a choice of
provender in conformity with the strict laws of entomological
classification. To nourish their larvæ each confines itself to
Orthoptera. The first hunts grasshoppers, the second crickets, and the
third ephippigers.
These prey are so different outwardly that to associate them and seize
their analogies, either the practised eye of the entomologist, or the
not less expert one of the Sphex is needed. Compare the grasshopper
with the cricket: the former has a round, stumpy head; it is short and
thickset, quite black, with red stripes on its hind thighs; the latter
is grayish and slim, with a small conical head, springing suddenly by
unbending its long hind legs, and carrying on this spring with fanlike
wings. Now compare both with the ephippiger, who carries his musical
instrument on his back, two harshly toned cymbals, shaped like hollow
scales, and who drags his obese body heavily along, ringed with pale
green and butter colour, and ending in a long dagger. Place these three
species side by side, and own with me that to be able to choose
creatures so unlike, and yet keep to the same entomological order, the
Sphex must have such an eye as not only a fairly observant person, but
a practised entomologist would not be ashamed of.
In the presence of these singular predilections, which seem to have
limits laid down by some master of classification,—a Latreille for
instance—it becomes interesting to inquire if foreign Sphegidæ hunt
game of the same order. Unfortunately information as to this is scanty
or absolutely nil as regards most species. This regrettable lack is
chiefly caused by the superficial method generally adopted. An insect
is caught, transfixed with a long pin, fastened in a box with a cork
bottom; a ticket with a Latin name is put under its feet, and all is
said. This way of looking at entomological history does not satisfy me.
It is useless to tell me that such a species has so many joints in its
antennæ, so many nerves in its wings, so many hairs on a part of the
abdomen or thorax; I do not really know the creature until I have
learned its manner of life, its instincts and habits. And observe what
a luminous superiority has a description of the latter kind, given in
two or three words over long descriptions, sometimes so hard to
understand. Let us suppose that you want to introduce Sphex occitanica
to me; you describe the number and arrangement of the wing nerves, and
you speak of cubital and recurrent nerves; next follows the written
description of the insect. Here it is black, there rusty red, smoky
brown at the wing tips, at such a spot it is black velvet, at another
silvery down, and at a third smooth. It is all very precise, very
minute—one must grant that much justice to the clear-sighted patience
of him who describes; but it is very long, and besides, not always easy
to follow, to such a degree that one may be excused for being sometimes
a little bewildered, even when not altogether a novice. But add to the
tedious description just this—hunts ephippigers, and with these two
words light shines at once; there can be no mistake about my Sphex,
none other selecting that prey. And to illuminate the subject thus,
what was needed? Real observation, and not to let entomology consist in
rows of impaled insects. But let us pass on and consider such little as
is known as to the manner in which foreign Sphegidæ hunt. I open
Lepeletier de St. Fargeau’s History of Hymenoptera, and find that on
the other side of the Mediterranean, in our Algerian provinces, S.
flavipennis and S. albisecta have the same tastes that characterise
them here. In the land of palms they catch Orthoptera just as they do
in the land of olives. Although separated by the width of the sea,
these sporting fellow citizens of the Kabyle and the Berber hunt the
same game as their relatives in Provence. I see mentioned a fourth
species, S. afra, as hunting crickets round Oran. Moreover, I have a
recollection of having read—I know not where—of a fifth species, which
makes war on crickets upon the steppes in the neighbourhood of the
Caspian Sea. Thus in the lands bordering the Mediterranean we have five
different species whose larvæ all live on Orthoptera.
Now let us cross the equator, and descend in the other hemisphere to
the Mauritius and Réunion Islands, and we shall find, not a Sphex but a
Hymenopteron, nearly allied, of the same tribe, Chlorion or Ampulex,
chasing the horrid kakerlacs, the curse of merchandise in ships and
colonial ports. These kakerlacs are none other than cockroaches, one
species of which haunts our houses. Who does not know this stinking
insect, which, thanks to its flat shape, like that of an enormous bug,
insinuates itself into gaps in furniture and partitions, and swarms
everywhere that there is food to devour. Such is the cockroach of our
houses—a disgusting likeness of the not less disgusting prey beloved by
the Chlorion. Why does a near relation of our Sphex select the kakerlac
as prey. The reason is simple: With its buglike form the kakerlac is an
Orthopteron by the same rights as the grasshopper, ephippiger, and
cricket. From these six examples, the only ones known to me, and from
such widely distant localities, may we not conclude that all Sphegidæ
hunt Orthoptera? Without adopting so sweeping a conclusion, one at
least sees what the usual food of their larvæ must be.
There is a reason for this surprising choice. What is it? What motives
fix a diet which in the strict limits of one and the same entomological
order is now composed of ill-smelling kakerlacs, now of dry, but
well-flavoured crickets, and in yet another of plump grasshoppers, or
corpulent ephippigers? I confess that to me it is incomprehensible, and
I leave the problem to others. Observe, however, that the Orthoptera
rank among insects as the ruminants do among mammalia. Endowed with a
mighty paunch and a placid character, they feed on herbage, and easily
get corpulent. They are numerous and met with everywhere, slow of gait,
and thus easy to catch, and, moreover, of a size just right for prey.
Who can say if the Sphegidæ—vigorous hunters which require a large
prey—do not find in these ruminants among insects what we find in our
domestic ruminants—the sheep and ox, peaceful victims rich in flesh?
This is, however, a mere supposition.
I have more than a supposition in another case, equally important. Do
the consumers of Orthoptera ever vary their diet? Should their
favourite game fail, can they do with another? Does S. occitanica think
that except a fat ephippiger, there is nothing in the wide world worth
eating. Does S. albisecta admit nothing but crickets to her table, and
S. flavipennis only grasshoppers? Or according to time, place, and
circumstance, does each replace the favourite food by some equivalent?
It would be of the highest importance to bring forward such facts if
they exist, as they would tell us whether the suggestions of instinct
are absolute and immutable, or if they vary, and within what limits. It
is true that in the cell of a Cerceris are buried most varied species
of Buprestids or of the Weevil group, which shows that she has a great
latitude of choice; but such an extension of hunting ground cannot be
supposed for the Sphex, which I have found so faithful to one exclusive
prey, invariable for each species, and which, moreover, finds among the
Orthoptera kinds of very different shapes. I have, however, had the
good fortune to meet with one case—only one—of complete change in the
larva’s food, and I mention it the more willingly in the archives of
the Sphegidæ because such facts, scrupulously observed, will one day be
corner-stones for him who may desire to build the psychology of
instinct on solid foundations.
This is my fact. The scene is on a jetty by the Rhône. On one side is
the great river, with its thunder of waters, on the other, a dense
thicket of osiers, willows, and reeds, and between the two a narrow
path with a bed of fine sand. A yellow-winged Sphex appears, hopping
and dragging its prey along. What do I see! It is no grasshopper, but a
common Acridian! And yet the Hymenopteron really is the Sphex so well
known to me (S. flavipennis), the energetic huntress of grasshoppers! I
can hardly believe my eyes. The burrow is not far off; she enters and
stores her booty. I seat myself, determined to await a new
expedition—wait hours if need be to see if so extraordinary a capture
is repeated. Seated there I occupy the whole width of the path. Two
simple conscripts come up, new-clipped, with that incomparable,
automaton-look conferred by the first days of barrack life. They are
chattering together—no doubt talking of their homes and the girls they
left behind them; each is peeling a willow switch with a knife. A fear
seizes me; ah! it is not easy to try an experiment on the public way,
where, when some fact watched for during long years does present
itself, a passer-by may disturb or annihilate chances which may never
occur again! I rise anxiously to make way for the conscripts; I
withdraw into the osier bed, and leave the narrow way free. To do more
was not prudent; to say, “My good fellows, do not go that way,” would
have made bad worse. They would have supposed some snare hidden in the
sand, and questions would have arisen to which no reply that would
satisfy them could have been given. My request, moreover, would have
turned these idlers into lookers-on, very embarrassing company in such
studies, so I resolved to say nothing, and trust to my luck. Alas!
alas! my star betrayed me. The heavy regulation boot was planted
exactly on the Sphex’s roof. A shudder ran through me as though I had
myself received the impress of the iron heel.
The conscripts gone I proceeded to the salvage of the contents of the
ruined burrow. There was the Sphex mutilated by the pressure, and there
were not only the cricket which I saw carried down, but two
others—three crickets in all instead of the usual grasshoppers. What
was the reason of this strange variation? Were there no grasshoppers
near the burrow, and did the distressed Hymenopteron do the best she
could with Acridians—contenting herself as it were with blackbirds for
want of thrushes, as the proverb says? I hesitate to believe it, for
there was nothing in the neighbourhood to denote absence of her
favourite game. Some happier means may unriddle this new problem. In
any case S. flavipennis, either from imperious necessity, or from
motives unknown to me, sometimes replaces her favourite prey, the
grasshopper, by another, the Acridian, altogether unlike outwardly to
the former, but still an Orthopteron.
The observer on whose authority Lepeletier de St. Fargeau speaks of
this Sphex’s habits witnessed in Africa, near Oran, a similar storing
of Acridians. S. flavipennis was surprised by him dragging along an
Acridian. Was it an accidental case, like the one seen by me on the
banks of the Rhône? Was it the exception, or was it the rule? Were
grasshoppers wanting around Oran, and did the Hymenopteron replace them
by Acridians? Circumstances compel me to ask the question without
finding a reply.
Here should be interpolated a certain passage from Lacordaire’s
Introduction to Entomology, [6] against which I long to raise my voice
in protest. Here it is: “Darwin, who has written a book on purpose to
prove the identity of the intellectual principle which produces action
in man and animals, walking one day in his garden noticed on the ground
in a shady walk a Sphex which had just caught a fly nearly as big as
itself. He saw it cut off with its mandibles the victim’s head and
abdomen, keeping only the thorax, to which the wings remained attached.
It then flew away, but a breath of wind striking the fly’s wings
twirled the Sphex round, and hindered its progress. Thereupon it lit
again on the walk, cut off first one wing and then the other from the
fly, and having thus removed the cause of its difficulties, flew off
with the remainder of its prey. This fact indicates manifest signs of
reasoning. Instinct might have induced the Sphex to cut off the wings
of its victim before transporting it to the nest, as do some species of
the same genus, but here were consecutive ideas and results of those
ideas quite inexplicable, unless one admits the intervention of
reason.”
This little story, which so lightly bestows reason on an insect, is
wanting not only in truth but in mere probability—not in the act
itself, which I do not question at all, but in its motives. Darwin saw
what he relates, but he was mistaken as to the hero of the drama; as to
the drama itself, and as to its meaning—profoundly mistaken, and I can
prove it.
First and foremost the old English savant ought to have known enough
about the creatures which he so freely ennobles to call things by their
right name. Let us therefore take the word Sphex in its strictly
scientific sense. Then by what strange aberration does this English
Sphex, if English ones there are, choose a fly as its prey when its
fellows hunt such different game—namely, Orthoptera? And even if we
grant, what I consider inadmissible, a Sphex catching flies, other
difficulties crowd in. It is now proved on evidence that the burrowing
Hymenoptera do not carry dead bodies to their larvæ, but merely prey
benumbed and paralysed. What, then, is the meaning of this prey whose
head, abdomen, and wings are cut off? The torso carried away is but a
portion of a corpse that would infect the cell and be useless to the
larva, not yet to be hatched for several days. It is perfectly clear
that Darwin’s insect was not a Sphex, strictly speaking. What, then,
did he see? The word fly, by which the captured prey is designated, is
a very vague term which might be applied to the greater part of the
immense order of Diptera, and therefore leaves us uncertain among
thousands of species. Probably the name of Sphex is used equally
vaguely. When Darwin’s book appeared, not only the real Sphegidæ were
so called, but also the Crabronides. Now among these last some provide
their larvæ with Diptera, the prey required for the unknown
Hymenopteron of the English naturalist. Was then Darwin’s Sphex a
Crabro? No, for these hunters of Diptera, like the hunters of any other
game, require prey which will keep fresh and motionless, but half alive
for the fortnight or three weeks needed before the eggs hatch, and for
the complete development of the larvæ. These little ogres require meat
not decayed, nor even high, but fresh. I know no exception to this
rule, and therefore the name Sphex cannot have been used in its old
meaning.
Instead of dealing with a precise fact, really worthy of science, we
have an enigma to find out. Let us continue to examine it. Several of
the Crabronides are so like wasps in figure and form and shape and
their yellow and black livery, that they might deceive any eye
unpractised in the delicate distinctions of entomology. In the eyes of
every one who has not made a special study of the subject, a Crabro is
a wasp. Is it not possible that the English observer, regarding things
from a lofty height, and considering unworthy of close examination the
petty fact, which, however, was to serve to corroborate his
transcendent views and grant reason to animals, may have in his turn
committed an error, conversely and very excusably, by taking a wasp for
one of the Crabronides? I could almost declare it is so, and for the
following reasons. Wasps, if not always at any rate frequently, bring
up their family on animal food, but instead of provisioning each cell
they distribute nourishment singly to the larvæ, and several times in
the day; feeding them from their mouths with soft pap, as the father
and mother do young birds. This pap consists of mashed insects, ground
down in the jaws of the nursing wasp; the insects preferred for it are
Diptera, especially the common fly; if fresh meat offers itself it is
largely used. Who has not seen wasps penetrate into our kitchens, or
dart on the joints in a butcher’s shop, cut off some scrap of flesh
which suits them, and carry away a tiny spoil for the use of their
larvæ? When half-closed shutters allow a ray of light to fall on the
floor of a room where the house-fly is taking a comfortable nap, or
brushing its wings, who has not seen a wasp suddenly enter, pounce upon
it, crush it in its jaws, and flee with the booty? This again is a
dainty meal for the carnivorous nurslings. Sometimes the prey is at
once dismembered, sometimes on the way, sometimes at the nest. The
wings, in which there is no nourishment, are cut off and rejected; the
feet, poor in juices, are also sometimes disdained. There remains a
mutilated corpse, head, thorax, abdomen, or part thereof, which the
wasp chews repeatedly to reduce into a pap for the larvæ to feast on. I
have tried to bring up larvæ myself on fly-paste. The experiment was
tried on a nest of Polistes gallica, the wasp which fixes her little
rose-shaped nest of gray paper cells on the bough of some shrub. My
kitchen apparatus was a piece of marble slab, on which I crushed up the
fly-paste after cleaning my game—in other words, having taken away the
parts which were too tough—wings and feet; and the feeding-spoon was a
slender straw, at the end of which, going from cell to cell, I handed
the food to larvæ, which opened their mouths just like young birds in a
nest. I did just the same and succeeded just as well in the days when I
used to bring up broods of sparrows—that joy of childhood! All went on
as well as heart could wish as long as my patience held out against the
trials of a bringing up so absorbing and full of small cares.
The obscurity of the enigma is replaced by the full light of truth,
thanks to the following observation, made with all the leisure that a
strict precision demands. In the first days of October two great clumps
of blossoming asters at the door of my study became the rendezvous of a
quantity of insects, among which the hive bee and Eristalis tenax were
the most numerous. A gentle murmur arose from them, like that of which
Virgil wrote, “Sæpe levi somnum suadebit inire susurro.” But if the
poet finds in it only an invitation to slumber, the naturalist finds a
subject for study; these small folk luxuriating on the last flowers of
the year may perhaps afford him some new information. So I am on the
watch before the two clumps with their countless lilac corollas.
The air is perfectly still; the sun burns, the air is heavy—all signs
of a coming storm; but these are conditions eminently favourable to the
labours of the Hymenoptera, which seem to foresee to-morrow’s rain, and
redouble their activity in turning the present hour to profit. The bees
work ardently; the Eristalis fly clumsily from flower to flower. Now
and then, into the midst of the peaceable throng who are swilling
nectar, bursts a wasp, insect of rapine, attracted there by prey, not
honey.
Equally ardent in carnage, but unequal in strength, two species divide
the chase; the common wasp, Vespa vulgaris, which catches Eristalis,
and the hornet, V. crabro, which hunts hive bees. Both carry on the
chase in the same way. They fly fast backwards and forwards over the
flowers, and suddenly throw themselves on the prey which is on its
guard and flies off, while their impulse carries them headfirst against
the deserted flower. Then the chase is continued in the air, just as a
sparrowhawk hunts a lark. But bee and Eristalis foil the wasp by their
sudden turns, and it goes back to fly above the blossoms. By and by
some insect less swift to escape gets captured. The common wasp
instantly drops on the turf with its Eristalis, and I drop down too at
the same moment, putting aside with both hands the dead leaves and bits
of grass which might hinder my seeing clearly, and this is the drama
which I behold, if proper precautions be taken not to scare the wasp.
First there is a wild struggle among the blades of grass between the
wasp and an Eristalis bigger than itself. The Dipteron is unarmed but
strong, and a shrill hum tells of desperate resistance. The wasp
carries a poignard, but does not know how to use it methodically, and
is ignorant of the vulnerable points so well known to the hunters which
need flesh that must keep good for a considerable time. What its
nurslings want is a paste made of flies newly crushed, so that it
matters little how the game is killed. The sting is used
blindly—anywhere, pointed at the head, sides, thorax, or under part of
the victim, as chance directs while the two wrestle. The Hymenopteron,
paralysing its victim, acts like the surgeon, who directs his scalpel
with a skilled hand; the wasp when slaying acts like a common assassin
stabbing blindly in a struggle. Thus the resistance of the Eristalis is
long, and its death rather the result of being cut up by a pair of
scissors than of stabs with a dagger. These scissors are the wasp’s
mandibles, cutting, disembowelling, and dividing. When the game has
been garroted and is motionless between the feet of its captor, a bite
of the mandibles severs the head from the body; then the wings are
shorn off at the junction with the shoulder; the feet follow, cut off
one by one; then the abdomen is rejected, but emptied of its interior,
which the wasp appears to preserve with her favourite part, the thorax,
which is richer in muscle than the rest of the Eristalis. Without
further delay she flies off, carrying it between her feet. Having
reached the nest she will mash it up and distribute it to the larvæ.
The hornet having seized a bee acts almost in the same way, but it is a
giant of a robber, and the fight cannot last long, despite the sting of
the victim. Upon the very flower where the capture was made, or oftener
on some twig of a neighbouring shrub, the hornet prepares its dish.
First of all the bag of the bee is torn open, and the honey lapped up.
The prize is thus twofold—that of a drop of honey, and the bee itself
for the larvæ to feast on. Sometimes the wings are detached, as well
as the abdomen, but generally the hornet is contented with making a
shapeless mass of the bee which is carried off whole. It is at the nest
that the parts valueless for food are rejected, especially the wings.
Or the paste may be prepared on the spot, the bee being crushed at once
between the hornet’s mandibles, after wings, feet, and sometimes the
abdomen are cut off.
Here, then, in all its details is the fact observed by Darwin. A wasp,
Vespa vulgaris, seizes Eristalis tenax; with her mandibles she cuts off
head, wings, and abdomen of the victim, keeping only the thorax, with
which she flies away. But we need no breath of air to explain why they
were cut off; the scene takes place in perfect shelter, in the grass.
The captor rejects such parts as are useless for the larvæ, and that is
all.
In short, a wasp is certainly the heroine of Darwin’s story. What,
then, becomes of that reasoning which made the creature, in order
better to contend with the wind, deprive its prey of abdomen, head, and
wings, leaving only a thorax? It becomes a very simple fact, whence
flow none of the great consequences that were drawn from it,—the very
trivial fact that a wasp began at once to cut up her prey, and only
considered the trunk worthy of her larvæ. Far from discovering the
least indication of reasoning, I see only an act of instinct so
elementary that it is really not worth consideration.
To abase man and exalt animals in order to establish a point of
contact, then a point of fusion,—such has been the usual system of the
advanced theories now in fashion. Ah! how often do we not find in these
sublime theories that are a sickly craze of our day, proofs
peremptorily asserted, which under the light of experiment would appear
as absurd as the Sphex of the learned Erasmus Darwin!
X
THE SPHEX OF LANGUEDOC
When the chemist has ripely considered his plan of research, he mixes
his reactives at whatever moment suits him best, and sets his retorts
on the fire. He is master of time, place, and circumstance, chooses his
own hour, isolates himself in his laboratory, where he will be
undisturbed, and brings about such or such conditions as reflexion may
suggest. He is searching out the secrets of brute nature, whose
chemical activities science can arouse at will.
The secrets of living nature—not those of anatomy, but those of life in
action, especially of instinct—offer conditions far more difficult and
delicate to the observer. Far from being able to take his own time, he
is the slave of season, day, or hour, even of the moment. If an
opportunity offer, it must be seized at once—it may be very long ere it
comes again. And as it usually comes just when one is thinking least
about it, nothing is ready whereby to turn it to account. One must
improvise there and then one’s little means of experiment, combine
one’s plan, devise one’s wiles, imagine one’s tactics, and feel only
too fortunate if inspiration come quickly enough to allow one to profit
by the chance offered. Moreover, such chances come only to one who
looks out for them, watches for days and days,—here on sandy slopes
exposed to the burning sun, there in the cauldron of some path enclosed
by high banks, or on some shelf of sandstone, the solidity of which is
not always such as to inspire confidence. If it be granted you to set
up your observatory under the scanty shade of an olive that you may
think will shelter you from a pitiless sun, then bless the fate which
is treating you like a sybarite; your lot is in Eden. Above all—keep a
sharp lookout. The spot is promising, and who knows? Any moment the
chance may come.
It has come! tardily, it is true, but it has come. Ah! could one but
observe now, in the peace of one’s study, isolated, absorbed, thinking
only of what one is studying, far from the profane passer-by who will
stop, seeing you so preoccupied where he sees nothing, will overwhelm
you with questions and take you for a diviner of springs with the magic
hazel wand, or worse, as a doubtful character, seeking by incantations
old pots full of money hidden underground. Even if you seem to him to
have the look of a Christian, he will come near, look at what you are
looking at, and smile in a fashion which leaves no possible doubt as to
his humble opinion of people who spend their time in watching flies.
You would only be too happy if this annoying visitor would depart,
laughing in his sleeve, but without disturbing everything and repeating
the disaster caused by the soles of my two conscripts.
Or if it is not the passer-by who is perplexed by your unaccountable
proceedings, it will be the garde-champêtre, that inexorable
representative of the law amid the fallow fields. Long has he had his
eye upon you. He has so often seen you wandering like a troubled ghost
for no reason that he can perceive; has so often caught you seeking
something in the ground, or knocking down some bit of wall in some
hollow way with infinite precaution that he begins to look on you as a
suspicious character, a vagabond, a gipsy, a tramp, or, at all events,
a maniac. If you have a botanical tin, to him it is the ferret-cage of
the poacher, and it will be impossible to convince him that you are not
destroying all the rabbits in the neighbouring warrens, regardless of
the laws of the chase and the rights of the owner. Beware! However
thirsty you may be, lay no finger on a cluster in the vineyard hard by;
the man of the municipal livery would be there, delighted to bear
witness and get at last an explanation of your exasperatingly
perplexing conduct.
I must do myself the justice to say that I have never committed such a
misdeed, and yet one day when I was lying on the sand, absorbed in the
domestic affairs of a Bembex, I heard beside me, “In the name of the
law, I summon you to follow me!” It was the garde-champêtre of Les
Angles, who having vainly watched for an opportunity of catching me in
some offence, and being daily more desirous of an answer to the riddle
which tormented him, had finally decided on a summons. An explanation
became necessary. The poor man did not appear in the least convinced.
“Bah! bah!” said he, “you’ll never get me to believe that you come and
roast yourself in the sun just to watch flies. I keep my eye on you,
you know, and the first time.... Well, that’s enough.” He departed. I
have always believed that my red ribbon had a good deal to do with this
departure, and I ascribe to that ribbon other similar services during
my botanical or entomological rambles. It seemed to me—was it an
illusion?—it did seem to me that during my botanical expeditions on
Mont Ventoux, the guide was more manageable than usual and the donkey
less obstinate.
The little dark red ribbon has not always protected me from the
tribulations the entomologist must expect when carrying on experiments
upon the highway. Since dawn I had been lying in ambush at the bottom
of a ravine; Sphex occitanica was the object of my early visit. A party
of three women vintagers passed on their way to work. A glance was cast
on the seated figure apparently lost in thought. “Good day” was
politely offered and politely answered. At sunset the women returned
with full baskets. The man was still there, seated on the same stone,
his eyes fixed on the same spot. My motionless figure, my persistent
stay in that lonely place, must have struck them greatly. As they
passed I saw one tap her forehead, and heard her whisper, “A poor
innocent, pe’caïre! a poor innocent!” and all three made the sign of
the cross.
An innocent, an idiot, a poor inoffensive creature who is deficient;
and all three crossed themselves—an idiot being one to them marked by
God’s seal. “How?” said I. “What cruel mockery of fate! You who are
labouring to discover what is instinct and what reason in the animal;
you yourself are a half-wit in the eyes of these women! What
humiliation! However, pe’caïre, that term of supreme commiseration in
Provençal, uttered from the bottom of the heart, made me quickly forget
the Innocent.”
It is to that same ravine that I invite my reader, if he is not
repelled by the small annoyances of which I have given him a foretaste.
S. occitanica haunts these parts, not in numbers giving one another
rendezvous when nidification is going on, but solitary individuals far
apart, wherever their vagabond peregrinations have led them. Just as
their relative S. flavipennis seeks the society of relations and the
animation of a work-yard and company, so, on the other hand, does the
Languedocian Sphex prefer calm, isolation, and solitude. Graver in
behaviour, more formal in manner, more elegant of figure, and in more
sombre attire, she always lives apart, careless of what others are
doing, disdaining companionship, a very misanthrope among Sphegidæ. S.
flavipennis is sociable; S. occitanica is unsociable—a profound
difference, alone sufficient to characterise them.
This suggests how greatly the difficulty of observing the latter is
increased. No long meditated experiment is possible, nor can one
attempt to repeat it a second time if the first has failed. If you make
preparations beforehand,—for instance, if you put in reserve a piece of
game to substitute for that of the Sphex,—it is to be feared, indeed it
is almost certain, that she will not appear, or if she comes, your
preparations turn out useless. Everything must be improvised at
once—conditions which I have not always been able to realise as I could
have wished.
Let us take courage; the position is good. Many a time I have here
surprised the Sphex reposing on a vine-leaf, exposed to the full rays
of the sun. The insect, lying flat and spread out, is voluptuously
enjoying the delights of warmth and light. From time to time a kind of
frenzy of pleasure bursts forth in her; she thrills with well-being,
drums rapidly on her resting-place with the points of her feet, and
produces a sound somewhat like the roll of a drum, or heavy rain
falling on foliage perpendicularly. You may hear this joyous drumming
several paces off. Then again comes perfect stillness, followed by a
fresh nervous commotion, and that waving of tarsi which is a sign of
supreme happiness. I have known some of these ardent sun-worshippers
suddenly leave a half-finished burrow to settle on a neighbouring vine
and take a bath of sun and light, returning reluctantly to give a
careless sweep to the hole, and finally abandon the workshop, unable
longer to resist the temptation of luxuriating on a vine leaf. Perhaps
this voluptuous resting-place is also an observatory whence to inspect
the neighbourhood, and espy and choose prey. This Sphex catches only
the ephippiger of the vine, scattered here and there on the leaves or
on any convenient bush. The game is succulent—all the more that only
females full of eggs are selected.
Let us pass over numerous expeditions, fruitless researches, and the
tedium of long waiting, and present the Sphex to the reader just as she
shows herself to the observer. Here she is, at the bottom of a hollow
way with high sandy banks. She comes on foot, but aids herself with her
wings in dragging along her heavy captive. The ephippiger’s antennæ,
like long fine threads, are the harness ropes. With her mandibles and
holding her head high, she grasps one of them, passing it between her
feet, and the prey is dragged on its back. If some unevenness of ground
should oppose itself to this style of haulage, she stops, clasps the
ample provender, and transports it by very short flights, going on foot
between whiles whenever this is possible. One never sees her undertake
sustained flights for long distances carrying prey, as do those strong
cruisers, the Bembex and Cerceris, which will carry perhaps for a good
half mile through the air, the former their Diptera, the latter their
weevils—very light prey compared with the huge ephippiger. The
overwhelming size of its captive forces S. occitanica to convey it
along the ground—a means of transit both slow and difficult. The same
reason—namely, the great size and weight of the prey—entirely upsets
the usual order followed by the Hymenoptera, in their labours,—an order
well known, and consisting in first hollowing a burrow and then
victualling it. The prey not being disproportioned to the size of the
spoiler, facility of transport by flight allows the Hymenopteron a
choice as to the position of her domicile. What matter if she has to
hunt at considerable distances? Having made a capture, she returns home
with rapid flight; it is indifferent to her whether she is near or far.
Therefore she prefers the spot where she was born, and where her
predecessors have lived; there she inherits deep galleries, the
accumulated labour of former generations; with a little repair they can
be used as avenues to new chambers, better defended than would be a
single excavation a little below the surface made annually. Such is the
case with Cerceris tuberculata and Philanthus apivorus, and even if the
inherited dwelling should not be solid enough to resist wind and
weather from one year’s end to another, and to be handed down to the
next generation, at all events the Hymenopteron finds conditions of
greater safety in spots consecrated by ancestral experience. There she
hollows out galleries, each serving as corridors to a group of cells,
thus economising the labour to be expended on the entire egg-laying.
In this way are formed, not true societies, there being no concerted
effort to a common end, but at least gatherings where the sight of
other Sphegidæ no doubt animates the labour of each. In fact, one can
notice between these small tribes, sprung from one and the same stock,
and the solitary miners, a difference in activity, recalling in one
case the emulation of a populous workshop, and in the other the dulness
of labourers in the tedium of isolation. For the animal as well as man
activity is contagious, and excited by its own example. Let us sum up.
Where there is a moderate weight for the spoiler, it is possible to
carry it on the wing for a great distance, and then the Hymenopteron
can arrange the burrows at pleasure, choosing by preference its
birthplace. From this preference of the birthplace results an
agglomeration—a coming together of insects of the same species, whence
arises emulation in their work. This first step towards social life is
the result of easy journeys. Is it not so with man? excuse the
comparison! Men, where ways are bad, build solitary cottages, while
where there are good roads, they collect in populous cities, served by
railroads, which, so to say, annihilate distance; they assemble in
immense human hives called London or Paris.
The Languedocian Sphex has quite another lot. Its prey is a heavy
ephippiger—a single morsel representing the whole sum of provender
amassed by the other predatory insects bit by bit. What the Cerceris
and other strong-flying insects do by dividing their labour is
accomplished by a single effort. The weight of the prey rendering
flight impossible, it must be brought home with all the delays and
fatigue of dragging it along the ground. This one fact obliges her to
accommodate the position of her burrow to the chances of the chase:
first the prey and then the dwelling. Hence no rendezvous at a general
meeting-place; no living among neighbours, no tribes stimulating
themselves by mutual example—only isolation where chance has led the
Sphex—solitary labour, unenthusiastic, though always conscientious.
First of all prey is sought, attacked, and paralysed. Then comes making
the burrow. A favourable spot is chosen as near as possible to that
where lies the victim, so as to abridge the toil of transport, and the
cell of the future larva is rapidly hollowed to receive an egg and food
as soon as possible. Such is the very different method shown by all my
observations. I will mention the chief of them.
If surprised in its mining, one always finds this Sphex alone—sometimes
at the bottom of some dusty niche a fallen stone has left in an old
wall—sometimes in a shelter formed by a projecting bit of sandstone,
such as is sought by the fierce-eyed lizard as a vestibule to its
retreat. The sun falls full upon it; the place is a furnace. The soil
is extremely easy to hollow, formed as it is by ancient dust which has
dropped little by little from the roof. The mandibles, which act as
pincers to dig with, and the tarsi, as rakes to clear away, soon hollow
the cavity. Then the Sphex flies off, but in a leisurely way, and
without any great expenditure of wing power, a manifest sign that the
expedition is not a long one. One’s eye can easily follow the insect
and discover where it alights, usually some ten yards off. Sometimes it
decides to go on foot. It sets out, hurrying to a spot where we will be
indiscreet enough to follow, our presence noways troubling it. Having
arrived on foot or on the wing it hunts about for a while, as one may
conclude from its indecision and short excursions on all sides. It
seeks and at last finds, or rather finds anew. The object found is an
ephippiger, half-paralysed, but still moving antennæ, tarsi, and
ovipositor—a victim which the Sphex certainly poignarded a little while
before with several stings, and then left her prey, an embarrassing
burden, while she still hesitated as to the choice of a domicile.
