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Title: Wasps - Social and Solitary
Author: Peckham, Elizabeth G., Peckham, George W.
Language: English
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WASPS
SOCIAL AND SOLITARY
[Illustration:
Page 266
PELOPÆUS ON NEST, GROUP OF FINISHED CELLS, AND TUBE OPENED TO SHOW
SPIDERS]
WASPS
SOCIAL AND SOLITARY
BY
GEORGE W. PECKHAM
AND
ELIZABETH G. PECKHAM
WITH AN INTRODUCTION BY
JOHN BURROUGHS
_ILLUSTRATIONS BY JAMES H. EMERTON_
“Bold sons of air and heat, untamed, untired.”—ILIAD, Book XVII
[Illustration: LOGO]
BOSTON AND NEW YORK
HOUGHTON, MIFFLIN AND COMPANY
The Riverside Press, Cambridge
1905
COPYRIGHT 1905 BY GEORGE W. PECKHAM AND ELIZABETH G. PECKHAM
ALL RIGHTS RESERVED
_Published April, 1905_
NOTE
A PART of the matter presented in this volume was published several
years ago by the Wisconsin Biological Survey, under the title
“Instincts and Habits of the Solitary Wasps.” These chapters have
been revised and modified, and new matter based upon later work has
been added, in the hope that in their present less technical form the
observations recorded will be of interest to the general reader.
For a number of the text cuts used in this volume we are indebted to
the courtesy of Dr. E. A. Birge, Director of the Wisconsin Geological
and Natural History Survey.
CONTENTS
CHAPTER PAGE
I. COMMUNAL LIFE 1
II. AMMOPHILA AND HER CATERPILLARS 15
III. THE GREAT GOLDEN DIGGER 56
IV. SEVERAL LITTLE WASPS 72
V. CRABRO 97
VI. AN ISLAND SETTLEMENT 119
VII. THE BURROWERS 141
VIII. THE WOOD–BORERS 178
IX. THE SPIDER–HUNTERS 196
X. THE ENEMIES OF THE GRASSHOPPER 248
XI. WORKERS IN CLAY 265
XII. SENSE OF DIRECTION 275
XIII. INSTINCT AND INTELLIGENCE 292
LIST OF ILLUSTRATIONS
PAGE
PELOPÆUS ON NEST, GROUP OF FINISHED CELLS, AND
TUBE OPENED TO SHOW SPIDERS (page 266) _Frontispiece_
WASP EATING 3
PAPER NEST WITH SIDE REMOVED TO SHOW CONSTRUCTION
OF COMBS 11
AMMOPHILA URNARIA CARRYING CATERPILLAR TO
NEST 19
AMMOPHILA URNARIA STINGING CATERPILLAR 27
CATERPILLAR WITH EGG OF AMMOPHILA URNARIA 29
NEST OF AMMOPHILA 31
AMMOPHILA URNARIA USING STONE TO POUND DOWN
EARTH OVER NEST 39
THOROUGH LOCALITY STUDY BY SPHEX 59
HASTY LOCALITY STUDY BY SPHEX 61
SPHEX DRAGGING GRASSHOPPER TO HER NEST 63
NEST OF SPHEX 69
OXYBELUS QUADRINOTATUS 75
NEST OF OXYBELUS 79
APORUS FASCIATUS 81
WASP HOMES IN THE LOG CABIN 85
NEST OF PERENNIS 89
NEST OF ANORMIS 91
SEXMACULATUS IN THE LINDEN ROOTS 99
CRABRO AND HER WHITE MOTHS 103
CRABRO STIRPICOLA 106
BOTTLE ON STEM TO MEASURE WORK OF CRABRO 107
NEST OF C. STIRPICOLA 113
AMMOPHILA SLEEPING IN THE GRASS (AFTER
BANKS) 115
NEST OF BEMBEX 125
BEMBEX SPINOLÆ LOOKING OUT OF NEST 131
BEMBEX 136
A CORNER OF THE BEMBEX COLONY 137
NEST OF CERCERIS NIGRESCENS 142
CERCERIS CLYPEATA 143
CERCERIS DESERTA: LOCALITY STUDY BEFORE LEAVING
NEST 153
PHILANTHUS PUNCTATUS 157
NEST OF PHILANTHUS PUNCTATUS 163
APHILANTHOPS GATHERING ANTS 169
TRYPOXYLON RUBROCINCTUM 185
MALE TRYPOXYLON AWAITING THE FEMALE 191
TORNADO WASP (POMPILUS QUINQUENOTATUS) DIGGING
NEST 197
POMPILUS QUINQUENOTATUS 199
EPEIRA STRIX PARALYZED AND HUNG UP ON BEAN
PLANT BY POMPILUS QUINQUENOTATUS, OUT OF
THE WAY OF ANTS 203
NEST OF P. QUINQUENOTATUS 213
POMPILUS MARGINATUS 223
THE HOME–COMING OF SCELESTUS 241
NEST OF AGENIA BOMBYCINA 244
LYCOSA KOCHII, FOUND IN NEST OF AGENIA BOMBYCINA
245
TACHYTES 249
NEST OF TACHYTES 251
CHLORION AND THE INDISCREET CRICKET 257
HORIZONTAL CELLS OF THE MUD–DAUBER 271
COURSE FOLLOWED BY POMPILUS FUSCIPENNIS IN
FINDING HER SPIDER, AND IN RETRACING HER
STEPS TO THE NEST 283
LOCALITY STUDY OF ASTATA BICOLOR 288
LOCALITY STUDY OF ASTATA UNICOLOR 289
SECOND LOCALITY STUDY OF ASTATA UNICOLOR 290
PARALYZED SPIDER HUNG UP ON SORREL BY QUINQUENOTATUS
WHILE SHE DIGS HER NEST 295
Introduction
NOT long since I wrote to a friend, a nature lover, as follows: “The
most charming monograph in any department of our natural history that I
have read in many a year is on our solitary wasps, by George W. Peckham
and his wife, of Wisconsin,—a work so delightful and instructive that
it is a great pity it is not published in some popular series of
nature books, where it could reach its fit audience, instead of being
handicapped as a State publication.” This end has now been brought
about, and the book—revised and enlarged with much new material and
many new illustrations—placed within easy reach of all nature lovers,
to whom it gives me pleasure to commend it. It is a wonderful record
of patient, exact, and loving observation, which has all the interest
of a romance. It opens up a world of Lilliput right at our feet,
wherein the little people amuse and delight us with their curious human
foibles and whimsicalities, and surprise us with their intelligence
and individuality. Here I had been saying in print that I looked upon
insects as perfect automata, and all of the same class as nearly alike
as the leaves of the trees or the sands upon the beach. I had not
reckoned with the Peckhams and their solitary wasps. The solitary ways
of these insects seem to bring out their individual traits, and they
differ one from another, more than any other wild creatures known
to me. It has been thought that man is the only tool–using animal,
yet here is one of these wasps, Ammophila, that uses a little pebble
to pound down the earth over her nest. She takes the pebble in her
mandibles, as you or I would take a stone in our hand, and uses it as
a hammer to pound down the soil above the cavity that holds her egg.
This is a remarkable fact; so far as I know there is no other animal on
this continent that makes any mechanical use of an object or substance
foreign to its own body in this way. The act stamps Ammophila as a
tool–using animal.
I am free to confess that I have had more delight in reading this book
than in reading any other nature book in a long time. Such a queer
little people as it reveals to us, so whimsical, so fickle, so fussy,
so forgetful, so wise and yet so foolish, such victims of routine
and yet so individual, with such apparent foresight and yet such
thoughtlessness, finding their way back to the same square inch of
earth in the monotonous expanse of a wide plowed field with unfailing
accuracy, and then at times finishing their cell and sealing it up
without the spider and the egg; hardly any two alike; one nervous
and excitable, another calm and unhurried; one careless in her work,
another neat and thorough; this one suspicious, that one confiding;
one species digging its burrow before it captures its game, others
capturing the game and then digging the hole; one wasp hanging its
spider up in the fork of a weed to keep it away from the ants while
it works at its nest, and then running to it every moment or two to
see that it is safe; another laying the insect on the ground while it
digs,—verily a queer little people, with a lot of wild nature about
them, and of human nature, too.
JOHN BURROUGHS.
WASPS
Social and Solitary
Chapter I
COMMUNAL LIFE
“For where’s the state beneath the firmament
That doth excel the wasps’ for government.”
“What is not good for the swarm is not good for the wasp.”
AS the tendency of mankind to crowd into towns grows stronger the joys
of country life and the workings of Nature are more and more excluded
from the daily experience of humanity. In a few the primal love of
the wild is too strong for suppression, and turning from the hot and
noisy streets they find it a refreshment of spirit to meet our little
brothers of earth and air in the wider spaces of their own territory.
We were walking through the woods one hot day in the middle of August
when our attention was attracted by a stream of yellow–jackets
issuing from the ground. They came in such surprising numbers and
looked so full of energy that we stopped to watch them, and this was
our introduction to the study of these “bold sons of air and heat,”
although a perusal of Fabre’s fascinating “Souvenirs Entomologiques”
had prepared us to feel a lively interest in them. We were at our
summer home near Milwaukee, where meadow and garden, with the wooded
island in the lake close by, offered themselves as hunting grounds,
while wasps of every kind, the socialistic tribes as well as the
extreme individualists of the solitary species, were waiting to be
studied.
The Vespas that had aroused our interest received our first attention,
and a nest in the ground proved to be a most convenient arrangement.
Experiments that would have been dangerous to life and limb had we
tried them with a paper nest hanging in the open, were easy here so
long as we kept calm and unflurried. Intent upon their own affairs,
and unsuspicious of evil, perhaps because they knew themselves to
be armed against aggression, they accepted our presence, at first
with indifference; but as we sat there day after day we must have
become landmarks to them, and perhaps before the summer was over they
considered us really a part of home.
[Illustration: WASP EATING]
While poor humanity takes comfort in a mid–day siesta, wasps love the
heat of noontide, and with every rise in temperature they fly faster,
hum louder, and rejoice more and more in the fullness of life. The
entrance to the Vespa nest was but an inch across; and once when they
were going in and out in a hurrying throng, jostling each other in
their eagerness, we counted the number that passed, one taking the
entrances and one the exits. In ten minutes five hundred and ninety–two
left the nest and two hundred and forty–seven went in, so that we saw
eight hundred and thirty–nine or about eighty to the minute. This must
be a strong swarm, wonderful indeed when we thought that it had all
come from a single queen mother. We imagined how she had made an early
start, digging a hole in the ground, building within it a paper comb
with five or six cells around a central column, and laying therein
some neuter eggs; how she had then spent a month in attending carefully
to the beginnings of things, feeding the young larvæ as they hatched,
and watching over them through their childhood and youth; and then how
her solicitude was rewarded by the filial devotion with which this
first set of workers took upon themselves the labor of excavating,
building, and feeding the young, everything indeed except the
egg–laying. These queens, surrounded though they are by respectful and
attentive subjects, have much the worst of it in our estimation, never
going out, and passing their lives in a dull routine. Through the early
summer only neuters are produced, but when fall approaches the future
generation is provided for by the development of males and females. The
activity of the little colony is limited by the season, for as the days
grow colder the males and females leave the nest and mate, and a little
later both males and workers lose ambition, become inactive and finally
die, while the queens hide away in protected corners to reappear in the
spring. The eggs and larvæ, left unfed and uncared for, become a prey
to moulds and to hordes of insects, and thus the swarm comes to an end.
We had once made some not very successful attempts to find out whether
spiders had a sense of color; and seeing that the conditions were
much more favorable with our present subjects, we thought it would be
a good plan to test their knowledge of the spectrum. Providing six
sheets of stiff paper two feet square, colored respectively red, blue,
green, pink, and two shades of yellow, and cutting a circular hole four
and one half inches in diameter in the centre of each, we began our
experiments by placing the red paper over the nest so that the entrance
was clearly exposed. The outgoing wasps dashed upward without noticing
it, but great was the confusion among the homecomers. Thrown out of
their reckoning, they clamored about us in ever increasing swarms. Like
Homer’s wasps,
“All rise in arms and with a general cry
Assert their domes and buzzing progeny,”
and a crisis (for us) was approaching, when one, a pioneer of thought,
determined to go into the hole, which did not look like the right hole,
although it was where the right hole ought to be; and so potent is
example that one by one the others followed. Three hours later they had
become accustomed to the change, and went in and out as usual.
They had noticed the paper; that was plain enough, but did they notice
the redness? To test this, we left things as they were for two days,
and then substituted blue paper for the red. Again the confusion, the
swarming of fervent legions, the noisy expostulations, the descent of
one after another; but this time they settled down to their ordinary
routine in a little more than two hours. On the following day we
removed the blue paper, leaving the grass around the nest exposed;
and this proved a new source of mystification, but not so serious as
the others. At the end of an hour twenty–five or thirty were still
buzzing about, needing the guidance of the blue paper to get inside,
and entering at once when it was replaced. As we tried new colors
from day to day a few of the wasps became entirely reconciled to our
interference, and paid no attention to the changes, while the others
grew more or less accustomed to the idea of mutability, and were but
little disturbed, although they still showed their consciousness of
each alteration by making a few circles before going in. We once placed
some dark red nasturtiums on light yellow paper near the nest, and
found that more than one third of the homecoming wasps flew to them
and hovered over them before entering. When light yellow nasturtiums,
nearly matching the paper in color, were substituted, only one out of
thirty–six noticed them; and as the odor was as strong in one case as
the other, it would seem that the color was the attracting force.
Our final color experiment was to let the blue paper remain for a day
or two, giving time for all the wasps to become familiar with it, and
then to leave it on the ground a foot and a half away, while replacing
it with yellow. This gave a false nest surrounded by the color that
they had been associating with the entrance, and a true nest surrounded
by a new color. In the next ten minutes two hundred and seventy wasps
came home, and every one of them went to the false nest. Many circled
above it, others entered the hole in the paper, and some began to
excavate, and made quite a depression in the ground; but gradually they
found their way home. Three hours later seventy–six wasps entered the
false nest in five minutes, and at evening they were still visiting
it in goodly numbers; but on the next day we saw only two that were
deceived.
On successive days we substituted red for yellow, green for red, and
so on, always with similar results, although the wasps became more and
more accustomed to the vicissitudes of their life, and after a time
seemed to look for the hole itself without relying upon the color to
guide them. They found their nest under a color new to them much more
readily than when the paper was taken entirely away and the ground
left exposed. Once when the green paper was around their nest, and the
wind blew it over the hole so that they could not enter, at least
one hundred collected, many of them settling in the false nest; when
we lifted the green paper, leaving the hole free, only three or four
entered, but when we put it back in place they rushed in six or seven
at a time. It was plainly the color that directed them.
This was a nearly rainless summer,—a condition extremely favorable
to wasp development. Nests multiplied and grew until the whole
country–side complained, and no wonder, for houses were full of them,
and at mealtimes they gathered at the table with the members of the
family. How did they know when dinner was ready? It could not have been
by the sight, unfamiliar to them, of cooked food; was it, then, through
the sense of smell?
Many were the questions that we asked in vain of our Vespas, but here
was one that they could readily be made to answer. We rolled up two
bundles, one of nothing but gauze, and another, like it in appearance,
but containing some warm chicken bones; these were laid to one side of
the nest, the color of the gauze matching that of the paper on which
it was placed. The wasps in returning to the nest, even though loaded
with food, could not resist the appetizing odor, and settled thickly
upon the bone bundle, trying their best to penetrate within, while
the empty gauze was unnoticed. As the bones grew cold and dry they
attracted less attention, but two days later they were occasionally
visited.
Having killed two wasps that had alighted on the ground, by striking
them with a folded paper, we took them up and placed one of them at a
distance, so that it was entirely hidden in the grass. Five settled
above it, and after they had carried it away the place was visited by
several others, while the spot upon which we had killed them drew to it
nine wasps within fifteen minutes. Thus they seemed very keen of scent
where animal matter was concerned; but the powerful oils of peppermint
and wintergreen, although noticed, aroused little attention, perhaps
because they indicated nothing of interest to them.
Our experiments on hearing met with negative results. The wasps seemed
insensible to any noise we could make or that we could produce by
whistles of various degrees of shrillness. This of course does not show
that they cannot hear, and any one who has been unfortunate enough to
disturb them in the neighborhood of their nest will remember how their
angry buzzing seemed to serve as a battle cry to gather all the members
of the clan for the attack.
Our Vespas began to work an hour or two after sunrise, and did not stop
until dusk. One cloudy evening when darkness fell early they continued
to return to the nest, being able to fly to the right spot without any
hesitation, although our vision did not permit us to see the opening
without going down on our knees and looking closely. At last it grew
perfectly dark, and we stuffed a handkerchief into the hole, with the
result that seventy–five, coming home without a ray of light to guide
them, were shut out, and were found clustered about the spot on the
following morning.
We wanted to estimate the amount of labor done by a worker in a day,
and so, rising one morning at the first bird call, we went out into the
freshness of dawn, and for an hour had the world to ourselves; but a
little before five a few straggling wasps that had stayed out all night
began to bring in loads, and by half past seven they were fairly under
way. From half past four until twelve we counted all that passed, 4534
going out and 3362 coming home; and with all this activity there seemed
to be no pleasure excursions, for each one carried food when returning,
and took out a pellet of earth when leaving. We once raised a little
garden from the pellets that were dropped on our porch table where we
kept a bowl of water. Wasps are great drinkers, and when they find
such a provision they come frequently to refresh themselves, dropping
their loads as they alight. This habit of holding on to their loads
until they settle down may perhaps make them a factor in extending the
boundaries of plant distribution, both under ordinary conditions and
when, as must often happen with little creatures flying so high, they
are blown to long distances from home.