Perhaps she abandoned it on the very spot of the capture, leaving it
rather obvious on a grass tuft the better to find it later, and
trusting to her good memory to return where lies the booty, set to work
to explore the neighbourhood and find a suitable spot to burrow. This
done she came back for the game which was found without much
hesitation, and now she prepares to convey it home. She bestrides the
insect, seizes one or both antennæ and sets off, pulling and dragging
with all the strength of loins and jaws.
Sometimes the journey is accomplished at one trial; more frequently she
leaves her load and hurries home. Perhaps it occurs to her that the
entrance door is not wide enough for this ample morsel, perhaps she
bethinks her of some defect of detail that might interfere with
provisioning the cell. Yes, she retouches her work, enlarges the
doorway, levels the threshold, consolidates the arch, all with a few
sweeps of the tarsi. Then she returns to the ephippiger, lying on its
back a few paces distant, and drags it on again. But a new idea seems
to flash across her lively mind. She had visited the gateway but had
not looked within; who knows if all be well there? She hastens back,
leaving the ephippiger midway. The interior is visited, and apparently
some touches as with a trowel are given by the tarsi, to lend a last
finish to the walls. Without lingering over these final touches the
Sphex returns to her prey, and harnesses herself to the antennæ.
Forward! Will the journey be accomplished this time? I would not answer
for it. I have known a Sphex, perhaps more suspicious than others, or
more forgetful of the minor details of architecture, set her omissions
right or allay her suspicions by abandoning her prey five or six times
successively, and hurrying to the burrow, which each time was touched
up a little or simply entered. It is true that others go straight home,
without even stopping to rest. I must add that when the Sphex comes
home to perfect her dwelling, she does not fail to give an occasional,
distant glance at the ephippiger left on the way, to make sure that
nothing touches it. This prudence recalls that of the Scarabæus sacer
issuing from the hole which it is digging to feel its dear ball, and
bring it a little nearer.
The deduction to be drawn from the facts just stated is evident. Since
every Sphex occitanica we surprise while it burrows—be it at the very
beginning, at the first stroke of her tarsi in the dust, or later, the
dwelling being ready—makes a short expedition on foot or on the wing,
and always finds a victim already stabbed, already paralysed, one may
conclude with certainty that she first makes her capture, and later
burrows, so that the place of capture decides that of the domicile.
This reversal of method which prepares the food before the larder,
while previously we saw the larder precede the food, I attribute to the
weight of the prey being too great to carry on the wing. It is not that
S. occitanica is ill-organised for flight; on the contrary, she can
soar splendidly, but her prey would overwhelm her if she depended only
on her wings. She needs the support of the ground and must drag her
prey, and displays wonderful vigour in doing this. Loaded with prey she
always goes on foot, or takes very short flights when these spare time
and toil. Let me quote an instance taken from my latest observations on
this curious Hymenopteron.
A Sphex appeared suddenly, whence I know not, dragging an ephippiger
apparently just caught hard by. As things were she had to burrow, but
the position was as bad as possible—a highway, hard as stone. There was
no time for difficult mining, since the prey must be stored as soon as
possible; she needed light soil where the cell could be quickly made. I
have already described her favourite soil—dust deposed by years at the
bottom of some hole in a wall, or in some little hollow of a rock. The
Sphex which I was observing stopped at the foot of a country house with
a newly whitewashed façade, and measuring from six to eight metres in
height. Instinct told her that under the roof tiles she would find
hollows rich in ancient dust. Leaving her prey at the foot of the
façade, she flew on to the roof. For some time I saw her seek vainly
about. Then, having found a suitable position, she set to work under
the hollow of a tile. In ten minutes or a quarter of an hour at most
the domicile was ready; she flew down, promptly found the ephippiger,
and then had to carry up her prey. Would it be on the wing, as
circumstances suggest? Not at all; the Sphex adopted the difficult
method of escalading a vertical wall with a surface smoothed by the
mason’s trowel and from six to eight metres high. Seeing her take this
road, dragging her game between her feet, I thought at first that it
was impossible, but was soon reassured as to the outcome of this
audacious attempt. Supporting herself by the little roughnesses of the
mortar, the vigorous insect, in spite of the embarrassment of her heavy
load, made her way up this vertical plane with the same security, the
same speed, as on horizontal ground. The top is reached without any
hindrance, and the prey provisionally deposited at the edge of the roof
on the rounded bark of a tile. While the Sphex was retouching her
burrow the ill-balanced prey slipped and fell to the foot of the wall.
She must begin again, and again by means of an escalade. The same
imprudence is repeated; once more left on the curved tile the prey
slips and falls to the ground. With a calm which such accidents cannot
disturb, the Sphex for the third time hoists the ephippiger by climbing
the wall, and, better advised, drags it straight to the bottom of the
hole.
If carrying the prey on the wing has not been attempted even in such
conditions as the above, it is clear that the Sphex is incapable of
flight with so heavy a load. To this impotence we owe the few details
of habits which are the subject of this chapter. A prey not too heavy
to be carried on the wing makes a semi-sociable species of S.
flavipennis—that is to say, one seeking the company of its fellows; a
heavy prey impossible to carry through the air renders S. occitanica a
species devoted to solitary labour—a kind of savage, disdainful of the
solace derived from neighbourhood of one’s fellows. The greater or
lesser weight of their prey decides the fundamental character.
XI
THE SCIENCE OF INSTINCT
I have no doubt that in order to paralyse her prey, Sphex occitanica
follows the method of the one that hunts grasshoppers, plunging her
sting repeatedly into the breast of the ephippiger in order to reach
the thoracic ganglia. She must be familiar with the operation of
injuring the nerve centres, and I am assured beforehand of her
consummate skill in the learned operation. It is an art familiar to all
the predatory Hymenoptera who bear a poisoned dagger, and it is not
given them for nothing. But I must own that I have never yet beheld the
deadly manœuvre, thanks to the solitary life of this Sphex.
When a number of burrows are made and then provisioned on some common
ground, one has only to wait there to see now one insect return from
the chase, now another, with her prey, and it is easy to substitute a
live victim for the one sacrificed, renewing the experiment at will.
Besides, the certainty that the subjects for experiment will not fail
when wanted allows everything to be prepared beforehand, while with S.
occitanica these conditions of success do not exist. To set out and
look for her with one’s preparations made is all but useless, so
sparsely are these solitary insects scattered. Moreover, if you do meet
with one, it will probably be during her idle hour when nothing is to
be learned. I repeat that it is almost always unexpectedly, when you
are not thinking about it, that the Sphex appears with her ephippiger.
This is the moment—the one propitious moment—to attempt a substitution
of prey and to induce her to let you witness those dagger thrusts. Let
us hasten; time presses; in a few moments the burrow will have enclosed
the provender, and the grand chance will be lost.
Need I speak of my mortification in these promising moments—a mocking
lure offered by fortune! Under my eyes is matter for curious
observations, and I cannot profit by it! I cannot steal the Sphex’s
secret, for I have no equivalent to offer for her prey. Just try, if
you like, to go about looking for an ephippiger when there are but a
few minutes to find it in! Why, it took me three days of wild search
before I could find weevils for my Cerceris! Yet twice did I make that
desperate attempt. Ah! if the garde-champêtre had caught me then
rushing about the vineyards, what a chance he would have had to believe
me guilty of theft, and of reporting me! Vines and grapes—nothing was
respected by my hurried steps, fettered by the vine garlands. I must
and would have an ephippiger, and have it then and there. And once I
did find one during one of these rapid expeditions. I beamed with joy,
little foreseeing the bitter disappointment awaiting me.
If only I can come in time! if only the Sphex is still dragging her
victim! Thank heaven! all favours me. She is still at some distance
from her hole, and is bringing along her prey. With my pincers I gently
draw it back. She resists, clutches the antennæ and will not let go. I
pull harder, even making her go backwards; it is in vain, she holds on.
I had with me a pair of delicate little scissors, part of my
entomological outfit, and I rapidly cut the harness, otherwise the long
antennæ of the ephippiger. The Sphex still advanced, but soon paused,
surprised by the sudden lightening of her load, which now indeed only
consisted of the antennæ detached by my malicious artifice. The real
burden, the heavy-bodied insect, remained behind, instantly replaced by
my living one. The Sphex turned, let go the ropes, which now drew
nothing, and retraced her steps. Now she is face to face with the prey
substituted for her own. She examines it, walks round it with
suspicious caution, stops, wets her foot with saliva and washes her
eyes. While thus meditating does she say to herself something of this
kind: “Well, am I awake or am I asleep? Do I see clearly or not? This
thing is not mine. Of what or whom am I the dupe?” At all events she is
in no haste to bite my prey. She holds aloof, and shows not the
smallest wish to seize it. To excite her I offered the insect with the
tips of my fingers, putting the antennæ almost in her jaws, well aware
of her audacious tameness, and that she will take from your fingers
prey withdrawn and then offered. What is this? She draws back,
disdaining my offers and the prey put within her reach. I put down the
ephippiger, which, unconscious of danger, goes straight to its
assassin. Now for it. Alas! no; the Sphex continues to draw back,
behaves like a veritable coward, and finally takes wing. I never saw
her again. Thus ended to my confusion an experiment which had so
excited my enthusiasm.
Later, and gradually, as I visited more burrows I came to understand my
want of success and the obstinate refusal of the Sphex. I always,
without exception, found stored a female ephippiger with an abundant
and succulent store of eggs inside her. This, it would seem, is the
favourite food of the larvæ. In my rush among the vines I had laid
hands on one of the other sex. It was a male which I offered to the
Sphex! More clear-sighted than I in the great victualling question, she
would have nothing to say to my game. “A male! Is that the kind of
dinner for my larvæ? And, pray, for whom do you take them?” How
sensitive must be these dainty eaters who appreciate the difference
between the tender flesh of the female and the comparatively dry body
of the male! What a penetrating glance which can distinguish instantly
the one sex from the other, though alike in form and colour! The female
has an ovipositor to bury her eggs with, and this is almost the only
outward difference between her and the male. This difference never
escapes the keen-sighted Sphex, and that is why my experiment made her
rub her eyes, immensely puzzled by a prey without an ovipositor, which
she was perfectly sure had one when it was caught. At such a
transformation what must have passed in her little Sphex brain?
Now let us follow her when, the burrow being ready, she returns to find
her victim, deserted not far from the place of capture, and after the
operation which paralysed it. The ephippiger is in a state like that of
the cricket slain by S. flavipennis—a certain proof that stings have
been darted into the ganglia of the thorax. Nevertheless, many
movements continue, but disconnected, though endowed with a certain
vigour. Unable to stand, the insect lies on one side or on its back,
moving its long antennæ and palpi rapidly, opening and closing its
mandibles, and biting as hard as in its normal condition. The abdomen
pants fast and deeply; the ovipositor is suddenly brought under the
stomach, which it almost touches. The feet move, but languidly and
irregularly, the middle ones seemingly more benumbed than the others.
If touched with a needle, the whole body starts wildly; efforts are
made to rise and walk without success. In short, the creature would be
full of life but for the impossibility of locomotion and even of
getting on its feet. There is then a paralysis altogether
local—paralysis of the feet, or rather partial abolition and ataxy of
movement in them. Is this very incomplete inertia caused by some
special disposition of the victim’s nervous system, or is it that only
a single stab is given, instead of wounding each ganglion of the
thorax, as does the huntress of grasshoppers? I cannot say.
However, for all its starts, its convulsions, its irregular movements,
the victim is none the less unable to harm the larvæ destined to
devour it. I have taken from the Sphex’s burrow ephippigers struggling
just as much as in the first moments of their semi-paralysis, and yet
the feeble grub, born but a few hours earlier, was biting the gigantic
victim with entire immunity. This striking result is caused by the
mother laying her egg in one particular spot. I have already told how
S. flavipennis glues her egg on the cricket’s breast, rather on one
side, between the first and second pairs of feet. S. albisecta chooses
the same place, and S. occitanica an analogous one, rather further back
toward the base of one of the large hind thighs, all three thus
evincing admirable knowledge as to where the egg will be safe.
For consider the ephippiger shut in the burrow. It is on its back,
absolutely incapable of turning over. Vainly does it struggle; the
irregular movements of its feet are useless, the cell being too wide
for them to gain support from the walls. What do the victim’s
convulsions matter to the larva? It is on a spot where it cannot be
reached by tarsi, mandibles, ovipositor, or antennæ—a point absolutely
motionless, where there is not even a shudder of the skin. There is
entire security unless the ephippiger can move, turn, and get on its
feet, and that one condition is admirably guarded against.
But with several, all in the same degree of paralysis, there would be
great risk for the larva. Though there would be nothing to fear from
the first insect attacked, as the larva is out of its reach, there
would be peril from the neighbourhood of the others, which in
stretching out their legs hither and thither might strike it and tear
it up with their spurs. Perhaps this is why S. flavipennis, which heaps
three or four grasshoppers in one cell, almost entirely paralyses them,
while S. occitanica, providing each burrow with a single victim, leaves
great power of motion to the ephippiger, simply preventing change of
place or rising to its feet, thus—though I cannot affirm it—economising
dagger thrusts.
If the half-paralysed ephippiger be harmless for the larva established
on a point of its body where defence is impossible, things are
otherwise for the Sphex itself, which has to get it home. First, the
prey clutches bits of grass with its tarsi as it is dragged along,
being still able to use them pretty freely, causing considerable
difficulty in getting it onward. The Sphex, heavily weighted by her
load, is exposed to exhaustion by her efforts to make her prey let go
its desperate hold on grassy places. But that is the least of the
difficulties; it has full use of its mandibles, which snap and bite
with their old vigour. Just in front of these terrible pincers is the
slender body of the spoiler, as the latter draws the victim along. The
antennæ are grasped not far from their root, so that the ephippiger,
lying on its back, has its mouth now opposite the abdomen, and now the
thorax of the Sphex, who, standing high on her long legs, watches, I am
convinced, in order not to be seized by the mandibles gaping beneath. A
moment of forgetfulness, a slip, a mere nothing, might bring her within
reach of a pair of strong nippers which would not let slip the chance
of a pitiless vengeance. In certain specially difficult cases, if not
always, the movement of these redoubtable pincers must be stopped, and
the harpoon-like tarsi prevented from adding to the difficulties of
transport.
What will the Sphex do to obtain this result? Man, and even a learned
man, would hesitate, bewilder himself with vain attempts, and perhaps
despair of success. Let him come and take a lesson from the Sphex, who,
without having learned, without ever seeing any one else at work, is
thoroughly up in her profession of operator. She knows that under her
victim’s skull lies a circlet of nerve-knots, somewhat analogous to the
brain of higher animals. She knows too that this chief nerve centre
directs the action of the mouth-parts, and, moreover, is the seat of
will, without whose command no muscle acts; finally, she is aware that
if this kind of brain be injured, all resistance will cease, the insect
no longer possessing will-power. As for the method of operation, it is
the easiest thing possible for her, and when we have studied at her
school we may try in our turn. The sting is no longer employed; in her
wisdom the Sphex decides compression to be preferable to the poisoned
sting. Let us bow to her decision, for we shall presently see how
prudent it is to be convinced of our ignorance compared with the
animal’s knowledge. Lest by re-writing my account I fail to do justice
to the sublime talent of this masterly operation, I transcribe my notes
written on the spot directly after witnessing the exciting spectacle.
The Sphex, finding that her prey resists too much, hooking itself here
and there to blades of grass, pauses to perform the singular operation
about to be described—a kind of coup de grâce. The Hymenopteron, still
astride her victim, makes the articulation in the upper part of the
neck, at the nape, to open wide. Then she seizes the neck with her
mandibles, groping as far forward as possible under the skull, but
making no outward wound, grasps and chews repeatedly the nerve-centres
of the head. This renders her victim quite motionless, and incapable of
the least resistance, whereas previously the feet, though unable to
move in the manner necessary for walking, vigorously resisted being
dragged along. This is the fact in all its eloquence. While leaving
intact the thin, supple membrane of the neck, the insect finds a way
into the skull with the point of its mandibles, and bruises the brain.
There is neither effusion of blood nor wound, but merely external
compression. Of course I kept the paralysed ephippiger under inspection
in order to watch the consequences of the operation at my leisure, and
equally of course I hastened to repeat on living specimens what the
Sphex had taught me. I will now compare my results with hers.
Two ephippigers, whose cervical ganglia I compressed with pincers, fell
quickly into a state like that of her victims, only they sounded their
harsh cymbals if irritated by the point of a needle, and their feet
made some irregular languid movements. The difference in the results
obtained doubtless arises from the fact that my victim had not been
previously stung in the thoracic ganglia, as those had been which the
Sphex had struck in the breast. Allowing for this important point, it
will be seen that I made no bad pupil, and imitated my teacher in
physiology, the Sphex, not ill. I own that it was not without a certain
satisfaction that I found I had done almost as well as the insect does.
As well! What have I just said? Wait a little, and it will be seen that
I had to attend the Sphex’s school for many another day. For my two
ephippigers speedily died—died outright, and after three or four days I
had only decaying bodies under my eyes. But the ephippiger of the
Sphex? Need I say that ten days after the operation this was perfectly
fresh, as it has to be for the larva whose destined prey it is. Yet
more, a few hours after the operation under the skull, there reappeared
as if nothing had happened movements of an irregular kind in feet,
antennæ, palpi, ovipositor, and mandibles—in short, the creature was
again in the same state as before the Sphex bit its brain. And the
movements went on, only feebler each day. The Sphex had only benumbed
her victim for a period amply sufficient to enable her to get it home
without resistance, while I, who thought myself her rival, was but a
clumsy, barbarous butcher, and killed mine. She, with her inimitable
dexterity, compressed the brain scientifically to cause a lethargy of a
few hours; I, brutal through ignorance, perhaps crushed this delicate
organ, primal source of life, with my pincers. If anything could
prevent my blushing at my defeat, it would be that few if any could
rival the Sphex in skill.
Ah! now I comprehend why she did not use her sting to injure the
ganglia of the neck. A drop of poison instilled here, at the centre of
vital force, would annihilate all nerve power, and death would soon
follow. But the Sphex does not at all desire death. Dead food by no
means suits the larvæ, and still less a body smelling of decay. All
that is needed is lethargy, a passing torpor, hindering resistance
while the victim is carted along—resistance difficult to overcome and
dangerous to the Sphex. This torpor is obtained by the proceeding known
in laboratories of experimental science as compression of the brain.
The Sphex acts like a Flourens who, baring an animal’s brain and
pressing on the cerebrum, abolishes at once sensibility, will,
intelligence, and motion. The pressure ceases and all reappears. So
reappear the remains of life in the ephippiger as the lethargic effects
of a skilful pressure go off. The ganglia of the skull, squeezed by the
mandibles, but without mortal contusions, gradually recover activity,
and put an end to the general torpor. It is alarmingly scientific!
Fortune has her entomological caprices; you run after her and do not
come up with her; you forget her, and lo, here she is tapping at your
door! How many useless excursions, how many fruitless plans, you made
to try to see Sphex occitanica sacrifice her victim! Twenty years go
by; these pages are already in the printer’s hands, when, in the first
days of this month (August 8, 1878), my son Emile darts into my study.
“Quick! quick!” he cries, “a Sphex is dragging along her prey under the
plane trees, before the door of the court!” Emile, initiated into the
affair by what I had told him, and, better still, by like facts seen in
our out-of-door life, was quite right. I hurried away, and saw a
splendid S. occitanica dragging a paralysed ephippiger by the antennæ.
She moved toward the poultry yard, seemingly desirous of scaling the
wall, to make her burrow under some roof tile. Some years before I had
seen a similar Sphex accomplish the ascent with her game, and choose
her domicile under the arch of an ill-joined tile. Perhaps this new one
was descended from her whose difficult ascent I have chronicled. A like
feat is probably about to be repeated, and this time before numerous
witnesses, for all the household working under the shade of the plane
trees formed a circle round the Sphex. They wonder at the audacious
tameness of the insect, noways disturbed by the gallery of interested
spectators. All are struck by her proud and robust bearing, as, with
raised head and the victim’s antennæ well grasped by her mandibles, she
drags after her the enormous burden. I alone among the spectators feel
some regret. “Ah, had I but some live ephippigers!” I could not help
saying, without the least hope of seeing my wish realised. “Live
ephippigers!” replied Emile; “why, I have some quite fresh, caught this
morning.” Four steps at a time he flew upstairs to his little study,
where barricades of dictionaries enclosed a park wherein was brought up
a fine caterpillar of Sphinx euphorbiæ. He brought back three
ephippigers as good as heart could wish—two females and one male. How
came these insects at hand just at the right moment for an experiment
vainly tried twenty years before? This is another story. A southern
shrike had nested on one of the tall plane trees in the avenue. Some
days before the Mistral, the rude wind of our parts, had blown so
violently that branches bent as well as reeds, and the nest overturned
by the undulations of its branch let fall the four nestlings it
contained. The next day I found the brood on the ground—three killed by
the fall, the fourth still alive. The survivor was entrusted to Emile,
who thrice a day went cricket-hunting on the turf in the neighbourhood
to feed his charge. But crickets are not very large, while the
nestling’s appetite was. Something else was preferred—ephippigers,
collected from time to time on the dry stalks and prickly leaves of the
Eryngium. The three insects brought me by Emile came from the shrike’s
larder. My pity for the fallen nestlings had brought me this
unhoped-for good luck.
Having made the circle of spectators draw back and leave free passage
for the Sphex, I took away her prey with my pincers, giving her
immediately in exchange one of my ephippigers with an ovipositor like
that of the one abstracted. Stamping was the only sign of impatience
shown by the bereaved Hymenopteron. She ran at the new prey, too
corpulent to try to avoid pursuit, seized it with her mandibles by the
saddle-shaped corslet, got astride, and curving her abdomen, passed its
end under the ephippiger’s thorax. There doubtless the stings are
given, but the difficulty of observation prevents me from telling how
many. The ephippiger—gentle victim—lets itself be operated on
unresistingly, like the dull sheep of our slaughter-houses. The Sphex
takes her time and manœuvres her lancet with a deliberation favourable
to the observer; but the prey touches the ground with the whole lower
part of its body, and what happens there cannot be seen. As for
interfering and lifting the ephippiger a little so as to see better, it
is not to be thought of; the murderess would sheath her weapon and
retire. The next act is easy to observe. After having stabbed the
thorax, the end of the abdomen appears under the neck, which she forces
widely open by pressing the nape. Here the sting enters with marked
persistence, as if more effective than elsewhere. One might suppose
that the nerve centre struck was the lower part of the œsophagean
collar, but the persistence of movement in the mouthpieces, mandibles,
jaws, and palpi, animated by this source of nerve power, shows that
this is not so. Through the neck the Sphex simply reaches the thoracic
ganglia, or at least the first, more easily attainable through the thin
skin of the neck than through the integuments of the chest.
All is over. Without one convulsion or sign of pain the ephippiger is
rendered henceforward an inert mass. For the second time I deprived the
Sphex of the subject operated on, replacing it by the second female at
my disposal. The same manœuvres were followed by the same result. Three
times, almost without a pause, the Sphex repeated her skilled surgery,
first on her own capture, then on those exchanged by me. Will she do so
a fourth time on the male which I still have? It is doubtful, not that
she is weary, but because the game does not suit her. I have never seen
a Sphex with any but female prey, which, filled as they are with eggs,
are the favourite food of the larvæ. My suspicion was well founded.
Deprived of her third capture, she obstinately refused the male which I
offered her. She ran hither and thither with hurried steps, seeking her
lost prey. Three or four times she approached the ephippiger, walked
round it, cast a disdainful glance at it, and finally flew away. This
was not what her larvæ wanted. Experiment reiterated it after twenty
years’ interval.
The three females, two stabbed under my eyes, remained mine. All the
feet were quite paralysed, Whether in its natural position or on its
back or side, the creature retains whichever is given it. Constant
oscillations of the antennæ, and, at intervals, some pulsations of the
stomach and movements of the mouthpieces, are the only sign of life.
Motion is destroyed but not feeling, for at the least prick where the
skin is thin, the whole body shudders faintly. Perhaps one day
physiology will discover in these victims a subject for fine studies on
the functions of the nervous system. The Hymenopteron’s sting,
incomparably skilful in reaching a given point and inflicting a wound
to affect it alone, will replace, with immense advantage, the brutal
scalpel of the experimenter, which disembowels where it should lightly
touch. Meanwhile, here are the results obtained from the three victims,
but from another point of view.
Only movement of the feet being destroyed, there being no injury save
that to the nerve centres, the source of motion, the creature perishes,
not from its wound, but from inanition. The experiment was tried thus:
Two uninjured ephippigers found in the fields were imprisoned without
food, one in the dark, the other in the light. In four days the latter
died of hunger, in five the former. This difference of a day is easily
explained. In the light the creature is more eager to recover liberty,
and as every movement of the animal machine causes a corresponding
expenditure of energy, greater activity used up sooner the reserves of
the organisation. With light, more agitation and shorter life; in
darkness, less movement and longer life; both insects fasted equally.
One of the three stabbed was kept in the dark and foodless. In this
case there was not only darkness and want of food, but the serious
wounds inflicted by the Sphex, and yet for seventeen days it
perpetually moved its antennæ. As long as this kind of pendulum
oscillates, the clock of life has not stopped. On the eighteenth day
the creature ceased to wave its antennæ and died. Thus the seriously
wounded insect lived in the same conditions as the uninjured one four
times as long. What seems as if it should be a cause of death is really
the cause of life.
However paradoxical it may at first appear, this result is perfectly
simple. Intact, the creature agitates and spends itself; paralysed, it
makes only those feeble, internal movements, inseparable from all
organised life, and the waste of substance is in proportion to the
amount of action employed. In the first case the animal machine works
and spends itself; in the second it is at rest and saves itself up.
Nourishment no longer repairing loss, the insect in motion spends in
four days its food reserves and dies; the motionless one does not spend
them, and lives eighteen. Physiology tells us that life is continual
destruction, and the Sphex’s victims are a most elegant demonstration
of this fact.
One more remark. Fresh food is absolutely necessary to larvæ of the
Hymenopteron. If the prey were stored intact, in four or five days it
would be a dead body, given up to decay, and the newly hatched grubs
would find no food but a corrupted mass. Touched by the sting it can
live two or three weeks—a period more than sufficient for the egg to
hatch and the grub to develop. The paralysis has thus a double
result—immobility, so as not to endanger the life of the delicate
larvæ, and long preservation of the flesh to assure wholesome
nourishment for them. Even when enlightened by science human logic
could find nothing better.
My two other ephippigers, stung by the Sphex, were kept in darkness
with food. To feed inert creatures, differing only from dead bodies by
the perpetual oscillation of their long antennæ, seems at first an
impossibility; however, the play of the mouth organs gave me some hope,
and I made the attempt. My success surpassed my expectations. There was
no question, of course, of offering them a lettuce leaf or any other
green thing on which they might have browsed in their normal condition;
they were feeble invalids, to be nourished with a feeding-cup, so to
say, and broth. I used sugar and water.
The insect being laid on its back, I put a drop of sugared liquid on
its mouth with a straw. Instantly the palpi stirred, mandibles and jaws
moved; the drop was consumed with evident satisfaction, especially if
the fast had been somewhat prolonged. I renewed the dose till it was
refused. The repast took place once or twice a day at irregular
intervals, as I could not devote myself very much to a hospital of this
kind.
Well, with this meagre diet one of the ephippigers lived twenty-one
days. This was little longer than the life of the one which I allowed
to die of inanition. It is true that twice the insect had had a bad
fall, having dropped from the experiment table to the floor through
some awkwardness of mine. The bruises consequent may have hastened its
end. As for the other, exempt from accidents, it lived six weeks. As
the nourishment offered, sugar and water, could not indefinitely
replace the natural food, it is very probable that it would have lived
longer still had its customary diet been available. Thus the point
which I had in view is demonstrated: victims pierced by the sting of
the Hymenopteron die from inanition and not of their wound.
XII
THE IGNORANCE OF INSTINCT
The Sphex has just shown us with what infallible, transcendent art she
acts, guided by the unconscious inspiration of instinct: she will now
show how poor she is in resources, how limited in intelligence, and
even illogical in cases somewhat out of her usual line. By a strange
contradiction, characteristic of the instinctive faculties, with deep
science is associated ignorance not less deep. Nothing is impossible to
instinct, however great be the difficulty. In constructing her
hexagonal cells with their floor of three lozenge-shaped pieces, the
bee resolves, with absolute precision, the arduous problems of maximum
and minimum, to solve which man would need a powerful, mathematical
mind. Hymenoptera, whose larvæ live on prey, have methods in their
murderous art hardly equalled by those of a man versed in the most
delicate mysteries of anatomy and physiology. Nothing is difficult to
instinct so long as the action moves in the unchanging groove allotted
to the animal, but, again, nothing is easy to instinct if the action
deviates from it. The very insect which amazes us and alarms us by its
high intelligence will, a moment later, astonish us by its stupidity
before some fact extremely simple, but strange to its usual habits. The
Sphex will offer an example.
Let us follow her dragging home an ephippiger. If fortune favour us, we
may be present at a little scene which I will describe. On entering the
shelter under a rock where the burrow is made, the Sphex finds, perched
on a blade of grass, a carnivorous insect which, under a most
sanctimonious aspect, hides the morals of a cannibal. The danger
threatened by this bandit in ambush on her path must be known to the
Sphex, for she leaves her game and runs bravely at the Mantis to
administer some sharp blows and dislodge, or at all events, alarm and
inspire it with respect. It does not move, but closes its deadly
weapons—the two terrible saws of the arm and forearm. The Sphex returns
to her prey, harnesses herself to the antennæ, and passes audaciously
under the blade of grass where the Mantis sits. From the direction of
her head one can see that she is on her guard, and is holding the enemy
motionless under her threatening eyes. Such courage is duly rewarded;
the prey is stored without further misadventure.
A word more of the Praying Mantis, the Prégo Diéou as it is called in
Provence, i.e. the Pray-to-God. And, indeed, its long, pale green
wings, like ample veils, its head upraised to heaven, its arms folded
and crossed on its breast, give it a false resemblance to a nun in
ecstatic devotion. All the same, it is a ferocious creature, bent on
carnage. Although not especially favourite hunting-grounds, the
workshops of various burrowing Hymenoptera are often visited by it.
Posted on some bush near the burrows, it waits until chance brings some
Sphex returning home within reach, thus achieving a double capture,
catching together Sphex and prey. Its patience is long tried; the Sphex
is suspicious and on her guard, but from time to time a rash one lets
herself be caught. By a sudden rustle of half-spread wings, as by a
convulsive movement, the Mantis terrifies the approaching Sphex, which
hesitates for a moment, and then with the suddenness of a spring the
toothed forearm folds back on an arm also toothed, and the insect is
seized between the blades of the double saw, as though the jaws of a
wolf trap were closing on the beast as it takes the bait. Then, without
unclosing the cruel machine, the Mantis gnaws little mouthfuls of its
victim. Such are the ecstasies, the prayers, and the mystic meditations
of the Prégo Diéou.
Among the scenes of carnage which the Mantis has left in my memory, let
me describe the following. It passes before a working-place of
Philanthus apivorus. These miners nourish their larvæ with hive-bees,
which they seize on flowers while collecting pollen and honey. If the
Philanthus feels that the bee is full of honey, it does not fail to
squeeze it before storing it, either on the way, or at the entrance of
the hole, to make it disgorge the delicious liquid; this it drinks by
licking the tongue of the unfortunate bee, which, dying, extends it at
full length. This profanation of a dying creature, squeezed by its
murderer to empty its body and enjoy the contents, has something so
hideous that I should call it a crime if a Philanthus could be held
responsible. In the midst of this horrible banquet I have seen both
murderer and prey seized by the Mantis; the robber was plundered by a
second robber. Horrible to relate, while the Mantis held it
transpierced by the points of the double saw, and was already gnawing
the under parts, the Philanthus went on licking the honey, unable to
abandon the delicious food even in the throes of death. Let us cast a
veil over these horrors.
We return to the Sphex, with whose burrow we must make acquaintance
before going further. It is made of fine sand, or rather in the fine
dust at the bottom of a natural shelter. Its passage is very short—an
inch or two without a turn, leading into a single spacious oval
chamber, and all is a rude, hastily made den, rather than a dwelling
hollowed with art and leisure. I have already said that the captured
prey, left for a brief moment or two where it was hunted, is the cause
of the simplicity of this abode and of there being but one chamber or
cell to each hollow. For who can say whither the chances of the day’s
hunt may lead? The dwelling must be near the heavy prey, and to-day’s
abode, too far off to admit of carrying the second ephippiger there,
cannot be used to-morrow. Thus each time prey is caught there must be
new digging out—a new burrow with its one cell, now here, now there.
Now let us try some experiments to see how the insect behaves amid
circumstances new to it.
First experiment.—A Sphex, dragging her prey, is at a few inches from
her burrow. Without disturbing her I cut the antennæ of the ephippiger,
which we already know serve as harness. Having recovered from her
astonishment at the sudden lightening of her load, the Sphex returns
and unhesitatingly seizes the base of the antennæ, the short stumps not
cut off. Very short they are—hardly a millimetre long; no matter, they
suffice for the Sphex, who grips what remains of her ropes and drags
anew. With many precautions not to hurt her, I cut off the two stumps,
now level with the skull. Finding nothing to seize at the parts
familiar to her, she takes hold on one side of one of the long palpi of
her victim, and drags it, not at all put out by this modification in
her style of harnessing herself. I leave her alone. The prey is got
home and placed with its head to the mouth of the burrow. The Sphex
enters to make a short inspection of the interior before proceeding to
store provisions. Her tactics recall those of S. flavipennis in like
circumstances. I profit by this brief moment to take the abandoned
prey, deprive it of all its palpi, and place it a little farther off—a
pace from the burrow. The Sphex reappears and goes straight to her
game, which she saw from her threshold. She seeks above the head, she
seeks below, on one side, and finds nothing to seize. A desperate
attempt is made; opening wide her mandibles she tries to grasp the
ephippiger by the head, but her pincers cannot surround anything so
large, and slip off the round, polished skull. She tries several times
in vain; at length, convinced of the futility of her efforts, draws
back, and seems to renounce further attempts. She appears
discouraged—at least she smooths her wings with her hind feet, while
with her front tarsi, first passing them through her mouth, she washes
her eyes, a sign among Hymenoptera, as I believe, that they give a
thing up.
Yet there were points by which the ephippiger might be seized and
dragged as easily as by the antennæ and palpi. There are the six feet,
there is the ovipositor—all organs slender enough to be thoroughly
grasped and used as traction ropes. I own that the easiest way of
getting the prey into the storehouse is to introduce it head first by
the antennæ; yet, drawn by one foot, especially a front one, it would
enter almost as easily, for the orifice is wide and the passage short,
even if there be one. How came it then that the Sphex never once tried
to seize one of the six tarsi or the point of the ovipositor, while she
did make the impossible, absurd attempt to grip with mandibles far too
short the huge head of her prey? Perhaps the idea did not occur to her.
Let us try to suggest it. I place under her mandibles first a foot,
then the end of the abdominal sabre. She refuses obstinately to bite;
my repeated solicitations come to nothing. A very odd kind of hunter
this to be so embarrassed by her game and unable to think of seizing it
by a foot if it cannot be taken by the horns! Perhaps my presence and
all these unusual events may have troubled her faculties; let us leave
her to herself, with her burrow and ephippiger, and give her time to
consider and to imagine in the calm of solitude some means of managing
the business. I walked away and returned in a couple of hours to find
the Sphex gone, the burrow open, and the ephippiger where I had laid
it. The conclusion is that the Sphex tried nothing, but departed,
abandoning home, game—everything, when to utilise them all that was
needed would have been to take the prey by one foot. Thus this rival of
Flourens, who just now startled us by her science when pressing the
brain to induce lethargy, is invariably dull when the least unusual
event occurs. The Sphex, which knows so well how to reach the thoracic
ganglia of a victim with her sting, and those of the brain with her
mandibles, and which makes such a judicious difference between a
poisoned sting that would destroy the vital influence of the nerves,
and compression causing only momentary torpor, cannot seize her prey in
a new way. To understand that a foot may be taken instead of the
antennæ is impossible; nothing will do but the antennæ or another
filament of the head or one of the palpi. For want of these ropes her
whole race would perish, unable to surmount this trifling difficulty.
Second experiment.—The Sphex is busy closing her burrow where the prey
is stored and the egg laid. With her fore tarsi she sweeps backward
before her door, and launches from the entrance a spurt of dust, which
passes beneath her, and springs up behind in a parabolic curve as
continuous as if it were a slender stream of some liquid, so rapidly
does she sweep. From time to time she chooses some sand grains with her
mandibles, strengthening materials inserted singly in the dusty mass.
To consolidate this she beats it with her head, and heaps it with her
mandibles. Walled up by this masonry, the entrance rapidly disappears.
In the midst of the work I intervene. Having put the Sphex aside I
clear out the short gallery carefully with the blade of a knife, take
away the materials which block it, and entirely restore the
communication of the cell with the outer air. Then, without injuring
the edifice, I draw the ephippiger out of the cell where it is lying
with its head to the far end, and its ovipositor to the entrance. The
egg is as usual on its breast, near the base of one of the hind legs—a
proof that the Sphex had given her last touch to the burrow, and would
never return. These dispositions made, and the ephippiger placed safely
in a box, I gave up my place to the Sphex, who had been watching while
her domicile was rifled. Finding the entrance open, she entered and
remained some moments, then came forth and took up her work where I
interrupted it, beginning to stop the entrance conscientiously,
sweeping the dust backward, and transporting sand grains to build them
with minute care, as if doing a useful work. The orifice being again
thoroughly blocked, she brushed herself, seemed to give a glance of
satisfaction at her work, and finally flew off.
Yet she must have known that the burrow was empty, since she had gone
inside, and made prolonged stay, but yet after this visit to the
plundered dwelling, she set to work to close it with as much care as if
nothing had happened. Did she propose to turn it later to account,
returning with a fresh prey, and laying a new egg? In that case the
burrow was closed to defend it from indiscreet visitors while the Sphex
was away. Or it was a measure of prudence against other miners who
might covet a ready-made chamber, or a wise precaution against internal
wear and tear, and, in fact, some predatory Hymenoptera are careful
when obliged to suspend work to defend the mouth of their burrow by
closing it up temporarily. I have seen certain Ammophilæ, whose burrow
is a vertical well, close the entrance with a little flat stone when
the insect goes a-hunting, or stops mining when the hour to leave off
work comes at sunset. But in that case the stoppage is slight—a mere
slab set on the top of the well. It takes but a moment when the insect
comes to displace the little flat stone, and the door is open. But what
we have just seen the Sphex construct is a solid barrier—strong
masonry, where layers of alternate dust and gravel occupy the whole
passage. It is definitive, and no temporary work, as is sufficiently
shown by the careful way in which it is constructed. Besides, as I
think I have already proved, it is very doubtful, considering the
manner in which she acted, whether the Sphex would return to use the
dwelling which she had prepared. A new ephippiger will be caught
elsewhere, and elsewhere too will the storehouse destined for it be
hollowed. As, however, these are but conclusions drawn by reasoning,
let us consult experiment, more conclusive here than logic. I let
nearly a week pass in order to allow the Sphex to return to the burrow
so methodically closed, and use it if she liked for her nest-laying.
Events answered to the logical deduction; the burrow was just as I had
left it, well closed, but without food, egg, or larva. The
demonstration was decisive; the Sphex had not returned.
Thus we see the plundered Sphex go into her house, pay a leisurely
visit to the empty chamber, and the next moment behave as if she had
not perceived the absence of the big prey which a little while before
had encumbered the cell. Did she not realise the absence of food and
egg? Was she really so dull—she, so clear-sighted when playing the
murderer—that the cell was empty? I dare not accuse her of such
stupidity. She did perceive it. But why then that other piece of
stupidity which made her close, and very conscientiously too, an empty
chamber which she did not mean to store? It was useless—downright
absurd—to do this, and yet she worked with as much zeal as if the
future of the larva depended on it. The various instinctive actions of
insects are then necessarily connected; since one thing has been done,
such another must inevitably follow to complete the first, or prepare
the way for the next, and the two acts are so necessarily linked that
the first must cause the second, even when by some chance this last has
become not only superfluous, but sometimes contrary to the creature’s
interest. What object could there be in stopping a burrow now useless,
since it no longer contained prey and egg, and which will remain
useless, since the Sphex will not return to it? One can only explain
this irrational proceeding by regarding it as the necessary consequence
of preceding actions. In the normal state of things the Sphex hunts her
prey, lays an egg, and closes the hole. The prey has been caught, the
egg laid, and now comes the closing of the burrow, and the insect
closes it without reflecting at all, or guessing the fruitlessness of
her labour.
Third experiment.—To know all and nothing, according as the conditions
are normal or otherwise, is the strange antithesis presented by the
insect. Other examples drawn from the Sphegidæ will confirm us in this
proposition. Sphex albisecta attacks middle-sized Acridians, the
various species scattered in the neighbourhood of her burrow all
furnishing a tribute. From the abundance of these Acrididæ the chase is
carried on near at hand. When the vertical well-like burrow is ready,
the Sphex merely flies over the ground near, and espies an Acridian
feeding in the sunshine. To pounce and sting while it struggles is done
in a moment. After some fluttering of the wings, which unfold like
carmine or azure fans, some moving of feet up and down, the victim
becomes motionless. Next it must be got home by the Sphex on foot. She
performs this toilsome operation as do her kindred, dragging her game
between her feet, and holding one of the antennæ in her mandibles. If a
grass thicket has to be traversed, she hops and flutters from blade to
blade, keeping firm hold of her prey. When within a few feet of her
dwelling she executes the same manœuvre as does S. occitanica, but
without attaching the same importance to it, for sometimes she neglects
it. The game is left on the road, and though no apparent danger
threatens the dwelling, she hurries toward its mouth, and puts in her
head repeatedly, or even partly enters, then returns to the Acridian,
brings it nearer, and again leaves it to revisit her burrow, and so on
several times, always with eager haste.
These repeated visits have sometimes annoying results. The victim,
rashly abandoned on a slope, rolls to the bottom, and when the Sphex
returns and does not find it where she left it, she must hunt for it,
sometimes in vain. If found, there will be a difficult climb, which,
however, does not prevent her leaving it once more on the perilous
slope. The first of these repeated visits to her cell is easily
explained. Before bringing her heavy load she is anxious to make sure
that the entrance is clear, and that nothing will hinder her carrying
in the prey. But what is the use of her other visits, repeated so
speedily one after another? Are the Sphex’s ideas so unstable that she
forgets the one just made, and hurries back a moment later, only to
forget that she has done so, and so on? It would indeed be a slippery
memory where impressions vanished as soon as made. Let us leave this
too obscure question.
At length the game is brought to the edge of the well, its antennæ
hanging into the mouth, and there is an exact repetition of the method
used by S. flavipennis, and, though in less striking conditions, by S.
occitanica. She enters alone, reappears at the entrance, seizes the
antennæ, and drags in the Acridian. While she was within I have pushed
the prey rather farther off, and have always obtained precisely the
same result as in the case of the huntress of crickets. In both
Sphegidæ there was the same persistence in plunging into their burrows
before dragging down their prey. We must recollect that S. flavipennis
does not always allow herself to be duped by my trick of withdrawing
the insect. There are elect tribes among them,—strong-minded
families,—who after a while find out the tricks of the experimenter,
and know how to baffle them. But these revolutionaries capable of
progress are the few; the rest, rigid conservatives in manners and
customs, are the majority, the crowd. I cannot say whether the hunters
of Acrididæ show more or less cunning in different districts.
But the most remarkable thing, and the one to which I want specially to
come, is this. After withdrawing the prey of S. albisecta several times
from the mouth of the hole, and obliging her to fetch it back, I
profited by her descent to the bottom of her den to seize and put the
prey where she could not find it. She came up, sought about for a long
time, and, when quite convinced that it was not to be found, went down
again. A few moments later she reappeared. Was it to return to the
chase? Not the least in the world; she began to close the hole, and
with no temporary cover, such as a small flat stone to mark the
orifice, but with a solid mass of carefully collected dust and gravel
swept into the passage until it was quite filled. S. albisecta only
makes a single cell at the bottom of her well, and puts in but one
victim. This one specimen had been caught and dragged to the edge of
the hole, and if it was not stored, that was my fault, not her’s. The
Sphex worked by an inflexible rule, and according to that rule she
completed the work by stopping up the hole even if empty. Here we have
an exact repetition of the useless labour of S. occitanica whose
dwelling I rifled.
Fourth experiment.—It is almost impossible to be certain whether S.
flavipennis, which makes several calls at the bottom of the same
passage, and heaps several grasshoppers in each, commits the same
irrational mistakes when accidentally disturbed. A cell may be closed,
although empty or imperfectly stored, and yet the Sphex will return to
the same burrow to make others. Yet I have reason to believe that this
Sphex is subject to the same aberrations as her two relations. The
facts on which I base my belief are these. When the work is completed,
there are generally four grasshoppers in each cell, but it is not
uncommon to find three or only two. Four appears to me the usual
number—first, because it is the most frequent, and secondly, when I
have brought up young larvæ dug up when eating their first grasshopper,
I found that all, even those only provided with two or three, easily
finished those offered, up to four, but after that they hardly touched
the fifth ration. If four grasshoppers are required by the larva to
develop fully, why is it sometimes only provided with three or even
only two? Why this immense difference in the amount of food? It cannot
be from any difference in the joints served up, since all are
unmistakably of the same size, but must come from losing prey on the
road. In fact, one finds at the foot of the slopes whose upper parts
are occupied by Sphegidæ, grasshoppers killed, and then lost down the
incline, when, for some reason or other, the Sphex has momentarily left
them. These grasshoppers become the prey of ants and flies, and the
Sphex who finds them takes good care not to pick them up, as they would
take enemies into the burrow.
These facts seem to demonstrate that if S. flavipennis can compute
exactly how many victims to catch, she cannot attain to counting how
many reach their destination, as if the creature had no other guide as
to number than an irresistible impulse leading her to seek game a fixed
number of times. When this number of journeys has been made,—when the
Sphex has done all that is possible to store the captured prey,—her
work is done, and the cell is closed, whether completely provisioned or
not. Nature has endowed her with only those faculties called for under
ordinary circumstances by the interests of the larva, and these blind
faculties, unmodified by experience, being sufficient for the
preservation of the race, the animal cannot go farther.
I end then as I began: instinct knows everything in the unchanging
paths laid out for it; beyond them it is entirely ignorant. The sublime
inspirations of science, the astonishing inconsistencies of stupidity,
are both its portion, according as the creature acts under normal
conditions or under accidental ones.
XIII
AN ASCENT OF MONT VENTOUX
By its isolation, which leaves it freely exposed on every side to the
influence of atmospheric agencies, and from the height which makes it
the culminating point of France on this side of the frontiers of Alps
or Pyrenees, the bare Provençal mountain, Mont Ventoux, lends itself
remarkably to studies of plant species according to climate. At the
base flourish the tender olive and that crowd of small semi-woody
plants whose aromatic scent requires the sun of southern regions. On
the summit, where snow lies at least half the year, the ground is
covered with a northern flora, partly borrowed from the arctic regions.
Half a day’s journey in a vertical line brings before one’s eyes a
succession of the chief vegetable types met with in the same meridian
in long travels from south to north. When you start your feet crush the
perfumed thyme which forms a continuous carpet on the lower slopes;
some hours later they tread the dusky cushions of Saxifraga
oppositifolia, the first plant seen by a botanist who lands in July on
the shores of Spitzbergen. In the hedges below you had gathered the
scarlet blossoms of the pomegranate, which loves an African sky; up
above you find a hairy little poppy sheltering its stalks under a
covering of small stony fragments, and which opens its large yellow
corolla in the icy solitudes of Greenland and the North Cape, just as
it does on the highest slopes of Ventoux.
Such contrasts have always a new charm, and twenty-five ascents have
not yet brought me satiety. In August 1865 I undertook the
twenty-third. We were eight persons—three who came to botanise, five
attracted by a mountain expedition and the panorama of the heights.
None of those who were not botanists have ever again desired to
accompany me. In truth, the expedition is a rough one, and a sunrise
does not atone for the fatigue endured.
The best comparison for Mont Ventoux is that of a heap of stones broken
up to mend the roads. Raise this heap steeply up to two kilometres, and
give it a base in proportion, cast on the white of its limestone the
blackness of forests, and you get a clear idea of the general look of
the mountain. This heap of débris—sometimes little chips, sometimes
huge masses of rock—rises from the plain without preliminary slopes or
successive terraces to render ascent less trying by dividing it into
stages. The climb begins at once, by rocky paths, the best of which is
not as good as a road newly laid with stones, and rising ever rougher
and rougher to the summit, a height of 1912 metres. Fresh lawns, glad
rivulets, the ample shade of ancient trees—all that gives such a charm
to other mountains is here unknown, replaced by an endless bed of
calcareous rock broken into scales which yield under one’s feet with a
sharp, almost metallic sound. For cascades Mont Ventoux has streams of
stones, the sound of which, as they roll downward, replaces the murmur
of falling water.
We have reached Bedoin, at the foot of the mountain, arrangements with
the guide are completed, the hour of departure is settled, provisions
chosen and prepared. Let us try to sleep, for the next night will be a
sleepless one on the mountain. But to fall asleep was the difficulty; I
have never achieved it, and this is the chief cause of fatigue. I would
therefore advise any readers who propose to botanise on Mont Ventoux
not to arrive at Bedoin on a Sunday night. They will thus avoid the
bustle of a country inn, endless conversations at the top of the
speakers’ voices, the echo of billiard balls, the clinking of glasses,
with the drinking-songs, the nocturnal couplets of passers-by, the
bellowing of wind instruments at the neighbouring ball, and the other
tribulations inseparable from this holy day of rest and enjoyment.
Could one sleep there on other nights? I hope so, but cannot answer for
it. I never closed an eye. All night long the rusty spit, labouring for
our benefit, groaned under my bedroom; only a thin plank separated me
from that diabolical machine.
But already the sky was growing light; a donkey brayed under the
windows; the hour had come to rise, and we might as well not have gone
to bed at all. Provisions and baggage were loaded, our guide cried “Ja!
hi!” and we set off. At the head of the caravan walked Triboulet with
his mule and ass—Triboulet, the eldest and chief of the Ventoux guides.
My botanical colleagues scrutinised the vegetation on either side of
the road by the early light; the others talked. I followed the party, a
barometer slung over my shoulder, a note-book and pencil in my hand.
My barometer, intended for ascertaining the height of the chief
botanical stations, soon became a pretext for attacks on the gourd of
rum. “Quick, the barometer!” some one would exclaim every time that a
remarkable plant was pointed out, and we would all press round the
gourd, the barometer coming later. The freshness of the morning and our
walk made us appreciate these references to the barometer so much that
the level of the tonic liquid lowered even faster than that of the
column of mercury. For the future it would be wise to consult
Torricelli’s tube less frequently.
The temperature grew colder; olive and ilex disappear, next vine and
almond, then mulberry, walnut, and white oak; box grows plentiful. We
enter on a monotonous region, stretching from the limit of cultivation
to the lower edge of the beech woods, where the chief plant is Satureia
montana, known here as pébré d’asé,—asses’ pepper,—from the acrid smell
of its small leaves, impregnated with essential oil. Certain little
cheeses which form part of our provisions are powdered with this strong
spice, and more than one of us casts a famishing glance at the
provision bags carried by the mule. Our rough, early expedition had
brought an appetite, nay, better still, a devouring hunger, “latrantem
stomachum,” as Horace wrote. I showed my companions how to still this
hunger until we came to our next halt, pointing out a little sorrel
with arrow-shaped leaves, springing among the loose stones, and to set
an example I gathered a mouthful. There was a laugh at the notion. I
let them laugh, and soon saw one busier than another gathering the
precious sorrel.
While chewing the acid leaves we came to the beeches, first large
solitary bushes, sweeping the ground, then dwarf trees, close together,
then strong trunks, forming a thick dark forest whose soil is a chaos
of limestone blocks. Overloaded in winter by snow, beaten all the year
round by fierce gusts of the Mistral, many are branchless, twisted into
strange shapes, or even prostrate. An hour or more was passed in
traversing the wooded zone, which, seen from a distance, looked like a
black girdle on the sides of the mountain. Now again the beeches became
stunted and scattered; we had reached their upper limit, and, despite
the sorrel, all were right glad to come to the spot chosen for our halt
and breakfast.
We were at the fountain of La Grave, a slender thread of water caught,
as it issues from the ground, in a line of long troughs made of beech
trunks, where the mountain shepherds water their flocks. The
temperature of the spring was 7 degrees Cent.—a freshness inestimable
for us who came up from the sultry heat of the plain. The cloth was
spread over a charming carpet of Alpine plants, among which glittered
the thyme-leaved Paronychia, whose large thin bracts are like silver
scales. The provisions are taken out of their bags, the bottles out of
their bed of hay. On this side are the solid dishes, legs of mutton
stuffed with garlic, and piles of bread; there the insipid chickens,
good to amuse one’s grinders when serious hunger has been appeased. Not
far off, in a place of honour, are the Ventoux cheeses sprinkled with
asses’ pepper, and hard by Arles sausages, whose pink flesh is marbled
with squares of bacon and whole pepper. In this corner are green olives
still dripping with pickle, and black ones seasoned with oil. In
another are melons from Cavaillon, some white, some orange, to suit all
tastes, and there a pot of anchovies which make a man drink hard and be
tireless on the march, and finally the bottles, cooling in the icy
water of a trough. Is nothing forgotten? Yes, we have not mentioned the
crown of the feast, raw onions eaten with salt. Our two Parisians, for
there are two among us, my fellow botanists, are at first taken
somewhat aback by this decidedly bracing bill of fare. They will be the
first, a little later, to break forth in its praise. All is ready. Let
us to table! Then began one of those homeric meals which make an epoch
in one’s life. The first mouthfuls have a touch of frenzy. Slices of
leg of mutton and bread succeed one another with alarming rapidity.
Each of us, without communicating his apprehensions, casts an anxious
look on the provender, and says inwardly, “If we go on at this rate,
will there be enough for this evening and to-morrow?” However, the
craving abated: first we devoured silently, then we ate and talked;
fears for the next day abated too; we did justice to him who ordered
the bill of fare, and who, foreseeing our voracity, arranged to meet it
worthily. Now came the time to appreciate the provisions as
connoisseurs; one praises the olives, stabbing them singly with the
point of his knife; another lauds the anchovies as he cuts up the
little yellow-ochre fish on his bread; a third speaks enthusiastically
of the sausages; and one and all agree in praising the asses’-pepper
cheeses, no bigger than the palm of one’s hand. Pipes and cigars are
lighted, and we lie on our backs in the sun upon the grass.
After an hour’s rest it is, “Up! time presses; we must go on!” The
guide and luggage were to go westward, along the wood, where there is a
mule path. He will wait for us at Jas or Bâtiment, at the upper limit
of the beeches, some 1550 metres above the sea. The Jas is a large
stone, but capable of sheltering man and beast at night. We were to go
upward to the crest which we should follow so as to reach the highest
part more easily. After sunset we would go down to the Jas, where the
guide would have long arrived; such was the plan proposed and adopted.
We have reached the crest. Southward extend, as far as eye can see, the
comparatively easy slopes by which we ascended on the north. The scene
is savagely grand, the mountain sometimes perpendicular, sometimes
falling in frightfully steep terraces, little less than a precipice of
1500 metres. Throw a stone, and it never stops till, bound after bound,
it reaches the valley where one can see the bed of the Toulourenc wind
like a ribbon. While my companions moved masses of rock and sent them
rolling into the gulf that they might watch the terrible descent, I
discovered under a big stone an old acquaintance in the entomological
world—Ammophila hirsuta, which I had always found isolated on banks
along roads in the plain, while here, on the top of Mont Ventoux, were
several hundreds heaped under the same shelter. I was trying to find
the cause of this agglomeration, when the southern breeze, which had
already made us anxious in the course of the morning, suddenly brought
up a bevy of clouds melting into rain. Before we had noticed them a
thick rain-fog wrapped us round, and we could not see a couple of paces
before us. Most unluckily one of us, my excellent friend, Th. Delacour,
had wandered away looking for Euphorbia saxatilis, one of the botanical
curiosities of these heights. Making a speaking trumpet of our hands we
all shouted together. No one replied. Our voices were lost in the dense
fog and dull sound of the wind in the whirling mass of cloud. Well,
since the wanderer cannot hear us we must seek him. In the darkness of
the mist it was impossible to see one another two or three paces off,
and I alone of the seven knew the locality. In order to leave no one
behind, we took each other’s hands, I placing myself at the head of the
line. For some minutes we played a game of blindman’s buff, which led
to nothing. Doubtless, on seeing the clouds coming up, Delacour, well
used to Ventoux, had taken advantage of the last gleams of light to
hurry to the shelter of Jas. We also must hurry there, for already the
rain was running down inside our clothes as well as outside, and our
thin white trousers clung like a second skin. A grave difficulty met
us: our turnings and goings and comings while we searched had reduced
me to the condition of one whose eyes have been bandaged, and has then
been made to pirouette on his heels. I had lost the points of the
compass, and no longer knew in the very least which was the southern
side. I questioned one and another; opinions were divided and very
uncertain. The conclusion was that not one of us could say which was
the north and which the south. Never—no, never have I realised the
value of the points of the compass as at that moment. All around was
the unknown of gray cloudland; below we could just make out the
beginning of a slope here or there, but which was the right one? We
must make up our minds to descend, trusting to good fortune. If by ill
luck we took the northern slope we risked breaking our necks over those
precipices the very look of which had so inspired us with fear. Perhaps
not one of us would survive. I went through some moments of acute
perplexity.
“Let us stay here,” said the majority, and wait till the rain stops.
“Bad advice,” said the others, and I was of the number; “bad advice.
The rain may last a long while, and drenched as we are, at the first
chill of night we shall freeze on the spot.” My worthy friend, Bernard
Verlot, come from the Jardin des Plantes at Paris on purpose to ascend
Mont Ventoux with me, showed an imperturbable calm, trusting to my
prudence to get out of the scrape. I drew him a little on one side so
as not to increase the panic of the others, and told him my terrible
apprehensions. We held a council of two, and tried to supply the place
of the magnetic needle by reasoning. “When the clouds came up,” said I,
“was it not from the south?” “Certainly from the south.” “And though
the wind was hardly perceptible, the rain slanted slightly from south
to north?” “Yes, I noticed that until I got bewildered. Is not that
something to guide us? Let us descend on the side whence the rain
comes.” “I had thought of that, but felt doubtful; the wind was too
light to have a clearly defined direction. It might be a revolving
current such as are produced on a mountain top surrounded by cloud.
Nothing assures me that the first direction has been continuous, and
that the current of air does not come from the north.” “And in that
case?” “Ah! there is the crux! I have an idea! If the wind has not
changed, we ought to be wettest on the left side, since the rain came
on that side till we lost our bearings. If it has changed we must be
pretty equally wet all round. We must feel and decide. Will that do?”
“It will.” “And if I am mistaken?” “You will not be mistaken.”
In two words the matter was explained to our friends. Each felt
himself, not outside, which would not have been sufficient, but under
his innermost garment, and it was with unspeakable relief that I heard
one and all announce the left side much wetter than the right. The wind
had not changed. Very good, let us turn toward the rainy quarter. The
chain was formed again, Verlot as rearguard, to leave no straggler
behind. Before starting, I said once more to my friend, “Shall we risk
it?” “Risk it; I follow you,” and we plunged into the awful unknown.
Twenty of those strides which one cannot moderate on a steep slope, and
all fear was over. Under our feet was not empty space but the
longed-for ground covered with stones which gave way and rolled down
behind us in streams. To one and all this rattle denoting terra firma
was heavenly music. In a few minutes we reached the upper fringe of
beeches. Here the gloom was yet deeper than on the mountain top; one
had to stoop to the ground to see where one was setting foot. How in
the midst of this darkness were we to find the Jas, buried in the depth
of the wood? Two plants which always follow man, Good King Henry
(Chenopodium Bonus Henricus) and the nettle, served me as a clue. I
swept my free hand through the air as I walked, and at each sting I
knew there was a nettle and an indication. Verlot, our rearguard, made
similar lunges, and supplied the want of sight by the burning stings.
Our companions showed no faith in this style of research. They talked
of continuing the wild descent and of returning if necessary to Bedoin.
More confident in the botanical instinct so keen in himself also,
Verlot joined with me in persisting in our search, reassuring the most
demoralised, and showing that it was possible by questioning plants
with our hands to reach our destination in the darkness. They yielded
to our reasoning, and shortly after, from one clump of nettles to
another, the party arrived at the Jas.
Delacour was there, as well as the guide with the baggage, sheltered in
good time from the rain. A blazing fire and change of garments soon
restored our usual cheerfulness. A block of snow, brought from the
neighbouring valley, was hung in a bag before the hearth. A bottle
caught the melted water. This would be our fountain for the evening
meal. The night was spent on a bed of beech leaves, well crushed by our
predecessors, and they were many. Who knows for how many years the
mattress had never been renewed? Now it was a hard-beaten mass. The
mission of those who could not sleep was to keep up the fire. Hands
were not wanting to stir it, for the smoke, with no other exit than a
large hole made by the partial falling in of the roof, filled the hut
with an atmosphere made to smoke herrings. To get a mouthful of
breathable air one must seek it with one’s nose nearly level with the
ground. There was coughing; there was strong language, and stirring of
the fire; but vain was every attempt to sleep. By 2 a.m. we were all on
foot to climb the highest cone and behold the sunrise. The rain was
over, the sky splendid, auguring a radiant day.
During the ascent some of us felt a kind of sea-sickness, caused partly
by fatigue and partly by the rarefaction of the air. The barometer sank
140 millimetres; the air we breathed had lost one-fifth of its density,
and was consequently one-fifth poorer in oxygen. By those in good
condition this slight modification would pass unnoticed, but, added to
the fatigue of the previous day and to want of sleep, it increased our
discomfort. We mounted slowly, our legs aching, our breathing
difficult. Every twenty steps or so one had to halt. At last the summit
was gained. We took refuge in the rustic chapel of St. Croix to take
breath and counteract the biting cold by a pull at the gourd, which
this time we emptied. Soon the sun rose. To the farthest limit of the
horizon Mont Ventoux projected its triangular shadow, tinted violet
from the effect of the diffracted rays. Southward and westward
stretched misty plains, where, when the sun rose higher, one would
distinguish the Rhône as a silver thread. On the north and east an
enormous cloud-bed spreads under our feet like a sea of cotton wool,
whence the dark tops of the lower mountains rise as if they were islets
of scoriæ, while others with their glaciers shine glorious on the side
where the Alps uplift their chain of mountains.
But botany calls, and we must tear ourselves from this magic spectacle.
August, the month when we made our ascent, is somewhat late; many
plants were out of blossom. Those who really want to be successful
should come up here in the first fortnight of July, and, above all,
should forestall the arrival of the herds and flocks on these heights.
Where a sheep has browsed one finds but poor remains. As yet spared by
the grazing flocks, the stony screes on the top of Mont Ventoux are in
July literally a bed of flowers. Memory calls up the lovely dew-bathed
tufts of Androsace villosa, with white flowers and rosy centres; Viola
cenisia, opening great blue corollas on the shattered heaps of
limestone; Valeriana saliunca, with perfumed blossoms, but roots that
smell like dung; Globularia cordifolia, forming close carpets of a
crude green, starred with little blue heads; Alpine forget-me-not, blue
as the sky above it; the iberis of Candolle, whose slender stalk bears
a dense head of tiny white flowers and creeps down among the loose
stones; Saxifraga oppositifolia and S. muscoides, both making dark
thick little cushions, the former with purple blossoms, the latter with
white, washed with yellow. When the sun is hotter one sees a splendid
butterfly flutter from one blossomed tuft to another, its white wings
marked by four patches of vivid rose-carmine encircled with black. It
is Parnassius apollo, the graceful dweller in Alpine solitudes, near
the eternal snows. Its caterpillar lives on saxifrages. With the Apollo
let us end this sketch of the joys which await the naturalist on the
top of Mont Ventoux and return to the Ammophila hirsuta, crouching in
great numbers under a sheltering stone, when the rain came up and
surrounded us.