[Illustration: PAPER NEST WITH SIDE REMOVED TO SHOW CONSTRUCTION OF
COMBS]
Having kept close track not only of the numbers, but of the hours,
each count being made to cover five minutes, we were able to calculate
that an average trip occupied forty–three minutes. When we met these
wasps in the garden they never seemed to be hurrying, and had the air
of amusing themselves; but they must be faithful workers to accomplish
so much. The curious fact has been established that when food is very
plentiful the workers begin to lay male eggs, thus taking from the
queen a part of her burden and leaving her free to produce neuters and
females. The nest that we were watching was found, at the end of the
season, to contain 4661 wasps in various stages of development, and
others that we opened had from two to four thousand. This is nothing to
the social wasps of China, where a single household is made up of from
fifteen to twenty thousand members; but China is a thickly populated
country, and perhaps with wasps as with human beings several families
live in a single domicile.
Outside of their wonderful social instincts our wasps are found wanting
in the higher gifts of emotion and intellect. When we killed a number
of them and placed them near the nest, their nearest relatives wasted
no time in mourning, nor yet in revenge, but calmly cut up the bodies
and fed them to the ever hungry young ones. If we placed some rich and
tempting morsels at a distance, two or three would discover them, and
would go back and forth all day without telling the others about it, as
ants would have done under like circumstances. When we obstructed the
opening to their nest by lightly laying blades of grass across, the day
passed without its occurring to the wasps to lift them away, although
they suffered the greatest inconvenience in getting in and out,
crawling laboriously through, and in some instances giving up the task
and flying away.
Vespa maculata, building on trees and fences, has practically the
same habits as the ground wasp, germanica, the internal structure
of the nest following the same plan, while the outer wall is of a
papery substance like that of the combs, made from the scrapings of
weather–beaten wood. The genus Polistes builds combs similar to that of
Vespa, under porches or in any sheltered place, and does not inclose
them. All these wasps, when adult, enjoy fruit and flowers as well
as animal food; but only this last is used for the young, and many a
caterpillar creeping along with sinister design is snatched by them to
be chewed into a pulpy mass, and then fed to the larvæ. No calculation
has been made of the value of these wasps in agriculture, and one
of the things that farmers have yet to learn is to encourage their
presence in orchards and gardens.
Some species are said to sting the drones and larvæ to death at the
close of the season, but this habit is not followed by V. germanica
and V. maculata. Since there is no store of provision to be economized
through the winter the only object of such conduct would be the
merciful one of ending their sufferings at once instead of letting them
perish by slow starvation, and we find no evidence for such elevated
ideas. What makes for the welfare of the species they thoroughly attend
to, but beyond that point they do not go.
The socialism of wasps is in a less evolved state than that of bees and
ants, and yet there is in it sufficient sacrifice of self to the common
good to excite the respectful wonder of human beings, whose relations
to each other and to the state have such different standards.
Chapter II
AMMOPHILA AND HER CATERPILLARS
BEFORE we had worked long on our Vespa family we were beguiled by
tempting opportunities into running after the solitary wasps. The
solitaries, so far as species are concerned, are immensely more
numerous than the socials; but they have only two sexes, and the males
and females usually see but little of each other after the mating
is over, although we occasionally find them living happily together
until the end of the season. In the early summer they begin to emerge
from the nest in which the eggs were laid the year before. Solitary
indeed they come into the world, the generation that gave them birth
having perished in the fall. For a time their career is one of unmixed
pleasure, and yet, free and unguided though they are, basking in the
sunshine, feeding on the flowers, or sleeping at night under some
sheltering leaf, they are hourly acquiring experience, so that when
the cares of life descend upon them they are no longer creatures
of mere instinct. With these sobering cares an almost absurdly
heavy sense of responsibility for future generations transforms the
hitherto happy–go–lucky females into grown–up wasps with serious views
on marketing and infant foods. Each one makes a separate nest and
provisions it by her own labor; and in many cases a new nest is made
for each egg. There is no coöperation among them; although in certain
genera, as Aphilanthops and Bembex, a number of individuals build
close together, forming a colony. The nests may be made of mud, and
attached for shelter under leaves, rocks, or eaves of buildings, or
may be burrows hollowed out in the ground, in trees or in the stems of
plants. The adult wasp lives upon fruit or nectar, but the young grub
or larva must have animal food; and here the parent wasp shows a rigid
conservatism, each species providing the sort of food that has been
approved by its family for generations, one taking flies, another bugs,
and another beetles, caterpillars, grasshoppers, crickets, locusts,
spiders, cockroaches, aphides, or other creatures, as the case may be.
When the egg–laying time arrives the female secures her prey, which
she either kills or paralyzes, places it in the nest, lays the egg
upon it, and then, in most cases, closes the hole and takes no further
interest in it, going on to make new nests from day to day. In some
genera the female maintains a longer connection with her offspring,
not bringing all the provision at once, but returning to feed the larva
as it grows, and leaving the nest permanently only when the grub has
spun its cocoon. The males never acquire this interest, so admirable
for the development of character, and aid little, if at all, in the
care of the family. The egg develops in from one to three days into a
footless, maggot–like creature which feeds upon the store provided for
it, increasing rapidly in size, and entering the pupal stage in from
three days to two weeks. In the cocoon it passes through its final
metamorphosis, emerging as a perfect insect, perhaps in two or three
weeks, or, in many cases, after the winter months have passed and
summer has come again.
Most graceful and attractive of all the wasps—“_taille effilée,
tournure svelte_,” as Fabre describes them, the Ammophiles, of all the
inhabitants of the garden, hold the first place in our affections.
Not so beautiful as the blue Pelopæus, nor so industrious as the
little red–girdled Trypoxylon, their intelligence, their distinct
individuality, and their obliging tolerance of our society make
them an unfailing source of interest. They are, moreover, the most
remarkable of all genera in their stinging habits, being supposed to
use the nicest surgical skill in paralyzing their caterpillars; and few
things have given us deeper pleasure than our success in following
the activities and penetrating the secrets of their lives. In our
garden we have two species of Ammophila, urnaria Cresson, and gracilis
Cresson, both of them being very slender–bodied wasps of about an inch
in length, gracilis all black, and urnaria with a red band around
the front end of the abdomen. A. polita and A. vulgaris, which look
much like urnaria, are common in the sandy fields west and south of
Milwaukee.
[Illustration: AMMOPHILA URNARIA CARRYING CATERPILLAR TO NEST]
During the earlier part of the summer we had often seen these wasps
feeding upon the nectar of flowers, especially upon that of the sorrel,
of which they are particularly fond; but at that time we gave them but
passing notice. One bright morning, however, we came upon an urnaria
that was so evidently hunting, and hunting in earnest, that we gave up
everything else to follow her. The ground was covered, more or less
thickly, with patches of purslain, and it was under these weeds that
our Ammophila was eagerly searching for her prey. After thoroughly
investigating one plant she would pass to another, running three or
four steps and then bounding as though she were made of thistledown and
were too light to remain upon the ground. We followed her easily, and
as she was in full view nearly all of the time we had every hope of
witnessing the capture; but in this we were destined to disappointment.
We had been in attendance on her for about a quarter of an hour when,
after disappearing for a few moments under the thick purslain leaves,
she came out with a green caterpillar. We had missed the wonderful
sight of the paralyzer at work; but we had no time to bemoan our loss,
for she was making off at so rapid a pace that we were well occupied in
keeping up with her. She hurried along with the same motion as before,
unembarrassed by the weight of her victim. For sixty feet she kept to
open ground, passing between two rows of bushes; but at the end of this
division of the garden, she plunged, very much to our dismay, into a
field of standing corn. Here we had great difficulty in following her,
since, far from keeping to her former orderly course, she zigzagged
among the plants in the most bewildering fashion, although keeping a
general direction of northeast. It seemed quite impossible that she
could know where she was going. The corn rose to a height of six feet
all around us; the ground was uniform in appearance, and, to our eyes,
each group of cornstalks was just like every other group, and yet,
without pause or hesitation, the little creature passed quickly along,
as we might through the familiar streets of our native town.
At last she paused and laid her burden down. Ah! the power that has led
her is not a blind, mechanically perfect instinct, for she has traveled
a little too far. She must go back one row into the open space that she
has already crossed, although not just at this point. Nothing like a
nest is visible to us; the surface of the ground looks all alike, and
it is with exclamations of wonder that we see our little guide lift two
pellets of earth which have served as a covering to a small opening
running down into the ground.
The way being thus prepared, she hurries back with her wings quivering
and her whole manner betokening joyful triumph at the completion of
her task. We, in the mean time, have become as much excited over the
matter as she is herself. She picks up the caterpillar, brings it to
the mouth of the burrow, and lays it down. Then, backing in herself,
she catches it in her mandibles and drags it out of sight, leaving us
full of admiration and delight.
How clear and accurate must be the observing powers of these wonderful
little creatures! Every patch of ground must, for them, have its own
character; a pebble here, a larger stone there, a trifling tuft of
grass—these must be their landmarks. And the wonder of it is that their
interest in each nest is so temporary. A burrow is dug, provisioned and
closed up, all in two or three days, and then another is made in a new
place with everything to learn over again.
From this time on to the first of September our garden was full of
these wasps, and they never lost their fascination for us; although,
owing to a decided difference between their taste and ours as to what
constituted pleasant weather, all our knowledge of them was gained by
the sweat of our brows. When we wished to utilize the cool hours of
the morning or of the late afternoon in studying them, or thought to
take advantage of a cloud which cast a grateful shade over the sun at
noonday, where were our Ammophiles? Out of sight entirely, or at best
only to be seen idling about on the flowers of the onion or sorrel. At
such a time they seemed to have no mission in life and no idea of duty.
But when the air was clear and bright and the mercury rose higher and
higher, all was changed. Their favorite working hours were from eleven
in the morning to three in the afternoon, and when they did work they
threw their whole souls into it. It was well that it was so, for they
certainly needed all the enthusiasm and perseverance that they could
muster for such wearisome and disappointing labor. Hour after hour was
passed in search, and often there was nothing to show at the end of
it. Urnaria hunted on bare ground, on the purslain, and most of all
on the bean–plants. These were examined carefully, the wasp going up
and down the stems and looking under every leaf; but the search was so
frequently unsuccessful that in estimating their work we are inclined
to think that they can scarcely average one caterpillar a day.
In this species, as in every one that we have studied, we have found a
most interesting variation among the different individuals, not only in
methods, but in character and intellect. While one was beguiled from
her hunting by every sorrel blossom she passed, another stuck to her
work with indefatigable perseverance. While one stung her caterpillar
so carelessly and made her nest in so shiftless a way that her young
could survive only through some lucky chance, another devoted herself
to these duties not only with conscientious thoroughness, but with an
apparent craving after artistic perfection that was touching to see.
The method employed by the Ammophiles in stinging their prey is more
complex than that of any other predatory wasp. The larvæ with which
they provision their nests are made up of thirteen segments, and
each of these has its own nervous centre or ganglion. Hence if the
caterpillar is to be reduced to a state of immobility, or to a state
so nearly approaching immobility that the egg may be safely laid upon
it, a single sting, such as is given by some of the Pompilidæ to their
captured spiders, will be scarcely sufficient. All this we knew from
Fabre’s “Souvenirs,” and yet we were not at all prepared to believe
that any plain American wasp could supply us with such a thrilling
performance as that of the Gallic hirsuta, which he so dramatically
describes. We were, however, most anxious to be present at the
all–important moment that we might see for ourselves just how and where
urnaria stings her victim.
For a whole week of scorching summer weather we lived in the bean
patch, scorning fatigue. We quoted to each other the example of
Fabre’s daughter Claire, who followed Odynerus with unfaltering zeal
until a sunstroke laid her low. We attended scores of wasps as they
hunted; we ran, we threw ourselves upon the ground, we scrambled along
on our hands and knees in our desperate endeavors to keep them in
view, sometimes with our eyes upon the wasps themselves and sometimes
pursuing their shadows, which, like those of coming events, were cast
before; and yet they escaped us. After we had kept one in sight for an
hour or more, some sudden flight would carry her far away, and all our
labor was lost.
At last, however, our day came. We were doing a little hunting on our
own account, hoping to find some larvæ which we could drop in view of
the wasps and thus lead them to display their powers, when we saw an
urnaria fly up from the ground to the underside of a bean leaf and
knock down a small green caterpillar. Breathless with an excitement
which will be understood by those who have tasted the joy of such a
moment, we hung over the actors in our little drama. The ground was
bare, we were close by and could see every motion distinctly. Nothing
more perfect could have been desired.
The wasp attacked at once, but was rudely repulsed, the caterpillar
rolling and unrolling itself rapidly and with the most violent
contortions of the whole body. Again and again its adversary descended,
but failed to gain a hold. The caterpillar, in its struggles, flung
itself here and there over the ground, and had there been any grass
or other covering near by it might have reached a place of partial
safety; but there was no shelter within reach, and at the fifth attack
the wasp succeeded in alighting over it, near the anterior end, and in
grasping its body firmly in her mandibles. Standing high on her long
legs and disregarding the continued struggles of her victim, she lifted
it from the ground, curved the end of her abdomen under its body, and
darted her sting between the third and fourth segments. From this
instant there was a complete cessation of movement on the part of the
unfortunate caterpillar. Limp and helpless, it could offer no further
opposition to the will of its conqueror. For some moments the wasp
remained motionless, and then, withdrawing her sting, she plunged it
successively between the third and the second, and between the second
and the first segments.
The caterpillar was now left lying on the ground. For a moment the wasp
circled above it, and then, descending, seized it again, further back
this time, and with great deliberation and nicety of action gave it
four more stings, beginning between the ninth and tenth segments and
progressing backward.
Urnaria, probably feeling—as we certainly did—a reaction from the
strain of the last few minutes, and a relief at the completion of her
task, now rested from her labors. Alighting on the ground close by, she
proceeded to smooth her body with her long hind legs, standing, in the
mean time, almost on her head, with her abdomen directed upward. She
then gave her face a thorough washing and rubbing with her first legs,
and not until she had made a complete and satisfactory toilet did she
return to the caterpillar.
We saw Ammophila capture her prey only three times during the whole
summer; but from these observations and from the condition of her
caterpillars taken at various times from nests, her method seems to be
wonderfully close to that of hirsuta, with just about the same amount
of variation in different individuals.
Thus in our second example, she stung the first three segments in
the regular order, the third, the second, and lastly (and most
persistently) the first. She then went on, without a pause, to sting
the fourth, fifth, sixth, and seventh, stopping at this point and
leaving the posterior segments untouched. In our first example, it will
be remembered, the middle segments were spared. The stinging being
completed, she proceeded to the process known as _malaxation_, which
consists in repeatedly squeezing the neck of the caterpillar, or other
victim, between the mandibles, the subject of the treatment being
turned around and around so that all sides may be equally affected.
[Illustration: AMMOPHILA URNARIA STINGING CATERPILLAR]
In our third case a caterpillar which we had caught was placed in front
of a wasp just after she had carried the second larva into her nest.
She seemed rather indifferent to it, passing it once or twice as she
ran about, but finally picked it up and gave it one prolonged sting
between the third and fourth segments. She then spent a long time in
squeezing the neck, pinching it again and again, after which it was
left on the ground; and as she showed no further interest in it we
carried it home for further study.
In the three captures, then, that came under our observation, all
the caterpillars being of the same species and almost exactly of the
same size, three different methods were employed. In the first, seven
stings were given at the extremities, the middle segments being left
untouched, and no malaxation was practiced. In the second, seven
stings again, but given in the anterior and middle segments, followed
by slight malaxation. In the third, only one sting was given, but the
malaxation was prolonged and severe.
Let us now compare these variations with those of Fabre. In his first
case the sting entered at twelve different points, beginning between
the first and second segments and progressing regularly backward. There
was no malaxation. In his second example the third, second, and first
segments were stung in the order given, and thereafter each succeeding
segment up to the ninth, nine stings being given in all, with careful
malaxation following. In his later experiments, which seem to have been
numerous, he found that as a usual thing all the segments were stung,
although the posterior three or four were occasionally spared, but that
the order in which they were operated upon, as well as the amount of
malaxation, was very variable.
Our conclusions, then, as to Ammophila’s methods of stinging agree
fairly well with those of Fabre; but there is one important exception.
In his cases the middle segments, upon one of which the egg is laid
in our species as well as in his, were invariably stung, and this he
considers a point of extreme importance. In one of our cases the middle
segments were not touched.
[Illustration: CATERPILLAR WITH EGG OF AMMOPHILA URNARIA]
The point in which our observations differ most widely from those of
Fabre is in the condition of the caterpillars after the stinging.
He seems to have found that they always lived a long time, but in a
motionless or nearly motionless state; and he dwells at length upon the
necessity of both of these conditions, since he believes that while the
wasp larva must have perfectly fresh food, any violent motion would
imperil its safety. As a matter of fact we found a wide variation in
the thoroughness with which the wasps performed their task. We had, in
all, fifteen caterpillars upon which urnaria had worked her will; and
while a few of them fulfilled to a nicety the conditions which Fabre
believes to be imperative, most of them were far from doing so. Some
of them lived only three days, others a little longer, while still
others showed signs of life at the end of two weeks. Urnaria stores
two caterpillars, and in more than one instance the second one died
and became discolored before the first one was entirely eaten. The
wasp larva did not, as might have been expected, find fault with this
arrangement, but proceeded to attack number two with good appetite, ate
it all up, and then spun its cocoon as though nothing unpleasant had
occurred.
The second condition was also violated. In one case the bite of the
newly hatched larva caused the caterpillar to rear upon end in so
violent a manner that it looked as though the little creature would
surely be dislodged. Another caterpillar kept up a continuous wriggling
without any external stimulation, and when it was touched it rolled
about almost as these larvæ do in a healthy state, and yet the egg was
not shaken off. The caterpillar which received but a single sting,
although not motionless, would have been a safer repository for the egg
than either of these. Others fulfilled Fabre’s condition perfectly,
lying immovable except when stimulated, and then responding only by a
slight quivering of the legs or skin.