XIV
THE EMIGRANTS
I have already told how on the top of Mont Ventoux, some 6000 feet
above the sea, I had one of those pieces of entomological good luck,
which would be fruitful indeed did they but occur often enough to allow
of continuous study. Unhappily mine is a unique observation, and I
despair of repeating it. Future observers must replace my probabilities
by certainties. I can only found conjectures on it.
Under the shelter of a large flat stone I discovered some hundreds of
Ammophila hirsuta, heaped in a mass almost as compact as a swarm of
bees. As soon as the stone was lifted all the small people began to
move about, but without any attempt to take wing. I moved whole
handfuls, but not one seemed inclined to leave the heap. Common
interests appeared to unite them indissolubly. Not one would go unless
all went. With all possible care I examined the flat stone which
sheltered them, as well as the soil and immediate neighbourhood, but
could discover no explanation of this strange assemblage. Finding
nothing better to do, I tried to count them, and then came the clouds
to end my observations and plunge us into that perplexing darkness I
have already described. At the first drops of rain I hastened to put
back the stone and replace the Ammophila people under shelter. I give
myself a good mark, as I hope the reader also will, for having taken
the precaution of not leaving the poor things, disturbed by my
curiosity, exposed to the downpour.
Ammophila hirsuta is not rare in the plain, but is always found singly
on the edge of a road or on sandy slopes, now digging a well, now
dragging a heavy prey. It is solitary, like Sphex occitanica, and I was
greatly surprised by finding such a number gathered under one stone at
the top of Mont Ventoux. Instead of my solitary acquaintance, here was
a great assembly. Let us try to educe the probable causes of this
agglomeration. By an exception very rare among mining Hymenoptera,
Ammophila hirsuta builds in the first days of spring. Toward the end of
March, if the season be mild, or at least in the first fortnight of
April, when the grasshoppers take their adult form, and painfully cast
off their first skin on their thresholds,—when Narcissus poeticus
expands its first flowers, and the bunting utters its long-drawn note
from the top of the poplars in the meadow,—Ammophila hirsuta sets to
work to hollow and provision a home for her larvæ, whereas other
species and the predatory Hymenoptera in general undertake this labour
only in autumn, during September and October. This very early
nidification, preceding by six months the date adopted by the immense
majority, at once suggests certain considerations. One asks if those
found burrowing so early in April are really insects of that year—i.e.
whether these spring workers completed their metamorphosis and came out
of their cocoons during the preceding three months. The general rule is
that the Fossor becomes a perfect insect, leaves its burrow, and
occupies itself with its larvæ all in one season. It is in June and
July that the greater part of the hunting Hymenoptera come from the
galleries where they lived as larvæ, and in August, September, and
October they follow their occupations as burrowers and hunters.
Does a similar law apply to Ammophila hirsuta? Does the same season
witness the final transformation and the labours of the insect? It is
very doubtful, for the Hymenoptera, occupied with mining at the end of
March, would have to complete their metamorphosis and break forth from
the cocoon in winter, or at latest in February. The severity of the
climate at that date forbids any such conclusion. It is not when the
bitter Mistral howls for a fortnight at a time and freezes the ground,
nor when snow-storms follow its icy breath, that the delicate
transformations of the nymph state can take place, and the perfect
insect venture to quit the shelter of its cocoon. It needs the soft
dampness of earth under a summer sun before it can leave its cell.
If I did but know the exact date at which Ammophila hirsuta leaves the
cocoon it would greatly help me; but, to my deep regret, I do not. My
notes, gathered day by day, show the confusion inseparable from
researches that are generally dealing with points that cannot be
foreseen, and are silent on this point, whose importance I fully
realise now that I want to arrange my materials in order to write these
lines. I find mention of the Ammophila of the sands coming out of the
egg on June 5, and A. argentata on the 20th; but I have nothing in my
archives regarding the hatching of A. hirsuta. It is a detail left
unnoticed through forgetfulness. The dates for the two other species
accord with the general law, the perfect insect appearing at the hot
time of year. By analogy I fix the same date for the coming forth of A.
hirsuta from the cocoon.
Whence, then, come those which one sees at work on their burrows at the
end of March and April? We must conclude that they were hatched in the
previous year and emerged from their cells at the usual time in June
and July, lived through the winter, and began to build as soon as
spring came. In a word, they are insects that hibernate. Experience
fully confirms this conclusion.
Do but search patiently in a vertical bank of earth or sand well
exposed to the sun, especially where generations of the various
honey-gathering Hymenoptera have followed one another year after year,
riddling the ground with a labyrinth of passages till it looks like a
huge sponge, you are nearly sure to see in the heart of winter A.
hirsuta either alone or in little parties of three or four, crouched in
some warm retreat, waiting inactive till summer shall come. This
cheering little meeting, amid the gloom and cold of winter, with the
graceful insect which at the first notes of the bunting and the cricket
enlivens the grassy paths, is one that I have been able to enjoy at
will. If the weather be calm and the sun has a little power, the chilly
insect comes out to bask on its threshold, luxuriating in the hottest
beams, or it will venture timidly outside and walk slowly over the
spongy bank, brushing its wings. So, too, does the little gray lizard,
when the sun begins to warm the old wall which is its home.
But vainly would one seek in winter, even in the most sheltered spots,
for a Cerceris, Sphex, Philanthus, Bembex, and other Hymenoptera with
carnivorous larvæ. All died after their autumn labours, and their race
is only represented by the larvæ benumbed down in their cells. Thus, by
a very rare exception, Ammophila hirsuta, hatched in the hot season,
passes the following winter in some warm refuge, and this is why it
appears so early in the year.
With these data let us try to explain the Ammophila swarm on the crest
of Mont Ventoux. What could these numerous Hymenoptera under their
sheltering stone have been about? Were they meaning to take up winter
quarters there and await under their flat stone, benumbed, the season
propitious to their labours? Everything points to the improbability of
this. It is not in August, at the time of the greatest heat, that an
animal is overcome with winter sleep. Want of their food—the honey
juice sucked from flowers—cannot be suggested. September showers will
soon come, and vegetation, suspended for a while by the heat of the dog
days, will assume new vigour and cover the fields with a flowery carpet
almost as varied as that of spring. This period—one of enjoyment for
most of the Hymenoptera—cannot possibly be one of torpor for A.
hirsuta. Again, can one suppose that the heights of Ventoux, swept by
the gusty Mistral, uprooting beech and pine,—summits where the bise
whirls about the snow for six months of the year,—crests wrapped for
the greater part of the year by cold clouds and mist,—can be adopted as
a winter refuge by such a sun-loving insect? One might as well make it
hibernate among the ice fields of the North Cape! No, it is not there
that A. hirsuta must pass the cold season. The group observed there
were making a temporary halt. At the first indication of rain, which,
though it escaped us, could not escape the insect so eminently
sensitive to the variations of the atmosphere, the wayfarers had taken
refuge under a stone, and were waiting for the rain to pass before they
resumed their flight. Whence came they? Where were they going?
In this same month of August, and especially in September, there come
to the warm olive region flocks of little migratory birds; descending
by stages from the lands where they have loved,—fresher, more wooded,
more peaceful lands than ours,—where they have brought up their broods.
They come almost to a day in an invariable order, as if guided by the
dates of an almanac known only to themselves. They sojourn for a while
in our plains, where abound the insects which are the chief food of
most of them; they visit every clod in our fields where the ploughshare
has turned up innumerable worms in the furrows, and feast on them, and
with this diet they speedily lay on fat,—a storehouse and reserve to
serve as nutrition against toils to come, and thus well provided for
the journey they go on southward, to reach winterless lands where
insects are always to be found, such as Spain and Southern Italy, the
isles of the Mediterranean and Africa. This is the season for the
pleasure of shooting and for succulent roasts of small birds.
The Calandrelle, or Crèou, as Provence calls it, is the first to
arrive. As soon as August has begun it may be seen exploring the stony
fields, seeking the seeds of the Setaria, an ill weed affecting
cultivated ground. At the least alarm it flies off, making a harsh
guttural sound sufficiently expressed by its Provençal name. It is soon
followed by the whinchat, which preys quietly on small weevils,
crickets, and ants in old fields of luzern. With the whinchat begins
the long line of small birds suitable for the spit. It is continued in
September by the most celebrated of them—the common wheat-ear,
glorified by all who are capable of appreciating its high qualities.
Never did the Beccafico of the Roman gourmet, immortalised in Martial’s
epigrams, rival the delicious, perfumed ball of fat the wheat-ear makes
when it has grown scandalously obese on an immoderate diet. It consumes
every kind of insect voraciously. My archives as a sportsman-naturalist
give a list of the contents of its gizzard. All the small people of the
fallows are in it,—larvæ and weevils of every kind, crickets,
chrysomelides, grasshoppers, cassidides, earwigs, ants, spiders,
hundred-legs, snails, wire-worms, and ever so many more. And as a
change from this spicy diet there are grapes, blackberries, and
cornel-berries. Such is the bill of fare sought incessantly by the
wheat-ear as it flutters from clod to clod, the white feathers of its
outspread tail giving it the look of a butterfly on the wing. Heaven
only knows to what amount of fat it can attain.
Only one other bird surpasses it in the art of fattening itself, and
that is its fellow emigrant,—another voracious devourer of insects,—the
bush pipit as it is absurdly styled by those who name birds, while the
dullest of our shepherds never hesitate to call it Le Grasset, i.e. the
fattest of the fat. The name is sufficient to point out its leading
characteristic. Never another bird attains such a degree of obesity. A
moment arrives when, loaded all over with fat, it becomes like a small
pat of butter. The unfortunate bird can hardly flutter from one
mulberry tree to another, panting in the thick foliage, half choked
with melting fat, a victim to his love of weevil.
October brings the slender gray wagtail, pied ash colour and white,
with a large black velvet gorget. The charming bird, running and
wagging its tail, follows the ploughman almost under the horses’ feet,
picking up insects in the newly turned furrow. About the same time
comes the lark,—first in little companies thrown out as scouts, then in
countless bands which take possession of cornfield and fallow, where
abounds their usual food, the seeds of the Setaria. Then on the plain,
amid the sparkle of dewdrops and frost crystals suspended to each blade
of grass, a mirror shoots intermittent flashes under the morning sun.
Then the little owl, driven from shelter by the sportsman, makes its
short flight, alights, stands upright with sudden starts and rolling of
alarmed eyes, and the lark comes with a dipping flight, anxious for a
close inspection of the bright thing or the odd bird. There it is, some
fifteen paces away—its feet hanging, its wings outspread like a
saint-esprit. The moment has come; aim and fire. I hope that my readers
may experience the emotions of this delightful sport.
With the lark, and often in the same flocks, comes the titlark—the
sisi—another word giving the bird’s little call. None rushes more
vehemently upon the owl, round and round which it circles and hovers
incessantly. This may suffice as a review of the birds which visit us.
Most of them make it only a halting-place, staying for a few weeks,
attracted by the abundance of food, especially of insects; then,
strengthened and plump, off they go. A few take up winter quarters in
our plains, where snow is very rare, and there are countless little
seeds to be picked up even in the heart of the cold season. The lark
which searches wheat fields and fallows is one; another is the titlark,
which prefers fields of luzern and meadows.
The skylark, so common in almost every part of France, does not nest in
the plains of Vaucluse, where it is replaced by the crested lark—friend
of the highway and of the road-mender. But it is not necessary to go
far north to find the favourite places for its broods; the next
department, the Drôme, is rich in its nests. Very probably, therefore,
among the flocks of larks which take possession of our plains for all
autumn and winter many come from no farther than the Drôme. They need
only migrate into the next department to find plains that know not
snow, and a certainty of little seeds.
A like migration to a short distance seems to me to have caused the
assemblage of Ammophila on the top of Mont Ventoux. I have proved that
this insect spends the winter in the perfect state, sheltering
somewhere and awaiting April to build its nest. Like the lark it must
take precautions against the cold season; though capable of fasting
till flowers return, the chilly thing must find protection against the
deadly attacks of the cold. It must flee snowy districts, where the
soil is deeply frozen, and, gathering in troops like migrant birds,
cross hill and dale to seek a home in old walls and banks warmed by a
southern sun. When the cold is gone, all or part of the band will
return whence they came. This would explain the assemblage on Mont
Ventoux. It was a migrant tribe, which, on its way from the cold land
of the Drôme to descend into the warm plains of the olive, had to cross
the deep, wide valley of the Toulourenc, and, surprised by the rain,
halted on the mountain top. Apparently A. hirsuta has to migrate to
escape winter cold. When the small migratory birds set out in flocks,
it too must journey from a cold district to a neighbouring one which is
warmer. Some valleys crossed, some mountains overpassed, and it finds
the climate sought.
I have two other instances of extraordinary insect gatherings at great
heights. I have seen the chapel on Mont Ventoux covered with
seven-spotted ladybirds, as they are popularly called. These insects
clung to the stone of walls and pavement so close together that the
rude building looked, at a few paces off, like an object made of coral
beads. I should not dare to say how many myriads were assembled there.
Certainly it was not food which had attracted these eaters of Aphidæ to
the top of Mont Ventoux, some 6000 feet high. Vegetation is too
scanty—never Aphis ventured up there.
Another time, in June, on the tableland of St. Amand, at a height of
734 mètres, I saw a similar gathering, only less numerous. At the most
projecting part of the tableland, on the edge of an escarpment of
perpendicular rocks, rises a cross with a pedestal of hewn stone. On
every side of this pedestal, and on the rocks serving as its base, the
very same beetle, the seven-spotted ladybird of Mont Ventoux, was
gathered in legions. They were mostly quite still, but wherever the
sunbeams struck there was a continuous exchange of place between the
newcomers, who wanted to find room, and those resting, who took wing
only to return after a short flight. Neither here any more than on the
top of Mont Ventoux was there anything to explain the cause of these
strange assemblages on arid spots without Aphidæ and noways attractive
to Coccinellidæ,—nothing which could suggest the secret of these
populous gatherings upon masonry standing at so great an elevation.
Have we here two examples of insect migration? Can there be a general
meeting such as swallows hold before the day of their common departure?
Were these rendezvous whence the cloud of ladybirds were to seek some
district richer in food? It may be so, but it is very extraordinary.
The ladybird has never been talked of for her love of travel. She seems
a home-loving creature enough when we see her slaying the green-fly on
rose trees, and black-fly on beans, and yet with her short wings she
mounts to the top of Ventoux and holds a general assembly where the
swallow herself only ascends in her wildest flights. Why these
gatherings at such heights? Why this liking for blocks of masonry?
XV
THE AMMOPHILA
A slender waist, a slim shape, an abdomen much compressed at the upper
part, and seemingly attached to the body by a mere thread, a black robe
with a red scarf on its under parts,—such is the description of these
Fossors; like Sphegidæ in form and colouring, but very different in
habits. The Sphegidæ hunt Orthoptera, crickets, ephippigers, and
grasshoppers, while the Ammophila chases caterpillars. This difference
of prey at once suggests new methods in the murderous tactics of
instinct.
Did not the name sound pleasant to the ear, I should be inclined to
quarrel with Ammophila, which means sand-lover, as being too exclusive
and often erroneous. The true lovers of sand—dry, powdery, and slippery
sand—are the Bembex, which prey on flies: but the caterpillar-hunters,
whose history I am about to tell, have no liking for pure, loose sand,
and even avoid it as being too subject to landslips which may be caused
by a mere trifle. Their vertical pits, which must remain open until the
cell is stored with food and an egg, require more solid materials if
they are not to be blocked prematurely. What they want is a light soil,
easy to mine, where the sandy element is cemented by a little clay and
lime. The edges of paths—slopes of thin grass exposed to the sun,—such
are the places they favour. In spring, from the first days of April,
one sees Ammophila hirsuta there; in September and October there are A.
sabulosa, A. argentata, and A. holosericea. I will make an abstract of
the notes furnished by these four species.
For all four the burrow is a vertical shaft, a kind of well, with at
most the dimension of a large goose quill, and about two inches deep.
At the bottom is a single cell, formed by a simple widening of the
shaft. To sum up, it is a poor dwelling, obtained at small expense, at
one sitting, affording no protection if the larva had not four wrappers
in its cocoon, like the Sphex. The Ammophila excavates alone,
deliberately, with no joyous ardour. As usual, the anterior tarsi do
duty as rakes and the mandibles as mining tools. If some grain of sand
offer too much resistance, you may hear rising from the bottom of the
well a kind of shrill grinding sound, produced by the vibration of the
wings and entire body as if to express the insect’s struggles.
Frequently the Hymenopteron comes up with a load of refuse in its jaws,
some bit of gravel which it drops as it flies some little way off, in
order not to block up the place. Some appear to merit special attention
by their form and size,—at least the Ammophila does not treat them like
the rest, for instead of carrying them away on the wing, she goes on
foot and drops them near the shaft. They are choice material—blocks
ready prepared to stop up the dwelling by and by.
This outside work is done with a self-contained air and great
diligence. High on its legs, its abdomen outstretched at the end of its
long petiole, it turns round and moves its whole body at once with the
geometrical stiffness of a line revolving on itself. If it has to throw
away to a distance the rubbish it decides to be only encumbrances, it
does this with little silent flights, often backwards, as if, having
come out of the shaft tail first, it thought to save time by not
turning round. Species with long-stalked bodies, like A. sabulosa and
A. argentata, are those that chiefly display this automaton-like
rigidity. Their abdomen, enlarged to a pear-shape at the end of a
thread, is very troublesome to manage; a sudden movement might injure
the fine stalk, and the insect has to walk with a kind of geometrical
precision, and if it flies, it goes backward to avoid tacking too
often. On the other hand, A. hirsuta, which has an abdomen with a short
petiole, works at its burrow with swift easy movements such as one
admires in most of the miners. It can move more freely, not being
embarrassed by its abdomen.
The dwelling is hollowed out. Later on, when the sun has passed from
the spot where the hole is bored, the Ammophila is sure to visit the
little heap of stones set aside during her burrowing, intent to choose
some bit which suits her. If she can find nothing that will do she
explores round about, and soon discovers what she wants—namely, a small
flat stone rather larger than the mouth of her well. She carries it off
in her mandibles, and for the time being closes the shaft with it. Next
day, when it is hot again, and when the sun bathes the slopes and
favours the chase, she will know perfectly well how to find her home
again, secured by the massive door, and she will return with a
paralysed caterpillar, seized by the nape of its neck and dragged
between its captor’s feet; she will lift the stone, which is just like
all the others near, and the secret of which is known only to her, will
carry down the prey, lay an egg, and then stop the burrow once for all
by sweeping into the shaft all the rubbish kept near at hand.
Several times I have seen this temporary closing of the hole by A.
sabulosa and A. argentata when the sun grew low and the late hour
obliged them to wait until the next day to go out hunting. When they
had put the seals on their dwellings I too waited for the morrow to
continue my observations, but first I made sure of the spot by taking
my bearings and sticking in some bits of wood in order to rediscover
the well when closed, and always, unless I came too early, if I let the
Hymenopteron profit by full sunshine, I found the burrow stored and
closed for good and all.
The fidelity of memory shown here is striking. The insect, belated at
its work, puts off completing it until the morrow. It passes neither
evening nor night in the new-made abode, but departs after marking the
entrance with a small stone. The spot is no more familiar to it than
any other, for like Sphex occitanica the Ammophila lodges her family
here and there as she may chance to wander. The creature came here by
chance, like the soil, and dug the burrow, and now departs. Whither?
Who knows? Perhaps to the flowers near, to lick up by the last gleam of
day a drop of sugary liquid at the bottom of their cups, just as a
miner after labouring in his dark gallery seeks the consolation of his
bottle when evening comes. The Ammophila may be enticed farther and
farther by the inviting blossoms. Evening, night, and morning pass, and
now she must return to her burrow and complete her task,—return after
all her windings and wanderings in the chase that morning, and the
flight from flower to flower, and the libations of the previous
evening. That a wasp should return to the nest and a bee to the hive
does not surprise me; these are permanent abodes, and the ways back are
known by long practice, but the Ammophila, who has to return after so
long an absence, has no aid from acquaintance with the locality. Her
shaft is in a place which she visited yesterday, perhaps for the first
time, and must find again to-day when quite beyond her bearings, and,
moreover, when she is encumbered by heavy prey. Yet this exploit of
topographical memory is accomplished, and sometimes with a precision
which left me amazed. The insect made straight for the burrow as if
long used to every path in the neighbourhood; but at other times there
would be long visitation and repeated searches.
If the difficulty become serious, the prey, which is an embarrassing
load in a hurried exploration, is laid in some obvious place, on a tuft
of thyme or grass, where it can be easily seen when wanted. Freed from
this burden the Ammophila resumes an active search. As she hunted about
I have traced with a pencil the track made by her. The result was a
labyrinth of lines, with curves and sudden angles, now returning inward
and now branching outward—knots and meshes and repeated intersections—a
maze, showing how perplexed and astray was the insect.
The shaft found and the stone lifted, she must return to the prey, not
without some uncertainty when comings and goings have been too many.
Although it was left in a place obvious enough, the Ammophila often
seems at a loss when the time comes to drag it home; at least, if there
be a very long search for the burrow, one sees her suddenly stop and go
back to the caterpillar, feel it and give it a little bite, as if to
make sure that it is her very own game and property, hurrying back to
seek for the burrow, but returning a second time if needful, or even a
third, to visit her prey. I incline to believe that these repeated
visits are made to refresh her memory as to where she left it.
This is what happens in very complex cases, but generally the insect
returns without difficulty to the spot whither its vagrant life may
have led it. For guide it has that local memory whose marvellous feats
I shall later have occasion to relate. As for me, in order to return
next day to the burrow hidden under the little flat stone, I dared not
trust to my memory, but had to use notes, sketches, to take my
bearings, and stick in pegs—in short, a whole array of geometry.
The temporary closing of the burrow with a flat stone as practised by
A. sabulosa and A. holosericea appears unknown to the two other
species; at least I never saw their homes protected by a covering. This
is natural in the case of A. hirsuta, for, I believe, this species
hunts the prey first and then burrows near the place of capture. As
provender can therefore be at once stored it is useless to take any
trouble about a cover. As for A. holosericea, I suspect there is
another reason for not using any temporary door. While the two others
only put one caterpillar in each cell, she puts as many as five, but
much smaller ones. Just as we ourselves neglect to shut a door where
some one is constantly passing to and fro, perhaps this Ammophila
neglects to place a stone on a well which she will go down at least
five times within a short space of time. All four lay up caterpillars
of moths for their larvæ. A. holosericea chooses, though not
exclusively, those slender, long caterpillars known as Loopers. They
move as a compass might by opening and closing alternately, whence
their expressive French name of Measurers. The same burrow includes
provisions of varied colours—a proof that this Ammophila hunts all
kinds of Loopers so long as they are small, for she herself is but
feeble and the larva cannot eat much, in spite of the five heads of
game set before it. If Loopers fail, the Hymenopteron falls back on
other caterpillars equally small. Rolled up from the effect of the
sting which paralysed them, all five are heaped in the cell; the top
one bears the egg for which the provender is destined.
The three other Ammophilæ give but one caterpillar to each cell.
True—size makes up for this; the game selected is corpulent, plump,
amply sufficing the grub’s appetite. For instance, I have taken out of
the mandibles of A. holosericea a caterpillar fifteen times her own
weight—fifteen times!—an enormous sum if you consider what an
expenditure of strength it implies to drag such game by the nape of its
neck over the endless difficulties of the ground. No other Hymenopteron
tried in the scales with its prey has shown me a like disproportion
between spoiler and capture. The almost endless variety of colouring in
the provender exhumed from the burrows or recognised in the grasp of
the various species also proves that the three have no preference, but
seize the first caterpillar met with, provided it be neither too large
nor too small, and belongs to the moths. The commonest prey are those
gray caterpillars which infest the plant at the junction of a root and
stem just below the soil.
That which governs the whole history of the Ammophila, and more
especially attracted my attention, was the way in which the insect
masters its prey and plunges it into the harmless state required for
the safety of the larva. The prey, a caterpillar, is very differently
organised from the victims which we have hitherto seen
sacrificed—Buprestids, Weevils, Grasshoppers, and Ephippigers. It is
composed of a series of segments or rings set end to end, the three
first bearing the true feet which will be those of the future
butterfly; others bear membranous or false feet special to the
caterpillar and not represented in the butterfly; others again are
without limbs. Each ring has its ganglion, the source of feeling and
movement, so that the nerve system comprehends twelve distinct centres
well separated from each other, without counting the œsophageal
ganglion placed under the skull, and which may be compared to the
brain.
We are here a long way from the nerve centralisation of the Weevil and
Buprestis that lends itself so readily to general paralysis by a single
stab; very far too from the thoracic ganglia which the Sphex wounds
successively to put a stop to the movements of her crickets. Instead of
a single centralised point—instead of three nerve centres—the
caterpillar has twelve, separated one from another by the length of a
segment and arranged in a ventral chain along the median line of the
body. Moreover, as is the rule among lower animals, where the same
organ is very often repeated and loses power by diffusion, these
various nervous centres are largely independent of each other, each
animating its own segment, and are but slightly disturbed by disorder
in neighbouring ones. Let one segment lose motion and feeling, yet
those uninjured will none the less remain long capable of both. These
facts suffice to show the high interest attaching to the murderous
proceedings of the Hymenopteron with regard to its prey.
But if the interest be great, the difficulty of observation is not
small. The solitary habits of the Ammophila,—their being scattered
singly over wide spaces, and their being almost always met with by mere
chance,—almost forbid, as in the case of Sphex occitanica, any
experiment being prepared beforehand. Long must a chance be watched for
and awaited with unalterable patience, and one must know how instantly
to profit by it when at last it comes just when least expected. I have
waited for such a chance for years and years, and then, all at once, I
got the opportunity with a facility for observation and clearness of
detail which made up for the long waiting.
At the beginning of my observations I succeeded twice in watching the
murder of the caterpillar, and saw, as far as the rapidity of the
operation allowed, that the sting of the Hymenopteron struck once for
all at the fifth or sixth segment of the victim. To confirm this I
bethought myself of making sure which ring was stabbed by examining
caterpillars which I had not seen sacrificed, but had carried off from
their captors while they were being dragged to the burrow; but it was
vain to use a microscope,—no microscope can show any trace of such a
wound. This was the plan adopted. The caterpillar being quite still, I
tried each segment with the point of a fine needle, measuring the
amount of sensibility by the greater or less pain given. Should the
needle entirely transpierce the fifth segment or the sixth, there is no
movement. But prick even slightly one in front or behind, the
caterpillar struggles with a violence proportioned to the distance from
the poisoned segment. Especially does the least touch on the hinder
ones produce frantic contorsions. So there was but one stab, and it was
given in the fifth or sixth segment.
What special reason is there that one or other of these two should be
the spot chosen by the assassin? None in their organisation, but their
position is another thing. Omitting the Loopers of Ammophila
holosericea, I find that the prey of the others has the following
organisation, counting the head as the first segment:—Three pairs of
true feet on rings two, three, and four; four pairs of membranous feet
on rings seven, eight, nine, and ten, and a last similar pair set on
the thirteenth and final ring; in all eight pairs of feet, the seven
first making two marked groups—one of three, the other of four pairs.
These two groups are divided by two segments without feet, which are
the fifth and sixth.
Now, to deprive the caterpillar of means of escape, and to render it
motionless, will the Hymenopteron dart its sting into each of the eight
rings provided with feet? Especially will it do so when the prey is
small and weak? Certainly not: a single stab will suffice if given in a
central spot, whence the torpor produced by the venomous droplet can
spread gradually with as little delay as possible into the midst of
those segments which bear feet. There can be no doubt which to choose
for this single inoculation; it must be the fifth or sixth, which
separate the two groups of locomotive rings. The point indicated by
rational deduction is also the one adopted by instinct. Finally, let us
add that the egg of the Ammophila is invariably laid on the paralysed
ring. There, and there alone, can the young larva bite without inducing
dangerous contorsions; where a needle prick has no effect, the bite of
a grub will have none either, and the prey will remain immovable until
the nursling has gained strength and can bite farther on without
danger.
With further researches doubts assailed me, not as to my deductions,
but as to how widely I might extend them. That many feeble Loopers and
other small caterpillars are disabled by a single stab, especially when
struck at so favourable a point as the one just named, is very probable
in itself, and, moreover, is shown both by direct observation and by
experiments on their sensibility with the point of a needle. But
Ammophila sabulosa and hirsuta catch huge prey, whose weight, as
already said, is fifteen times that of the captor. Can such giant prey
be treated like a poor Looper? Can a single stab subdue the monster and
render it incapable of harm? If the fearsome gray worm strike the cell
walls with its strong body, will it not endanger the egg or the little
larva? One dares not imagine a tête-à-tête in the small cell at the
bottom of the burrow between the frail, newly-hatched creature and this
kind of dragon:—still able to coil and uncoil its lithe folds.
My suspicions were heightened by examination as to the sensitiveness of
the caterpillar. While the small game of Ammophila holosericea and
hirsuta struggle violently if pricked elsewhere than in the part
stabbed, the large caterpillars of A. sabulosa, and above all of A.
hirsuta, remain motionless, no matter which segment be stimulated. They
show no contortions or sudden twisting of the body, the steel point
only producing as a sign faint shudderings of the skin. As the safety
of a larva provided with such huge prey requires, motion and feeling
are almost quite destroyed. Before introducing it into the burrow, the
Hymenopteron turns it into a mass—inert indeed, yet not dead.
I have been able to watch the Ammophila use her instrument on the
robust caterpillar, and never did the infused science of instinct show
me anything more striking. With a friend—alas! soon after snatched from
me by death—I was returning from the tableland of Les Angles after
preparing snares to put the cleverness of Scarabæus sacer to the proof,
when we caught sight of an Ammophila hirsuta very busy at the foot of a
tuft of thyme. We instantly lay down very close by. Our presence noways
alarmed the insect, which alighted for a moment on my sleeve, decided
that since her visitors did not move they must be harmless, and
returned to her tuft of thyme. Well used to the ways of Ammophila, I
knew what this audacious tameness meant—she was occupied by some
serious affair. We would wait and see. The Ammophila scratched in the
ground round the collar of the plant, pulling up thin little grass
roots, and poked her head under the tiny clods which she raised up, ran
hurriedly, now here, now there, round the thyme, visiting every crack
which gave access under it; yet she was not digging a burrow, but
hunting something hidden underground, as was shown by manœuvres like
those of a dog trying to get a rabbit out of its hole. And presently,
disturbed by what was going on overhead and closely tracked by the
Ammophila, a big gray worm made up his mind to quit his abode and come
up to daylight. It is all over with him; the hunter is instantly on the
spot, gripping the nape of his neck and holding on in spite of his
contortions. Settled on the monster’s back the Ammophila bends her
abdomen, and methodically, deliberately—like a surgeon thoroughly
familiar with the anatomy of his subject—plunges a lancet into the
ventral surface of every segment, from the first to the last. Not one
ring is omitted; with or without feet each is stabbed in due order from
the front to the back.
This is what I saw with all the leisure and ease required for an
irreproachable observation. The Hymenopteron acts with a precision of
which science might be jealous; it knows what man but rarely knows; it
is acquainted with the complex nervous system of its victim, and keeps
repeated stabs for those with numerous ganglia. I said “It knows; is
acquainted”: what I ought to say is, “It acts as if it did.” What it
does is suggested to it; the creature obeys, impelled by instinct,
without reasoning on what it does. But whence comes this sublime
instinct? Can theories of atavism, of selection, of the struggle for
life, interpret it reasonably? For my friend and myself it was and is
one of the most eloquent revelations of the ineffable logic which rules
the world and guides the unconscious by the laws which it inspires.