Among the fifteen caterpillars that we have taken from the nests of
urnaria three kinds are represented, twelve of them belonging to one
species, two to the second, and one to the third.
The egg, which is laid upon the side of the sixth or seventh segment,
hatches in from two to three days; the larva spends from six days to
two weeks in eating, and then spins its pale yellowish cocoon.
[Illustration: NEST OF AMMOPHILA]
The nesting habits of urnaria closely resemble those of the other
members of the genus, as reported by various observers. The spot chosen
is in firm soil, sometimes in open ground, but much more frequently
under the leaves of some plant. The plan is a very simple one. A
tunnel of about an inch in length leads to the pocket in which the
caterpillars are stored. There is no hardening of the walls in any
part. We took pains to draw every nest that we opened, and there was a
very considerable variation in the minor details, such as the obliquity
of the entrance tunnel, the shape of the pocket, and the angle at
which the tunnel and pocket were joined.
The work is done with the mandibles and the first legs. When it has
proceeded so far that the wasp is partly hidden, she begins to carry
the earth away from the nest. In doing this she backs up to the edge
of the opening and, flying a little way, gives a sort of flirt which
throws the pellet that she carries in her mandibles to a distance. She
then alights where she is and pauses a moment before she runs back
to the hole, or, in some cases, darts back on the wing. We watched
the process of nest–making five times during the summer. In the first
instance Ammophila, having made her excavation, ran off and after some
search returned with a good–sized lump of earth. This she laid over
the opening, which was now entirely hidden. She then flew to the bean
patch close by, but after ten minutes she came back and looked at her
nest. It was so neatly covered as to be almost indistinguishable, but
to this fastidious little creature something seemed lacking. She pulled
away the cover, carried out three or four more loads, and then began to
search for another piece for closing. After a time she came hurrying
back with a lump of earth, but when close to the nest she concluded
that it would not do, dropped it, and ran off in another direction.
Presently she found one which fitted into the hole exactly, and after
placing it she brought a much smaller piece which she put above and to
one side. She then stood back and surveyed the whole, and it seemed to
us that we could read pride and satisfaction in her mien. She then flew
away, and we supposed that that stage of the work was completed. Upon
coming back two hours later, however, we found that she had been trying
some more improvements, as a number of little pellets had been piled
up over the nest. This wasp, by the way, never succeeded in finding a
caterpillar, since when we opened the burrow a few days later it was
still empty. Perhaps she came to some untimely end.
Of the other wasps that we saw making a temporary closure of their
nests, one wedged a good–sized stone deep down into the neck of the
burrow and then filled the space above, solidly, with smaller stones
and earth. Another placed two lumps of earth just below the surface
of the ground, filled the opening with pellets loosely thrown in, and
then kicked some light dust over the whole. The others used only two or
three lumps of earth, which they fitted neatly into the opening just
below the surface. Although it is usual for urnaria to leave her nest
closed while she is off searching for her prey, there is no invariable
rule in the matter, even for single individuals. Once having seen a
wasp dig her nest and close it up, we drew some radiating lines from
the spot, in the light dust that covered the place, that we might find
it again. When we returned, two hours later, the same wasp had made a
nest four or five inches distant from the first one, and had left it
wide open, while she had gone off to search for her caterpillar. She
had probably been alarmed by the marks that we had made, and had felt
it necessary to dig a new nest, but being in a hurry to lay her egg had
omitted the usual process of closing it. We witnessed the storing of
the caterpillar and the final closing.
From Fabre we learn that argentata and sabulosa close the nest as soon
as it has been made, at least when the provisioning is to be postponed
until the next day, while holosericea leaves it open until it is
completely stored. He suggests an explanation for this variation by
dwelling upon the inconvenience that would result if it were opened
every time that the wasp brought in a caterpillar, since holosericea
stores up five or six small larvæ instead of one or two large ones. But
what, then, shall be said of polita and yarrowii, which, while they
also store a number of small caterpillars, take pains to close and
conceal the entrance every time they come out? We see the same habit
in other genera where the mother continually passes in and out, as in
Bembex and Oxybelus.
Fabre thinks that hirsuta has the habit, unusual for Ammophila, of
catching her prey first and then digging the hole in which she bestows
it. As she takes only one large caterpillar she is thus relieved of the
necessity of closing the nest more than once.
As has been said, urnaria usually hunts a long time before she finds
her caterpillar, and one or two days may pass before anything is put
into the nest. During this prolonged search she often revisits the
spot, and thus keeps fresh the memory of its locality. As soon as the
first caterpillar is stored she lays an egg on it, and then closes the
nest as before. The second one may be brought in within a few hours;
but in one instance that came under our notice we feel sure that the
interval was as much as three days. We saw the interment of the second
caterpillar, and upon excavating, found on the first one a larva at
least a day old; we suppose that at least two days had elapsed between
the laying and the hatching of the egg.
When the provisioning is completed the time arrives for the final
closing of the nest; and in this, as in all the processes of Ammophila,
the character of the work differs with the individual. For example, of
two wasps that we saw close their nests on the same day, one wedged
two or three pellets into the top of the hole, kicked in a little
dust, and then smoothed the surface over, finishing it all within five
minutes. This one seemed possessed by a spirit of hurry and bustle, and
did not believe in spending time on non–essentials. The other, on the
contrary, was an artist, an idealist. She worked for an hour, first
filling the neck of the burrow with fine earth which was jammed down
with much energy,—this part of the work being accompanied by a loud and
cheerful humming,—and next arranging the surface of the ground with
scrupulous care, and sweeping every particle of dust to a distance.
Even then she was not satisfied, but went scampering around, hunting
for some fitting object to crown the whole. First she tried to drag a
withered leaf to the spot, but the long stem stuck in the ground and
embarrassed her. Relinquishing this, she ran along a branch of the
plant under which she was working and, leaning over, picked up from the
ground below a good–sized stone; but the effort was too much for her,
and she turned a somersault on to the ground. She then started to bring
a large lump of earth; but this evidently did not come up to her ideal,
for she dropped it after a moment, and seizing another dry leaf carried
it successfully to the spot and placed it directly over the nest. A
third instance of the final closing of the nest was intermediate
between these two, the work occupying twenty minutes. The wasp first
put a plug well down, then dropped in several large pellets, brushed in
a quantity of fine earth, and finally smoothed the surface over.
We had another much less worthy example, one, indeed, that went to
the extreme of carelessness. We first saw her in the morning carrying
her caterpillar across the field. She frequently dropped it and ran
or flew to a little distance, and when she took it again the venter
was sometimes up and sometimes down, whichever way it happened. Her
nest was a very poor affair just beneath the surface, and after the
caterpillar was carried in, it was visible from above. She filled the
hole with loose particles of earth and then scratched the surface of
the ground a little in a perfunctory sort of way, as different as
possible from the painstaking labor that we had been accustomed to
in her sisters. That afternoon we opened the nest and removed its
contents. The next morning we saw this wasp bringing home her second
caterpillar. She was much puzzled and disturbed at the destruction
of her nest, and hunted for it for an hour and a half, leaving the
caterpillar on the ground near by. We could not help feeling sorry that
we had interrupted the contented routine of her life. She finally gave
up in despair, and we took possession of the deserted caterpillar.
Just here must be told the story of one little wasp whose individuality
stands out in our minds more distinctly than that of any of the others.
We remember her as the most fastidious and perfect little worker
of the whole season, so nice was she in her adaptation of means to
ends, so busy and contented in her labor of love, and so pretty in
her pride over the completed work. In filling up her nest she put her
head down into it and bit away the loose earth from the sides, letting
it fall to the bottom of the burrow, and then, after a quantity had
accumulated, jammed it down with her head. Earth was then brought from
the outside and pressed in, and then more was bitten from the sides.
When, at last, the filling was level with the ground, she brought a
quantity of fine grains of dirt to the spot, and picking up a small
pebble in her mandibles, used as it a hammer in pounding them down
with rapid strokes, thus making this spot as hard and firm as the
surrounding surface. Before we could recover from our astonishment at
this performance she had dropped her stone and was bringing more earth.
We then threw ourselves down on the ground that not a motion might be
lost, and in a moment we saw her pick up the pebble and again pound
the earth into place with it, hammering now here and now there until
all was level. Once more the whole process was repeated, and then the
little creature, all unconscious of the commotion that she had aroused
in our minds,—unconscious, indeed, of our very existence and intent
only on doing her work and doing it well,—gave one final, comprehensive
glance around and flew away.
[Illustration: AMMOPHILA URNARIA USING STONE TO POUND DOWN EARTH OVER
NEST]
We are claiming a great deal for Ammophila when we say that she
improvised a tool and made intelligent use of it, for such actions are
rare even among the higher animals; but fortunately our observation
does not stand alone, although we supposed this to be the case at the
time that it was made. Some weeks later, seeing a note of a similar
occurrence by Dr. S. W. Williston, of Kansas University, we wrote to
him on the subject. In his reply he said that he had waited for a year
before venturing to publish his observation, fearing that so remarkable
a statement would not be credited. His account is so interesting that
we quote it at length.
Even the casual observer, to whom all insects are bugs, cannot help but
be struck by the great diversity and number of the fossorial Hymenoptera
of the plains. Water is often inaccessible, trees there are few or
none, and only in places is the vegetation at all abundant. A much
larger proportion of insects, hence, find it necessary to live or breed
in holes in the ground, than is the case in more favored localities.
Especially is this the case with the Hymenoptera, great numbers and many
species of which thus breed in excavations made by themselves.
While packing specimens on an open space, uncovered by buffalo grass,
in the extreme western part of Kansas, the early part of last July, the
attention of a friend and myself was attracted by the numerous wasps
that were constantly alighting upon the ground. The hard, smooth baked
surface showed no indications of disturbance, and it was not till we
had attentively watched the insects that we learned what they were
doing. The wasp is a very slender one, more than an inch in length,
with a slender, pedicellate abdomen; it is known to entomologists as
Ammophila yarrowii Cres. They were so numerous that one was distracted
by their very multiplicity, but, by singling out different individuals,
we were enabled to verify each detail of their operations. An insect,
alighting, ran about on the smooth, hard surface till it had found a
suitable spot to begin its excavation, which was made about a quarter
of an inch in diameter, nearly vertical, and carried to a depth of
about four inches, as was shown by opening a number of them. The earth,
as removed, was formed into a rounded pellet and carefully carried to
the neighboring grass and dropped. For the first half of an inch or so
the hole was made of a slightly greater diameter. When the excavation
had been carried to the required depth, the wasp, after a survey of
the premises, flying away, soon returned with a large pebble in its
mandibles, which it carefully deposited within the opening; then,
standing over the entrance upon her four posterior feet, she (I say
she, for it was evident that they were all females) rapidly and most
amusingly scraped the dust with her two front feet, “hand over hand,”
back beneath her, till she had filled the hole above the stone to the
top. The operation so far was remarkable enough, but the next procedure
was more so. When she had heaped up the dirt to her satisfaction, she
again flew away and immediately returned with a smaller pebble, perhaps
an eighth of an inch in diameter, and then standing more nearly erect,
with the front feet folded beneath her, she pressed down the dust all
over and about the opening, smoothing off the surface, and accompanying
the action with a peculiar rasping sound. After all this was done, and
she spent several minutes each time in thus stamping the earth so that
only a keen eye could detect any abrasion of the surface, she laid
aside the little pebble and flew away to be gone some minutes. Soon,
however, she comes back with a heavy flight, scarcely able to sustain
the soft green larva, as long as herself, that she brings. The larva
is laid upon the ground, a little to one side, when, going to the spot
where she had industriously labored, by a few, rapid strokes she throws
out the dust and withdraws the stone cover, laying it aside. Next,
the larva is dragged down the hole, where the wasp remains for a few
minutes, afterwards returning and closing up the entrance precisely as
before. This, we thought, was the end, and supposed that the wasp would
now be off about her other affairs, but not so; soon she returns with
another larva, precisely like the first, and the whole operation is
again repeated. And not only the second time, but again and again, till
four or five of the larvæ have been stored up for the sustainment of
her future offspring. Once, while a wasp had gone down the hole with a
larva, my friend quietly removed the door stone that she had placed by
the entrance. Returning, she looked about for her door, but not finding
it, apparently mistrusted the honesty of a neighbor, which had just
descended, leaving her own door temptingly near. She purloined this
pebble and was making off with it, when the rightful owner appeared and
gave chase, compelling her to relinquish it.
The things that struck us as most remarkable were the unerring judgment
in the selection of a pebble of precisely the right size to fit the
entrance, and the use of the small pebble in smoothing down and packing
the soil over the opening, together with the instinct that taught them
to remove every evidence that the earth had been disturbed.
Since the Ammophiles of our species make their nests first and then do
their hunting it follows that they must sometimes carry their prey for
a considerable distance. The most ambitious attempt of this kind that
we ever witnessed was made by gracilis.
The wasp was first seen carrying a large green caterpillar, which
projected at both ends beyond her own body, across the potato field at
the lower end of the garden. We could not tell how far she had already
brought it, but judging by the direction from which she was coming, and
by the fact that we had never seen that species of caterpillar in the
garden, she had probably come through the fence from the woods beyond.
She moved along briskly over the remaining part of the potato field,
and then through an adjoining bean patch into the corn field. This had
been a place of much anxiety to us earlier in the summer; but now the
corn had been stacked and we could follow her without difficulty. So
far she had been going due south; but now she made a turn and plunged
into the long, tangled grass which grew around and among some large,
overgrown raspberry bushes. To keep track of her here seemed a hopeless
task, but we resolved to do our best, and followed anxiously after.
The wasp worked her way along about two inches above the ground and
very much below the top of the grass, clinging to the blades with her
feet and making surprisingly good progress. When half way through
the raspberry bushes she carried the caterpillar up on to a branch,
deposited it there, and after circling about to take her bearings, flew
away, doubtless to visit her nest and to make sure that she was going
in the right direction.
We, ourselves, were very glad of the chance to rest our tired eyes
and nerves from the strain of following her. The journey, so far, had
occupied nearly an hour, at almost every instant of which it had been
exceedingly difficult to keep her in view. But for our united efforts
we should certainly have failed.
While standing guard over the caterpillar we noticed that it moved its
head from side to side, showing that the first segment could not have
been severely stung, as is usually the case in the work of urnaria.
In five minutes the wasp returned, and, with the air of feeling that
everything was right, picked up her burden and carried it laboriously
through the remaining bushes and then through the grassy space that
edged the garden, as far as the rail fence which separated this part
of the grounds from the woods. Without a pause she climbed on to this
fence to the height of the second rail, passed through, and flew down
on the further side. Here she paused a moment, perhaps to take breath,
and we looked at each other in some dismay. Whither was she leading us?
We had now been following her for over an hour, and she looked equal
to as much again as she started off once more, rapidly this time, for
the grass was short here and the traveling was easy. Soon, however,
it became evident that things were going wrong, although we could not
determine what was the matter. The caterpillar was laid down while the
wasp absented herself for six minutes. She returned and carried it for
fifteen minutes, and then left it for half an hour. Once more she came
back, and carried it for ten minutes, and then she flew away. It was
now four o’clock, and we had been following her since two. We watched
over the caterpillar for an hour longer, but saw no more of the wasp.
Did she become discouraged at the magnitude of her task? It would have
been a thousand times easier for her to have dug her nest close by the
place of capture, but perhaps she had one larva already stored with her
egg upon it. The caterpillar was carried two hundred and sixty–one feet
while we watched her, with an unknown distance at each end to complete
the line between the place of capture and the nest. She could scarcely
have lost her way, since at every return she proceeded on her journey
in one general direction without any hesitation. It seems probable
then that she had hunted too far afield, and did not realize, when she
started with her booty, what an undertaking it would be to carry it to
the nest. We once saw A. vulgaris have a similar experience. She was
running along with a small green caterpillar, but became discouraged
either at the difficulty of finding her nest, or at the distance she
had to cover. She would carry the caterpillar a little way, drop it,
circle about a while, and then pick it up again; but finally she gave
up the whole undertaking and flew away.
The affairs of Ammophila must frequently go wrong, since in still
another of our few examples we saw much trouble and labor wasted. The
wasp, in this case an urnaria, captured her caterpillar successfully
and proceeded to carry it off. She was far from being in a hurry,
going along for a foot or so, and then making a long pause, during
which she would lay it down and either circle above it, perhaps to
take bearings, or spend the time in cleaning herself off, stroking and
smoothing every part of her body with the utmost care and deliberation.
Her stops were so frequent and so lengthy that nearly an hour was
occupied in going about twenty–five feet. When, at last, the nest was
reached, the plug was removed from the entrance and the caterpillar
dragged in, but almost immediately the wasp came out backwards with the
point of an egg projecting from the extremity of her abdomen. She ran
around and around the nest in a distracted way four or five times and
then went back, dragged the caterpillar out, and carried it away. The
egg came out further and further, and finally dropped on the ground
and was lost. The wasp, carrying the caterpillar, led us a long dance,
in a great semicircle over the field, coming back to the nest at last.
Instead of going in, however, she was about to start off on another
tour when we took her prey from her and placed it in the nest. The wasp
remained in the neighborhood for over an hour, but finally disappeared.
The nest was not closed, and when we dug it up on the following day it
contained only the caterpillar that we had put in.
We could usually enter into the feelings of the Ammophiles and
understand the meaning of their actions; but we were puzzled once,
when we saw an urnaria that had stored her second caterpillar and
closed her nest permanently, spend the rest of her morning in hunting.