Stirred to the heart by this flash of truth, both of us felt a tear of
emotion rise to our eyes.
XVI
THE BEMBEX
Not far from Avignon, on the right bank of the Rhône opposite the mouth
of the Durance, is one of my favourite points for the observations
about to be recorded. It is the Bois des Issarts. Let no one deceive
himself as to the value of the word “bois”—wood, which usually gives
the idea of a soil carpeted with fresh moss and the shade of lofty
trees, through whose foliage filters a subdued light. Scorching plains,
where the cicada grinds out its song under pale olives, know nothing of
such delicious retreats full of shade and coolness.
The Bois des Issarts is composed of thin and scattered groups of ilex,
which hardly lessen the force of the sun’s rays. When I established
myself during the dog days in July and August, I used to settle myself
at some spot in the wood favourable for observations. I took refuge
under a great umbrella, which later lent me most unexpected aid of
another kind, very valuable too, as my story will show in good time. If
I had neglected to equip myself with this article, embarrassing enough
in a long walk, the only way to avoid sunstroke was to lie at full
length behind some heap of sand, and when my temporal arteries beat
intolerably, the last resource was to shelter my head at the mouth of a
rabbit hole. Such are the means of getting cool in the Bois des
Issarts.
The soil, unoccupied by any woody vegetation, is almost bare and
composed of a fine, arid, very light sand, heaped by the wind in little
hillocks where the stems and roots of the ilex hinder its blowing
about. The slope of such hillocks is generally very smooth, from the
extreme lightness of the material, which runs down into the least
depression, thus restoring the regularity of the surface. It is enough
to thrust a finger into the sand, and then to withdraw it in order
immediately to cause a downfall, which fills up the cavity and
re-establishes the former state of things without leaving any trace.
But at a certain depth, varying according to the more or less recent
date of the last rains, the sand retains a dampness which keeps it
stable, and lends a consistency allowing of slight excavations without
roof and walls falling in. A burning sun, a radiant blue sky, sand
slopes yielding without the least difficulty to the strokes of the
Hymenopteron’s rake, abundant game for the larvæ, a peaceful site
rarely troubled by the foot of the passer-by,—all unite here in this
paradise of the Bembex. Let us see the industrious insect at work.
If the reader will come under my umbrella, or profit by my rabbit
burrow, this is the sight which will meet him towards the end of July.
A Bembex (B. rostrata) arrives of a sudden and alights without
hesitation or investigation at a spot which, as far as I see, differs
in nothing from the rest of the sandy surface. With her front tarsi,
which, armed with stiff rows of hairs, suggest at once broom, brush,
and rake, she begins to dig a subterranean dwelling, standing on her
four hind feet, the two last slightly apart, while the front ones
alternately scratch and sweep the loose sand. The precision and
rapidity of the action could not be greater were the circular movement
of the tarsi worked by a spring. The sand, shot backward under the
creature, clears the arch of its hind legs, trickling like a liquid in
a continuous thread, describing a parabola and falling some eight
inches away. This dusty jet, constantly fed for five or ten minutes, is
enough to show with what dizzy rapidity the tools are used. I could
quote no second example of equal swiftness, which yet in no way
detracts from the elegance and free movements of the insect as it
advances and retires, now on one side, now on another, without allowing
the parabola of sand to stop.
The soil hollowed is of the lightest kind. As the Hymenopteron
excavates, the sand near falls and fills the cavity. In the landslip
are mingled little bits of wood, decayed leaf-stalks, and grains of
gravel larger than the rest. The Bembex picks these up in her
mandibles, and, moving backward, carries them to a distance, returning
to sweep again, but always lightly, without attempting to penetrate
into the earth. What is the object in this surface labour? It would be
impossible to learn from a first glance, but after spending many days
with my dear Hymenoptera, and grouping together the scattered results
of my observations, I think I divine the motive of these proceedings.
The nest is certainly there—underground, at the depth of a few inches:
in a little cell, dug in cool firm sand, is an egg, perhaps a larva,
which the mother feeds daily with flies, the invariable food of Bembex
larvæ. She must be able at any moment to penetrate to this nest,
carrying on the wing, between her feet, the nursling’s daily ration,
just as a bird of prey arrives at its eyrie carrying game for its brood
in its claw. But while the bird returns to a nest on some inaccessible
shelf of rock, without any difficulty beyond the weight of its prey,
the Bembex must undertake each time the hard work of mining, opening
afresh a gallery blocked and closed by ever-sliding sand in proportion
as she proceeds. The only stable part of this underground abode is the
spacious cell inhabited by the larva amid the remains of a fortnight’s
feast; the narrow vestibule entered by the mother to go down to the
cell, or come forth for the chase, gives way each time, at all events
at the upper end, built in dry sand, rendered even looser by her
constant goings and comings. Thus at each entrance or exit the
Hymenopteron must clear out a passage. The exit offers no difficulties,
even should the sand have the same consistency as when first stirred;
the insect’s movements are free; it is safe under cover, can take its
time and use tarsi and mandibles at its leisure. Going in is another
matter. The Bembex is embarrassed by her prey, pressed to her body by
her feet, so that there is no free use of the mining tools. What is
more serious is that impudent parasites—veritable bandits in ambush—are
crouching here and there about the burrow watching her difficult
entrance to hurriedly drop their egg on the game just as it disappears
into the gallery. If they succeed, the son of the house, the
Hymenopteron’s nursling, will perish, starved by greedy guests.
The Bembex seems aware of this danger, and arranges so as to enter
quickly, without serious obstacles, so that the sand blocking the door
should yield to a mere push from her head, aided by a rapid sweep of
the forelegs. To this end she, so to say, sifts the materials round her
abode. In leisure moments, when the sun shines and the larva has its
food, and does not need her care, the mother rakes before her door, and
puts on one side all the tiny bits of wood, of over-large gravel or
leaves, which might get on her path and bar the passage at the perilous
moment of return. The Bembex which we saw so hard at work was busy
sifting so as to make access to her abode easier; the materials of the
vestibule are examined, minutely sorted, and cleared of every
encumbrance. Who can tell whether the rapid labour and joyous activity
of the insect do not express in their own way her maternal satisfaction
and happiness in caring for the roof of the cell which has received the
precious trust of the egg? As the Bembex confines herself to exterior
household cares without seeking to penetrate the sand, everything must
be in order within, and there is nothing pressing to do. We may wait,
but for the time the insect will teach us nothing more. Let us
therefore examine the underground dwelling.
By lightly scratching the bank with the blade of a knife just where the
Bembex was oftenest seen, one soon discovers the entrance hall, which,
blocked as it is for part of its length, is none the less recognisable
by the special look of the materials moved about. This passage, a
finger’s-breadth in size, rectilinear or winding, longer or shorter,
according to the nature of the ground, measures eight to twelve inches.
It leads to a single chamber, hollowed in damp sand, with walls
undaubed with mortar, which might prevent landslips and lend polish to
the rough surface. Enough if the ceiling lasts while the larva is being
fed up. Future falling-in matters little when the larva is enclosed in
its stout cocoon—a kind of strong box, which we shall see in process of
construction. In workmanship the cell is as rustic as possible, being
merely a rude excavation with no well-determined form, low roofed, and
of a size which might hold two or three nests.
Within lies one head of game—one only—quite small and quite
insufficient for the voracious nursling for whom it is destined. It is
a golden green-fly, Lucilia Cæsar, a dweller in tainted meat, and is
quite motionless. Is it really dead or only paralysed? This will be
cleared up later. Just now let us observe the cylindrical egg upon its
side, white, slightly curved, and a couple of millimetres in length. It
is a Bembex egg. As we have foreseen from the mother’s behaviour, there
is no pressing household business; the egg is laid and a first ration
provided for the needs of the feeble larva, which ought to hatch in
twenty-four hours. For some time the Bembex need not re-enter her hole,
confining herself to keeping a good lookout in the neighbourhood, or
possibly making new burrows and laying there egg after egg, always in a
separate cell.
This peculiarity of beginning to lay in food by a single small piece of
game is not peculiar to Bembex rostrata; all the other species do the
same. Open any cell after the egg is laid, and you always find it glued
to the side of a Dipteron—all the food there is; moreover, this first
ration is invariably small, as if the mother had sought some specially
tender mouthful for her frail nursling. Another motive, the freshness
of the food, may also have guided her choice. Later we will look
further into the matter. This first ration—always a moderate one—varies
much, according to the frequency of such or such a kind of game in the
neighbourhood. It is sometimes a Lucilia Cæsar, sometimes a Stomoxys,
or some small Eristalis, or a delicate Bombylius clad in black velvet,
but the commonest is a Sphærophoria with a slender abdomen. This fact
(and it has no exception) of storing the nest with but a single
Dipteron,—a ration far too meagre for a larva with a voracious
appetite,—at once puts us on the track of the most remarkable habit of
the Bembecidæ. Hymenoptera whose larvæ live on prey heap into each cell
the whole number of victims needed by the grub, which is hatched and
lives alone,—an egg having been laid on one fly and the dwelling closed
up. The larva has before it its whole store of food. But the Bembex is
an exception to this rule. First a head of game is brought to the cell
and an egg dropped on it. Then the mother leaves the burrow, which
closes of its own accord; besides which she takes care to rake the
surface smooth, and hide the entrance from every eye but her own.
Two or three days pass: the egg hatches and the small larva eats up its
choice ration. Meanwhile, the mother remains near: one may see her
licking the sugary exudations on the flower-heads of Eryngium campestre
for nourishment, then settling with enjoyment on the burning sand,
whence she doubtless surveys the exterior of her dwelling, or she sifts
the sand at its entrance, then flies off and vanishes—perhaps to
excavate other cells to be stored in a like manner. But however
prolonged her absence, she does not forget the young larva so scantily
provided for; maternal instinct teaches her the hour when the grub has
finished its food and needs new sustenance. Then she comes back to the
nest whose invisible entrance she knows right well how to find, and
penetrates the hollow—this time laden with a larger prey. This
deposited, she goes out again, and awaits outside the time for a second
expedition. It soon comes, for the larva shows a devouring appetite.
Again the mother arrives with fresh provender.
During almost a fortnight, while the larva is growing, the meals follow
each other thus, one by one, as it needs them, and so much the nearer
together as the nursling grows stronger. Toward the end of the
fortnight the mother requires all her activity to supply the glutton’s
appetite as it crawls heavily amid the remains of its repasts—wings,
feet, and horny rings of abdomens. Each moment she returns with a new
capture or comes forth for the chase. In short, the Bembex brings up
her family from hand to mouth without storing provisions, like the bird
which brings a beakful of food to the little ones still in the nest.
Among the numerous proofs of this method of upbringing—one very
singular in a Hymenopteron which feeds its family on prey—I have
already mentioned the presence of the egg in a cell where but one
little fly is found as provender—always one—never more. Another proof
is the following one, which does not require any special moment for its
ascertainment.
Let us examine the burrow of a Hymenopteron, which provides beforehand
for its larvæ. If we choose the moment when the insect enters with a
captive, we shall find in the cell a certain number of victims already
stored, but never a larva—not even an egg, for this is only laid when
the provisions are complete. The egg deposited, the cell is closed, and
the mother returns no more. It is, therefore, only in burrows where the
mother’s visits are no longer needed that one can find larvæ amid the
larger or smaller heap of food. Visit, on the other hand, the dwelling
of a Bembex as she enters with the produce of her chase, and you are
sure to find a larva, larger or smaller, amid the remains of food
already devoured. The ration now brought is to continue a repast which
has been going on for several days, and is to be prolonged upon the
produce of future expeditions. If we can make this examination towards
the end of the larva’s upbringing,—an advantage which I have enjoyed at
pleasure,—we shall find upon a great heap of fragments a portly larva,
to which the mother is still bringing food. The Bembex only ceases to
do so and to leave the cell definitely when the larva, distended by a
wine-coloured pap, refuses to eat, and reclines, thoroughly stuffed, on
the remains of wings and feet of the game which it has devoured.
Each time that she penetrates into the burrow on returning from the
chase, the mother brings but a single fly. Were it possible by means of
the remains contained in a cell where the larva is full grown to count
the victims served up, one would at least know how often the
Hymenopteron visited its burrow after the egg is laid. Unfortunately,
these broken meats—munched and munched again in moments of scarcity—are
for the most part unrecognisable. But on opening a cell with a less
advanced nursling, one can examine the provisions, some of the prey
being yet whole or nearly so, and others, more numerous, being trunks
in sufficiently good preservation to be distinguishable. Incomplete as
it is, the enumeration thus obtained strikes one with surprise, as
showing what activity the Hymenopteron must display to satisfy the
demands of such a table. Here is one of the bills of fare observed.
At the end of July around the larva of Bembex Julia, which had almost
reached the third of its full size, I found the prey of which the
following is the list:—Six Echinomyia rubescens—two whole and four in
pieces; four Syrphus corollæ—two whole, two in fragments; three Gonia
atra—all intact, and one just brought by the mother, which had enabled
me to discover the burrow; two Pollenia ruficollis—one whole, one
attacked; a Bombylius reduced to pulp; two Echinomyia intermedia in
bits; and finally two Pollenia floralis, also in bits—total, twenty.
Certainly we have here a bill of fare as abundant as varied, but as the
larva had only attained to a third of its complete size, the entire
bill of fare might well amount to sixty articles.
The verification of this magnificent sum-total is easily obtained. I
myself will undertake the maternal cares of the Bembex, and feed the
larva until it is thoroughly satisfied. I place the cell in a little
cardboard box furnished with a layer of sand. On this bed is placed the
larva with due regard to its delicate epidermis. Around it, without
omitting a single fragment, I arrange the provender with which it was
supplied, and return home with the box still in my hand, to avoid any
shake which might turn it topsy-turvy and endanger my charge during a
journey of several miles. Any one who had seen me on the dusty road to
Nîmes, exhausted with fatigue and bearing religiously in my hand, as
the only result of my painful journey, a wretched grub, distending
itself with a heap of flies, would assuredly have smiled at my
simplicity. The journey was achieved without hindrance; when I got home
the larva was peacefully consuming its flies as if nothing had
happened. On the third day the provisions taken from the burrow were
finished, and the grub with its pointed mouth was searching in the heap
of remains without finding anything to its taste. The dry, horny,
juiceless pieces which it got hold of were rejected with disgust. The
moment had come for me to continue the food supply. The first Diptera
within reach must content my prisoner; I slew them by squeezing them
between my fingers, but did not crush them. Three Eristalis tenax
composed the first ration, together with a Sarcophaga. In twenty-four
hours all were devoured. The next day I provided two Eristalis and four
house-flies. This sufficed for that day, but nothing was left over. I
went on thus for a week, giving the grub each morning a larger ration.
On the ninth day it refused to eat and began to spin its cocoon. The
bill of fare for the week’s high feeding amounted to sixty-two items,
chiefly Eristalis and house-flies, which, added to the twenty items
found entire or in fragments in the cell, formed a total of eighty-two.
Possibly I may not have brought up my larva with the wholesome
frugality which the mother would have shown; there may have been some
waste in the daily rations, provided all at once and left entirely to
the discretion of the grub. I fancied that in some particulars things
did not go on exactly as in the cell, for my notes have such details
as: “In the alluvial sands of the Durance I discovered a burrow into
which Bembex oculata had taken a Sarcophaga agricola. At the bottom of
the gallery was a larva, numerous fragments, and some Diptera
entire—namely, four Sphærophoria scripta, one Onesia viarum, and two
Sarcophaga agricola, counting that which the Bembex had brought under
my very eyes.” Now it must be remarked that one half of this game, the
Sphærophoria, was quite at the bottom of the cell—under the very jaws
of the larva, while the other half was still in the gallery—on the
threshold of the cell—consequently out of the grub’s reach, as it could
not leave its place. It would seem that when game abounds, the mother
disposes provisionally of her captures on the threshold of the cell,
and forms a reserve on which she draws as need arises, especially on
rainy days, when all labour is at a standstill. This economy in
distributing food would prevent the waste unavoidable with my larva
perhaps too sumptuously treated. I subtract then from the sum obtained,
and reduce it to sixty pieces of medium size, between that of the
house-fly and Eristalis tenax. This would be about the number of
Diptera given by the mother to the larva when the prey is middle-sized,
as is the case with all the Bembecids of my district except B. rostrata
and B. bidentata, which especially favour the gadfly. For these the
number of slain would be from one to two dozen, according to the size
of the Dipteron, which varies greatly in the gadfly species.
In order not to return to the kind of provisions, I give a list of the
Diptera observed in the burrows of the six kinds of Bembex, which are
the subject of this essay.
(1) B. olivacea, Rossi. Once only have I seen this species, at
Cavaillon, preying on Lucilia Cæsar. The five next are common round
Avignon.
(2) B. oculata, Jur. The Dipteron upon which the egg is laid is
generally a Sphærophoria, especially S. scripta; sometimes it is a
Geron gibbosus. Further provender consisted in Stomoxys calcitrans,
Pollenia ruficollis, P. rudis, Pipiza nigripes, Syrphus corollæ, Onesia
viarum, Calliphora vomitoria, Echinomyia intermedia, Sarcophaga
agricola, Musca domestica. The usual food was Stomoxys calcitrans, of
which I have found fifty or sixty in a single burrow.
(3) Bembex tarsata, Lat. It, too, lays its egg on Sphærophoria scripta;
but it also hunts Anthrax flava, Bombylius nitidulus, Eristalis æneus,
E. sepulchralis, Merodon spinipes, Syrphus corollæ, Helophilus
trivittatus, Zodion notatum. Its favourite prey consists in Bombylius
and Anthrax.
(4) Bembex Julii (a new species). The egg hatches either on a
Sphærophoria or a Pollenia floralis, and the provender is a mixture of
Syrphus corollæ, Echinomyia rubescens, Gonia atra, Pollenia floralis,
P. ruficollis, Clytia pellucens, Lucilia Cæsar, Dexia rustica,
Bombylius.
(5) Bembex rostrata. This is above all a captor of gadflies. It lays
its egg on a Syrphus corollæ, or a Lucilia Cæsar, but then only brings
to the larva large game belonging to the various kinds of Tabanus.
(6) Bembex bidentata. Another ardent hunter of gadflies. I have never
seen it with other game, and do not know on what the egg is laid.
This variety of provisions shows that the Bembecids have no exclusive
tastes, and attack one and all of the species of Diptera which are
offered by the chances of the chase. They seem, however, to have some
favourites—one species especially choosing Bombylius, another Stomoxys,
and a third and fourth, Gadflies.
XVII
HUNTING DIPTERA
After this bill of fare for Bembecids in the larva state, we must seek
the motive which causes these Hymenoptera to adopt a mode of storage
exceptional among Fossors. Why, instead of laying up sufficient food
and dropping an egg on it, which would allow the cell to be closed at
once without need of returning, does the Hymenopteron oblige itself to
come and go perpetually for a fortnight from the fields to the burrow
and back again, toiling every time through the sand to issue forth and
hunt, or bring back prey? The explanation is that the food must be
fresh—an all-important matter, for the grub absolutely refuses game
which is at all high, with a hint of decay; like the larvæ of all
Fossors, it must have fresh provisions—always fresh provisions.
We have seen in the case of the Cerceris, Sphex, and Ammophila how the
mother resolves the feeding problem, by placing beforehand in the cell
a sufficient quantity of game, and also that of keeping it for weeks
perfectly fresh—nay, almost alive, though motionless—in order to secure
the safety of the grub which feeds on the prey. This marvel is brought
about by the most skilful means known to physiology. The poisoned sting
is sent into the nerve centres once or oftener, according to the
construction of the nervous system, and the victim retains all which we
call life, except power of motion.
Let us see if the Bembex practises this deep science of murder. Diptera
taken from between the feet of their captor as the latter enters the
burrow mostly seem quite dead. They are motionless; only in rare cases
are there some slight convulsions of the tarsi—the last vestiges of
life soon to be extinct. The same appearance of complete death is
found, as a rule, in insects not really killed but paralysed by the
skilful stab of a Cerceris or a Sphex. The question as to life or death
can, therefore, only be decided by the manner in which the victims keep
fresh.
Placed in little paper twists or glass tubes, the Orthoptera of the
Sphex, the caterpillars of the Ammophila, the Coleoptera of the
Cerceris, preserve flexibility of limb and freshness of colour, and the
normal state of their intestines, for weeks and months. They are not
corpses, but bodies plunged in a lethargy from which there will be no
awakening. The Diptera of the Bembex behave quite otherwise. Eristalis,
Syrphus,—in short, all which are brightly coloured,—soon lose their
brilliance; the eyes of certain gadflies, magnificently gilded, and
with three purple bands, soon grow pale and dim, like the gaze of a
dying man. All these Diptera, great and small, placed in paper twists
where air circulates, dry up and grow brittle in two or three days,
while all kept from evaporation in glass tubes, where the air is
stagnant, grow mouldy and decay. So they are dead—really dead—when
carried to the larva. If some few preserve a little life, a few days, a
few hours ends all. Not being clever enough to use its sting, or for
some other reason, the assassin kills its victims outright.
Knowing this complete death of the prey at the moment when it is
seized, who would not admire the logic of the Bembecid’s manœuvres? How
methodical all is, and how one thing brings about another in all which
the wary Hymenopteron does! As the food could not be stored without its
decaying at the end of two or three days, it cannot be laid in
wholesale at the beginning of a phase of life destined to last at least
a fortnight, and there must be a hunt and distribution of provisions
day by day, in proportion to the larva’s growth. The first ration—that
on which the egg is laid—will last longer than the others, and must be
small, for the little grub will take several days to eat it, and if too
big it would go bad before it was finished. Therefore it will not be a
huge gadfly or a corpulent Bombylius, but a small Sphærophoria, or
something of that kind, as a tender meal for a still frail larva.
Later, and gradually larger, will come the bigger joints.
In the mother’s absence the burrow must be closed to prevent awkward
intrusions, but the entrance must be one opened quickly, without
serious difficulty, when the Hymenopteron returns loaded with prey, and
laid in wait for by audacious parasites. These conditions would be
wanting in a tenacious soil, such as that in which the mining
Hymenoptera habitually establish themselves. The wide-open entrance
would each time require long and painful labour, whether to close it
with earth or gravel, or to clear it. The domicile, therefore, must be
hollowed in earth with a very light surface, in dry, fine sand,
yielding at once to the least effort of the mother, and which slips and
closes the entrance like floating tapestry, which, pushed back by the
hand, allows entrance and then drops back. Such is the sequence of
acts, deduced by human reason, and put into practice by the wisdom of
the Bembex.
Why does the spoiler kill the prey instead of paralysing it? Is it want
of skill with the sting? Is it a difficulty arising from the
organisation of the Diptera or from the manœuvres of the chase? I must
own, at once, that I have failed to put a Dipteron, without killing it,
into that state of complete immobility into which it is so easy to
plunge a Buprestis, a Weevil, or a Scarabæus, by injecting a little
drop of ammonia, on the point of a needle, into the thoracic ganglia.
It is difficult to render your subject motionless; when it no longer
moves, actual death has occurred, as is proved by its speedy decay or
desiccation. But I have too much confidence in the resources of
instinct,—I have seen the ingenious solution of too many problems,—to
believe that a difficulty, though insurmountable for the experimenter,
can baffle an insect; therefore, without casting doubt on the Bembex’s
capacity for murder, I should be inclined to seek other motives.
Perhaps the Dipteron, so thinly cuirassed, of so little substance,—so
lean, in short,—could not, when paralysed by a sting, resist
evaporation, and would dry up in two or three weeks. Consider the
slender Sphærophoria—the larva’s first mouthful. What is there in this
body to evaporate? An atom—a mere nothing. The body is a thin strip—its
two walls touch. Could such prey form a basis for preserved food when a
few hours would evaporate its juices, unrenewed by nutrition? To say
the least, it is doubtful.
Let us proceed to consider the manner of hunting, by way of throwing a
final light on the subject. In prey withdrawn from the clasp of a
Bembex, one may not infrequently observe indications of a capture made
in haste, as best might be, in the chances of a wild struggle.
Sometimes the Dipteron has its head turned backward, as if its neck had
been twisted, its wings are crumpled, and its hairs, if it have any,
are ruffled. I have seen one with the body ripped open by a bite from
the mandibles, and legs lost in the battle. Usually, however, the prey
is intact.
No matter. Considering that the game has wings prompt in flight, the
capture must be made with a suddenness which it seems to me hardly
allows of obtaining paralysis without death. A Cerceris with its heavy
weevil, a Sphex engaged with a corpulent grasshopper or a paunched
ephippiger, an Ammophila holding its caterpillar by the nape of its
neck, have all three the advantage over a prey too slow to avoid
attack. They may take their time, choose at leisure the exact spot
where the sting shall penetrate, and, in short, can act with the
precision of a physiologist who uses his scalpel on a patient laid upon
the operating table; but for the Bembex it is another matter. At the
least alarm the prey is off, and its power of wing defies that of the
pursuer. The Hymenopteron must pounce on its prey, without measuring
its attack or calculating its blow, like a hawk hunting over the
fallows. Mandibles, claws, sting—all weapons—must be used at the same
moment in the hot battle, to end as fast as possible a struggle in
which the least indecision would give the prey time to escape. If these
conjectures agree with facts, the Bembex can only secure a dead body,
or, at all events, a prey wounded to death.
Well, my calculations are right. The Bembex attacks with an energy
which would do honour to a bird of prey. To surprise one on the chase
is no easy matter, and it would be useless to lay in a stock of
patience and watch near the burrow, for the insect flies to a distance,
and it is impossible to follow its rapid evolutions, and doubtless its
manœuvres would be still unknown to me but for the help of an article
from which I should assuredly never have expected a like
service—namely, the umbrella which served me as a tent amid the sands
of Issarts.
I was not the only one to profit by its shade; my companions were
usually numerous. Gadflies of different kinds would take refuge under
the silken canopy, and roost peacefully here and there on the outspread
silk, rarely failing to appear when the heat was overpowering. To pass
the hours when I was unemployed, I used to observe with pleasure their
great gilded eyes shining like carbuncles under my canopy, or their
grave movements when some spot of their ceiling became too much heated,
and they were forced to move a little way.
One day—ping! ping! the tense silk was resounding like the parchment of
a drum. Perhaps an acorn has fallen on my umbrella. Soon after, close
together, came ping! ping! Has some idle jester come to disturb my
solitude, and fling acorns or little pebbles on my umbrella? I came out
of my tent and inspected the neighbourhood. Nothing! The blow was
repeated. I looked upward, and the mystery was explained. The Bembecids
of the neighbourhood, which prey on gadflies, had found out the rich
store of food which was keeping me company, and were darting
audaciously under my shelter to seize the gadflies on the ceiling.
Nothing could have been better. I had only to keep quiet and observe.
Every moment a Bembex entered like a sudden flash, and darted up to the
silken ceiling, which resounded with a dull thud. A tumult went on
aloft, in which one could not distinguish attacker from attacked, so
lively was the mêlée. The struggle was very brief; almost at once the
Hymenopteron retired with a captive between its feet. The dull band of
gadflies drew a little back all round on this sudden irruption, which
decimated them, but without leaving the treacherous shelter. It was so
hot outside; wherefore move? Plainly, such swift attack and prompt
departure with the prey does not allow the Bembex to use a poignard
according to rules. The sting no doubt fulfils its office, but is
directed with no precision towards such spots as are exposed by the
chances of the combat. To slay outright the half-murdered gadfly, still
struggling between the feet of its assassin, I have seen the Bembex
chew the head and thorax of her victim. This habit, peculiar to the
Bembecids, shows that the Bembex desires death, not paralysis, since
she ends the life of the Diptera with so little ceremony. Everything
considered, I think that on the one side the nature of the prey, so
quickly dried up, and on the other, the difficulties of so vehement an
attack, are the reasons why the Bembecids serve up dead prey to their
larvæ, and consequently provide it daily.
Let us follow the Hymenopteron when it returns with its captive closely
clasped to the burrow. Here is one—B. tarsata—coming loaded with a
Bombylius. The nest is placed at the sandy foot of a vertical slope,
and the approach of the Bembex is announced by a sharp humming,
somewhat plaintive, and only ceasing when the insect has alighted. One
sees her hover above the bank, then descend, following the vertical
line slowly and cautiously, still emitting the sharp hum. If her keen
gaze should discover anything unusual, she delays her descent, hovers a
moment, ascends again, redescends, then flies away, swift as an arrow.
In a few moments she returns. Hovering at a certain height she appears
to inspect the locality, as if from the top of an observatory. The
vertical descent is resumed with most circumspect deliberation;
finally, she alights without hesitation at a spot which to my eye has
nothing to distinguish it from the rest of the sandy surface. The
plaintive note ceases at once. She must have alighted somewhat by
chance, since the most practised eye could not distinguish one spot
from another on the sandy tract. She will have dropped down somewhere
near her hole, whose entrance she will now seek, marked since her last
exit not only by the natural falling in of materials, but by her
scrupulous sweeping. No! she does not hesitate in the least—does not
feel about—does not seek. All have agreed that the organs fitted to
direct insects in their researches reside in the antennæ. At the moment
of returning to the nest I see nothing special in their play. Without
once losing hold of the prey the Bembex scratches a little in front of
her just where she alighted, pushes with her head, and straightway
enters clasping the Dipteron to her body. The sand falls in, the door
closes, and the Hymenopteron is at home.
I have watched the Bembex return home a hundred times, yet it is always
with fresh astonishment that I see the keen-sighted insect at once
detect an entrance which nothing indicates, and which indeed is
jealously hidden—not indeed when she has entered (for the sand, more or
less fallen in, does not become level, and now leaves a slight
depression, now a porch incompletely obstructed), but always after she
comes out, for when going on an expedition she never neglects to efface
the traces of the sliding sand. Let us await her departure, and we
shall see that she sweeps before her door and levels everything
scrupulously. When she is gone, I defy the keenest eye to rediscover
the entrance. To find it when the sandy tract was of some extent I was
forced to have recourse to a kind of triangulation, and how often did
my triangle and efforts of memory prove vain after a few hours’
absence! I was obliged to have recourse to a stake—in other words, a
grass stalk planted before the entrance—a means not always effectual,
for it often disappeared during the frequent settings to rights of the
outside of the Bembex’s nest.
XVIII
A PARASITE—THE COCOON
I have just described the Bembex hovering, loaded with her prey, above
the nest, and descending with a vertical flight—very slow, and
accompanied by a plaintive hum. This cautious, hesitating mode of
arrival might suggest that the insect was examining from above in order
to find her door, and trying to recall the locality before alighting.
But I shall show that there is another motive. In ordinary conditions,
when nothing alarms her, she comes suddenly, without hovering or
plaintive hum or hesitation, and alights at her threshold, or close by.
So faithful is her memory that she has no need to search about. Let us
find out the cause of the hesitating arrival just described.
The insect hovers, descends slowly, mounts again, flies off and
returns, because serious danger threatens. That plaintive hum is a sign
of anxiety, and is never produced unless there is peril. But who is the
enemy? Is it I, sitting by and watching? Not in the least; I am quite
unimportant—a block unworthy of notice. The dreaded enemy—the foe who
must be avoided at any price—is on the ground, perfectly still upon the
sand, near the nest. It is a small Dipteron—nothing at all to look
at—of inoffensive aspect. This petty fly is the terror of the Bembex.
That bold assassin of Diptera, who so promptly twists the neck of
colossal gadflies, full fed on blood from an ox’s back, dares not enter
her home because she sees herself watched by another Dipteron—a mere
pigmy, which would scarce make one mouthful for her larva.
Why not pounce on it and get rid of it? The Bembex flies fast enough to
overtake it, and, small as it is, the larvæ would not disdain it, since
they eat all and every Diptera. Yet the Bembex flies in terror before
an enemy which one bite would hew in pieces. I really feel as though I
saw a cat wild with terror before a mouse. The ardent pursuer of
Diptera is driven away by a Dipteron, and that one of the smallest! I
bow before the facts without any hope of ever comprehending this
reversal of parts. To be able to get rid easily of a mortal enemy, who
is meditating the ruin of your family, and who might make a feast for
them—to be able, I say, to do this, and not to do it when the foe is
there, within reach, watching you, defying you,—is the height of folly
in an animal. Folly, however, is not rightly the word: let us rather
talk of the harmony of creatures, for since this wretched little
Dipteron has its small part to play in the great whole of things, the
Bembex must needs respect it and basely flee before it,—otherwise long
ago there would have been no more Dipteron of this species in the
world.