Why in hunting? She had not dug a nest, she could not lay another egg
at once, she did not want a caterpillar, for when we offered her one
she stung it and then left it lying on the ground. The sun was bright,
the sorrel–blossoms invited her. Surely it would have been the part of
a rational wasp to have passed the rest of the day in feasting and fun.
We have said that urnaria stores two caterpillars, but this rule is
not without its exception. It was on the last day of the summer that
on a visit to our dear and fruitful potato field, we came upon a wasp
of almost double the ordinary size, that made, when flying, a loud hum
that at once attracted attention. She was just completing and closing
her nest, and we determined to watch and see what kind of a victim she
would bring in, as it seemed improbable that this great creature would
content herself with the ordinary fare of the species. The opening to
the nest measured half an inch in diameter.
It was eleven o’clock when she flew away. At half past twelve she
reappeared, coming from the direction of the woods, opened her nest,
and took out a few more pellets. Then she flew to a bush which grew
against the fence, three feet away, and following her quickly we saw
an immense green caterpillar placed high up on a branch. It must have
taken both strength and perseverance to lift this heavy weight so far
from the ground. She seized it at once and carried it down, not flying,
as these wasps sometimes do when they are descending with a burden, and
then dragged it into her nest, where it fitted rather tightly. This
nest was so shallow and so obliquely directed that the caterpillar was
plainly visible after it had been taken in.
After she had laid her egg she crawled out, getting past the
caterpillar with some difficulty, and closed the nest. There was
certainly no room for any further store of provisions, and from the
size of the caterpillar we judged that it would furnish sufficient
nourishment even for the offspring of this wasp. We were, therefore,
not surprised, upon opening the nest two days later, to find that
nothing more had been brought. We have said that the wasp larvæ spend
from six days to two weeks in eating. To be more exact, all that we
watched, with the exception of the one which developed from the egg
of this big creature, ate from six to eight days and then spun their
cocoons; but this one seemed determined to reach the size of its
mother, and ate continuously for fourteen days. Of course long before
this time had expired the remnant of the caterpillar had become a dry,
dark–colored mass which looked little likely to tempt the appetite, but
the great larva ate away with unabated relish, gradually acquiring the
color and almost the thickness of the caterpillar it had destroyed.
Ammophila polita, which we have never seen in the country, is very
common in the sandy fields to the south of Milwaukee. On the tenth of
September, in bright clear weather, we found half a dozen individuals
working within a few rods of each other, their method being similar to
that of A. yarrowii, described by Dr. Williston, and having an especial
interest, as it shows a transition stage between the wasps that
provide the store of food all at once and those that feed their young
all through the larval period. Urnaria rarely flies with her prey;
but this wasp, although her caterpillars, are not very much smaller,
and she herself is no larger, carries her booty lightly on the wing,
alighting only occasionally to run a few steps. She has to do more work
than urnaria, taking five or six caterpillars instead of two, and this
method of progression has the advantage of rapidity.
The first wasp that we saw was just alighting with a medium–sized
green caterpillar near a partly closed nest. When disturbed she flew
away, but soon returned, dropped her prey half an inch from the nest,
proceeded to clear the opening, ran inside to see that all was right,
and then backed in with the caterpillar. Emerging after a few minutes,
she placed a small pebble in the doorway, which was thus partly closed,
and flew away. She brought three more caterpillars at intervals of
thirty minutes, and then, after wedging a pebble into the neck of
the opening, she began to fill it in solidly, scratching in dirt and
packing in lumps of earth which were brought in her mandibles. We
did not allow her to complete this operation, as it would have made
excavation more difficult, but caught her and dug out the nest. The
tunnel ran down obliquely for five inches, being two inches below the
surface at the pocket. In it we found a wasp larva, which was at least
three days old, and four caterpillars. There were no signs of the
banqueting which must have already taken place. We carried this larva
home with us, and it ate the caterpillars up clean, finishing with a
fifth which we supplied from another nest, and going into its cocoon
on September sixteenth. The caterpillars all wriggled about on the
slightest stimulation, and remained in this lively state until they
were eaten. They belonged to four different species.
In a second nest to which food was being carried, we found four
caterpillars and a larva about three days old, all the conditions being
like those in the other example. Evidently the larva had been fed from
day to day, since four or five days must have elapsed since the making
of the nest.
Westwood states that Ammophila, when she has captured her prey, walks
backward, dragging it after her;[1] but in all the cases that came
under our notice she went forward, the caterpillar being grasped near
the anterior end, in her mandibles, and either lifted above the ground
or allowed to drag a little if long and heavy. It is usually held
venter up, but in one case, in which the wasp, while carrying it to her
nest, frequently laid it down and picked it up again, it was held with
the venter down or up indifferently.
The all–important lesson that Fabre draws from his study of the
Ammophiles is that they are inspired by automatically perfect
instincts, which can never have varied to any appreciable extent from
the beginning of time. He argues that deviation from the regular rule
would mean extinction. For example, if the wasp should sting ever so
little to one side of the median line the prey would be imperfectly
paralyzed and the egg would consequently be destroyed; or a sting in
the wrong place might cause the death of the caterpillar and thus the
death of the wasp larva, which, he thinks, can be nourished only by
perfectly fresh food.
The conclusions that we draw from the study of this genus differ
from these in the most striking manner. The one preëminent,
unmistakable, and ever present fact is variability. Variability in
every particular,—in the shape of the nest and the manner of digging
it, in the condition of the nest (whether closed or open) when left
temporarily, in the method of stinging the prey, in the degree of
malaxation, in the manner of carrying the victim, in the way of closing
the nest, and last, and most important of all, in the condition
produced in the victims of the stinging, some of them dying and
becoming “veritable cadavers,” to use an expressive term of Fabre’s,
long before the larva is ready to begin on them, while others live long
past the time at which they would have been attacked and destroyed if
we had not interfered with the natural course of events. And all this
variability we get from a study of nine wasps and fifteen caterpillars!
In his chapter on “Méthode des Ammophiles” Fabre says that each species
has its own tactics, allowing no novitiate. “Not one could have left
descendants if it were not the handy workman of to–day. Any little
slip is impracticable when the future of the race depends upon it.” And
yet we find that the prey may be stung so slightly that it can rear
and wriggle violently or so severely that it dies almost at once, and
in neither case is a break made in the generations of the Ammophiles,
since in the former the egg or larva is so firmly fastened as to keep
its hold, while in the latter the dead and decomposing caterpillar is
eaten without dissatisfaction or injury.
Nor do we, in gathering evidence for the evolution of the instincts of
these wasps, need to rely entirely upon our own observations. Fabre
himself gives many facts which point in the same direction, but he
draws a line between those actions which are the result of mechanical
and unvarying instinct and those which come within the sphere of
reason, and in relation to which the insect must consider, compare,
and judge. Yet this line, even in the light of his own work, is so
extremely variable, needing readjustment with every new species and
often among the individuals of the same species, that it loses for
others the meaning which it has for its author. He himself speaks of
certain individuals of the genus Sphex which refuse to be duped when
he withdraws their prey to a distance. These, he says, are the élite,
the strong–headed ones, which are able to recognize the malice of the
action and govern themselves accordingly, but these revolutionists, apt
at progress, he goes on to say, are few in numbers. The others, the
conservators of old usages and customs, are the majority, the crowd.
Yes, but is it not always the strong–minded few that direct the destiny
of a race?
Chapter III
THE GREAT GOLDEN DIGGER
THIS wasp (Sphex ichneumonea Linn.) is one of our most beautiful
species, its great size and its brilliant color, as it flies among the
flowers, serving to make it well known to all observers of nature.
During the later part of July, all through August, and even in the
early days of September it is commonly found at work making or storing
its burrow. It is rare in our garden, however, and we thought ourselves
fortunate in being able to keep track of one individual from the
making to the closing of the nest. Although large and powerful it is
gracefully formed. In color it is brown, varied with bright yellow.
On the morning of the third of August, at a little after ten o’clock,
we saw one of these hunters start to dig a nest on the side of a stony
hill. After making some progress in the work she flew off and selected
a second place, where she dug so persistently that we felt confident
that this was to be her final resting–place; but when the hole was two
and one half inches deep, it too was deserted. Again our wasp chose
a spot and began to burrow. She worked very rapidly, and at twenty
minutes before twelve the hole was three inches deep. At high noon she
flew away, and was gone forty minutes. The day was excessively hot,
about 98° Fahr., and we ourselves were only deterred from taking a
noonday rest by our fixed determination not to leave the place until we
had seen all that there was to be seen in the manœuvres of ichneumonea.
On returning she appeared very much excited, fairly quivering with
vitality as she resumed her work. She came up backward, carrying the
earth with her mouth and anterior legs, and went back from the opening
some little distance, when it was dropped, and she at once went in
again. While in the burrow we could hear her humming, just as the
Pelopæi do when, head downward in the wet mud, they gather their loads
for nest–building. In five or six trips a little mass of earth would
accumulate, and then she would lie quite flat on the heap and kick the
particles away in all directions. As the work progressed the earth was
carried further and further away before it was placed on the ground,
and as she backed in different directions the material brought out was
well spread about from the down–hill side of the nest. Sometimes she
would spend several moments in smoothing the débris all around, so
that the opening presented much the appearance of an immense ant–hill,
only the particles were much larger. During the first hour that we
watched her she frequently turned directly toward us, and, sometimes
remaining on the ground and sometimes rising on her wings to a level
with our faces, appeared to be eyeing us intently for four or five
seconds. Her attitude was comical, and she seemed to be saying, “Well,
what are you hanging around here for?”
[Illustration: THOROUGH LOCALITY STUDY BY SPHEX]
As the afternoon wore on she worked more calmly and her fidgety and
excited manner disappeared, the excavation progressing steadily until
half–past three. At that time she came out and walked slowly about in
front of her nest and all around it. Then she rose and circled just
above it, gradually widening her flight, now going further afield and
now flying in and out among the plants and bushes in the immediate
vicinity. The detailed survey of every little object near her nest was
remarkable; and not until her tour of observation had carried her five
times entirely around the spot did she appear satisfied and fly away.
All her actions showed that she was studying the locality and getting
her bearings before taking her departure. A fact that impressed us very
much was that with the two nests that she had begun and then deserted
she had taken no such precau tion, but simply came up and flew off.
Had she made up her mind, if we may be allowed to use the term, that
the localities were in some way unsuitable and that hence she had no
occasion to return to them? Had she decided, in the last instance, that
she would return and so must get her bearings? We wondered how far the
different acts were instinctive, or were, as Huber has it, an evidence
of a “little dose of judgment.” Bates, in speaking of Monedula signata,
says that he often noticed it taking a few turns about the locality
of its nest, and that he was convinced that it was doing so for the
purpose of getting its bearings. Belt, having described how he fed a
specimen of Polistes carnifex with a caterpillar, which the wasp cut
into two parts, goes on to say: “Being at the time amidst a thick mass
of fine–leaved climbing plant, it proceeded, before flying away, to
take note of the place where it was leaving the other half. To do this,
it hovered in front of it for a few seconds, then took small circles
in front of it, then larger ones around the whole plant. I thought it
had gone, but it returned again, and had another look at the opening
in the dense foliage down which the other half of the caterpillar
lay.”[2] He then remarks that when the wasp came back for the remaining
half it flew straight to its nest without taking any further note of
the locality. Both of these writers believe that many of the actions
of insects that are ascribed to instinct are really evidence of the
possession of a certain amount of intelligence.
[Illustration: HASTY LOCALITY STUDY BY SPHEX]
To return to our Sphex. When she flew away we naturally supposed that
she had gone in search of her prey, and we were on the _qui vive_ to
observe every step in her actions when she came home. Alas! when she
came back half an hour later, she was empty–handed. She dug for four
minutes, then flew off and was gone two minutes, then returned and
worked for thirty–five minutes. Another two minutes’ excursion, and
then she settled down to work in good earnest and brought up load
after load of earth until the shadows grew long. We noticed that on
these later trips she flew directly away, depending upon her first
careful study of the surroundings to find her way back. At fifteen
minutes after five the patient worker came to the surface, and made a
second study, this time not so detailed, of the environment. She flew
this way and that, in and out among the plants, high and low, far and
near, and at last, satisfied, rose in circles, higher and higher, and
disappeared from view. We waited for her return with all the patience
at our command, from fifteen minutes after five until fifteen minutes
before seven. We felt sure that when she came back she would bring her
victim with her, and when we saw her approaching we threw ourselves
prone on the ground, eagerly expecting to see the end of the drama; but
her search had been unsuccessful,—she carried nothing. In the realms
of wasp–life, disappointments are not uncommon, and this time she had
us to share her chagrin, for we felt as tired and discouraged as she
perhaps did herself. When we saw her entering without any provision
for her future offspring, we were at a loss what to do next; and it
may be that this state of mind was shared by her also, for she at once
began to fill in the entrance to her nest. We now thought it time to
act, and decided to capture her, to keep her over night in one of our
wasp–cages, and to try to induce her to return to her duty on the
following day. We therefore secured her in a large bottle, carried her
to the cottage, and having made every possible arrangement for her
comfort, left her for the night.
[Illustration: SPHEX DRAGGING GRASSHOPPER TO HER NEST]
On the next morning, at half after eight o’clock, we took Lady Sphex
down to her home, and placed the mouth of the bottle so that when she
came out she had to enter the nest. This she did, remaining below,
however, only a moment. When she came up to the surface she stood still
and looked about for a few seconds, and then flew away. It surprised
us that having been absent from the place for so many hours, she made
no study of the locality as she had done before. We thought it a very
unpromising sign, and had great fears that she was deserting the place
and that we should see her no more. One would need to watch a wasp
through the long hours of a broiling hot day to appreciate the joy
that we felt when at nine o’clock we saw her coming back. She had no
difficulty in finding her nest, nor did she feel any hesitation as to
what ought to be done next, but fell to work at once at carrying out
more dirt. The weather, although still hot, had become cloudy and so
threatening that we expected a down–pour of rain every moment, but
this seemed to make no difference to her. Load after load was brought
up, until, at the end of an hour, everything seemed completed to her
satisfaction. She came to the entrance and flew about, now this way,
and now that, repeating the locality study in the most thorough manner,
and then went away. At the expiration of an hour we saw her approaching
with a large light green meadow–grasshopper, which was held in the
mouth and supported by the fore legs, which were folded under. On
arriving, the prey was placed, head first, near the entrance, while the
wasp went in, probably to reassure herself that all was right. Soon
she appeared at the door of the nest and remained motionless for some
moments, gazing intently at her treasure. Then seizing it (we thought
by an antenna) she dragged it head first into the tunnel.
The laying of the egg did not detain her long. She was up in a moment
and began at once to throw earth into the nest. After a little she went
in herself, and we could plainly hear her humming as she pushed the
loose material down with her head. When she resumed the work outside we
interrupted her to catch a little fly that we had already driven off
several times just as it was about to enter the nest. The Sphex was
disturbed and flew away, and this gave us an opportunity to open the
burrow. The grasshopper was placed on its back, with its head next to
the blind end of the pocket and the legs protruding up into the tunnel.
We found that the egg of the wasp, which was seven millimeters long,
and rather slender, was placed on the under face of the thorax at a
right angle to its length, and parallel with the femur of the second
leg. This leg had apparently been stung so that it had swollen and
folded over the free end of the egg, which was thus firmly held in
place at both extremities.[3] Upon examination we found that the
abdomen of the grasshopper was beating regularly and automatically,
but the closest observation failed to discover any other movements,
nor would any part respond when stimulated. At three o’clock in the
afternoon we found the abdomen still pulsating, and, in addition, that
both antennæ moved several times when we lifted off the cover of the
jar that contained the insect. On the next morning the grasshopper was
very lively, the antennæ and labial palpi moving without stimulation.
It had passed fæces, and was able to lift its abdomen, which was
curved over toward the head, as it lay on its back, frequently and
with considerable violence. On the next afternoon there was no change
in the movements, but the egg was dead. On the seventh the grasshopper
responded to stimulation by a slight movement of the palpi and the
end of the abdomen. The pulsation of the abdomen continued until the
afternoon of the eighth, when it ceased, no effort of ours succeeding
in starting it again. The movements of the antennæ and palpi grew
weaker and weaker on the ninth, and on the morning of the tenth the
insect was dead, a period of five and a half days having elapsed since
it was brought into the nest.
We had not supposed that the digging up of her nest would much disturb
our Sphex, since her connection with it was so nearly at an end; but
in this we were mistaken. When we returned to the garden about half an
hour after we had done the deed, we heard her loud and anxious humming
from a distance. She was searching far and near for her treasure
house, returning every few minutes to the right spot, although the
upturned earth had entirely changed its appearance. She seemed unable
to believe her eyes, and her persistent refusal to accept the fact
that her nest had been destroyed was pathetic. She lingered about the
garden all through the day, and made so many visits to us, getting
under our umbrellas and thrusting her tremendous personality into our
very faces, that we wondered if she were trying to question us as to
the whereabouts of her property. Later we learned that we had wronged
her more deeply than we knew. Had we not interfered she would have
excavated several cells to the side of the main tunnel, storing a
grasshopper in each. Who knows but perhaps our Golden Digger, standing
among the ruins of her home, or peering under our umbrella, said to
herself: “Men are poor things: I don’t know why the world thinks so
much of them.”
[Illustration: NEST OF SPHEX]
Dr. Packard describes Sphex ichneumonea as nesting in gravelly walks,
where it digs to a depth of from four to six inches, using its jaws
and fore legs to do the excavating. While the wasps that he observed
completed the hole in half an hour, ours was actually at work a little
over four hours. Her nest, as is shown in the drawing, measured
seven and one half inches to the beginning of the pocket, which was
three quarters of an inch wide by one and one half inches long. The
yellow–winged Sphex, a native of France, was found by Fabre to take
several hours to make her nest, working in hard ground; while another
species, also studied by this observer, dug in soft earth, either in
the ground or in the accumulations on the roofs of buildings, and
completed her work in fifteen minutes at the most. These variations in
the habits of closely related species should be carefully studied in
any attempt toward an explanation of their instincts.