Let us trace the history of this parasite. Among Bembex nests there are
found, and that frequently, some which are occupied at the same time by
the larvæ of the Hymenoptera and by other larvæ—strangers to the family
and greedily sharing their food. These strangers are smaller than the
nursling of the Bembex—shaped like a tear, and of the colour of wine,
from the food paste which can be seen through their transparent bodies.
Their number varies from six to ten or more. They belong to a kind of
Dipteron, as may be perceived from their form and from the pupæ which
one afterwards finds in their place. The demonstration is completed by
bringing them up one’s self in a box, where, fed daily with flies, and
laid on sand, they turn into pupæ, whence issue the following year
little Diptera—Tachinids of the genus Miltogramma.
This is the Dipteron which, when lying in wait near the burrow, awakens
such alarm in the Bembex. Her terror is only too well founded. This is
what happens in the dwelling. Around the heap of food which the mother
wears herself out in providing in sufficient quantity, sit in company
with the legitimate nursling from six to ten hungry guests, who put
their sharp mouths into the general heap as unceremoniously as if they
were at home. Concord seems to reign at table. I have never seen the
legitimate larva take offence at the indiscretion of the strangers, nor
observed these attempt to trouble its repast. All keep themselves
together, and eat peaceably without annoying their neighbours.
So far all would be well, were it not that a grave difficulty arises.
However active may be the mother-nurse, it is clear that she cannot
meet such a consumption of food. She has to be incessantly on the wing
to feed one larva: what must happen if there are a dozen gluttons to
provide for? The result of this enormous increase of family can only be
want, or even famine, not for the larvæ of the Dipteron (which develop
more rapidly than that of the Bembex, profiting by the days when
abundance still reigns, their host being yet in early youth), but for
the latter, who reaches the moment of metamorphosis without being able
to make up for lost time. Besides, when the first guests become pupæ
and leave the table free to it, others come, as long as the mother
visits the nest, and complete its starvation.
In burrows invaded by numerous parasites the Bembex larva is
undoubtedly much smaller than one would expect from the heap of food
consumed, the remains of which encumber the cell. Limp, emaciated,—only
half or a third of its proper size,—it vainly tries to spin a cocoon,
the silk for which it has not got, and it perishes in a corner of the
cell, amid the pupæ of guests more fortunate than itself. Or its end
may be yet more tragic. Should provender fail, or the mother delay too
long in returning with food, the Diptera devour it. I ascertained this
black deed by bringing up the brood myself. All went well as long as
food was plentiful, but if through neglect, or on purpose, the daily
supply failed, next day or the day after I was sure to find the Diptera
larvæ greedily rending that of the Bembex. Thus, when the nest is
invaded by parasites, the legitimate larva is fated to perish either by
hunger or a violent death, and this it is which makes the sight of
Miltogramma prowling round the nest so odious to the Bembex.
The Bembex is not the only victim of these parasites: the burrows of
one and all of the mining Hymenoptera are invaded by Tachinids,
especially by the Miltogramma. Various observers—notably Lepeletier de
Saint Fargeau—have spoken of the manœuvres of these impudent Diptera;
but as far as I know none have perceived the very curious case of
parasitism at the expense of the Bembex—very curious, because the
conditions are quite different. Nests of other Fossors are stored
beforehand, and the Miltogramma drops an egg on the prey just as it is
being carried in. The provender stored and her egg laid, the
Hymenopteron closes up the cell where thenceforward live the legitimate
larva and the strangers, unvisited in their prison. Thus, the robbery
committed by the parasite is unknown to the mother, and must
consequently remain unpunished.
With the Bembex it is quite otherwise. The mother constantly returns
during the fortnight that she is bringing up the larva; she knows that
her offspring is living among numerous intruders, who appropriate the
greater part of the food; every time that she brings provender she
touches and feels at the bottom of her den these detestable guests,
who, far from contenting themselves with remains, seize what is best.
She must perceive, however small her powers of arithmetic may be, that
twelve are more than one; besides, she would discover this from the
disproportion between the consumption of food and her means of hunting,
and yet, instead of seizing these bold intruders and bundling them out,
she serenely tolerates them. Tolerates! Why, she feeds them and brings
them their rations, and perhaps feels as much tenderness for them as
for her own larva. It is a new version of the cuckoo story in yet more
singular circumstances. The theory that the cuckoo, almost as big as a
sparrowhawk and coloured like it, should look imposing enough to
introduce an egg unresisted into the nest of the weak hedge-sparrow,
and that the latter, overawed perhaps by the alarming look of her
toad-faced nursling, should accept and care for the stranger, has
something in its favour. But what shall we say of a sparrow which,
turning parasite, should go with splendid audacity and intrust her eggs
to the eyrie of a bird of prey—the nest of the sparrowhawk itself—the
sanguinary devourer of sparrows? What should we say of the bird of prey
who should accept the charge and bring up the brood tenderly? It is
precisely thus that the Bembex acts,—she, a captor of Diptera who yet
brings up other Diptera—a huntress who distributes food to a prey whose
last repast will be her own disembowelled offspring! I leave to
cleverer people the task of explaining these amazing relations.
Let us observe the tactics employed by the Tachinid, whose object is to
confide her egg to the nest of the miner. It is an invariable rule that
the fly should never penetrate into the burrow, even if left open and
the owner absent. The crafty parasite would take good care not to
entangle itself in a passage, where, having no possibility of flight,
it might pay dearly for its effrontery. The only moment for its
designs—a moment watched for with the greatest patience—is that when
the Hymenopteron enters the gallery, clasping her prey. At that
instant, brief as it is, when the Bembex or any other miner has half
her body within the entrance, and is about to disappear underground,
the Miltogramma arrives on the wing, perches on the prey slightly,
projecting beyond the hinder end of the Bembex, and while she is
delayed by the difficulties of entering, the Miltogramma, with
unparalleled promptitude, lays an egg on the prey, or two, or even
three eggs, successively. The hesitation of the Bembex, embarrassed by
her load, lasts but the twinkling of an eye; but that matters not—it is
long enough for the fly to accomplish its misdeed without being dragged
beyond the threshold. What must not be the suppleness of organs to
achieve this instantaneous laying of the egg! The Bembex disappears,
herself introducing the enemy, and the Tachinid goes and crouches in
the sun, close to the burrow, and meditates fresh crimes. If one would
make sure that the Dipteron’s eggs have really been deposited during
this rapid manœuvre, it suffices to open the burrow and follow the
Bembex to the bottom of her abode. The prey which one takes from her
bears underneath at least one egg—sometimes more, according to the
length of the delay at the entrance. These very minute eggs could only
belong to a parasite, and if any doubt remained, you can bring up the
brood in a box, and the result will be Diptera larvæ—later pupæ, and
finally Miltogramma.
The fly shows wonderful sagacity in the moment selected by it—the only
one which could permit of her carrying out her purpose with neither
peril nor vain efforts. The Bembex, half-way through the entrance,
cannot see her enemy audaciously perched on the hind quarters of the
prey, or, if she suspects the bandit’s presence, cannot drive it away,
having no freedom of movement in the strait passage, and in spite of
all precautions to facilitate speedy entrance, cannot always vanish
underground with the celerity required, so quick is the parasite. In
fact, this is the only propitious moment, since prudence forbids the
Dipteron to penetrate into the den, where other Diptera, far stronger
than itself, are served up as food for the larvæ. Outside, in the open
air, the difficulty is insurmountable, so great is the vigilance of the
Bembex. Let us give a moment to the arrival of the mother, when the
nest is being watched by the Miltogramma.
Some of these flies—more or fewer, generally three or four—have settled
on the sand and are quite motionless, all gazing at the burrow, the
entrance of which they know very well, carefully hid though it be.
Their dull-brown colour, their large crimson-red eyes, their intense
stillness, have often made me think of bandits who, dressed in a dark
material, with a red kerchief over their heads, are lying in wait to do
some evil deed. The Hymenopteron comes, loaded with prey. Had she no
anxieties she would alight straightway at her door. Instead, she hovers
at a certain height, descends slowly and circumspectly, hesitates, and
vibrates her wings, producing a plaintive hum denoting apprehension.
She must have seen the malefactors. They too have seen the Bembex. The
movement of their red heads shows that they are following her with
their eyes; every gaze is fixed on the coveted booty. Then come marches
and counter-marches of cunning versus prudence.
The Bembex drops straight down with an imperceptible flight, as if she
let herself sink gently, making a parachute of her wings. Now she is
hovering just above the ground; the flies take wing, placing themselves
one and all behind her,—some nearer, some farther,—in a geometrical
line. If she turns round to disconcert them, they turn too, with a
precision which keeps them all in the same straight line; if she
advances, so do they; if she draws back, they draw back too, measuring
their flight, now slow, now stationary, on that of the Bembex at the
head of the file. They do not attempt to fling themselves on the
desired object, their tactics being merely to hold themselves in
readiness in the position of rearguard, so as to avoid any hesitation
when the rapid final manœuvre shall come.
Sometimes, wearied out by their obstinate pursuit, the Bembex alights,
and the flies instantly settle on the sand, still behind her, and keep
quite still. She rises again, with a sharper hum—the sign no doubt of
increasing indignation; the flies follow her. One last means remains to
throw the tenacious Diptera off the track; the Bembex flies far
away—perhaps hoping to mislead the parasites by rapid evolutions over
the fields. But the crafty flies are not taken in; they let her go, and
settle down again on the sand round the burrow. When the Bembex returns
the same manœuvres begin again until the obstinacy of the parasites has
exhausted her prudence. At a moment when her vigilance fails, the flies
are instantly there. Whichever is at the most favourable point drops
upon the vanishing prey, and the thing is done—the egg is laid.
There is ample evidence that the Bembex is conscious of danger, and
knows how disastrous for the future of her nest is the presence of the
hated fly; her long efforts to throw the parasites off her track, her
hesitation and flights, leave not a doubt on the subject. How is it
then, I ask myself once more, that the enemy of Diptera should allow
herself to be annoyed by another Dipteron—a tiny robber, incapable of
the least resistance, which, if she chose, she could destroy instantly?
Why, when once free from the prey which hampers her, does she not
pounce on these ill-doers? What is needed to exterminate the evil brood
around her burrow? Merely a battle which would take but a few instants.
But the harmony of those laws which govern the preservation of species
will not have it so, and the Bembex will always allow herself to be
harassed without ever learning from the famous “struggle for life” the
radical means of extermination. I have seen some which, pressed too
closely, let fall their prey and flew off wildly, but without any
hostile demonstration, although dropping their game left them full
liberty of action. The prey, so ardently desired a moment earlier by
the Tachinidæ, lay on the ground at the mercy of them all, and not one
cared about it. It had no value for the flies, whose larvæ need the
shelter of a burrow. It was valueless also to the Bembex, who came
back, felt it for an instant and left it disdainfully. The little break
in her custody of it had rendered her suspicious of it.
Let us end this chapter by the history of the larva. Its monotonous
life offers nothing remarkable during the two weeks while it eats and
grows. Then comes making a cocoon. The slight development of
silk-producing organs does not allow of a dwelling of pure silk, like
those of the Ammophila and Sphegidæ—made of several wrappers which
protect the larva, and later the nymph, from damp in the ill-protected,
shallow burrow during autumn rains and winter snows. Yet this Bembex
burrow is in worse conditions than those of the Sphex, being made at a
depth of only a few inches in very permeable soil. To fashion a
sufficient shelter the larva supplements by its industry the small
amount of silk at its disposal. With grains of sand artistically put
together and connected by silky matter, it constructs a most solid
cocoon—impenetrable to damp.
Three general methods are employed by fossorial Hymenoptera to
construct the dwelling in which metamorphosis is to take place. Some
hollow burrows at a great depth under a shelter, and then the cocoon
consists of a single wrapper, so thin as to be transparent. Such is the
case with Philanthidæ and Cerceris. Others are content with a shallow
burrow in open ground; but in that case they have silk enough for
manifold wrappings of the cocoon, as with Sphegidæ, Ammophila, and
Scolia; or if the quantity be insufficient, they use agglutinated
sand—as, for instance, the Bembex and Palarus. One might take a Bembex
cocoon for a solid kernel, so compact and resistant is it. The form is
cylindrical—one end rounded, the other pointed. The length is about two
centimetres. Outside it is slightly wrinkled and coarse, but within the
walls are smoothed by a fine varnish.
Rearing at home has enabled me to follow every detail of the
construction of this curious piece of architecture—a real strong box
which can brave all the severity of the weather. First of all the larva
pushes away the remains of its feast into a corner of the cell, or the
compartment arranged for it in a box with paper partitions. Having
cleared a space, it affixes to the walls of its abode threads of a
beautiful white silk, forming a spidery web which keeps the heap of
food-remains at a distance, and serves as scaffolding for the work to
come.
This work consists of a hammock, suspended far from anything that can
defile it, in the centre of threads stretched from wall to wall. Fine,
beautiful white silk is the only material used. The shape is that of a
sack open at one end, with a wide circular orifice, closed at the other
and ending in a point; a fisherman’s basket gives a very fair idea of
it. Then the edges of the aperture are permanently kept apart by
numerous threads fastened to the neighbouring walls. The tissue of the
bag is extremely fine, allowing all that the grub does to be seen.
Things had been in this state since the previous evening, when I heard
the larva scratching in the box. On opening, I found my captive busy
scratching the cardboard walls with the tips of its mandibles, its body
half out of the bag. Already it had made considerable progress, and a
heap of little fragments were piled before the opening of the hammock,
to be utilised later. For lack of other materials it would doubtless
have used these scrapings for its constructions, but I thought it
better to provide according to its tastes and give it sand. Never did
Bembex larva build with such sumptuous material. I poured out for my
prisoner sand for drying writing,—sand well sprinkled with gilded
grains of mica,—before the opening of the bag, which was in a
horizontal position, suitable to the work which would follow. The
larva, half out of its hammock, chose its sand almost grain by grain,
routing in the heap with its mandibles, and, if one too bulky presented
itself, it was seized and cast aside. The sand being sorted, the larva
introduced a certain quantity with its mouth into the silken fabric,
then retired into its sack and began spreading the materials in a
uniform layer on the inner surface, then glued together various grains
and inlaid them in the fabric, with silk for cement. The outer surface
was constructed more slowly. These grains were carried singly and fixed
on with silk gum.
This first deposit of sand only concerns the anterior part of the
cocoon—that half which ends in the opening. Before turning round to
work at the back part, the larva renews its store of materials and
takes certain precautions, so as not to be embarrassed in its masonry.
The sand heaped before the entrance might slip inside and hinder the
builder in so narrow a space. The grub foresees this, and glues some
grains together, making a coarse curtain of sand, which stops up the
orifice, imperfectly indeed, but enough for the purpose. These
precautions taken, the grub labours at the back part of the cocoon.
From time to time it turns round to get fresh materials from outside,
tearing away a corner of the protecting curtain, and through this
window grasping the materials needed. The cocoon is still
incomplete—wide open at the upper end and without the spherical cap
needed to close it. For this final bit of work the grub provides itself
abundantly with sand, and then pushes away the heap before the
entrance. A silken cap is now woven and fitted close to the mouth of
this primitive basket. On this silken foundation are deposited, one by
one, the sand grains kept in the interior and cemented with
silk-spittle. This lid completed, the larva has only to give the last
finish to the interior of the dwelling and glaze the walls with
varnish, to protect its tender skin from the roughness of the sand.
The hammock of pure silk and the cap which later closes it are
evidently only scaffolding intended to support the masonry of sand and
to give it a regular curve. One might compare them to the constructions
used by builders when making an arch or vault. The work being
completed, the silken support disappears, partly lost in the masonry,
and partly destroyed by contact with rough earth, and no trace remains
of the ingenious method employed to put together a construction
perfectly regular, yet made of a material so little coherent as is
sand. The spherical cap which closes the original basket is a separate
work, adjusted to the main body of the cocoon. However well the two
pieces are fitted and soldered, the solidity is not such as the larva
would obtain had it built the whole dwelling continuously. Thus, on the
circumference of the cover there is a circular line less capable of
resistance, but this is not a fault of construction. On the contrary it
is a fresh perfection. The insect would experience grave difficulty in
issuing from its strong box, so thick are the walls, did not the line
of junction, weaker than the rest, apparently save much effort, as it
is usually along this line that the cover is detached when the perfect
Bembex emerges.
I have called the cocoon a strong box. It is indeed a solid article,
both from its shape and the nature of its materials. Landslips or
falling sand cannot alter its form, since the strongest pressure of
one’s fingers cannot always crush it. Thus it matters little to the
larva if the ceiling of its burrow, dug in loose soil, should sooner or
later fall in, and it need not fear, even should a passing foot press
down the thin covering of sand; it runs no risks when once enclosed in
its stout shelter. Nor does damp endanger it. I have immersed Bembex
cocoons for a fortnight in water without finding any trace of damp
inside them. Ah! why cannot we have such waterproof for our dwellings?
To sum up: the cocoon, of graceful oval shape, appears rather the
product of patient art than the work of a grub. For any one not behind
the scenes, the cocoons which I saw in process of construction with the
sand from my inkstand might well have been precious articles of some
unknown industry—great beads starred with golden dots on a ground of
lapis lazuli, destined for the necklace of some Polynesian belle.
XIX
THE RETURN TO THE NEST
The Ammophila digging her well late in the day leaves her work after
stopping the entrance with a stone, flits away from one flower to
another, goes into a new neighbourhood, and yet next day can return
with a caterpillar to the abode hollowed out the evening before,
notwithstanding her want of acquaintance with the locality—often new to
her; the Bembex, loaded with prey, alights with almost mathematical
precision on the threshold of a dwelling blocked by sand and rendered
uniform with the rest of the sandy surface. Where my sight and memory
are at fault, theirs have a certainty verging on infallibility. One
would say that the insect possessed something more subtle than mere
recollection—a kind of intuition of locality with which nothing in us
corresponds—in short, an indefinable faculty which I call memory for
lack of any other expression by which to designate it. The unknown
cannot be named. In order to throw if possible a little light on this
point in the psychology of animals I instituted a series of
experiments, which I will now describe.
The first had for its subject Cerceris tuberculata, which hunts the
Cleonus. About 10 a.m. I took a dozen females busy at the same bank and
of the same colony, either hollowing or storing burrows. Each was
enclosed in a twist of paper, and all were put into a box. About two
kilometres from the nests I freed my captives, first marking them with
a white dot in the middle of the thorax by means of a straw dipped in
an indelible colour, in order to recognise them later. They flew on
every side—some here, some there, but only a few paces, alighting on
blades of grass and passing their forelegs over their eyes for a
moment, as if dazzled by the bright sunshine to which they were
suddenly restored. Then they took flight—some earlier, some later; and
one and all took unhesitatingly a straight line south, i.e. in the
direction of their home. Five hours later I returned to the common
territory of the nests. Almost directly I saw two of my white-dotted
Cerceris working at their burrows. Soon a third came in, with a weevil
between her feet. A fourth soon followed—four out of twelve in a
quarter of an hour was enough for conviction; I judged it useless to
wait longer; what four could do, the others could, if indeed they had
not already done it, and one may very well suppose that the eight
absentees were out hunting, or perhaps had retired into the depths of
their burrows. Thus, carried to a distance of two kilometres, in a
direction and by a way which they could not possibly perceive from the
depths of their paper prison, the Cerceris—at all events part of
them—had returned home.
I do not know to what distance they go hunting; possibly they know the
country round for some two kilometres. In that case they would not have
been far enough away, and came home by their local knowledge. The
experiment had to be tried again at a greater distance, and from a
point which the Cerceris could not possibly know.
I therefore took nine females from the colony whence I had got them in
the morning; three of these had been already experimented upon. Again
they were conveyed in a dark box—each imprisoned in a paper twist. The
starting-place was to be the neighbouring town of Carpentras, about
three kilometres from the burrows. I meant to release them not amid
fields as before, but in a street in the midst of a populous quarter,
where the Cerceris, with their rustic habits, had assuredly never
penetrated. As the hour was late I put off the experiment, and my
captives spent the night in their prison cells.
The next morning, towards eight o’clock, I marked them with a double
white spot on the thorax to distinguish them from those of the evening
before, which had only one, and set them free successively in the
middle of the street. Each mounted vertically, as if to get as soon as
possible from between the houses and gain a wide horizon, then rising
above the roofs, instantly and energetically turned its flight south.
And it was from the south that I brought them into the town, and their
burrows are south. Nine times with my nine prisoners did I obtain this
striking result—that an insect quite beyond its bearings should not
hesitate a moment what direction to take to regain its nest.
Some hours later I too was at the burrows. I saw several of my
yesterday’s Cerceris with a white dot, but none of the last set free.
Had they been unable to find the way back? Were they out hunting, or in
their galleries recovering from the excitement of such a trial? I do
not know. The next morning I came again, and had the satisfaction of
finding at work, as active as if nothing extraordinary had happened to
them, five Cerceris with two white dots. Three kilometres of
distance,—the town with its houses, roofs, and smoky chimneys—all so
novel to my rustic Cerceris,—had proved no obstacle to their return
home.
Taken from its brood and carried an enormous distance, the pigeon
returns promptly to its dovecote. If one were to consider the length of
journey in proportion to the size of the animal, how superior to the
pigeon is the Cerceris carried away three kilometres and returning to
its burrow! The size of the insect does not equal a cubic centimetre,
while that of the pigeon must quite equal the cube of a decimetre, if
it does not exceed it. The bird, a thousand times larger than the
Hymenopteron, ought, in order to rival it, to find its dovecote at a
distance of 3000 kilometres—thrice the greatest length of France from
north to south. I do not know if a carrier-pigeon has ever shown such
prowess, but wing-power and yet more lucidity of instinct cannot be
measured by yards. Nor can we here consider the question of size, and
one can only see in the insect a worthy rival to the bird without
deciding which has the advantage.
Are the two guided by memory when placed by man beyond their bearings
and carried to great distances—into regions with which they are
unacquainted and in unknown directions? Is memory as quick when, having
reached a certain height at which they can in some sort take their
bearings, they launch themselves with all their power of wing towards
that part of the horizon where are their nests? Is it memory which
traces their aerial way across regions seen for the first time?
Evidently not. It is not possible to recollect the unknown. The
Hymenopteron and the bird know nothing of their surroundings; nothing
can have taught them the general direction which they followed when
carried thither, for it was in the darkness of a closed box that the
journey was made. Locality, orientation,—all is unknown, and yet they
find their way. They have then as guide something better than simple
memory—a special faculty, a kind of topographic consciousness of which
we can form no idea, possessing nothing analogous to it.
I am now about to establish experimentally how subtle and precise is
this faculty in the narrow cycle where it is applied, and also how
limited and obtuse when it has to move out of habitual conditions. Such
is the invariable antithesis of instinct.
A Bembex, actively engaged in feeding her larva, has left her burrow.
She will return immediately with the product of the chase. The entrance
is carefully stopped with sand—swept backward by the insect before
departing. Nothing distinguishes it from the rest of the sandy surface.
But this offers no difficulty to the Hymenopteron, who finds her
doorway again with a sagacity which I have already described. Let us
plan some treachery; let us perplex her by altering the state of the
place. I cover the entrance with a flat stone as large as my hand. She
soon returns. The complete change made upon her threshold during her
absence does not seem to cause her the slightest hesitation; at all
events she alights immediately upon the stone, and tries for an instant
to hollow it, not at a chance spot, but exactly over the opening of her
burrow. Quickly turned aside from this attempt by the hardness of the
obstacle, she traverses the stone in every direction, goes round it,
slips underneath, and begins to dig in the precise direction of her
dwelling.
The flat stone is too trifling an obstacle to disconcert the clever
fly; let us find something better. I did not allow the Bembex to
continue her excavation, which I saw would soon prove successful, and
drove her far off with my handkerchief. The absence of the frightened
insect for a considerable time allowed me to prepare my snares
leisurely. What materials must now be employed? In these improvised
experiments one must know how to turn all things to profit. Not far off
on the high road is the fresh dropping of a beast of burden; here is
wood for our arrow. The dropping was collected, crushed, and spread in
a layer at least an inch thick on the threshold of the burrow and its
surroundings over more than a quarter of a yard. Assuredly here was
such a façade as never Bembex knew. Colour, the nature of the material,
the effluvium,—all combined to deceive the Hymenopteron. Can she take
this stretch of manure—this dung—for the front of the dwelling? She
does! Here she comes; studying from above the unusual condition of the
place, and settling in the middle of the layer, just opposite the
entrance, routing about, making a way through the fibrous mass, and
penetrating to the sand, she promptly discovers the mouth of the
passage. I stop and drive her away a second time.
Is not the precision with which the Bembex settles before her dwelling,
though masked in a way so novel, a proof that sight and memory are not
in such a case the only guides? What further can there be? Smell,
perhaps. That is very doubtful, for the emanations from the dung could
not baffle the perspicacity of the insect. Nevertheless, let us try
another odour. I happen to have with me, as part of my entomological
outfit, a little phial of ether. The covering of manure is swept off
and replaced by a cushion of moss, not very thick, but covering a wide
surface, on which I pour the contents of my phial the moment I see the
Bembex coming. The over-strong emanations keep her off, but only for an
instant. She alights on the moss, still reeking of ether, traverses the
obstacle and penetrates to her dwelling. The etherised effluvia did not
disturb her any more than did those of the manure; something surer than
smell tells where her nest is.
The antennæ have been often suggested as the seat of a special sense to
guide insects. I have already shown how the suppression of these organs
appears to offer no obstacle to the researches of the Hymenoptera. Let
us try once more in wider conditions. The Bembex is caught, its antennæ
amputated to the roots, and is then released. Stung by the pain—wild
with terror at being held between my fingers—the insect flies off
swifter than an arrow. I had to wait a whole hour, uncertain as to its
return. However, it came, and with its invariable precision alighted
quite close to its doorway, whose look I had changed for the fourth
time, having covered the site with a large mosaic of pebbles the size
of a nut. My work, which, compared to the Bembex, surpassed what for us
are the Megalithic monuments of Brittany, or the lines of Menhirs at
Carnac, was powerless to deceive the mutilated insect. Though deprived
of antennæ it found the entrance in the midst of my mosaic as easily as
would have done an insect under other conditions. This time I let the
faithful mother go home in peace.
The site transformed four times over, the outworks of the abode changed
in colour, scent, and material, the pain of a double wound,—all failed
to disconcert the Hymenopteron or even to make her doubtful as to the
precise locality of her doorway. I had exhausted my stratagems, and
understood less than ever how the insect, if it have no special guide
in some faculty unknown to us, can find its way when sight and smell
are baffled by the artifices of which I have spoken. Some days later an
experience gave me the opportunity to take up the problem from a new
point of view. The Bembex burrow had to be bared in its whole extent,
without quite destroying it, to which operation its shallowness and
almost horizontal direction, and the light soil in which it was made,
lent themselves readily. The sand was gradually scraped off with the
blade of a knife, and thus, deprived of roof from end to end, the
underground abode became a semi-canal or conduit, straight or curved,
some eight inches long, open where was the entrance, and ending in a
cul-de-sac where lay the larva amid its food.
The dwelling was uncovered in full sunshine; how would the mother
behave on her return? Let us consider the question scientifically. The
observer may be greatly embarrassed: what I have already seen leads me
to expect it. The mother’s impulse is to bring food to her larva, but
to reach this larva she must first find the door. Grub and entrance are
the points which appear to deserve being separately examined; therefore
I take away grub and food, and the end of the passage is cleared. There
is nothing more to do but arm one’s self with patience.
At last the Bembex arrives and makes straight for her absent door, only
the threshold of which remains. There for a good hour did I see her
dig, sweep the surface, send the sand flying, and persist, not in
making a new gallery, but in seeking the loose sand barrier which
should yield to the mere pressure of her head and let her pass easily.
Instead of loose materials she finds firm soil not yet disturbed.
Warned by this resistance she limits her efforts to exploring the
surface, always close to where the door should be, only allowing
herself to deviate a few inches. She returns to sound and sweep places
already sounded and swept some twenty times, unable to leave her narrow
circle, so obstinately convinced is she that the door must be there and
nowhere else. With a straw I pushed her gently and repeatedly to
another point. She would have none of it, and came back at once to
where the door ought to have been. Now and then the gallery, turned
into a semi-canal, appeared to attract her attention, but very faintly.
She would go a few steps along it, still raking, and then return to the
entrance. Two or three times I saw her go the whole length of the
gallery and reach the cul-de-sac where the larva should be, do a little
careless raking, and hurry back where the entrance used to be, and
continue searching with a patience which exhausted mine. More than an
hour had passed, and still she sought on the site whence the door had
disappeared.
What would happen in the presence of the larva? That was the second
part of the question. To continue the experiment with the same Bembex
would not have offered sufficient guarantee, as the creature, rendered
more obstinate by her vain search, seemed possessed by a fixed idea,
and this would have interfered with the facts which I wanted to prove.
I required a new subject, concerned solely with the impulses of the
actual moment. An opportunity soon came. The burrow was uncovered, as I
have just said; but I did not touch the contents; larva and food were
left in their places,—all was in order inside, the roof only was
wanting. Well, with this open dwelling, whose every detail the eye
could embrace,—vestibule, gallery, cell at the far end, with the grub
and its heap of provender,—this dwelling turned into a roofless gallery
at the end of which the larva was moving restlessly, under the hot sun,
its mother continued the manœuvres already described. She alighted just
where the entrance had been, and there it was that she hunted about and
swept the sand—there that she always returned after some hasty attempt
elsewhere in a circuit of a few inches. No exploration of the
gallery—no anxiety for the distressed larva; though the grub, whose
delicate skin has just exchanged the gentle moisture of a cave for
burning sunshine, is writhing on its heap of chewed Diptera, the mother
takes no notice of it. For her it is no more than any one of the
objects strewn on the sand,—a little pebble, a clod, a scrap of dried
mud,—nothing more. It is undeserving of attention. This tender,
faithful mother, who wears herself out in efforts to reach her
nursling’s cradle, cares nothing just now but for her entrance door—the
door she is used to. That which goes to her maternal heart is the
longing to find the well-known passage. Yet the way is open; nothing
holds her back, and under her eyes wriggles the grub, the final object
of her anxiety. With one spring she would be at the side of the unhappy
larva who so needs help. Why does she not rush to her beloved nursling?
She could dig a new habitation and get it swiftly underground. But
no—she persists in seeking a way which no longer exists, while her son
is grilled under her eyes. I was boundlessly surprised by this obtuse
maternity, since maternity is the most powerful and most fertile in
resource of all feelings which move the animal. Hardly could I have
believed my eyes but for endless experiments on the Cerceris and
Philanthidæ, as well as on Bembecidæ of different species. Stranger
still, the mother, after long hesitation, at length entered the
unroofed passage—all that was left of the corridor. She advanced, drew
back, and gave a few careless sweeps without stopping. Guided by vague
recollections, and perhaps by the smell of venison exhaled from the
heap of Diptera, she came occasionally as far as the end of the
gallery, the very spot where lay the larva. Mother and son had met. At
this moment of reunion after long anxiety, were there earnest
solicitude, sign of tenderness, or of maternal joy? Whoever thinks so
has only to repeat my experiment to convince himself of the contrary.
The Bembex did not recognise her larva at all; it was a worthless
thing, in her way,—nothing but an embarrassment. She walked over it and
trampled it unheeding, as she hurried backwards and forwards. If she
wanted to dig at the bottom of the cell, she rudely kicked it behind
her,—pushed, upset, expelled it, as she might have treated a large bit
of gravel which got in her way while at work. Thus maltreated, the
larva bethought itself of defence. I have seen it seize her by one
tarsus with no more ceremony than she would have shown in biting the
foot of a Dipteron caught by her. The struggle was sharp, but at last
the fierce mandibles let go, and the mother flew wildly away with her
sharpest hum. This unnatural scene of the son biting the mother, and
perhaps even trying to eat her, is unusual, and brought about by
circumstances which the observer is not always able to conjure up. What
one can always witness is the profound indifference of the Hymenopteron
for its offspring, and the brutal disdain with which that inconvenient
heap, the grub, is treated. Once she has raked out the far end of the
passage, which is done in a moment, the Bembex returns to her favourite
point, the threshold, to resume her useless researches. As for the
grub, it continues to struggle and wriggle wherever the maternal kicks
may have landed it. It will perish unaided by its mother, who could not
recognise it because she was unable to find the passage she was used
to. If we return to-morrow, we shall find it in the gallery,
half-broiled by the sun, and already a prey to the flies—once its own
prey.
Such is the connection in acts of instinct; one leading to the next in
an order that the most serious circumstances have no power to alter.
After all, what was the Bembex seeking? Her larva, evidently. But to
reach this larva she had to enter the burrow, and to enter the burrow
she had to find the door, and the mother persists in seeking this door
while the gallery lay open with provender and larva all before her. The
ruined abode, the endangered family, were for the moment unimportant;
all she could think of was the familiar passage reached through loose
sand. Let all go—habitation and inhabitant—if this passage be not
found! Her actions are like a series of echoes, awaking one another in
a fixed order, the following one only sounding when the preceding has
sounded. Not because there was any obstacle; the burrow was all open,
but for want of the usual entrance the first action could not take
place. That decides everything; the first echo is mute, and so all the
rest are silent. What a gulf between intelligence and instinct! Through
the ruins of the shattered dwelling a mother guided by intelligence
rushes straight to her son; guided by instinct she stops obstinately
where once was the door.
XX
MASON BEES
Réaumur has dedicated one of his studies to the Chalicodoma of walls,
which he calls the Mason Bee. I propose to resume this study, to
complete it, and especially to consider it from a point of view
entirely neglected by that illustrious observer. And first of all I am
tempted to state how I made acquaintance with this Hymenopteron. It was
when I first began to teach—towards A.D. 1843. On leaving the Normal
School of Vaucluse a few months previously, with my certificate, and
the naïve enthusiasm of eighteen, I was sent to Carpentras to manage
the primary school belonging to the college. A singular school it was,
upon my word, notwithstanding its fine title of “Upper”!—a kind of vast
cellar breathing out the damp engendered by a fountain backing on it in
the street. Light came in through a door opening outward when the
weather allowed of it, and a narrow prison-window, with iron-bars, and
little diamond panes set in lead. For seats there was a plank fastened
to the walls all round the room; in the middle was a chair guiltless of
straw, a blackboard, and a bit of chalk.
Morning and evening, at the sound of a bell, there tumbled in some
fifty young rascals, who, having failed to master De viris and the
Epitome, were devoting themselves, as one said then, to “some good
years of French.” The failures at “Rosa, a Rose,” came to me to learn a
little spelling. Children were mingled with tall lads at various stages
of education, and all distressingly agreed in playing tricks on the
master—no older, even younger, than some of themselves.
I taught the little ones to read syllables, the middle ones to hold a
pen in the right way while writing a few words of dictation on their
knees; for the eldest I unveiled the secrets of fractions, and even the
mysteries of the hypotenuse. And the only means I had to keep this
restless crowd in order, give each mind appropriate food, arouse
attention, expel dulness from the gloomy room whose very walls dripped
melancholy, were my tongue and a bit of chalk.
For that matter there was equal disdain in the other classes for all
which was not Latin or Greek. One instance will suffice to show the
style in which physical science was treated, now so large a part of
education. The principal of this college was an excellent man—the
worthy Abbé X, who, not anxious himself to grow green peas and bacon,
turned over such matters to some relation of his, and undertook to
teach physical science.
Let us attend one of his lessons, which happens to be on the barometer.
By good luck the college owned one. It was an old article, very dusty,
hung high out of reach of profane hands, and bearing on its face in
large letters the words, Storm, Rain, Fine. “The barometer,” began the
good abbé, addressing himself to his disciples—he used a fatherly
second person singular to each,—“the barometer gives notice of good or
bad weather. Thou seest the words written here—Storm, Rain—thou seest,
Bastien?” “I see,” replies Bastien, the most mischievous of the troop.
He has run through his book, and knows more about the barometer than
does his professor. “It is composed,” the abbé goes on, “of a curved
glass tube full of mercury which rises and falls according to the
weather. The small branch of this tube is open; the other—the other—we
shall see as to the other. Bastien—Get on this chair, and just feel
with the tip of thy finger if the long branch is open or closed. I do
not quite remember.” Bastien goes to the chair, stands as high as he
can on tip-toe, and feels the top of the long column with a finger tip.
Then, with a slight smile under the down of his dawning moustache, he
replies, “Yes, exactly; yes, the long branch is open at the top. I can
feel the hollow.” And to corroborate his mendacious statement he went
on moving his forefinger on the top of the tube, while his
co-disciples, accomplices in mischief, stifled their laughter as best
they could. The abbé said calmly, “That will do. Come down, Bastien.
Gentlemen, write in your notes that the long branch of the barometer is
open. You might forget it. I had forgotten it myself.”
Thus were physics taught. Things mended, however; a master came, and
came to stay,—one who knew that the long branch of a barometer is
closed. I obtained tables on which my pupils could write instead of
scrawling on their knees, and as my class grew daily larger, it ended
by being divided. As soon as I had an assistant to look after the
younger ones, things changed for the better.
Among the subjects taught, one pleased master and pupils equally. This
was out-of-door geometry, practical surveying. The college had none of
the necessary outfit, but with my large emoluments—700 francs, if you
please!—I could not hesitate as to making the outlay. A measuring chain
and stakes, a level, square, and compass were bought at my expense. A
tiny graphometer, hardly bigger than one’s palm, and worth about 4s.
2d., was furnished by the college. We had no tripod, and I had one
made. In short, my outfit was complete. When May came, once a week the
gloomy class-room was exchanged for the fields, and we all felt it as a
holiday. There were disputes as to the honour of carrying the stakes,
divided into packets of three, and more than one shoulder as we went
through the town felt glorified in the sight of all by the learned
burden. I myself—why conceal it?—was not without a certain satisfaction
at carrying tenderly the most precious part of the apparatus, the
famous four-and-twopenny graphometer. The scene of operations was an
uncultivated pebbly plain—a harmas, as we call it in these parts. No
curtain of live hedge, no bushes, hindered me from keeping an eye upon
my followers; here—an all important condition—I need not fear
temptation from green apricots for my scholars. There was free scope
for all imaginable polygons; trapezes and triangles might be joined at
will. Wide distances suggested plenty of elbow room, and there was even
an ancient building, once a dovecote, which lent its vertical lines to
the service of the graphometer.
Now from the very first a suspicious something caught my attention. If
a scholar were sent to plant a distant stake I saw him frequently
pause, stoop, rise, seek about, and stoop again, forgetful of straight
line and of signals. Another, whose work it was to pick up pegs, forgot
the iron spike and took a pebble instead; and a third, deaf to the
measurements of the angle, crumbled up a clod. The greater number were
caught licking a bit of straw, and polygons stood still, and diagonals
came to grief. What could be the mystery? I inquired, and all was
explained. Searcher and observer born, the scholar was well aware of
what the master was ignorant of—namely, that a great black bee makes
earthen nests on the pebbles of the harmas, and that in these nests
there is honey. My surveyors were opening and emptying the cells with a
straw. I was instructed in the proper method. The honey, though
somewhat strong-flavoured, is very acceptable; I in turn acquired a
taste for it, and joined the nest-hunters. Later, the polygon was
resumed. Thus it was that for the first time I saw Réaumur’s Mason Bee,
knowing neither its history nor its historian.
This splendid Hymenopteron, with its dark violet wings and costume of
black velvet, its rustic constructions on the sun-warmed pebbles among
the thyme, its honey, which brought diversion from the severities of
compass and square, made a strong impression on my mind, and I wished
to know more about it than my pupils had taught me—namely, how to rob
the cells of their honey with a straw. Just then my bookseller had for
sale a magnificent work on insects, The Natural History of Articulated
Animals, by de Castelnau, E. Blanchard, and Lucas. It was enriched with
many engravings which caught the eye. But alas, it had a price—such a
price! What did that matter? My 700 francs ought surely to suffice for
everything—food for the mind as well as for the body. That which I
bestowed on the one I retrenched from the other—a balance of accounts
to which whoever takes science for a livelihood must needs resign
himself. The purchase was made. That day I bled my university stipend
abundantly; I paid away a whole month of it. It took a miracle of
parsimony to fill up the enormous deficit.
The book was devoured—I can use no other word. There I learned the name
of my black bee, and there I read for the first time details of the
habits of insects, and found, with what seemed to my eyes an aureole
round them, the venerated names of Réaumur, Huber, Léon Dufour; and
while I turned the pages for the hundredth time, a voice whispered
vaguely, “Thou too shalt be a historian of animals!” Naïve illusions!
where are you? But let us banish these recollections, both sweet and
sad, and come to the doings of our black bee.
Chalicodoma, house of pebbles, rough-cast mortar, a name which would be
perfect did it not look odd to any one not well up in Greek. It is a
name applied to those Hymenoptera that build cells with materials such
as we use for our dwellings. It is masonry, but made by a rustic
workman, better used to dried clay than to hewn stone. A stranger to
scientific classification (and this causes great obscurity in some of
his memoirs), Réaumur called the worker after the work, and named our
builders in dried clay Mason Bees, which paints them exactly. We have
two kinds, C. muraria, whose history is admirably given by Réaumur, and
C. sicula, which is not special to the land of Etna, as the name
suggests, but is found in Greece, Algeria, and the Mediterranean region
of France, especially in the department of Vaucluse, where in May it is
one of the most common Hymenoptera. The two sexes of C. muraria are so
unlike in colouring that a novice observing both coming out of the same
nest would take them for strangers to one another. The female is of a
splendid velvet black, with dark violet wings; in the male the black
velvet is replaced by a bright iron-red fleece. The second species—a
much smaller one—has not this difference of colour, both sexes wearing
the same costume—a general mixture of brown, red, and ashy tints. Both
begin to build in the beginning of May. The wing-tips, washed with
violet on a bronze ground, faintly recall the rich purple of the first
species.
As Réaumur tells us, C. muraria in the northern provinces chooses as
the place to fix her nest a wall well exposed to the sun and not
plastered, as the plaster might come off and endanger her cells. She
only entrusts her constructions to a solid foundation, such as a bare
stone. I see that she is equally prudent in the south, but, for some
reason unknown to me, she generally chooses some other base than the
stone of a wall. A rolled pebble, often hardly larger than one’s
fist,—one of those with which the waters of the glacial period covered
the terraces of the Rhône valley,—is her favourite support. The great
ease with which such a one is found may influence her; all our slightly
raised plateaux, all our arid thyme-clad ground, are but heaped pebbles
cemented with red earth. In the valleys the bee can also use the stones
gathered in torrent beds; near Orange, for instance, her favourite
spots are the alluviums of the Aygues, with their stretches of rolled
boulders no longer visited by water. Or if a pebble be wanting, she
will establish her nest on a boundary stone or an enclosing wall.
Chalicodoma sicula has a yet greater variety of choice. Her favourite
position is under a tile projecting from the edge of a roof. There is
scarcely a little dwelling in the fields that does not thus shelter her
nests. There, every spring, she establishes populous colonies, whose
masonry, transmitted from one generation to another, and yearly
enlarged, finally covers a very considerable surface. I have seen such
a one under the tiles of a shed, which spread over five or six square
yards. When the colony were hard at work, their number and humming
fairly made one dizzy. The underpart of a balcony pleases them equally,
or the frame of an unused window,—above all, if closed by a
sun-shutter, which offers a free passage. But these are great
meeting-places, where labour, each for herself, hundreds and thousands
of workers. If alone, which not seldom occurs, Chalicodoma sicula
establishes herself in the first little spot she can find, so long as
it has a solid basis and heat. As for the nature of this basis it
matters little. I have seen nests built on bare stones and brick, on a
shutter, and even on the glass panes in a shed. One thing only does not
suit the bee—namely, the stucco of our houses. Prudent, like her
retainer C. muraria, she would fear ruin to her cells did she entrust
them to a support which might fall.
Finally, for reasons which I cannot yet satisfactorily explain, C.
sicula often entirely changes her manner of building, turning her heavy
mortar dwelling, which seems to require a rock to support it, into an
aerial one, hung to a bough. A bush in a hedge,—no matter
what—hawthorn, pomegranate, or Paliurus,—offers a support, usually
about the height of a man, Ilex and elm give a greater height. The bee
chooses in some thicket a bough about as thick as a straw, and
constructs her edifice on this narrow base with the same mortar which
would be used under a balcony or the projecting edge of a roof. When
finished, the nest is a ball of earth, traversed literally by the
bough. If made by a single insect it is the size of an apricot, and of
a fist if several have worked at it; but this seldom occurs.
Both species use the same materials, a calcareous clay, mixed with a
little sand and kneaded with the mason’s own saliva. Damp spots which
would facilitate labour and spare saliva to mix mortar are disdained by
the Chalicodoma, which refuses fresh earth for building, just as our
builders refuse old plaster and lime. Such materials when soaked with
humidity would not hold properly. What is needed is a dry powder, which
readily absorbs the disgorged saliva, and forms with the albuminous
principles of this liquid a kind of Roman cement, hardening
quickly,—something like what we obtain with quicklime and white of egg.
A beaten road, formed of calcareous boulders crushed by passing wheels
into a smooth surface like paving stones, is the quarry whence
Chalicodoma sicula prefers to get mortar; whether she builds on a
branch, in a hedge, or under the jutting roof of some rural habitation,
it is always from a neighbouring path, or a road, or the highway, that
she seeks materials—indifferent to the constant passing of beasts and
travellers. You should see the active bee at work when the road is
dazzling white in the hot sunshine. Between the neighbouring farm where
she is building and the road where the mortar is prepared, there is the
deep hum of the bees perpetually crossing each other as they come and
go. The air seems traversed by constant trails of smoke, so rapid and
direct is their flight. Those who go carry away a pellet of mortar as
big as small shot; those who come settle on the hardest and driest
spots. Their whole body vibrates as they scratch with the tips of their
mandibles, and rake with their forefeet to extract atoms of earth and
grains of sand, which, being rolled between their teeth, become moist
with saliva and unite. They work with such ardour that they will let
themselves be crushed under the foot of a passer-by rather than move.
Chalicodoma muraria, however, which seeks solitude, far from human
habitation, is rarely seen on beaten paths; perhaps they are too
distant from the places where she builds. If she can find dry earth,
rich in small gravel, near the boulder chosen as the basis of her nest,
she is contented. She may either make quite a new nest in a spot
hitherto unoccupied, or over the cells of an old one, after repairing
them. Let us consider the first case.
After choosing a boulder, she comes with a pellet of mortar in her
mandibles, and arranges it in a ring on the surface of the pebble. The
forefeet, and above all the mandibles, which are her most important
tools, work the material, which is kept plastic by the gradually
disgorged saliva. To consolidate the unbaked clay, angular pieces of
gravel, as large as a small bean, are worked in singly on the outside
of the still soft mass. This is the foundation of the edifice. Other
layers are added until the cell has the required height of three or
four centimetres. The masonry is formed by stones laid on one another
and cemented with lime, and can stand comparison with our own. True, to
economise labour and mortar, the bee uses coarse materials,—large bits
of gravel, which in her case answer to hewn blocks. They are chosen
singly—very hard ones, almost always with angles which, fitted
together, give mutual support, and add solidity to the whole. Layers of
mortar, sparingly used, hold them together. The outside of the cell
thus assumes the look of a piece of rustic architecture, in which
stones project with their natural inequalities; but over the inside,
which requires a smoother surface in order not to wound the tender skin
of the larva, is spread a wash of pure mortar—artlessly, however, as if
by broad sweeps of a trowel; and when it has eaten up its honey paste,
the grub takes care to make a cocoon and hang the rude wall of its
abode with silk. The Anthophora and Halictus, whose larvæ spin no
cocoon, varnish the inside of their earthen cells delicately, giving
them the polish of worked ivory.
The construction, the axis of which is always nearly vertical, with an
orifice opening upward, so that the fluid honey may not run out,
differs a little in form, according to its basis. On a horizontal
surface it rises like a little oval tower; on a vertical or slanting
one it resembles half a thimble cut down its length. In this case the
support—the pebble itself—completes the surrounding wall. The cell
completed, the bee sets to work at once to store it. The neighbouring
flowers, especially those of Genista scorpius, which in May turn the
alluviums of the torrents golden, furnish sugared liquid and pollen.
She comes with her crop swelled with honey, and all yellow underneath
with pollen dust, and plunges head first into the cell, where for some
moments one may see her work her body in a way which tells that she is
disgorging honey. Her crop emptied, she comes out, but only to go in
again at once—this time backwards. With her two hind feet she now frees
herself from her load, of pollen by brushing herself underneath. Again
she goes out, and returns head first. She must stir the materials with
her mandibles for a spoon, and mix all thoroughly together. This labour
of mixing is not repeated after every journey, but only from time to
time, when a considerable quantity has been collected. When the cell is
half full, it is stored; an egg must be laid on the honey paste, and
the door has to be closed. This is all done without delay. The orifice
is closed by a cover of undiluted mortar, worked from the circumference
to the centre. Two days at most seem required for the whole work,
unless bad weather or a cloudy day should interrupt it. Then, backing
on the first cell, a second is built and stored in the same way, and a
third and fourth, etc., follow, each one with honey and an egg, and
closed before another is begun. Work once begun is continued until it
is completed, the bee never building a new cell until the four acts
required to perfect the preceding one are performed—namely,
construction, provisioning, an egg, and sealing the cell.
As Chalicodoma muraria always works alone on her chosen boulder, and
shows great jealousy if her neighbours alight there, the number of
cells clustered on one pebble is not great—usually six to ten. Are some
eight larvæ her whole progeny, or will she establish a more numerous
family on other boulders? The surface of the stone would allow of more
cells if she had eggs for them, and the bee might build there very
comfortably without hunting for another, or leaving the one to which
she is attached by habit and long acquaintance. I think, therefore,
that most probably all her scanty family are settled on the same
stone—at all events when she builds a new abode.
The six or ten cells composing the group are certainly a solid
dwelling, with their rustic covering of gravel, but the thickness of
their walls and lids—two millimetres at most—hardly seems sufficient
against rough weather. Set on its stone in the open air, quite
unsheltered, the nest will undergo the heat of summer suns which will
turn every cell into an oven; then will come the autumn rains which
will slowly eat away the masonry, and then winter frosts which will
crumble what the rain may have respected. However hard the cement may
be, can it resist all these attacks, and if it can, will not the larvæ,
sheltered by so thin a wall, suffer from over-heat in summer and too
keen cold in winter?
Without having gone through all these arguments, the bee acts wisely.
When all the cells are completed she builds a thick cover over the
whole group, which, being of a material impermeable to water and almost
a non-conductor, is at once a defence against heat and cold and damp.
This material is the usual mortar, made of earth and saliva, only with
no small stones in it. The bee lays it on,—one pellet after another,
one trowelful and then a second,—till there is a layer a centimetre
thick over all the cells, which disappear entirely under it. The nest
is now a rude dome, about as big as half an orange; one would take it
for a clod of mud, half crushed by being flung against a stone where it
had dried. Nothing outside betrays its contents—no suggestion of
cells—none of labour. To the ordinary eye it is only a chance splash of
mud.
This general cover dries as rapidly as do our hydraulic cements, and
the nest is almost as hard as a stone. A knife with a strong blade is
needed to cut it. In its final shape the nest recalls in no degree the
original work; one would suppose the elegant turrets adorned with
pebble work, and the final dome, looking like a bit of mud, to be the
work of two different species. But scratch away the cover of cement and
we recognise the cells and their layers of tiny pebbles. Instead of
building on a boulder yet unoccupied, Chalicodoma muraria likes to
utilise old nests which have lasted through the year without notable
injury. The mortared dome has remained much as it was at the beginning,
so solid was the masonry; only it is pierced by a number of round holes
corresponding to the chambers inhabited by the larvæ of the past
generation. Such dwellings, only needing a little repair to put them in
good condition, economise much time and toil; so Mason Bees seek them,
and only undertake new constructions when old nests fail them.
From the same dome come forth brothers and sisters—reddish males and
black females—all descendants of the same bee. The males lead a
careless life, avoiding all labour, and only returning to their clay
dwellings for a brief courtship of their ladies; and they care nothing
for the deserted dwelling. What they want is nectar from flower-cups,
not mortar between their mandibles. But there are the young mothers,
who have sole charge of the future of the family—to which of them will
fall the inheritance of the old nest? As sisters they have an equal
right to it—so would human justice decide, now that it has made the
enormous progress of freeing itself from the old savage right of
primogeniture; but Mason Bees have not got beyond the primitive basis
of property—the right of the first comer.
So when the time to lay has come, a bee takes the first free nest which
suits her and establishes herself there, and woe to any sister or
neighbour who thenceforward disputes possession of it. A hot reception
and fierce pursuit would soon put the new-comer to flight; only one
cell is wanted at the moment out of all which gape like little wells
around the dome, but the bee calculates that by and by the rest will be
useful, and she keeps a jealous watch on them all and drives away every
visitor. I cannot remember having seen two Mason Bees working on the
same pebble.
The work is now very simple. The bee examines the inside of the old
cell to see where repairs are needed, tears down the rags of cocoon
hanging on the walls, carries out the bits of earth fallen from the
vault pierced by the inhabitant in order to get out, mortars any places
out of repair, mends the orifice a little, and that is all. Then comes
storage, laying an egg, and stopping up the cell. When these are
successively completed, the general cover, the mortar dome, is repaired
if necessary, and all is finished.
Chalicodoma sicula prefers a sociable life to a solitary one, and
hundreds—nay, several thousands—will establish themselves on the under
surface of the tiles on a hovel, or the edge of a roof. It is not a
real society with common interests, dear to all, but merely a gathering
where each works for herself and is not concerned for the rest—a throng
recalling the swarm of a hive only by their number and industry. They
use the same mortar as Chalicodoma muraria, equally resistant and
waterproof, but finer and without pebbles. First the old nests are
utilised. Every free cell is repaired, stored, and shut up. But the old
ones are far from sufficing to the population, which increases rapidly
year by year, and on the surface of the nest, where the cells are
hidden below the old general mortar covering, new ones are built as
required. They are placed more or less horizontally, one beside
another, with no kind of order. Every constructor builds as the fancy
takes her, where and as she wills; only she must not interfere with her
neighbour’s work, or rough treatment will soon call her to order. The
cells accumulate in chance fashion in this workyard, where there is no
general plan whatever. Their form is that of a thimble divided down the
axis, and their enclosure is completed either by adjacent cells, or the
surface of the old nest. Outside they are rough, and look like layers
of knotted cords corresponding to the layers of mortar. Inside the
walls are level but not smooth; a cocoon will replace the absent
polish.
As soon as a cell is built it is stored and walled up, as we have seen
with Chalicodoma muraria. This work goes on through the whole of May.
At length all the eggs are laid, and the bees, without any distinction
as to what does or does not belong to them, all set to work on a common
shelter of the colony—a thick bed of mortar, filling up spaces and
covering all the cells. In the end the nests look like a large mass of
dry mud—very irregular, arched, thickest in the middle, the primitive
kernel of the establishment, thinnest at the edges, where there are
fewest cells, and very variable in extent, according to the number of
workers, and consequently to the time when the nest was begun. Some are
not much larger than one’s hand, while others will occupy the greater
part of the edge of a roof, and be measured by square yards.
If Chalicodoma sicula works alone, as she often does, on the shutter of
an unused window or on a stone or a branch, she behaves in just the
same way. For instance, if the nest is on a bough, she begins by
solidly fixing the basis of her cell on the slender twig. Then the
building rises into a little vertical tower. This cell being stored and
ceiled, another follows, supported both by the bough and the first
cell, until six to ten cells are grouped one beside the other, and
finally a general cover of mortar encloses them all together with the
bough, which gives them a firm foundation.
XXI
EXPERIMENTS
Built on small pebbles which one can carry whither one will, remove, or
interchange, without disturbing either the work of the constructor or
the quiet of the inhabitants of the cells, the nests of Chalicodoma
muraria lend themselves readily to experiment—the only method capable
of throwing a little light on the nature of instinct. Profitably to
study the physical faculties of the animal it is not enough to know how
to turn to account such circumstances as a happy chance may offer to
the observer: one must be capable of originating others, and vary them
as much as possible and submit them to mutual control; in short, to
give science a solid basis of fact one must experiment. Then some day
will vanish before the evidence of exact documents the fantastic
legends which cumber our books, such as the Scarabæus inviting his
comrades to help in dragging his ball out of a rut, or a Sphex cutting
up a fly to carry it in spite of the wind, and much more which is
misused by those who desire to see in the animal world that which is
not there. Thus, too, will materials be prepared which, used sooner or
later by a learned hand, will cast premature and baseless theories back
into oblivion.
Réaumur generally confines himself to stating facts as they offered
themselves to him in the normal course of things, and does not attempt
to penetrate further into the powers of the insect by means of
conditions brought about artificially. In his day there was everything
to do, and the harvest was so great that the illustrious reaper hurried
on to what was most urgent,—the gathering of it in, leading his
successors to examine grain and ear in detail. Nevertheless, he
mentions an experiment made on Chalicodoma muraria by his friend Du
Hamel. The nest was placed in a glass funnel, the mouth of which was
closed by a piece of gauze. Three males were hatched, which, though
they had penetrated mortar hard as a stone, either did not attempt to
pierce the thin gauze, or thought it beyond their power to do so. All
three died under the glass. Insects generally only know how to execute
that which they need to do in the common order of nature, adds Réaumur.
For two reasons the experiment does not satisfy me. First of all, to
give gauze to be pierced by insects with tools made to pierce lumps as
hard as tufa does not seem a happy idea; you cannot expect a navvy’s
pickaxe to do the same work as the scissors of a seamstress. Secondly,
the transparent glass prison seems ill chosen. As soon as it had opened
a way through the thickness of its earthen dome, the insect found
itself in daylight, and to it daylight means final deliverance and
freedom. It strikes against an invisible obstacle—the glass, and glass
does not suggest an obstacle to it. Beyond, it sees a free space bathed
in sunshine. It exhausts itself in efforts to fly there, unable to
comprehend the uselessness of struggling against this strange,
invisible barrier, and perishes, obstinate and exhausted, without a
glance at the gauze which closes the conical tube. The experiment must
be repeated under better conditions.
The obstacle I selected was common gray paper—opaque enough to keep the
insect in the dark—thin enough not to offer serious resistance to the
prisoner’s efforts. As there is a vast difference by way of obstacle
between a paper partition and a vault of unbaked clay, let us see first
if Chalicodoma muraria knows how, or rather if it is able, to pierce
such a barrier. The two mandibles—pickaxes adapted to pierce hard
mortar—are they also scissors capable of cutting thin material? That is
the point to be ascertained.
In February, when the insect is already in the perfect state, I
withdrew a certain number of cocoons uninjured from their cells, and
placed each separately in a piece of reed, closed at one end naturally,
open at the other. The pieces of reed represented the nest-cells. The
cocoons were introduced so that the head of the insect should turn to
the opening. Finally, my artificial cells were closed in various ways.
Some had a stopper of kneaded earth, which, when dry, answered in
thickness and consistency to the mortar of the nest; others were shut
by a cylinder of Sorghum vulgare at least a centimetre thick, and
others with a stopper of gray paper, solidly fixed by its edges. All
these bits of cane were arranged side by side, vertically, in a box,
with the artificial roof at the top, so that the insects were in the
exact position they had in a nest. To open them they must do as they
would had I not intervened—break through the wall overhead. I protected
all with a large bell glass, and awaited the month of May when they
would emerge.
The result greatly surpassed my expectations. The earthen stopper made
by me was pierced with a round hole, noways differing from that made by
the mason bee through its mortar dome. The vegetable barrier, so new to
my prisoner,—namely, the Sorghum cylinder,—was likewise opened by a
hole, apparently made by a single effort, and the gray paper allowed
the insect to pass, not by bursting through, but once more by a neat
round hole. So my bees were capable of work for which they were not
created. To issue from their reed cells they did what probably none of
their race ever did before; they perforated the Sorghum pith and made a
hole in the paper just as they would have done with their natural clay
ceiling. When the moment came to free themselves, the nature of the
obstacle was no hindrance so long as it was not too strong for them,
and thenceforward the plea of incapacity could not be evoked where a
mere paper barrier was in question.
At the same time as the reed cells, two intact nests on their pebbles
were placed under the glass bell. On one I pressed closely a sheet of
gray paper over the mortar dome, so that to come forth the insect must
first pierce the dome and then the paper, no space being left between
them; while a little cone of gray paper was gummed on the stone round
the other nest, so that, as in the first case, there was a double
barrier, an earthen and a paper one, with, however, this
difference—that the two barriers were not close together, there being a
space between them of about a centimetre at the base, and increasing as
the cone rises. The results of these two experiments were quite unlike.
The Hymenoptera from the nest where paper had been applied to the dome
came forth by piercing the double barrier, the outer one being pierced
by a clean round hole, as in the reed cells closed in the same way. For
the second time it is shown that if the bee is stopped by a paper
barrier, the cause is not incapacity to deal with such an obstacle. On
the other hand, after they had pierced their earthen vault, the
dwellers in the second nest who found the sheet of paper a little way
off, made no attempt to overcome the obstacle over which they would so
easily have triumphed had it been attached to the nest. They died under
the cover without an effort for freedom. So had perished Réaumur’s bees
under his glass tube when there was but a bit of gauze between them and
freedom. This fact appears to me rich in consequences. What! Here are
strong insects which find penetrating tufa mere play, and a stopper of
thin wood or a sheet of paper quite easy to pierce, new as these are to
them, and yet these vigorous insects let themselves stupidly perish
imprisoned in a cone of paper which they might have torn to bits with
one bite of their mandibles. They might—but they never dreamed of doing
so. The motive of their dull inertness can be only this—the insect is
excellently endowed with tools and instinctive faculties, in order to
accomplish the final act of its metamorphosis, i.e. issuing from the
cocoon or cell. Its mandibles furnish it with scissors, file, pick, and
lever to cut, gnaw, and pull down not only its cocoon and wall of
mortar, but any other barrier not too tenacious which may be
substituted for the natural wall of its nest. Moreover,—and this is a
chief condition, without which its outfit would be useless,—there is, I
will not say the will to use these tools, but an inward stimulus
inviting it to employ them. The hour to come forth having arrived, this
stimulus awakens, and the insect sets to work to bore a passage.
In that case it matters little whether the material to be pierced is
natural mortar, Sorghum pith, or paper. The imprisoning cover will not
resist long. It even matters little if the obstacle be thickened and a
paper barrier be added to the earthen one. Both count as one if there
be no interval between them, and the insect passes through them because
this coming forth seems to it a single action. With the paper cone,
whose wall is at a short distance, the conditions are changed, although
the total thickness of barrier is really the same. The insect has done
all that it was destined to do in order to free itself. To move freely
on the mortar dome means to it that deliverance is achieved. It has
bored its way out; the work is accomplished. But round the nest another
barrier presents itself—the paper wall. To pierce through, the action
already accomplished must be repeated—that action which the insect has
to perform but once in its life. It must double that which naturally is
but single; and it cannot, simply because it has not the will to do it.
It perishes for lack of the smallest ray of intelligence. Yet in this
singular intellect it is the fashion nowadays to see a rudiment of
human reason! The fashion will pass and the facts remain, bringing us
back to the good old ideas of the soul and its immortal destinies.
Réaumur relates, too, how his friend Du Hamel, having seized a mason
bee with his pincers when it had entered half-way into its cell, head
first, to fill it with bee-bread, carried it into a room at a
considerable distance from the spot where he caught it. The bee escaped
and flew through the window. Du Hamel immediately returned to the nest.
The mason bee reached it almost at the same time, and resumed work. It
only seemed a little wilder, says the narrator.