Fabre’s account of the genus Sphex, as it appears in France, is
most interesting. He says that the yellow–winged species, living in
colonies, first digs her nest and then secures her cricket, which is
brought, on the wing, to the neighborhood of the burrow, the last part
of the journey being accomplished on foot. The cricket is dragged by
one of the antennæ, and is not left until the nest is reached. It is
then placed so that the antennæ reach precisely to the opening, and
there it is left while the wasp descends hurriedly into the depths of
the burrow. In a few seconds she reappears, showing her head outside,
seizes the antennæ of the cricket, and drags it below. These manœuvres
are repeated with a striking degree of invariability.
The other Sphex first secures her prey, which is too large and heavy
to be carried far, and then digs her nest in the neighborhood of the
capture. This being done, she returns to her victim, and straddling it
drags it by one or both of the antennæ. Sometimes the whole journey is
accomplished at once, but oftener the wasp suddenly drops her burden
and runs rapidly to her nest. Perhaps it seems to her that the entrance
is not large enough to accommodate a creature of such size; perhaps she
imagines some imperfections of detail which would impede the process
of storing it up. The work is retouched, the doorway enlarged, the
threshold smoothed. Then she returns to her booty and again starts
with it. After a few steps the Sphex seems to be seized with another
idea. She has visited the doorway, but has not seen the interior. Who
knows whether all is well within? She drops her prey and again runs
off. The visit to the interior is made, more touches are given, and
once more she returns. Will the journey be accomplished this time?
Impossible to say. Some wasps, more given to worry than others or more
forgetful of the small details of architecture, to repair their neglect
or to clear up their suspicions, abandon their booty five or six times
in succession to retouch the nest or simply to visit the interior. The
prey, once brought to the nest, is carried in without the preliminaries
that are common to the other species.
Chapter IV
SEVERAL LITTLE WASPS
In a search for the nest of one of our garden wasps we found, in the
woods beyond the fence, an old, weather–beaten stump which was riddled
with holes both large and small. The large ones were evidently the
passage–ways of ants, and were in constant use. The small ones seemed
to be uninhabited; but thinking they might contain the nests we were
in search of, and hoping that if we watched long enough we might see
our wasps flitting in and out, we settled ourselves close by. We
were resolved to stay as long as was necessary, and we blessed the
fate that made it our duty to sit on the grass under the shade of a
wide–spreading oak rather than in the distressing glare and heat of the
garden; for this was on the tenth of July, and the weather was what the
farmers call “seasonable.”
Twenty, thirty, forty minutes passed. Our eyes ached with persistent
gazing, and we had nearly made up our minds that the likely–looking
little holes were untenanted, when lo! a tiny wasp, carrying something
which we could not see distinctly, darted into one of them. It was
gone so quickly that we could not be sure that it was the species we
were looking for, and when it reappeared, after two or three minutes,
we saw that it was not. This point being determined, we watched the
hole with redoubled interest.
It was wearisome work, for the wasp stayed away a long time, and we
dared not let our gaze wander lest she should slip in without our
knowledge. At the end of thirty–five minutes she returned, but again
we failed to see what she carried. She flew with great rapidity, and
we scarcely caught sight of her before she vanished into her nest.
We could not but wonder at the ease and certainty with which she
recognized her own doorway among the hundreds of holes on the side of
the stump. This power of localization, while it is one of the most
common among wasps, is surely also one of the most remarkable.
Our little Rhopalum pedicellatum, for that proved to be her name, made
six more journeys within the next two hours. At the end of this time
we opened the tunnel, and, after a great deal of sawing and cutting,
succeeded in finding the nest five inches from the surface. It was
nothing but a slight enlargement of the gallery, in the soft decaying
wood. In it we found thirty–three gray gnats, all of them, except two,
being dead. On one of the dead ones was the egg, which had probably
been laid within a few hours.
The egg hatched two days later, on July twelfth, but on the fifteenth
the larva died. By this time many of the gnats looked very dry,
although we had tried to arrange for both moisture and ventilation by
packing the bottom of the tube with pith and covering the top with
muslin.
Further watching gave us one more wasp of this species, in the same
stump. This time the nest was only two inches from the surface. It
contained four dead gnats and two live ones, but no egg, showing that
the egg is not always laid on the first ones stored.
Much later in the season, toward the end of August, we found another
species of Rhopalum which proved to be new, and for which Mr. Ashmead
has proposed the name rubrocinctum, since it wears a red girdle around
the front end of the abdomen, being otherwise dressed in black like
pedicillatum. It makes its home in the stalks of raspberry bushes.
We opened a stem which contained thirteen compartments, separated by
partitions of pith. These were filled with black, gray, and green
gnats, which were packed in so closely that they were doubled over and
pressed out of shape. Each cell contained from twenty–five to thirty
gnats. In some of them were cocoons, in others larvæ, and in one was
an egg. The gnats were very carefully examined, and all of them, from
the cells that had been filled last as well as from those provisioned
earlier, were dead.
Other species of Rhopalum are said to prey upon spiders and aphides.
In studying the species that come in our way we are continually
developing distinct likings for some kinds above others. The appearance
of one of these favorites is always hailed with delight, and when the
season’s work is over we remember them with lively pleasure.
[Illustration: OXYBELUS QUADRINOTATUS]
It is thus, dear little Oxybelus, that we dwell upon the thought of you
and your pretty ways. No other wasp rose so early in the morning, no
other was so quick and tidy about her work, so apt and business–like
without any fuss or flurry. No other was more rapid and vigorous in
pursuit of her prey, and we think with admiration and gratitude of
the number of flies that you must have destroyed in the course of the
summer.
O. quadrinotatus is only one–quarter of an inch long, and is dark gray
with four whitish spots on the abdomen. It was before nine o’clock
in the morning that, while out on an early inspection tour in the
garden, we saw one of these wasps descend upon a sandy spot, and after
a moment’s rapid scratching with her first legs enter the hole that
she had opened. Under her body she was carrying a fly which looked
like the common domestic species. It was upside down, its head being
tightly clasped with the third pair of legs, and all of its abdomen
projected beyond the abdomen of the wasp. Ashmead quotes from Fabre the
remarkable statement that Oxybelus carries her flies home impaled on
her sting, an idea that probably arose from the fact that nearly the
whole body of the fly is visible.
Our new–found wasp stayed only a moment in her nest, although, as we
afterward found, it was long enough for her to lay her egg on the fly.
When she came out she quickly smoothed the sand over the spot with her
head and legs so that there was nothing to mark the nest, and flew
away. In three minutes she returned with another fly. She alighted two
or three inches away, and scratched for an instant, but quickly saw her
mistake, and found the right spot.
Again and again the pretty little worker went and came, while we sat
watching close by, admiring her deft handiwork in opening and closing
the nest and wondering at the ease with which she found it at each
return. There was nothing tiresome or dilatory about this species, and
within twenty minutes we had seen six flies stored up. The nest was
closed and the place smoothed over every time before she went away, but
when she entered she left the door open behind her. We once tried to
make her drop the fly, but when disturbed she flew up and alighted on a
plant near by, keeping her hold on it. The whole performance was brisk
and business–like, but without the feverish hurry of Ammophila and
Pompilus.
After the sixth fly was taken in we were afraid to let her go again,
thinking that the nest must now be completely provisioned, and that she
would not return. She was such a charming little wasp, scarcely bigger
than a fly herself and yet so useful in her industry, that we hated to
disturb her; but as we were obliged to have her for identification we
first caught her, and then opened the nest. It contained only the flies
that we had seen taken in, the egg being attached to the one lowest
down, on the left side, between the head and the thorax. It was long
and cylindrical. The flies were dead, but showed no marks of violence.
We learned later that it takes Oxybelus two hours to make her nest so
that this one must have been prepared the day before.
The egg, which was laid just before nine o’clock on the morning of
August seventh, hatched at a little after nine on the morning of August
eighth. The larva began to eat at once, and devoured all the inside
of the thorax and abdomen of the fly to which it was attached, in the
first twenty–four hours. On August twelfth it had reached the sixth
fly, and we supplied it with three more. On August fourteenth these
were gone, and we again replenished its larder, this time with two
flies. The larva had partly eaten these when something went wrong. Its
appetite failed, and on August sixteenth it died.
On further acquaintance this wasp lost none of her charm,—indeed, she
gained in interest from the almost human curiosity that she showed
about the affairs of other people. Where several were living close
together one of them would sometimes stop digging her own nest to perch
on a weed and watch the labor of another, and we once saw an especially
inquisitive character burrow through the closed door and enter the home
of her next–door neighbor.
[Illustration: NEST OF OXYBELUS]
We find but meagre notes on the genus Oxybelus. Ashmead says that
no observations have been made on the American species, but that in
Europe they are found to burrow in sand and to provision their nests
with dipterous insects. He says also that according to Verhoeff the
species in this genus do not paralyze their prey by stinging, as they
are unable to do so on account of the rigidity of the abdomen, but
that instead they crush the thorax with the mandibles just beneath
the wings, the centre of the nervous ganglia. He found in one nest
a dozen flies, and all had the thorax crushed and were dead. In the
case of our wasp we do not know how the flies were killed, but there
was no crushing of the thorax. The larva devoured, in all, ten flies.
At the time of its death it had probably finished the larval stage
of its existence, since nine days had elapsed since the hatching
of the egg. It may be that this period just before pupation is a
critical point in the life history of a wasp, for we lost several of
our nurslings at this time, and Fabre has noted that when, on account
of the presence of parasites, the larva of Bembex rostrata had lacked
something of its usual amount of nourishment, it perished miserably at
the end of its larval stage, not having strength enough to spin its
cocoon. No waspling in our charge ever died from lack of nourishment—on
that score our consciences are clear; but it was difficult to make
their conditions quite normal, and for this reason we may have been,
indirectly, the cause of their death.
The way in which our Oxybelus carries its prey is peculiar to itself.
Bembex and Philanthus also hold their prey under the body, but use the
second pair of legs, so that it does not project behind except at the
moment of entrance into the nest. Quadrinotatus, as we could distinctly
see, since she passed close to us several times in quick succession,
clasps the head of her victim in the third pair of legs, and flying
thus, with its whole body sticking out behind her, she certainly
presents a very remarkable appearance.
[Illustration: APORUS FASCIATUS]
Aporus fasciatus is a dark gray species, and is less than half an inch
in length. We were working one hot day in the melon field, when we
saw one of these little wasps going backward and dragging a female of
Mævia vittata which was much larger than she was herself. She twice
left it on the ground while she circled about for a moment, but soon
carried it up on to one of the large melon leaves, and left it there
while she made a long and careful study of the locality, skimming close
to the ground in and out among the vines; at length she went under a
leaf that lay close to the ground and began to dig. After her head
was well down in the ground we broke off the leaf that we might see
her method of work. She went on for ten minutes without noticing the
change, and then, without any circling, flew off to visit her spider.
When she tried to return to her hole it was evident that some landmark
was missing. Again and again she zigzagged from the spider to the
nesting–place, going by a regular path among the vines from leaf to
leaf and from blossom to blossom, but when she reached the spot she did
not recognize it. At last we laid the leaf back in its place over the
opening, when she at once went in and resumed her work, keeping at it
steadily for ten minutes longer. At this point she suddenly reversed
her operations and began to fill the hole that she had made, kicking
in the earth until the entrance was hidden. She then glanced at the
spider, selected a new place, and began to dig again. Surprisingly
large pellets of earth were carried out, backward, and loose dirt was
kicked under the body by the first legs. At the end of two or three
minutes she paused and remained perfectly still for a time, considering
the situation. Her conclusion was adverse to the locality, for she
soon filled in the hole, looked once more at the spider, and started a
third nest in a new place. This in turn was soon abandoned, as was also
a fourth. The fifth beginning was made under a leaf that lay close to
the ground, so that we could not see her at all. Fasciatus! had we had
the naming of her she should have gone down the ages as exasperans! We
had now watched her for an hour in the intense heat; the bell for the
noonday meal had sounded, hunger and thirst had descended upon us, and
most devoutly did we hope that she was suited at last, but no—after
twenty minutes’ work this place also was abandoned, and a sixth nest
started. This, however, was the final choice, and after forty–five
minutes spent in digging, it was completed. As the spider was brought
toward the nest it was left again and again while the nervous little
wasp flew to the hole, went in, examined, and came out again. At last
she backed in, caught the spider by the abdomen, and dragged it down.
It was too big—the head stuck in the hole; but she pulled from below
while we pushed gently from above, and it slowly disappeared. When she
came out we opened the nest and took the spider. The egg was fastened
to the middle of the left side of the abdomen. This one, as was also
the case with a second and third afterward taken from fasciatus, was
much less affected by the poison than is usual among the victims
of solitary wasps, moving from the time it was taken, without any
stimulation, and improving rapidly from day to day. Our second spider
appeared to be blind, and died upon the sixteenth day, while the third
had entirely recovered by the seventeenth day after it was stung, and
was released. Fasciatus, then, probably depends upon packing her victim
in tightly to keep it quiet.
It was three days and a half before the egg that we had taken hatched.
The larva developed rapidly, retaining its hold at the spot to which
the mother had fastened it. The spider remained alive for six days,
and the larva continued to grow for two days longer, when it died
also, being at the time about two thirds grown. We had great trouble in
protecting our growing larvæ from the inroads of fungi, and this was
one of the many that perished from that cause.
The next example of fasciatus that came under our notice was a
remarkable contrast to the one that we have just described, being as
slow and dignified as the other was nervous and hurried. She chose
a place and kept to it, her steady labor being interrupted only by
occasional visits to the spider; but it took her fifty minutes to
complete the nest. When finished it was a small gallery running down
obliquely for an inch and a half into the ground.
The only habit that this species can claim as peculiar to itself is the
strange and useless one of filling up the partly made nests that it is
about to abandon. We have never seen the sense of order carried to so
high a point in any other wasp.
[Illustration: WASP HOMES IN THE LOG CABIN]
On a hillside near our cottage stands a log cabin, deserted and
untenanted save for small creatures of the wild, which, though a
favorite spot with wood–boring wasps, is an unprofitable place for
study because of the difficulty of cutting out their nests without
destroying property. One day in early July, however, when we were
in the full fervor of hunting and longed to utilize every moment,
the wasps in our garden seemed to have resolved that enjoyment
and enjoyment only was their destined end and way, and became so
exasperatingly idle that in disgust we turned to the cabin. For half
an hour we saw nothing more exciting than a Trypoxylon immuring her
victims and a Pompilus hunting spiders under the eaves, but at the end
of that time Passolocus annulatus, a tiny wasp new to us, came flying
quietly along and entered one of the holes with which the ends of the
logs were riddled. She was carrying an aphis in her mandibles, and when
this was duly stored she reappeared and flew away. She had probably
just renewed her work after a spell of rest, since from this time on
for nearly an hour she came back regularly every four or five minutes.
She nearly always alighted on a blade of grass before going into the
nest, but did not appear to be malaxing her prey. Presently another
stage in the game was reached. She no longer brought aphides, but
little pellets of mud with which she plastered up the opening. After
she had finished this task and departed, we carefully chiseled into the
log and laid bare the nest. The tunnel ran in for about three inches,
and ended in three pockets which were well stocked with dead aphides,
there being fifty–seven in all. The innermost cell contained a larva,
and in the others were eggs, one of which hatched on the next day and
one on the day following. This second one was probably laid just before
the nest was sealed, giving forty hours for the egg stage; and it
proved to be the healthiest of the three. The others perished in early
infancy; but this one passed twelve days in eating, not only its own
share of provisions, but those destined for the other members of the
family as well, and then spun its cocoon.
We afterwards saw many of these wasps working in the logs of the cabin,
and noticed that they seemed to have seasons of leisure alternating
with spells of active work, as though when one cell had been filled up
and the egg laid they felt at liberty to amuse themselves for a time
before beginning on another. When an entirely new residence was to be
chosen they went house–hunting among the old holes in the logs; and
whether they had a high standard of sanitary conditions, or whether
they objected to making extensive repairs, a great many places were
examined and rejected before they settled down. The choice once made,
many loads of pith were carried out before the little householder was
satisfied. After the new abode was put to rights, the wasp would pass
a whole day in rest, spending much of the time in looking out of her
doorway and perhaps in observing the doings of her neighbors, but when
she began to work she was very industrious, and allowed nothing to
interfere with her labors, paying no more attention to us, no matter
how closely our curiosity led us to interrogate her, than if we had
been trees blown about by the wind.
[Illustration: NEST OF PERENNIS]
Some of the wasps dig deep into the stems of bushes to form galleries
for their nests, but we found one wise genus that went in only far
enough to make one or two cells, thus saving the trouble of carrying
her cuttings thirty or forty centimeters in direct opposition to the
force of gravity. This was Odynerus, whose nests we found in July, in
blackberry and raspberry stems. Our first species was perennis, whose
nests bear her mark in the shape of a pellet of earth placed above
each mud partition. One of her cells contained a wasp larva and about
sixteen caterpillars, nearly one third of which were dead, while the
rest were more or less lively. They seemed to have been stung near
the anterior part, as the last three or four segments were jerked up
violently when touched. The larva went on eating, and the caterpillars
went on dying from hour to hour. At the end of the eighth day, the baby
wasp finished its meal, having eaten all that had been provided for
it, as well as two dead caterpillars from another nest.
Much interest attaches to the way in which Odynerus lays her egg, since
instead of following the common fashion of fastening it to the prey she
suspends it by a tiny filament of web from the wall or ceiling of her
cell. Thus in O. reniformis, nesting in the ground, it is hung from
the ceiling, a mass of very imperfectly paralyzed caterpillars being
collected below, and when the larva comes out the thread lengthens
until the tiny jaws reach the food supply. Startle it ever so slightly
and the waspling retreats by way of its web, descending again only when
everything is quiet. For twenty–four hours it retains this path to
safety, and then, growing bold, it drops down and feeds at its ease.
We had opened hundreds of plant stems in quest of these suspended eggs
without being so fortunate as to find one, and were therefore much
pleased when our kind friend, Dr. Sigmund Graenicher, whose interest
in bees keeps him in touch with out–of–door happenings, and who has
given us much valuable help, brought us two stalks, one of which had
in it a nest of O. conformis, while the other contained two freshly
provisioned cells of O. anormis. In all three the egg had been hung
from the side of the cell about one third of the way down, and in
the nest of conformis, from which all but one of the caterpillars had
fallen, it hung loose against the wall. In the other nests the lower
part was packed tightly with sixteen small larvæ, upon which lay the
egg, supported in a horizontal position, although attached to the side
wall exactly as in conformis, and above were eight more caterpillars,
the whole forming a compact mass shut in by the usual partition of mud.
So closely were they crammed in that after counting them we were unable
to get them all back again, and although motionless in their narrow
quarters they became quite active when relieved from pressure. This
is an entirely different arrangement from that of O. reniformis, and
since the larva is in contact with the caterpillars from the moment of
hatching the manner of the egg–laying has no significance in relation
to the safety of the young.
[Illustration: NEST OF ANORMIS]
Conformis hatched on the morning after we received it, sloughing off
the skin of the egg, but remaining attached to it, and thus doubling
the length of the thread by which it hung. The caterpillar was slightly
separated from it, and it seemed to have no notion of feeling about
for its food, eating nothing for twenty–four hours, but growing and
developing nevertheless. We now piled up some caterpillars in contact
with it, and it began to eat, but after its own caterpillar and as many
as we dared take from anormis were gone it stubbornly refused to take
soft, tender little spiders, or caterpillars out of our garden; and it
perished, a victim to prejudice.
The two eggs of anormis were probably laid within a few hours of each
other, since they had both hatched on the morning of the third day,
and had broken from their attachment, beginning to eat at once. They
cocooned on the fifth day after hatching.
We had long wished to find a nest of O. capra, and early in September
fortune favored us. A neighbor of ours keeps a large tin horn hanging
under the porch. One day when she wished to use it, no amount of
blowing would bring forth a sound; and when she unscrewed the
mouthpiece to investigate the matter, out tumbled several small green
caterpillars and a quantity of dry mud. When we heard of this incident
we begged that if it should be repeated the nest and its contents
might be saved for us; and on the second of September we received the
mouthpiece of the horn with a message to the effect that a wasp had
been working at it for some days. Examination showed that there were
three cells, each containing a larva and a supply of caterpillars,
of which there were ten in the cell most lately formed, and only one
left uneaten in the oldest. The caterpillars, all of them being alive,
together with the wasp larvæ, were transferred to a place in which they
could be conveniently watched. None of the caterpillars died until
they were attacked. The larvæ ate all the food that was provided, the
oldest one cocooning on the fourth, and the second one on the seventh
of September. Of the third, we have no record, excepting that the
caterpillars had all been eaten on September eighth.
We happened to be passing through our neighbor’s grounds at nine
o’clock on the morning of September fifth, and calling to ask whether
there had been any more visits from the wasp, we learned that capra had
been seen making a mud partition in the horn on the day before. While
we were speaking she arrived and entered the mouthpiece, where she
remained for about ten minutes. When she departed we found that she had
laid her egg, which we carried away with us, wishing to determine the
length of the egg stage. This proved to be longer than that of any wasp
that we had heretofore known, for not until the morning of September
ninth did the larva make its appearance, the egg skin bursting and
leaving its tenant free to crawl away. In other genera the egg changes
into a larva imperceptibly, there being no sloughing off of the skin.
Capra, then, first finds a suitable crevice, and builds a partition
across the inner end, the earth being scratched up from some dry, bare
spot, and moistened in her mouth. Before gathering the ten or twelve
small caterpillars that are to provision the cell, she lays her egg;
and although we could not be sure, we thought that in this case as in
the others it was suspended.
Unless the cell is tightly packed at the beginning, capra certainly
needs the filament, for her caterpillars were so far from being
reduced to a state of decent immobility that we had to press wads of
cotton into the tubes in which they were kept to prevent them from
wriggling out of the way of the larva. None of our larvæ, not even the
one–day–old ones, were injured by their activity; but had the egg been
left to its fate among them it might have perished.
Later in September we found O. vagus bringing pellets from a
sharp–edged hole in the ground. Her method was to carry each load on
the wing to a distance of ten or twelve inches, where it was dropped
without the lively fling with which Ammophila discards her lump of
dirt. The red end of a match stuck into the ground two inches away
proved very disquieting to the dainty little wasp. These colored
matches were a great convenience in marking nests, and as we were
using them constantly, we did not guess, for a time, what the trouble
was. For half an hour she went and came, circling about, alighting
upon plants, and seeming entirely absorbed in examining them with
the minutest care, even alighting upon our hands with most engaging
friendliness, but pretending all the time that the nest was naught to
her. When the offending object was removed she hurried in at once and
resumed her work. The storing was not begun until the next morning,
when she took in six caterpillars of very different sizes, at intervals
of from ten to twenty minutes, and then filled the hole. We hoped to
find the little chamber arranged as in reniformis, but had not skill
enough to excavate in such a way as to show the internal plan. It is
remarkable that this genus, with only one set of tools for all its
species, has worked out such different styles of architecture, the
ground nests bearing no resemblance to those cut out of woody stalks;
and its flexibility is shown in the use of empty snail shells by a
foreign species, as well as by capra’s habit of partitioning off
convenient crevices found ready made.
The prettiest nests that we have seen in stems are those of Plenoculus
peckhamii, which separates its cells, not by solid partitions, but by
numerous granules of earth, which are used by the larvæ for forming
the case of the cocoon. One raspberry stalk that we opened had at the
bottom six of these mud cocoons, and above these three larvæ eating,
each in its own compartment, the provision in this case consisting
of immature bugs of the genus Pamera. Sometimes the stalk which is
being filled by Plenoculus attracts the fancy of a bee or of another
wasp, as is shown by the upper cells being filled by Osmia or Crabro,
or sometimes Plenoculus builds above the bee cells. When a number of
wasp eggs are placed in a plant stem, the last one laid is the first
to hatch. The different habits of the Hymenoptera in this respect are
very interesting. In the case of Ceratina dupla, the small carpenter
bee, the egg first laid hatches first, those above following in regular
order. The lower ones wait patiently in their cells until the one in
the top cell has matured, and then they all come out at once. When two
species occupy the same stalk, the lack of adjustment probably results
in the destruction of those lower down, excepting in the case of the
cuckoo flies, which have acquired the habit of gnawing their way out at
the side of the stem.
Chapter V
CRABRO
THE highest point of the island is crowned by a great group of linden
trees; and one day their perfume, carried by the wind far over field
and wood, was calling everything that had wings to gather the richest
of all the gifts that July can offer. We, too, were drawn to the spot,
and found the great blossoming domes thrilling and vibrating with life.
For miles around, the bees, wasps, and butterflies had gathered to the
feast; and we seemed to touch the high–tide of the year in the scent of
the flowers, the humming throng of happy creatures, and the vision of
it all against the summer sky.
Below, in a great root that had pushed above ground, five little
wasps, by name sexmaculatus, of the worthy but unimaginative genus
Crabro, resisting the intoxication of the linden flowers, were sawing
and cutting in the most humdrum and practical manner. One of them,
presumably the earliest riser, was well down in the root, and came
backing up once in a while, pushing a lot of wood dust out of the
hole. This was spread out by means of legs and mandibles, and was then
blown away by the fanning wings of the little worker, who circled about
just above the ground until the last grain had disappeared. Here was
another way of protecting the home. The fresh dust might attract the
attention of some cuckoo–like insect who would lay her egg within; and
therefore it was dispersed, just as Ammophila carried out her pellet
and flung it to a distance, and Sphex spread evenly over the ground the
mass of earth that she carried from her hole.
After this series of actions had been repeated several times the wasp
flew away to hunt. We afterward found that she had finished the third
in a set of cells leading from a main gallery. On her return we delayed
her to see what she was carrying. She showed no fear, but alighted
close by, and while she was trying to transfer to the third pair of
legs the fly that she was clasping with the second pair, it escaped and
flew gayly away. Flies are plenty, however, and she soon had another
which she was permitted to store; and from that time she worked busily
until we left her at noon. It took her from two to ten minutes to
catch her fly, and at each return two or three minutes were spent in
the nest. On opening her tunnel some days later, we found within not
only flies, but long–bodied gnats, and all of them seemed to have been
brought home uninjured. When the freshest cell was opened some flew
away, others were walking about, and all were lively. The wasp egg
was laid on the under side of the neck; and although we could not be
certain of the exact time of laying we thought it hatched at the end
of thirty–six hours. From ten to sixteen flies were provided for each
larva.
[Illustration: SEXMACULATUS IN THE LINDEN ROOTS]
A month later we found Crabro lentus nesting in the ground. Her
tunnel ran down obliquely for six and one half centimeters, and had
an enlargement at the end. Two bugs and a fly were in the nest, when
we opened it before the provision was completed. To find sexmaculatus
taking both flies and gnats was surprising, so rigid are the family
traditions of the wasps; still, she might feel that so long as she drew
the line at Diptera she was all right. But to believe that one wasp, a
Crabro, too, with all the marks of conservatism about her, would take
such diverse things as bugs and flies, is almost too much to believe.
It is true that Crabro wesmæli is said to use both flies and bugs;[4]
but some accident may have led to this supposition, and stronger
evidence is needed to prove that there is variability in so deeply
seated an instinct.
[Illustration: CRABRO AND HER WHITE MOTHS]
The Crabro wasps all have pleasant ideas as to where they want to
live, but interruptus excels in the choice of a dwelling place. We
lately found ten or twelve of them in Milwaukee, nesting in an old log
on the shore of Lake Michigan, and when they opened their doors in
the morning they had before them the splendor of the great bay; but
calm in the midst of the glory they never paused on the threshold, as
Cerceris would have done, to take a look at the world before going to
work. One morning the earliest riser in our little colony was beginning
the day at half past nine. Of good size for a Crabro, with a square
determined–looking head and very direct and business–like manners, she
proceeded to cut out a new chamber for provisioning. These chambers are
nothing more than enlargements of the long gallery, such as are made
in stems by related species. At ten o’clock she departed on a hunting
excursion among the bushes on the bank above us, and came back in eight
minutes, carrying, much to our surprise, a white–winged moth, which
was clasped under the body by the second and third pairs of legs, and
was passed back to the third pair as she alighted before entering. A
moth is an innovation, a delicacy new to the accepted idea of what a
Crabro larder, accustomed to Diptera, should contain. A moment later
she was off again, but this time did not succeed so quickly, coming
back twice empty–handed for brief visits, and bringing in a load at
the end of half an hour. It took six moths to provision the cell, and
as the number neared completion her interest and energy seemed to wax
greater, the hunting intervals shortening to five, and even to two
minutes. We found afterwards that some of the moths were alive and some
dead, and that she packed them lengthwise, one after another, into the
closely fitting chamber. At a little before eleven o’clock the cell
was filled, and the wasp retired from sight, closing the door behind
her. We thought that she was resting, but presently the protrusion of
wood dust showed that she was enlarging her house, and an hour later
she came out and began to hunt again. By this time half a dozen were
working. Before leaving for the first time in the morning each one made
a thorough study of the place, and on returning they entered their own
doors, which were standing open, without hesitation, the long white
wings of the moths trailing behind them. Four species were represented
in the nests that we opened.
[Illustration: CRABRO STIRPICOLA]
Many species of Crabro make their nests in the stems of plants, and
among these is stirpicola, which is seen in numbers, through the middle
of July, flying about in a leisurely way, though it is only toward the
end of the month, or in the early days of August, that they settle
down to the work of making their homes. On the afternoon of July
twenty–seventh, after some very lively work in the heat of the day, we
walked down to the berry garden at half past five o’clock, rather to
rest ourselves than with the thought of undertaking anything new; but
a wasp–hunter cannot afford to choose his own hours, and we thankfully
accepted the sending of fortune when we came upon a stirpicola busy at
work in digging out her nest. She had only begun to excavate, and had
reached a length just equal to that of her own body. Her manners were
an agreeable contrast to those of the wasps that we had been watching
through the day. The feverish excitement of their ways seemed quite in
keeping with the burning heat of noon, while Crabro’s slow and gentle
movements harmonized perfectly with the long shadows of evening. To
fully appreciate the difference between Pompilus or Ammophila and
Crabro it is necessary to see them at work. The one is the embodiment
of all that is restless, vying with the humming–birds in swiftness and
energy, while the other is calm, quiet, and stately in all that she
does.
[Illustration: BOTTLE ON STEM TO MEASURE WORK OF CRABRO]
Some ten feet away was a second stirpicola, and this one, to judge
from the depth to which she had penetrated, must have been at work
for about two hours. We watched them both, and saw them bring up load
after load of pith. They bit out the pellets with their mandibles, and
passed them back between the legs and under the body until a quantity
had accumulated above the tip of the abdomen. They then walked backward
up the stem, and thus pushed out the mass as they came to the top.
Often they used the hind legs to assist in getting it out of the way,
sometimes kicking it to a little distance. Once in every two or three
trips they would come out far enough to expose part of the thorax.
They appeared and disappeared with the regularity of a machine, never
stopping to rest.
We remained with them until seven o’clock, when we placed a long bottle
over each stem in such a way that while it did not interfere with the
work of the wasp, it caught the chips of pith as they fell out. At the
end of an hour we noted the amount of accumulation in the tube, and
thus had a measure of their rate of work. The drawing gives an idea of
the arrangement of the tube on the stem. When we left them they were
still digging and delving.
At half past nine we took a lantern and went down to visit our charges.
We expected to find them at rest, and asleep; but on the contrary
they were working as busily as ever, and upon examining the measuring
glasses we found that they had not paused since we left them. We
measured the depth of the débris in the bottles, and then emptied them.
At four o’clock on the next morning we went to the garden, and
were much surprised to find that the two wasps had worked without
intermission throughout the night. Indeed they seemed to have shortened
a little the time that it took to make a round trip down the gallery
and up to the opening again, since there was more pith in the bottles
than we could have expected if they had worked at only their former
rate. Neither the coolness of the air nor the darkness of the night
had made the slightest difference to them. After watching them a few
minutes, and marveling at their powers of endurance, we cleared out the
tubes and returned to bed. At half past eight we found them still at
work. Unlike us, they had taken no morning nap, but had gone on with
their tunneling in their usual steady way.
From this time their ways diverged, and they must be described
separately. At nine o’clock the one that we had first seen came up to
the opening, walking head first, and flew off, remaining away seven
minutes. When she returned she at once resumed her work, and kept at
it without a pause until two in the afternoon. At this hour she went
away, and we never saw her again. We suppose that she was killed, for
it seems improbable that so faithful a creature could have deserted her
half–finished home. Pompilus quinquenotatus often deserted a partly
finished nest for some more enticing spot, and Sphex started several
excavations before making a final choice; but we cannot believe that
there was anything fickle about Crabro.
The second wasp came up head first to the entrance of her hole at
two minutes after nine, as though she had been influenced, in some
subtle way, by her neighbor’s example; but after looking about for a
moment she went back. She repeated this observation several times, and
finally, at twenty–five minutes after nine, came out and flew to a leaf
near by. Then she circled around, alighting a number of times, and at
last departed. Her stay was brief, for at just thirty–five minutes
after nine she returned, and at once settled down to her work.
We now began to make notes as to the length of time that it took her
to go down and bring back her load. We timed her again and again, and
found that she was remarkably regular, each of her trips occupying from
forty–five to fifty seconds.
All that day we kept her under strict surveillance, and never once did
she suspend her operations either for rest or refreshment. Late in the
afternoon, while we sat watching her as she appeared and disappeared
with almost the regularity of clockwork, we found it difficult to
realize that the patient little creature had been at work for more than
twenty–four hours, with only one brief intermission. Without hurry or
flurry she kept at her task, reminding us, in her business–like ways,
of the social wasps of the genus Vespa. When we left her, at dusk, we
attached the recording tube to the stem, and at ten o’clock in the
evening we found that she had not stopped working. We emptied the
glass, and left her.
At seven o’clock in the morning of July twenty–ninth we paid her a
visit, and could scarcely believe the testimony of our senses when we
saw that the record was one of unceasing toil through the long hours
of the second night. We began to wonder if she would ever finish her
task. Wonderful though she was, we had grown a little weary of our
long session of watching. We had been glad that she worked through the
first night; it was creditable to her and interesting to us, and we
admired her even more for sticking to it through the second, but when
it looked as though we might have to remain by her side through another
long day, watching an endless series of loads as they were carried out,
we confess that we thought she was rather overdoing it. Gradually,
however, she slowed up her work, taking two or three minutes to make a
journey down and up. At last, at just nine o’clock, her head appeared
at the top of the stalk, and after a slight hesitation she flew away.
The nest was completed.