Why were you not with me, venerated master, on the banks of the Aygues,
with their stretches of pebbles, dry for three parts of the year, and
an enormous torrent when it rains? I would have shown you something far
better than the fugitive escaped from your pincers. You should have
seen, and shared my surprise thereat, not the short flight of a mason
bee, which, carried into a room near at hand, escapes and returns
straight home in a neighbourhood familiar to her, but long journeys by
unknown ways. You would have seen the bee, carried away by me to a long
distance, return with a geographical precision which the swallow would
not disown, or the martin, or the carrier-pigeon, and you would have
asked yourself, as I did, what inexplicable knowledge of the map of the
country guides this mother in seeking her nest. Let us come to the
facts. We must repeat on the mason bee my earlier experiments with the
Cerceris—namely, carrying the insect in darkness far from the nest,
marking and setting it free. In case any one should wish to repeat the
experiment, I will explain my method of operation, which may make it
easier for a beginner. The insect destined for a long journey must of
course be captured with certain precautions. No nippers, no pincers
which might maim a wing, strain it, and endanger power of flight. While
the bee is absorbed in work within her cell, I cover the latter with a
little glass tube. As she flies out she goes into this, and thus,
without touching her, I can transfer her to a twist of paper and close
it quickly. A botanical tin serves as a means of transporting the
captives, each in its paper prison.
It is on the spots chosen as starting-places that the most delicate
operation takes place—namely, marking each captive before freeing her.
I use chalk powdered fine and moistened with a strong solution of gum
arabic. Dropped somewhere on the insect with a straw, it leaves a white
mark, which dries quickly and adheres to the bee’s fleece. If a mason
bee has to be marked, so as to distinguish her from another in an
experiment of short duration, such as I shall presently describe, I
only touch the tip of the abdomen with a straw charged with colour
while the insect is half inside the cell, head down-wards. The bee does
not notice the slight touch and works on undisturbed; but the mark is
not very durable, nor at a spot favourable for its preservation, since
the bee frequently brushes her body to detach pollen, and sooner or
later effaces it. It is therefore in the very middle of the
thorax—between the wings—that I drop the gummed chalk.
In such work it is hardly possible to wear gloves. The fingers require
all their dexterity to seize the mason bee with sufficient delicacy,
and to master her struggles without rough pressure. It is evident that
if nothing else be gained, one is sure of stings; with a little address
they can generally be avoided, but not always; one must take them with
resignation. Besides, a mason bee’s sting is by no means so painful as
that of a hive bee. The white spot dropped on the thorax—off goes the
mason bee, and the mark dries as she goes.
The first time I tried the experiment I took two mason bees busy at
their nests on the boulders covering the alluvial lands along the
Aygues, not far from Serignan, and carried them to my home at Orange,
where I freed them after marking each. According to the Ordnance map
the distance between the two places is about four kilometres in a right
line. The captives were freed in the evening at an hour when bees begin
to leave off work, so it was likely that my two would spend the night
somewhere near.
The next morning I returned to the nests. It was still too cold, and
work was suspended. When the dew was dried the masons set to work. I
saw a bee, but without the white spot, taking pollen to one of the two
nests whence had come the travellers whom I expected. A stranger,
having found the cell unoccupied, and having expatriated the owner, had
established herself there, unaware that it was the property of another.
Perhaps she had been storing it since the previous evening. Towards ten
o’clock, at the hottest time, suddenly the proprietor arrived. Her
rights as first occupier were inscribed as far as I was concerned in
irrefutable characters in white chalk on her thorax. Here was one of my
travellers come back.
Over waves of corn, over fields of red sainfoin, she had accomplished
the four kilometres, and returned to her nest after collecting booty on
the way, for she came,—worthy creature that she was!—all yellow
underneath with pollen. To return from the verge of the horizon was a
marvel, but to do so with a well-furnished pollen brush was really
sublime economy! A journey, even if compulsory, is always for a bee an
opportunity of collecting food. She found the stranger in her nest.
“What’s all this? You just wait!” and fell furiously on the other, who
perhaps had thought no wrong. Then there were hot pursuits through the
air. From time to time the two hovered almost motionless, facing one
another with a couple of inches between them, doubtless measuring each
other with their eyes, and humming abuse at one another. Sometimes one,
sometimes the other alighted on the nest in question. I expected to see
a wrestle, and stings used; but I was mistaken. The duties of maternity
spoke too imperiously to allow them to risk life, and wipe out the
injury in a mortal duel. All was limited to hostile demonstrations and
a few tussles leading to nothing.
However, the proprietor seemed to draw redoubled courage and strength
from consciousness of her rights. She encamped permanently on the nest
and received the other bee each time that she ventured to approach with
an irritated quiver of the wings in token of just indignation. The
stranger finally withdrew discouraged, and instantly the mason resumed
work as actively as if she had not undergone the chances and changes of
a long journey.
Yet another word as to rights of property. While a mason bee is absent
it is not unusual for some homeless vagabond to visit the nest, take a
liking to it, and set to work, sometimes at the same cell, sometimes at
the next, if there are several free, as often happens with old nests.
When the first occupant returns she does not fail to drive away the
intruder, who always ends by getting the worst of it, so lively and
invincible is the real owner’s sense of property. Reversing the savage
Prussian maxim, “Strength before right,” here right comes before
strength; otherwise the constant retreat of the intruder would be quite
inexplicable, since the latter’s strength is in no way inferior to that
of the real owner. If she has less audacity it must come from not
feeling braced by the sovereign strength of being right, which decides
among equals, even in the brute creation.
The second of my two travellers did not appear, either on the day when
the first came, nor later. I decided to make another experiment—this
time with five subjects. Place of starting and arrival, distance and
hours, were the same. I found three at the nests on the following day;
two were missing.
It is therefore quite clear that Chalicodoma muraria carried away four
kilometres, and, set free where she certainly could never have been
before, can return home. But why did one out of two, and two out of
five, fail to do so? What one could do, why not another? Are they not
equally gifted with the faculty which guides them through the unknown?
Is it not rather inequality in the power of flight? I recollected that
my Hymenoptera did not all fly off with the same energy; hardly were
some out of my fingers, launching themselves impetuously into the air,
than I lost sight of them, while others let themselves drop a few paces
off after a short flight. It seems certain that these had suffered
during the journey—perhaps from the concentrated heat in the furnace of
my box, or I may have harmed the jointure of the wings while marking
them—an operation difficult to perform when one has to avoid being
stung. These are maimed, weak creatures—unable to go on with all sail
spread, as they ought, for this journey. The experiment must be tried
again, only counting those bees which instantly leave my fingers with a
swift, strong flight. We shall omit those which hesitate or linger
close by on some bush. Moreover, I will do my best to compute the time
employed in returning to the nest.
Such an experiment requires a considerable number of subjects, as the
weak and maimed, who may be many, must be rejected. Chalicodoma muraria
cannot furnish the quantity needed; it is not common enough, and I am
anxious not to disturb the small people by the Aigues whom I want for
other observations later. Fortunately I have near my house, under the
projecting edge of the roof of a shed, a magnificent colony of
Chalicodoma sicula in full activity. I can draw at pleasure on the
populous city. The insect is small—less than half the size of C.
muraria; no matter—all the more merit if it can traverse the four
kilometres which I have in reserve for it, and find its nest. I took
forty, isolating them as usual in paper cones.
A ladder was placed against the wall in order to reach the nest; it was
to be used by my daughter Aglaë, to allow her to mark the exact instant
when the first one returned. I set the clock on the mantelpiece and my
watch together, that I might compare the moment of departure and
arrival. Then I carried off my forty captives to the spot where
Chalicodoma muraria works beside the Aygues. The expedition had a
double scope—to observe Réaumur’s mason bee and set the Sicilian one
free. The latter would have to fly back four kilometres.
At length my prisoners were released—all marked with a large white dot
in the middle of the thorax. It is not for nothing that one
successively handles forty wrathful Hymenoptera which forthwith
unsheath and make play with their poisoned stings. Before the mark
could be made, too often the stab was given, and my burning fingers
moved in self-defence sometimes against my will; I handled them with
more consideration for myself than for the insect, and sometimes
squeezed my bees too hard. To experiment in order to lift a small
corner of the veil that covers a truth is a beautiful and noble thing,
which can enable one to brave many perils, yet surely one may show a
little impatience if in a brief space of time one’s finger tips get
stung forty times. If any one should reproach me for my clumsy
handling, I would suggest that he make the experiment, and then judge
how far the situation was pleasant.
In short, either from the fatigue of the journey, or because I pressed
too hard and injured some articulations, out of my forty Hymenoptera
only twenty flew off strongly and unhesitatingly; the rest strayed over
the herbage near at hand, unable to keep their balance, or remained on
the willows where I had put them, refusing to fly even when excited by
a straw. These faint-hearted ones, these maimed ones, these incapables
hurt by my fingers, must be struck off the list. Twenty started with an
unhesitating flight. That was amply sufficient.
At the moment of departure there was nothing special in the direction
taken—nothing of that straight line to the nest which the Cerceris took
in a like case. As soon as they were free the Chalicodoma fled
scared—one in this direction, one to a completely opposite point; but,
as far as their fiery flight allowed, I think I saw a rapid return of
those bees which had flown in the wrong direction for their nests, and
most seemed to go to that side of the horizon. I leave this point with
the doubts unavoidable with regard to insects lost sight of at some
twenty metres distance. So far the experiment had been favoured by calm
weather, but now things grew complicated. The heat was stifling, and
the sky grew stormy. Rather a strong wind rose, blowing from the
south—the very direction which my bees should take to return home.
Could they overcome this contrary current and cleave this aerial
torrent with their wings? If they try it they must keep close to the
ground, as I saw those Hymenoptera doing which continued to work, but
it appeared out of the question to soar into the high regions where
they might obtain a clear acquaintance with the surrounding country. It
was therefore with great apprehension as to the success of my
experiment that I returned to Orange after again trying to learn some
secret from the bees on the Aygues pebbles.
Hardly had I entered my house when I saw Aglaë, flushed with
excitement. “Two,” she cried—“two came at twenty minutes to three, all
laden with pollen!” A friend chanced to have come in—a grave legal
personage, who, hearing what was on hand, forgot the Code and stamped
paper, and insisted on also watching for the arrival of my homing
pigeons. The result interested him more than did the lawsuit about the
partition wall. In a Senegalian sun and furnace heat reflected from the
wall, every five minutes did he mount the ladder bareheaded, with no
other protection against sunstroke than his thick, gray locks. Instead
of the single watcher whom I had posted I found two good pairs of eyes
watching the bees’ return. I had freed them about two o’clock, and the
first two returned to the nest at twenty minutes to three, so that
three-quarters of an hour had sufficed for travelling four
kilometres,—a very striking result, especially if we remember that the
bees worked on the road, as was proved by the pollen on their bodies,
and besides they must have been hindered by having the wind against
them. Two more came back under my eyes, and they had signs of having
worked on the way by their load of pollen. As it was growing late,
observations could not be continued. When the sun goes down the mason
bees leave the nest and take refuge I know not where—here and
there—perhaps under roof tiles and in little shelters in walls. I could
not count on the arrival of the others until work was resumed in full
sunshine.
The next day, when sunshine recalled the scattered workers, I again
counted the bees with white dots on their thorax. My success surpassed
all my hopes; I counted fifteen—fifteen of the deported bees storing or
building as if nothing had happened! Then the storm, which had
threatened more and more, burst, and a succession of rainy days stopped
all further observations.
Such as it was, the experiment sufficed. Out of twenty bees which
seemed fit for the journey when released, fifteen at least had come
back—two in the first hour, and three in the course of the evening, and
the rest next morning. They had come back in spite of having the wind
against them, and—a yet greater difficulty—in spite of their
unfamiliarity with the place whither I had transported them. There
could be no question that it was for the first time that they saw the
osier beds of the Aygues which I had chosen as the starting-place.
Never on their own account had they gone so far afield, for they find
all they want by way of building material and food close to my shed.
The road at the foot of the wall furnishes mortar; the meadows round my
house offer nectar and pollen. Economical of time as they are, they
would not fly four kilometres to procure what abounds close to the
nests. I see them daily taking material from the road, and making a
harvest on the meadow flowers, especially on Salvia. According to all
appearance they do not fly beyond a circle of a hundred metres. How
then did my exiles return? What guided them? Not memory, certainly, but
some special faculty, which we can only recognise by its astonishing
effects without pretending to explain it, so far outside our own
psychology is it.
XXII
AN EXCHANGE OF NESTS
Let us continue our series of experiments on Chalicodoma muraria. From
its position on a stone which one can move at will, its nest lends
itself to very interesting trials. This is the first of them. I change
the place of a nest by carrying the pebble it is placed on some couple
of yards away. Edifice and base forming but one, the move was made
without at all disturbing the cells. I set the pebble in an open place
well in sight, as it was before. When the bee returned, she could not
fail to see it.
After a few minutes the owner arrived and went straight where the nest
used to be. She hovered gently just above the vacant spot, looked, and
alighted just where the stone used to lie. There she walked about,
searching pertinaciously, then soared up and flew away. Her absence was
short; she came back speedily and resumed her search on foot or on the
wing—always on the spot formerly occupied by the nest. A new fit of
irritation expressed by a sudden flight through the osier bed, then as
sudden a return and resumption of the vain search—always over the
impression left by the pebble which I had carried away. These sudden
flights, prompt returns, and obstinate examinations of the empty place,
were repeated very many times before the mason bee could believe her
nest was gone. She certainly must have seen it in its new position, for
sometimes she flew only a few inches above it, but she did not care
about it. For her it only represented the nest of another bee.
Often the experiment ends without so much as a visit to the stone
carried three or four yards away; the bee departs and does not return.
If the distance be less—say a yard—sooner or later she alights on the
pebble on which her nest is built. She will visit the cell which she
was making or storing a little while earlier, plunge in her head
several times, examine the surface of the stone narrowly, and after
much hesitation return to search over the original spot. The nest,
which is no longer in its right place, is altogether abandoned, though
it be but a yard away. Vainly does the bee alight on it; she cannot
recognise it as hers. I convinced myself of this by finding it several
days later in just the same state as when I moved it. The cell, half
filled with honey, was still open, allowing the ants to pillage it; the
cell in process of construction was unfinished, without a single new
course of mortar. Of course the bee may have returned, but she had not
resumed her work. The displaced abode was abandoned for ever.
I shall not deduce the strange paradox that a bee, capable of returning
home from a great distance, is yet incapable of finding it a yard off;
the interpretation of the facts does not involve this. The conclusion
appears to be that she retains a tenacious impression of the spot
occupied by the nest, returning there with an indefatigable obstinacy
when the nest is gone. But of the nest itself she has a very vague
notion—does not recognise her own masonry kneaded with her own saliva,
nor the honey paste she had collected. Vainly does she visit her work,
the cell; she abandons it, not acknowledging it any more, since the
place where lies the pebble is no longer the same.
We must own that insect memory is a strange one, so lucid in general
knowledge of locality, so limited as to its home. I should be disposed
to name it topographical instinct; the creature knows the localities,
but not the dear nest—the dwelling. The Bembex led us to a like
conclusion. The nest being laid open, she cared nothing for the
family—for the larva writhing distressfully in the sun unrecognised.
What they do recognise, what they seek, and find with marvellous
precision, is the place where no longer exists anything of the entrance
door—not even a threshold.
If any doubt remain as to the powerlessness of Chalicodoma muraria to
know her nest except by the place which the pebble occupies on the
ground, this may set it at rest. I substituted a nest of one mason bee
for that of another, as alike as might be, both in masonry and storage.
Of course this exchange and those of which I shall speak later were
made during the absence of the owner. In the nest not hers, but placed
where her own had been, she established herself without hesitation. If
she had been building, I offered her a cell in process of construction,
and she worked on with the same care and zeal as if the work already
done had been her own. If she were bringing honey and pollen, I offered
a cell partly stored. Her journeys continued, with honey in her crop
and pollen underneath her body to complete filling the store of another
bee.
Thus the bee does not suspect the exchange, nor distinguish what is and
is not hers. She thinks she is continuing to work at a cell really her
own.
After leaving her for a time in possession of the exchanged nest, I
restored her own. The fresh change passed unobserved; her labour was
continued in the cell restored to her, at the point at which it had
arrived in the substituted one. Then I once more substituted the
strange nest, and still she persisted in her labour. Thus alternating
nests at the same spot, I thoroughly convinced myself that the insect
cannot perceive the difference between that which is her own and that
which is not. Whether the cell be hers or not, she works with equal
fervour, provided that the basis for the edifice—the stone—remains in
its original position.
One may lend a livelier interest to the experiment by using two
neighbouring nests—work at which is about equally advanced. I transpose
them, placing one where the other was; the distance is hardly a cubit.
Despite this close neighbourhood, which allows the bees to see both
nests at once and choose between them, the two bees on arriving each
immediately alighted on the substituted nest and went on working at it.
We may change the two nests at pleasure; we shall still see the two
mason bees keep to the spot chosen by them and work in turn—now at
their own cell, now at that of the other.
It may be thought that the confusion was caused by a close resemblance
between the two nests, since, at first little expecting the results
obtained, I began by choosing those as much alike as possible, lest the
bees should be repelled. My caution presupposed a clear-sightedness the
insect did not possess. I now took two nests exceedingly unlike, except
that in each the bee found a cell advanced in its work to the same
point. The first was an old nest, with the dome pierced with eight
holes, the orifices of cells of a preceding generation; one of these
had been restored, and the bee was storing it. The second was a new
nest, with no dome, and composed of a single cell with little stones on
the outside. Here too the bee was storing her paste. Certainly no two
nests could differ more: the one with its eight vacant rooms, and its
ample dome of clay, the other with a single cell—bare, and at most the
size of an acorn.
Well, the two mason bees did not hesitate long before the two exchanged
nests—hardly a yard apart. Each went to the site of its former abode.
The owner of the old nest found but a single cell. She rapidly
inspected the stone, and without further ceremony first plunged her
head into the cell to disgorge honey, and then her hind-quarters to
drop pollen. And this was no action performed to rid herself as soon as
possible of a trying burden, for she flew away and quickly returned
with fresh stores to be laid up. This bringing provisions to another’s
larder was repeated as often as I would allow. The other bee, finding,
instead of one cell a spacious building with eight chambers, was at
first considerably embarrassed. Which of the eight was the right
one?—in which was her heap of bee bread? She plunged down into each
room, and at length found what she was seeking—a condition like that
which she had left when she took her last journey, the beginning of a
store of food. From that moment she behaved like her neighbour, and
carried honey and pollen to a cell not made by her.
Let us restore the nests to their natural places, exchanging them
afresh. Each bee, after a little hesitation, sufficiently explained by
the very great difference between the two nests, will work alternately
in her own cell and the strange one. At length the egg is laid and the
cell closed, whichever the nest may be that she is occupied with at the
moment when the provisions are sufficient. Such facts show clearly why
I hesitate to give the name of memory to the singular faculty that
brings back the insect so accurately to the site of her nest, yet does
not allow her to distinguish her work from that of another, however
great may be the difference of appearance between them.
Now let us experiment on Chalicodoma muraria from another psychological
point of view. Here is a mason bee at work on the first course of her
cell; in exchange I give her one not only completed, but half full of
honey, which I stole from an owner who would speedily have laid an egg
there. What will the mason do with this munificent gift which spares
her the labour of building and storage? Leave her mortar, of course,
lay an egg, and close all up. Not at all! the animal finds our logic
illogical. The insect obeys an inevitable, unconscious impulse. It has
no choice as to what it shall do,—no discernment as to what is and is
not desirable,—but glides, as it were, down an irresistible slope
prepared for it beforehand to bring it to a determined end. The facts
still to be stated affirm this strongly.
The bee, which is building, and to which I offer a cell ready made and
full of honey, will not give up building for that; she is following her
trade as mason, and once on that tack, led on by unconscious impulse,
she must needs build, even if her labour be superfluous and contrary to
her interests. The cell I give her is certainly quite complete in the
opinion of its own constructor, since the bee from whom I subtracted it
was finishing the store of honey. To touch it up, and, above all, to
add to it is useless and absurd. All the same the bee which is building
will build. On the orifice of the honey store she lays another layer of
mortar, then another and another, until the cell is actually a third
beyond its usual height. Now the task is done—not as well indeed as if
the bee had continued the cell whose foundations she was laying when
the nests were exchanged, but certainly in a way more than enough to
demonstrate the irresistible impulse which drove the builder on. Then
came the storing, likewise abridged, for otherwise the honey would
overflow by the union of the stores of two bees. Thus the mason bee,
which is beginning to build, and to which one gives a cell completed
and filled with honey, alters nothing in the order of her work. First
she builds and then she stores; only she shortens her labours—instinct
warning her that the height of the cell and quantity of honey are
beginning to assume proportions too great.
The reverse of this is not less conclusive. To a mason bee which was
laying up food I would give a cell only just sketched out and unable to
receive the honey paste. This cell, still damp from the constructor’s
saliva, might or might not be accompanied by other cells, recently
closed and containing an egg and honey. The bee, whose half-filled cell
is thus replaced, seems greatly puzzled on arriving with her load at
this shallow hollow offering no place for the honey. She will examine
it, measure it with her eye, try it with her antennæ, and recognise its
insufficient depth. For a time she hesitates, departs, returns, flies
off again, and comes back in haste to dispose of her load. Her
embarrassment is visible; I could not help saying inwardly: “Take some
mortar—take some mortar, and finish your storehouse. It will only
require a few moments to make it deep enough.” The bee was of a
different opinion. She was laying in food, and food she must lay up,
happen what might. She could not decide to lay aside the pollen brush
for the mason’s trowel, and nothing could induce her to delay the
harvest which occupied her in order to take up that work of building
for which it is not the due moment. Rather would she seek another cell,
in the desired condition, and will penetrate there to store the honey,
even if received with fury by the owner. In fact, this happened. I
wished her success, knowing myself to be the cause of this desperate
act. My curiosity had turned an honest worker into a thief.
Matters may take a yet more serious turn, so obstinate and imperious is
the desire to harvest the store securely. The unfinished cell that the
bee refuses to accept instead of her own complete one, with its honey,
is sometimes, as I have said, among several containing paste and egg,
and newly closed. In this case I have seen, though not always, the
following sight. Having ascertained unmistakably that the unfinished
cell will not do, the bee begins to gnaw the cover of a neighbouring
one. With her saliva she softens a spot in the mortar, and patiently
digs away atom by atom in the hard covering. A long half hour passes
before the tiny dimple excavated is big enough to receive a pin’s head.
I waited. Then I got out of patience, and, feeling sure that she wanted
to open the storehouse, I decided to help her and shorten the labour.
With the point of my knife I knocked off the top; but the crown of the
cell came off too, and its edge was a good deal broken. In my
clumsiness I had made a graceful vase into a wretched, shattered pot. I
was right; the bee wanted to break open the door, and without troubling
herself as to the fragmentary state of the orifice, she immediately
established herself in the cell opened to her. Many times did she bring
honey and pollen, though the store was already complete. Finally, in
this cell containing an egg not hers she laid her own egg, and then
closed, as best she could, the shattered mouth. Thus this bee, who was
engaged in bringing food, neither could nor would be baffled by the
impossibility brought about by me of continuing her work unless she
completed the cell which replaced hers. What she was doing she
persisted in doing in spite of obstacles. She accomplished her task
thoroughly, but in the most absurd way,—by breaking into another bee’s
cell, continuing to store in a cell already overflowing, placing an egg
where the real owner had already laid one, and finally, closing an
orifice which needed serious repairs. Could one desire a better proof
of the irresistible impulse obeyed by the insect?
Finally, there are other rapid and consecutive actions so closely
connected that the execution of the second implies necessarily the
repetition of the first, even when this has become useless. I have
already said how Sphex flavipennis persists in going down into her
burrow alone, having brought near it the cricket which I cruelly
removed immediately. Her repeated discomfitures did not make her give
up the preliminary domiciliary visit, useless as it is when repeated
ten or twenty times. Chalicodoma muraria exhibits under another form a
like repetition of an act useless itself, but a necessary prelude to
the next one. Arrived with her booty, she goes through a double act of
storage. First she plunges head first into the cell to disgorge the
contents of her crop; then she comes out, returning at once backward to
brush off her load of pollen. At the moment when she is about to enter,
tail first, I gently put her aside with a straw, thus hindering her
second action. She begins all over again, going head first into the
cell, although her crop is empty. Then comes the turn of going in
backward. I instantly put her aside again, and again she goes in head
first. Once more I use my straw. And this goes on as long as the
observer pleases. Put aside just as she is about to introduce her
hinder parts into the cell, she returns to the orifice and persists in
descending head first. Sometimes she goes quite down—sometimes only
half-way, or perhaps there is a mere pretence at descending, and she
only stoops her head in the opening, but at any rate this quite useless
action—for the honey is already disgorged—invariably precedes the
entrance backward to deposit pollen. It is almost the movement of a
machine, not a wheel of which moves till the main one begins to turn.
DESCRIPTIVE NOTES
The following Hymenoptera appear new to me in the French fauna. I
append their description:—
Cerceris antoniæ, H. Fab.
Length—16–18 millimetres. Black, closely and strongly punctured;
clypeus raised like a nose, i.e. forming a convex projection, large at
the base, pointed at the end—like half a cone cut down its length;
crest between the antennæ projecting; a line above crest, cheeks, and a
large dot behind each eye, yellow; hood—yellow with black point;
mandibles, rusty yellow; tips, black. The 4th and 5th joints of
antennæ, rusty yellow, the rest brown. Two dots on prothorax, wing
scales and postscutellum, yellow; first segment of abdomen with two
dot-like spots; four next on posterior edge having a yellow band
sharply hollowed in triangle form, or even broken, and this the more as
the segment is a less distant one.
Under part of the body, black; feet entirely of rusty yellow colour;
wings slightly bronzed at tip. Female. Male unknown to me.
In colouring this species approaches Cerceris labiata, from which,
however, it differs remarkably in the form of the clypeus and the much
larger size of the insect. Observed round Avignon in July. I dedicate
this species to my daughter Antonia, whose help has often been valuable
to me in my entomological researches.
Cerceris julii, H. Fab.
Length—7–9 millimetres. Black, closely and strongly punctured; clypeus
flat; face covered with a fine silvery pubescence; a narrow yellow band
on each side, on the inner edge of the eyes; mandibles—yellow with
brown tips; antennæ—black above, pale red below; lower face of their
basal joint, yellow. Two small distant points on the prothorax; scales
of wings and postscutellum, yellow. A yellow band on third segment of
the abdomen, and another on the fifth; these two are deeply hollowed on
the anterior edge—the first in a semicircle, the second in a triangle.
Under part of the body all black; coxæ black; thighs of the hinder pair
of legs quite black; those of the two anterior pairs, black at base,
yellow at the ends; legs and tarsi, yellow; wings rather
smoke-coloured. Female.—Var. (1) Prothorax without yellow dots; (2) two
small yellow dots on second segment of abdomen; (3) wider yellow band
on inner side of the eyes; (4) front of clypeus edged with yellow.
Male unknown to me. This Cerceris, the smallest of my part of France,
feeds its larvæ on the smallest kinds of weevils (Bruchus granarius and
Apion gravidum). Observed round Carpentras, where it builds in
September in soft sandstone—locally called safre.
Bembex julii, H. Fab.
Length—18–20 millimetres. Black, with bristling whitish hairs on head,
thorax, and base of first segment of the abdomen; labrum lengthened,
yellow; clypeus, with a sloping ridge, forming as it were an angle of
three sides—one face—that of the outer edge—is all yellow, while each
of the two others is marked with a large rectangular black patch
bordering on its neighbour, and thus forming a stripe; both marks, as
well as the cheeks, are covered with a fine silvery down; cheeks on
line between the antennæ, yellow; posterior edge of eyes with a long
yellow border; mandibles—yellow, with brown tips; two first joints of
antennæ yellow beneath, black above, the rest black; prothorax—black;
sides and dorsal division, yellow; mesothorax—black; the callous point,
and a small one on each side above the base of the intermediate feet,
yellow; metathorax—black, with two yellow dots behind, and a larger one
on each side above the base of the hind feet. The two first dots are
sometimes wanting.
Abdomen—bright black above and without hairs, except at the base of the
first segment, which bristles with whitish ones. All the segments have
a wavy transverse band, wider on the sides than in the middle, and
approaching the posterior edge in proportion as the segment is further
back. On the fifth segment the yellow band reaches the posterior edge.
Anal segment—yellow, black at the base, bristling all over the dorsal
surface with papillæ of a rusty red, which serve as base to the hairs.
A row of like hair-bearing tubercules occupies also the posterior edge
of the fifth segment. Below, the abdomen is a brilliant black, with a
triangular yellow mark on each side of the four intermediate segments.
Coxæ—black; thighs yellow in front, black behind; legs and
tarsi—yellow; wings transparent.
Male.—The zig-zag mark on the clypeus is narrower, or even absent; face
then entirely yellow; abdominal bands very pale yellow, almost white.
The sixth segment has a band like the preceding ones, but shorter and
often reduced to two dots. The second segment has underneath it a
longitudinal keel, raised and spine-shaped behind. The anal one has
below it an angular, rather thick projection. Otherwise like the
female.
This Hymenopteron much resembles Bembex rostrata in size, shape, and
arrangement of the black and yellow colouring, but differs markedly in
the following characteristics:—The clypeus makes a triangle of three
sides, while in other Bembecids it is rounded and convex. Also at the
base is a large zig-zag band, formed by two rectangular marks joined
together and softened by a silvery down, very brilliant under certain
lights. The upper surface of the anal segment bristles with papillæ and
reddish hairs—likewise the further edge of the fifth segment. The
mandibles are only black at the tips, while in Bembex rostrata the base
is also black. Their habits are equally unlike; B. rostrata especially
hunts gadflies, while B. julii never catches large Diptera, but takes
smaller kinds of very varying size. It is frequent in the sandy land of
the Angles, round Avignon, and on the hill of Orange.
Ammophila julii, H. Fab.
Length—from 16–22 millimetres. Stalk of abdomen composed of the first
segment and half the second; third cubital narrowed towards the radial;
head—black, with silvery down on the face; antennæ—black; thorax—black,
with transverse stripes on its three segments, darker on prothorax and
mesothorax. Two marks on the sides and one behind either side of the
metathorax, covered with silvery down; abdomen bare, shining. First
segment—black; second—red in the part narrowing to the petiole and in
the widened part; third segment all red; the rest of a beautiful
metallic blue. Legs—black, with silvery down on the coxæ; wings
slightly reddish. Builds in October, and lays up two smallish
caterpillars in each cell. Nearly related to A. holosericea, having the
same shape, but differing markedly in the colour of the legs, which are
all black, by the much less downy head and thorax, and by the
transverse stripes on the three segments of the thorax.
I wish these three Hymenoptera to bear the name of my son Jules, to
whom I dedicate them.
Dear child! snatched so early from thy passionate love of flowers and
insects! Thou wert my fellow-worker; nothing escaped thy clear-sighted
glance; it was for thee that I was to write this book—for thee, to whom
its recital gave such delight, and thou wert one day to have continued
it. Alas! thou didst leave us for a better home, having heard but the
first few lines of the book. But at least let thy name appear in
it—borne by some of these industrious and beauteous Hymenoptera so dear
to thee!
J. H. F.
Orange, 3rd April 1879.
THE END
NOTES
[1] Souvenirs Entomologiques (Ch. Delagrave, 15 Rue Soufflot, Paris),
of which there are now seven series, this volume being a translation of
the first.
[2] The Scarabæus is also called Ateuchus.
[3] G. pilularius is a scavenger beetle nearly related to the
Scarabæus. As its name suggests, it too rolls balls of dung. It is
found very generally, even in the north, whereas S. sacer scarcely
leaves the shores of the Mediterranean.
[4] Fabre subsequently completed the whole life-history and published
it in the fifth series of his Souvenirs (1897).
[5] The beetles dug up belonged to the following species:—Buprestis
octoguttata, B. bifasciata, B. pruni, B. tarda, B. biguttata, B.
micans, B. flavomaculata, B. chrysostigma, B. novem-maculata.
[6] In a later essay, Fragments on Psychology, M. Fabre withdraws these
strictures on (Erasmus) Darwin, explaining that they are based on a
misquotation by Lacordaire, who writes “Sphex” where Darwin had said
“wasp.”
*** End of this LibraryBlog Digital Book "Insect life: Souvenirs of a naturalist" ***
Copyright 2023 LibraryBlog. All rights reserved.