We have studied wasps for a number of years, and we feel that we are
on terms of more or less intimacy with many of the species, but never
before have we known one to work after day was done. We have often
gone out with a lantern at bedtime for a tour of inspection among our
nests, and have always found the inhabitants quiet and presumably
asleep. The social wasps are very industrious, but during the hot
nights of July they are to be seen clustered together on the outside
of their paper nests in deep repose; and although the Vespa wasps
that nest in the ground sometimes come home late in the twilight, we
have never seen them work after it was really dark. Polistes fusca
may be said to share our cottage, so thickly does she hang her combs
under the shelter of our porches, and from observations taken at all
hours we know that she is quiet through the night. Sir John Lubbock, in
“Ants, Bees, and Wasps,” speaks of the great industry of wasps. He has
known them to work from early morning until dusk without any interval
for rest or refreshment; but here was our little Crabro toiling from
three in the afternoon of July twenty–seventh, through that night
and the day and night following until nine o’clock on the morning of
the twenty–ninth,—a period of forty–two consecutive hours with one
intermission of ten minutes on the morning of the twenty–eighth. Surely
she takes the palm for industry, not only from other wasps, but from
the ant and the bee as well.
[Illustration: NEST OF C. STIRPICOLA]
The nest was completed, but the work of storing it remained to be done.
The wasp flew away at nine o’clock, and ten minutes later came back
with something, we knew not what, for she dropped into her hole so
quickly that she was out of sight almost before we knew she was there.
Two minutes later she came up, and was off again. This time she was
gone twelve minutes, and when she returned we were again baffled in our
effort to see what she was carrying. When she came out she alighted
upon a leaf and attended to her toilet, cleaning both body and wings by
rubbing them off with her hind legs, and from this time on she never
started on a hunting expedition without paying this attention to her
personal appearance. On her third trip she was gone twenty minutes,
coming back with a small fly; and before we left her at ten o’clock,
she had stored six more. When we came back at half past two in the
afternoon she was working, and she kept up her goings and comings until
four o’clock, when she suspended operations for the day. On the next
morning we were called away, and know nothing of what she did, but on
the following day, Thursday, we resumed our observations. She worked
hard all the morning, but in the afternoon her trips were few, and were
made at long intervals. On Friday she worked from eight to nine, when
she departed, and never returned. We watched for her, at intervals,
all through that day and the next, when we were forced to conclude that
our faithful little worker had fallen a victim to some bird or beast.
We did not disturb the nest until four days later, when we cut the
stalk, and examined it.
We found that the tunnel was thirty–nine centimeters in length. This
was a long distance for her to excavate, and, all things considered,
her progress had been rapid. We have opened a number of stems that had
been stored by this species, and all the excavations were from thirty
to forty centimeters in length, the width of the gallery being about
three and one half millimeters, while on each side there was from one
to one and one half millimeters of pith that had not been cut away. Of
course these points varied with the diameter of the stem and also with
the size of the worker.
Our little stirpicola had stored one cell, had laid an egg, and had
built a partition of pith across the stem as a floor to the second
cell, before her untimely taking off. Had she lived, ten or twelve
cells would have been stored, one above the other. The completed cell
contained a larva and parts of eighteen flies of different sizes, four
species being represented. The flies had all been attacked by the
larva, the abdomens of some and the thoraces of others having been
eaten. The larva continued to eat for two days, and then spun its
cocoon. The flies found in this and in other nests of stirpicola were
all dead. All the pupæ that we kept wintered in the cocoon and came out
in the spring.
[Illustration: AMMOPHILA SLEEPING IN THE GRASS (AFTER BANKS)]
The females of Crabro, like those of other genera, seem to use their
galleries as sleeping places, but the males stop at any convenient
inn. We once entertained one of them for several nights in a hole in
one of the posts of our cottage porch. Other males, as in Philanthus,
spend time and care in digging a hole in the ground, to which they
return night after night. In Agenia the female keeps one cell ahead
of her needs, and tucks herself away in it very comfortably; but the
Pelopæi, instead of making this use of their tubes, congregate in the
evening where there are convenient crevices, and make as much fuss
about getting settled as a lot of English sparrows. Mr. Banks has
made a delightfully pretty as well as interesting observation on the
sleeping habits of Ammophila. In a corner of his garden where the grass
grew long, dozens of these wasps arrived every evening, and after a
good many changes in position, fell sound asleep, clinging to the stems
about one third of the way down. They registered at this hotel between
seven and eight o’clock, and departed before five in the morning. We
have seen a Pompilus take the greatest care in selecting a sheltered
spot under some leaves, where she afterward hung herself up, and
slept soundly until after eight the next day; and Mr. Brues has found
companies of Priononyx atrata passing the night on the stems of sweet
clover.
Chapter VI
AN ISLAND SETTLEMENT
OUR children often made themselves useful by reporting finds in the
shape of nests, and one day they returned from the island with a
wonderful tale of great numbers of big wasps that were digging in the
ground. “I don’t know what they are,” said the small boy, “but they act
to me like the maddest kind of hornets.” With this attractive picture
before us, we lost no time in going over to the spot, where we found
a thriving colony of Bembex spinolæ. On our approach they fell upon
us, “desire of blood, and rage, and lust of fight” in their mien, and
chased us to a distance, but without inflicting a single wound. This
temperance was not due to gentleness of disposition, but to the fact
that Bembex is not at all handy with her sting, her body being too
large and clumsy to curve and give the lightning stab as other wasps
do. With renewed courage we again approached them, more cautiously this
time, and soon learned that if we preserved an extremely composed and
dignified demeanor our presence on the field would be tolerated.
Bembex, like Philanthus, and some species of Sphex, lives in a sort of
semi–social state, a number of individuals occupying the same space
of ground, although each one has its separate nest. Bembex, however,
differs from these genera and from almost all of the solitary wasps in
her habit of feeding her young from day to day, or rather from hour to
hour, as long as it remains in the larval state. This difference in
her maternal cares as compared with those of other species results in
a less numerous progeny. The larva, for a period of two weeks, demands
constant attention from the mother, so that a second egg cannot be laid
until the first–born has gone into its cocoon, unless, indeed, she
feeds two larvæ at once, which does not seem probable. The season of
work is ten or twelve weeks, so that Wesenberg is probably correct in
allowing only five or six young ones to each mother for the summer.
In watching our wasps we found that the new nests were usually made
in the outskirts of the colony, which was thus continually extending
its limits. Like many other species, Bembex has great difficulty
in deciding just where to dig. Our Sphex made three beginnings
before finally settling down. The only Ammophila that we watched
from the beginning changed her place after working for ten minutes.
P. quinquenotatus often tried half a dozen places before she was
satisfied, and spinolæ is quite as difficult to please.
When, at last, the right place is found, the labor of excavation is
carried on vigorously. The mandibles are used for loosening the earth,
and for lifting, but the greater part of the work is done with the
first pair of legs, the tarsi of which are doubled up while the dirt is
swept out with the brush of stiff spiny hairs on the second joint. This
attitude gives them a very comical aspect, making them look as if they
were sweeping with their elbows. They sometimes lie far over to one
side while loosening the earth with their mandibles. While digging, the
body is held high by the straightening of the third pair of legs, and
the dirt comes out behind in a rapid stream, flying to a distance of
three or four inches. Before long the wasp is lost to sight, but every
few moments she comes backing out, pushing behind her the dirt that
she has displaced below. In about fifteen minutes the nest is ready,
and the wasp turns her attention to scattering all the dirt that has
been thrown out, sweeping the ground clean so that no sign of her work
remains. We have often speculated as to the meaning of the careful and
conscientious performance of this part of her task. With the wasps that
nest by themselves it is not easy to see what enemy they are providing
against in hiding the entrance to the nest; but the precaution seems
still less necessary—even absurd—in the Bembex field, where there is
no possibility of concealing the colony, and where the nests are only
an inch or two apart, so that an enemy might burrow anywhere with
the certainty of finding one. Moreover, the only enemy that we could
discover was the parasitic fly, which never attempts to enter when
the hole is closed. However, unmoved by our opinion on the subject,
spinolæ spends five or six minutes of her precious time in making the
neighborhood of her home quite tidy, and then she fills in the mouth of
the nest with a little loose earth before going away to catch her fly.
Oxybelus, though she is limited in choice by her small size, can
catch a fly in three or four minutes. Bembex is strong enough to take
anything that she sees, and she has no preference for one species
above another, yet she seldom finds one under twenty or twenty–five
minutes. When she comes back nothing of the fly is visible unless it
is unusually large, so closely is it held under her body by the second
pair of legs. She alights, and scratches away the loose earth at the
entrance of the nest with her first legs, and then, as she creeps
within, she passes the fly along from the second to the third pair, so
that the end of its body, projecting beyond the abdomen of the wasp,
is visible for an instant before it is carried inside. Sometimes she
drops the fly behind her, and then, turning around, pulls it in with
her mandibles. In other cases, where a longer portion of the tunnel has
been filled with earth, the fly is left lying on the ground while the
wasp clears the way. This offers a favorable opportunity to parasites,
especially as the fly is not placed with regard to its safety, but
is dropped anywhere. The dirt that is kicked out sometimes covers it
so that when the way is clear the careless proprietor must search it
out and clean it off before she can store it away. In one instance,
in which we had been opening a nest close by, the tunnel was entirely
blocked by the loose earth which we had disturbed, and the wasp worked
for ten minutes before she cleared a way to her nest. During part of
this time she held the fly, but when she realized that it was going to
be a long piece of work she laid it down near by. As the wasp enters
she sometimes leaves the hole open behind her, but oftener fills it by
pushing up earth from below. When she comes out again she throws in a
little dirt, and then begins to circle about the place. She seems not
quite easy about the nest, however, returning three or four times to
scratch earth over the entrance, before finally taking her departure.
We opened a good many nests in the course of the summer, and found
them all very much alike, much more so than is the case with other
species. The entrance tunnel runs in obliquely for from three to five
inches below the surface of the ground, and ends in a pocket.
We grow accustomed to marvels, and from our familiarity with other
wasps we take as a matter of course the unerring accuracy with which
Bembex swoops down upon the exact spot at which the entrance to her
nest is hidden. And yet how strange a power it is! There is not the
least sign to help her—not a stone, not a blade of grass is to be seen
on the field. Our method of marking a nest which we wished to find
again was to place tiny pebbles at exactly equal distances from it, one
on either side, so that the middle point of the straight line between
them gave us the desired spot; and the wasp doubtless uses the same
method, only her landmarks are sometimes so infinitesimal that we do
not recognize them.
Bouvier finds that when he cuts away the plants around the nest of B.
labiatus, clearing a space of twenty–eight or thirty inches square,
the wasp is much confused, flying about for a long time before she is
able to find her home. He once placed a flat stone over the entrance.
The wasp alighted upon it, and after scratching vainly for a while made
her way in. The stone was left in this position for two days, during
which time Bembex learned to regard it as a landmark, for upon its
being removed to a distance of eight inches she still followed it upon
returning with her fly, and insisted upon finding her nest near it.
[Illustration: NEST OF BEMBEX]
An observation of Marchand points to the same conclusion. He says:—
On July seventeenth, 1900, during a short sojourn at Pouliguen, on
returning from a hunt after Diptera and Hymenoptera in the cliffs of
Caudan, about eleven in the morning, in tropical heat, I paused to take
breath near the old mill of Caudan and looked about for a little shade
before continuing my walk to Pen–Château. I had seated myself on the
stones of a slope shaded from the sun and was wiping the perspiration
from my forehead, when I saw a large wasp arrive directly before me. I
instinctively followed it with my eyes; it paused some yards from the
mill on the side of the cliff, and began to open a nest which was placed
scarcely twenty inches from the foot of a swallow–wort, a rather common
plant in the neighborhood of the ruin. She was Bembex rostrata at work
at provisioning her nest.
Moved by curiosity, instead of going on to breakfast, I awaited the exit
from the nest, which took place in about five minutes. Bembex scratched
the sand and took flight from the side of the cliff. How long would she
be away? I looked at my watch and arose.
Ought I to go or to wait a little while? I took the latter decision. Out
of malice, and without any idea of trying a control experiment to the
admirable observations which science owes to the naturalist of Sérignan,
of whom I was not thinking at all, I cut close to the sand the stalk
of the swallow–wort and planted it a little nearer the mill, moving it
about two feet, and being careful to put in place of the plant a little
fragment of a bottle which I found in the mill. I seated myself in the
shade and waited. Twenty minutes later the wasp dropped straight on to
the place where I had cut the plant, that is to say, it deviated from
its nest by a distance about equal to the displacement to which I had
subjected the swallow–wort. It walked right and left, agitating its
antennæ, appearing confused as to the locality. I followed these goings
and comings for two or three minutes. Several times it flew away and
then returned, always searching about. Pitying it and desiring, since I
was now relieved of the fatigue which the heat had caused me, to go back
to breakfast, I took my net and drawing near, made as if to catch it,
swinging the pocket rapidly about. It veered away with a quick jerk of
the wings. I then took up the swallow–wort, lifting the fragment which
marked its original place, and replanted it in the sand.
I again looked at my watch to see whether I could consecrate yet a
few more minutes to curiosity without making my kind host, my friend
Dr. M^[ce] Rivron, and his wife, who honored me with the charming
hospitality of Kursac, wait too long. It was only half past eleven; we
usually did not breakfast until about noon; it would take only a quarter
of an hour to traverse the distance from the mill of Caudan to the
house. I could then, without fear of being chided, dispose of fifteen
minutes. This lapse of time would perhaps suffice to show me whether my
_bestiole_ would this time find the way to her nest without hesitation.
I waited a little; five minutes had not passed when my Bembex, coming
like an arrow, alighted on the sand near the plant, still holding the
prey which I had noticed when she departed at my chasing her, after
her vain attempts to find the entrance to her nest; but this time she
did not hunt long. She felt about a little to right and left, but soon
turned directly toward the entrance to the tunnel, distant scarcely two
inches from the place where she had settled. My Bembex had a memory.
A curious thing about these wasps, and one which shows how much common
feeling they have, is that they work in waves, all starting off on
their hunting expeditions within a few minutes of each other, and
returning together after the chase. At one time all the residents seem
to be present, digging their nests, carrying in their booty, dashing
at each other, and chasing the parasites with a tremendous amount of
humming and swooping about. Then suddenly they are all gone. Nothing
remains but multitudes of flies, which keep up a giddy dance over the
field, and for ten or fifteen minutes the place seems deserted. Then
the wasps begin to return, several coming at a time, and as if by magic
the whole scene awakens to life. More than half of the wasps bring
nothing home with them, and these fall to robbing their more fortunate
companions. Those that are carrying flies must pause a moment, burdened
as they are, to scratch away the earth at the entrance to the nest.
When unmolested they go in very quickly, but it is just at this point
that the marauders fall upon them, displaying an amount of persistence
and energy in their attacks that, were it properly directed, might
easily enable them to secure flies for themselves.
We once saw a wasp that had been fortunate enough, or perhaps
unfortunate enough, to catch an immense fly, the wings of which stood
out on both sides very conspicuously. This made her an especial mark
for her unprincipled relatives. Half a dozen of them chased her about,
like chickens pursuing one of their number that has found a worm. She
circled and settled, and circled and swooped around for five or six
minutes, continually pursued and attacked by the robbers, and quite
unable to get into her nest. At last, curious to see what she was
carrying, we made her drop her load, and secured it for ourselves.
We found it to be a horse fly, quite dead, but showing no marks of
violence. It was not wasted, for we afterward fed it to one of our wasp
nurslings at home.
At another time we saw one wasp attack another that was bringing in a
fly. In the struggle that ensued the owner lost her booty, as the two
rolled over and over on the ground, and as they parted it was seized by
the thief. They clinched again, and rolled on the ground as before, and
this time the fly was recovered by the rightful owner. At this point,
thinking that perhaps one of the wasps was a male, and that this might
be their style of courtship, we seized both of them; whereupon the fly
was dropped, and the two wasps turned their attention to attacking us.
Both proved to be females. Not only do the Bembecids fight in this way
for the possession of their prey—they quarrel even without apparent
cause. We have seen two females digging their nests at a little
distance apart, one of which was repeatedly attacked by the other,
although she did nothing to provoke the aggressor. They are certainly
very unneighborly, and have no idea of living in harmony. When flying
in a threatening manner, either at us or at each other, they have a way
of wagging their abdomens violently from side to side in a way well
calculated to inspire terror.
In warm sunny weather spinolæ works industriously through the middle
of the day, and seems determined to provide abundantly, not only for
her own offspring, but for any unbidden guests that it may be her
fate to care for. She never works more than four or five hours a day,
however, and in unfavorable weather she does not work at all. On going
over to the island one cloudy morning to spend some hours in watching
the Bembex activities, we found the spot quiet and lifeless. No one
seeing it for the first time would have dreamed of the multitudes of
living creatures beneath his feet. The nests seemed to be all closed,
but on peering curiously about we found one on sloping ground, in the
suburbs of the colony, of which the door was open. Just within was
the proprietor gazing out on the landscape, as she is shown in the
illustration. She seemed to be leaning on her elbows, and her face,
enlivened by two great goggle eyes, had an irresistibly comical
aspect. With the exception of the omnipresent flies, this wasp was
the only sign of life about the place. Even in good weather, and in
working hours, the wasps sometimes rest, for we have seen them go in
empty–handed, closing the door behind them, to remain for half an hour
at a time.
[Illustration: BEMBEX SPINOLÆ LOOKING OUT OF NEST]
There is one thought that must strike even a casual observer at the
sight of the hordes of parasites that hover over a Bembex colony:—
“The buzzing flies, a persevering train,
Incessant swarm, and chased return again.”
Why do not these wasps, fly–catchers as they are by profession, kill
the worthless wretches that infest their homes, thriving abundantly on
the fruits of their labor, a continual menace to the life and safety
of their offspring? To the uninitiated it would seem that these flies
might serve as food for the wasp larvæ quite as well as any of the
dozen species that they actually take; but even if the wasp–mother
believes that they possess indigestible qualities, it would be much
less trouble to kill them and throw them away than to be perpetually
chasing them to a little distance only to see them return as soon as
she gives her attention to anything else. Whatever the reason for it
may be, the relation between the wasps and the flies is certainly most
curious and puzzling. Fabre’s explanation is that since this miserable
little fly has its own part to play in nature, Bembex must respect it,
thus preserving harmony in the world of living things. The idea is
perfectly in accord with his own theories, but we find ourselves quite
unable to accept it.
There can be no doubt that the parasites are a grave danger to Bembex.
She suffers from them far more than any other wasp that we are
familiar with, her mode of feeding the young rendering her peculiarly
susceptible to their attacks. Of the ten or twelve nests that we
opened only one was free from them, the others containing from two
to five lively maggots nearly as large as the wasp larvæ, which were
sharing the food brought in by the mother. Fabre, who has studied the
question thoroughly, has found as many as ten parasitic larvæ in one
nest. He has also noticed that where the parasites are most numerous
the wasp–larva is proportionately small and emaciated, reaching only
one half or one third of its normal size. When it attempts to spin
its cocoon it has not strength enough to do so, and thus perishes
miserably among the pupæ of the interlopers, which have the advantage
of developing more rapidly. He has proved, by experiments upon nests
transported to his study, that although the invaders preserve friendly
relations with the rightful owner of the nest so long as food is
abundant, they nevertheless, at the first suggestion of scarcity, fall
upon the wasp larva and ruthlessly devour it. This “black action” he
has seen with his own eyes. In view of this base ingratitude, we are
more than ever impressed with the troubles of the poor Bembex mother,
as she tries to feed a dozen mouths where she has bargained for only
one.
We several times saw a fly follow a wasp into her nest, remaining
within for half a minute, and it is probable that they go in to lay
their eggs. According to Fabre, it is the habit of the flies that are
parasitic upon the half–dozen species of Bembex that he has studied
to seize the moment at which the fly projects from under the abdomen
of the wasp as she enters the nest; and he has even known them to lay
two or three eggs on one fly in the instant of time that its body was
exposed.
Fabre took a partly grown Bembex larva from the nest, where it was
surrounded by the remains of twenty flies. He fed it generously, and it
ate sixty–two more, making a total of eighty–two in the eight days that
passed before the spinning of the cocoon. Our experiments in this line
gave similar results. We took charge of a partly grown larva on the
afternoon of August tenth, and between that date and August fifteenth,
when it spun its cocoon, it ate forty–two house flies besides a big
Tabanus.
Fabre thinks that under natural conditions the mother does not give
the larva all it can eat at one time, but provides it with what she
considers a reasonable amount of food, and keeps anything that she
catches beyond this out of its reach. He draws his conclusion from the
fact that he has found several flies in the tunnel leading to the nest,
while the larva had as many more close to it. It would certainly be
convenient for Bembex to have a reserve of this kind in case of rainy
weather, but the forethought implied in such an action seems to require
a higher degree of intelligence than can be claimed for her.
In one nest we found a single fly with a long cylindrical egg attached
to the left side of the thorax just at the origin of the third leg. In
another, which we had seen made and provisioned, we found, six days
later, a larva which we judged to be four days old. Assuming that the
egg was laid on the first day, it must have taken it about two days
to hatch. Other nests gave us larvæ in all stages of development,
surrounded by the remains of Diptera, among which Syrphus, Tabanus, and
Musca were represented.
In regard to the condition of the flies captured by Bembex, we have
never seen the crushing of the thorax, which is noted by both Wesenberg
and Fabre. Indeed, the flies that we found were not always dead, since
in two instances they responded readily to stimulation. Similar results
have been obtained by Mr. S. W. Dunning of Hartford, Connecticut.
Twice we have seen our spinolæ, as she was bringing home her prey,
alight near the nest and sting it as it was held with the second pair
of legs. We could see the process distinctly, since she is slow and
clumsy, and, in one instance, had difficulty in reaching the fly,
falling over to one side in an awkward manner. It is probable, then,
that this is a habit with the wasp, but that the sting is usually given
at the place of capture.
We opened a number of Bembex nests, but succeeded in raising only one
larva, which we took when it was half grown. This one, during the five
days that passed before it spun the cocoon, ate forty–three flies.
Mr. Bates has some notes on Monedula signata, which takes nothing but
flies, and even confines itself to a single species, although it must
sometimes go half a mile away to find it. This reminds us of Pompilus
quinquenotatus, which never takes anything but Epeira strix.
[Illustration: BEMBEX]
A considerable contribution to our knowledge of the genus Bembex has
been made in the paper by Wesenberg (written in Danish) which has
already been referred to. This paper deals with Bembex rostrata. It was
translated for Mr. Ashmead by Mr. Martin Linell.
[Illustration: A CORNER OF THE BEMBEX COLONY]
It seems that rostrata makes its nest in solid sand, covering it up
with loose sand, and usually, also, with a little flat stone, to
prevent parasites from entering. The cell measures one cubic inch, the
entrance tunnel being one and one half centimeters long, and arcuate. A
cell contains four or five fresh flies (Lucilia, Eristalis, etc.), and
torn–off wings, sucked–out thoraces, and in the middle of these, a big
flat larva.
When the larva is hatched the mother brings more and more flies, the
flies being larger and larger as it grows. This adjustment of the size
of the fly to the growth of the larva has also been noted by Fabre.
Wesenberg says that fifty Bembecids will nest on a spot as big as
a room during a period of three months. The time required for the
development of the larva is two weeks, this giving five or six young
ones for the season. He queries, “Does each female have more than one
nest? and if so, how can she remember them?” To determine this point
we marked six wasps by touching them with differently colored paints,
putting near their nests pebbles painted to correspond with the owners,
and then watched them closely for three hours. During this time the
red wasp returned regularly to the red nest, the blue to the blue, and
so on. They were watched for an hour and a half on the following day
with the same result, so that it seems quite certain that spinolæ has
only one nest at a time. To feed two larvæ at once, with interlopers
thrown in, would be a heavier task than the most determined industry
could accomplish.
Chapter VII
THE BURROWERS
DUFOUR, in describing the fearful ravages of Cerceris ornata among the
bees, says that the wasps of this genus are among other insects what
eagles and hawks are among birds. While this characterization does not
seem to fit the American species, it is certainly true that the genus
stands out as one of those in which the distinctive peculiarities
are strongly marked. They might be considered the aristocrats in the
world of wasps, their habits of reposeful meditation and their calm,
unhurried ways being far removed from the nervous manners of the
Pompilidæ or the noisy, tumultuous life of Bembex. Their intelligence
is shown by their reluctance to betray their nests, and by their
uneasiness at any slight change in the objects that surround them.
It is not necessary to attempt to catch them or to make threatening
gestures, in order to arouse their sense of danger. If you are sitting
quietly by a nest when the wasp opens her door in the morning she will
notice you at once, and will probably drop out of sight as though she
resented your intrusion into her privacy. After a little she will come
up again and will learn to tolerate you, but at the least movement on
your part, almost at the winking of an eyelid, she will disappear.
[Illustration: NEST OF CERCERIS NIGRESCENS]
Our four representatives of this genus all prey upon beetles that
are injurious to vegetation, and therefore deserve the gratitude of
agriculturists. Nigrescens, with her pale grayish bands, is a very
trying wasp to deal with. We had seen her flying about in the garden
for weeks before we succeeded in tracking her home, and when we did
succeed she was so late about getting up in the morning, stayed away
from home so many hours at a time, and went to bed so early in the
afternoon, that we were not well repaid for watching her nest all day.
Fumipennis, large and handsome, with a broad yellow band at the front
of the abdomen, is another wasp that has no regard for the convenience
of the people who are watching her. You may sit by her big open hole
for hours without seeing her, and when she comes she drops in so
suddenly that, unless you are very much on your guard, you are not sure
even then what she is. Clypeata and deserta are better subjects for
study.
The nests of our species are all deep, tortuous, and very difficult
to excavate. We have never succeeded in finding their pockets; and
yet, for various reasons, we feel perfectly certain that all of them
are like C. ornata in provisioning, successively, a number of cells
which lead out of the main gallery. When one of these cells is filled
with food, and the egg deposited, it is probably closed up, and thus
separated from the runway. From our experience late in the season
with the nests of another wasp, we are inclined to think that we made
a mistake in looking for pockets at the lower end of the tunnel. Had
we searched higher up, at the point of the curve, we might have found
them, the lower part of the gallery probably being designed merely for
a dwelling–place for the mother of the family.
[Illustration: CERCERIS CLYPEATA]
But although we did not get distinct pockets, there was, in at least
one nest, a supply of food that would have far exceeded the wants of a
single larva. We did not succeed in finding eggs on different groups of
beetles; but from a nest into which the wasp was still carrying food we
took a half–grown larva which was identified as being hers. The fact,
too, that a wasp occupies a nest for so long a time as ten days or two
weeks points to the conclusion that she uses it for a number of eggs
which are laid at intervals.
Cerceris digs her nest, deep as it is, all at once. In this she is
a contrast to her near relatives of the genus Philanthus, who busy
themselves for an hour or so every morning with fresh excavations.
On the eighth of July the weather was so warm and bright that we went
down to the garden at half past eight o’clock, knowing that it was
rather early, but hoping that the hot sunshine would tempt the wasps
to industry. We had walked up and down several times, when suddenly,
right in the pathway, a nest appeared. A great quantity of loose earth
had been taken out and heaped up, probably on the preceding day, and
in the midst of this a little hole had been opened since we passed
before. The place looked so promising that we sat down to watch it,
and a few minutes later we were rewarded by a glimpse of some antennæ
down the gallery, and then a little face with yellow markings appeared
but quickly vanished. Now followed a very coquettish performance. The
wasp came slowly creeping up again and again, only to drop out of sight
as soon as she had reached the opening. After a time she grew bolder,
and sat in her doorway, twitching her head this way and that in a very
expressive manner, as though she were planning the work of the day; but
it was plain that although she was up early, business cares were not
weighing heavily upon her mind, for forty minutes passed before she
came out of the nest, and after making three or four circles about the
spot, flew away.
How much livelier and more interesting it would have been if we could
have followed her! We tried to guess at what she was doing, and
imagined her hunting industriously. After fifteen or twenty minutes
it seemed to us that she must have caught something, and that she was
surely returning. Most probably she was not working at all, but was
breakfasting leisurely and exchanging compliments with her neighbors;
for when she did come home after keeping us waiting for an hour and a
half, she brought nothing with her, and seemed quite unconscious of
the fact that greater things had been expected of her.
We had placed a stone upon a dead leaf near by, to mark the
neighborhood of the nest, thinking that even a Cerceris could not
object to so simple an arrangement of natural objects; but our wasp
noticed it at once, and evidently with much suspicion and disapproval.
She began by circling several times just above it. Then she alighted on
it and examined it carefully, walking over it, and creeping underneath,
perhaps to see whether it in any way menaced the safety of her nest,
perhaps as the completion of a locality study made the day before.
She then rose on her wings, and after a little more circling, dropped
suddenly into her hole.
So far we had not been getting on very rapidly, but from this time
things took a turn. Cerceris is never in a hurry, and yet she may be
relied upon to do a certain amount of work every day. The one that we
were now watching had probably come back for a final look at her newly
made nest before beginning to provision it; for she soon reappeared,
and this time really went to work, since in forty minutes she brought
home a beetle which she carried by the snout, venter up, in her
mandibles, supporting it with the second pair of legs while flying. She
was much annoyed at our presence, and circled about as before. Twice
she alighted near by, and walked around for a few minutes, and when she
did this all her feet came down to the ground, the beetle being allowed
to hang loosely. At last she made the best of a bad matter, and went
in. The rest of the morning was occupied with hunting, the capture of
each beetle taking about forty–five minutes. Every time that she came
home she spent fifteen or twenty minutes in the nest.
This species soon became very common, and for two weeks scarcely a
morning passed without our finding at least one newly–made nest. The
study of clypeata, however, consumes a great deal of time. For example,
we found, one morning, two nests within six inches of each other.
It turned out afterward that these were inhabited by two different
wasps; but at the moment we supposed that one of them had been dug and
deserted and then a second one made, and wishing to know which one was
occupied we resolved to watch and see. After waiting for three hours we
saw one wasp returning; but upon noticing us she veered off and began
to circle about. She was heavily laden, and her burden, instead of
being supported by the second pair of legs, as is sometimes the case,
hung down under the thorax and abdomen. After a moment she alighted on
a plant near by, and seemed to consider the situation, then circled
a little more, and flew away, remaining out of sight for fifteen
minutes, then another return, more circlings and hesitations. She
seemed to feel the weight of the beetle now, and alighted frequently
on the ground and walked about; yet she would not go in, so reluctant
was she to betray her nest. In this way she kept us waiting for a whole
hour, although we were not very near to her, and were as still as
statues. At last we retreated, and stood as far back as we could and
still keep the hole in view. She now came closer, and, after hanging
poised on her wings for a moment, dropped into her nest.
We once found a nest of this species in process of construction. A
large heap of fresh earth had been pushed out, which entirely covered
the spot; but at intervals there were upheavals from below which
betrayed the presence of the wasp. When we saw it first it was half
past eight o’clock, and we judged, from what had been accomplished,
that she must have been at work at least an hour. It was half past
nine before the excavation was complete. We had not been certain, up
to this time, as to what we were watching; but now we had the pleasure
of seeing her open her doorway from below and stand in the entrance
while she washed her face with her fore feet, like a cat. When they
rest at the mouth of the hole the first legs, which are yellow, are
bowed in a semicircle on each side of the yellow face, the distal
joints being bent up so that the wasps seem to be standing on their
elbows. This attitude, which is often seen in Bembex spinolæ, gives
them a delightfully amusing, bow–legged appearance. They usually open
their nests in the morning at about nine o’clock,—a little earlier
or later according to the time at which the sun strikes the spot.
Then they spend from forty minutes to an hour in taking a survey, the
least movement on the part of a watcher causing them to drop out of
sight as if the earth had given way beneath them. Sometimes there is
a little way–station an inch or two within the tunnel, and the wasp
falls back only to this point, and here she may be seen, if one peeps
in cautiously, either quietly awaiting the retreat of the intruder, or,
perhaps, performing her toilet in a leisurely and elegant manner.
Whenever she leaves her nest she makes three or four rapid circles
around the spot to freshen her memory of the locality. The most
thorough study that we saw made by clypeata was in the case of the wasp
mentioned before, that was so long in carrying her beetle in because
of our being on the ground. When she finally did go in she stayed only
an instant—just long enough to deposit her load—and then came out and
spent a long time in an investigation of all the surrounding objects,
flying in and out among the plants, now high, now low, and circling
again and again around the spot. It looked as though she had been
puzzled and disturbed by the presence of unaccustomed things. As soon
as the survey was over she went inside and closed the door, as though
its object had been not so much to strengthen her memory as to correct
former impressions.
The work of bringing in beetles goes on very irregularly, and as a rule
not more than two or three are stored in the course of a day. It is
not unusual for clypeata to spend three or four hours away from home
and then come back without anything; and often, even in the middle of
the day, she passes an hour or two in the seclusion of her nest. We
had several nests under observation for a week at a time without ever
once seeing the owners, although they were evidently occupied, since
they were sometimes open and sometimes closed. The outer entrance is
always left open when the wasp goes away, although possibly access
to the pockets may be barred below; but when she enters she closes
the door unless she means to come out again at once. The closing is
sometimes effected by pushing the earth up backwards, with the end of
the abdomen; but the hole is rather too large for this method, and
more frequently the wasp comes up head first, carrying a load of earth
in her front legs. This is placed just within and to one side of the
entrance, and then more armfuls are brought up, until, after two or
three trips, the opening is entirely filled.
We once captured the wasp in a bottle, as she returned, loaded, to the
nest. She dropped the beetle, but soon picked it up again and stung it
vigorously, _with intention_, as the French say, first under the neck,
and then further back, behind the first pair of legs. After this it was
dropped while the wasp fluttered about for a few minutes, but it was
then picked up again, and stung as before. We both saw this operation
repeated in exactly the same way, four different times, with intervals
of five or six minutes between.
In a nest which we excavated after watching it for nine days, we found
nothing until we had gone six inches down, and at this point the
tunnel was lost; but mixed with the crumbly earth that we took out of
the hole, we found eight beetles and a half–grown larva of clypeata.
The destruction of this nest was accomplished one morning, and when
we came back to the spot twenty–four hours later we found that a new
one had been made close by, doubtless by the same individual. We had
expected to find her bringing beetles and dropping them foolishly on
the ground like Paul Marchal’s Cerceris ornata, and were gratified that
she showed an advance in intelligence over that species, although to
be sure she would have been still wiser had she chosen an entirely new
neighborhood. Another individual was so much disturbed by our scrutiny
that she dropped her beetle at the entrance to her nest. She did not
pick it up again and utilize it, although it lay for three days in the
dust at the threshold.
As to the condition of the beetles stored by clypeata: in the first
nest that we opened we found eight, seven of which were dead, while
the eighth, which we had just seen stung several times, was alive, but
died on the following day. The second nest gave us five beetles, all of
them dead and dry. In the other nests that we opened we found nothing,
though we knew that the beetles were there had we only been skillful
enough to discover them.
Of Cerceris deserta, which closely resembles clypeata, but appears
later in the season, we had only a single example. We chanced to see
her dropping into a crevice among some lumps of earth, and at first
could scarcely believe that this was the dwelling–place of a wasp, as
there was nothing whatever about it to indicate a nest; and even after
we had removed the rough pieces of earth above, we could see nothing of
the loose material that must have been carried out.
She was much like clypeata in her manners, with the same habit
of surveying the world from her doorway, and manifesting the same
annoyance at our presence when she was returning to the nest; but she
carried in more beetles in the course of the day and worked much more
rapidly. Between nine and eleven o’clock one morning she brought in
five loads, and some of the journeys occupied only ten minutes.
[Illustration: CERCERIS DESERTA: LOCALITY STUDY BEFORE LEAVING NEST]
The first time that she found us sitting by her nest she circled about
for nearly an hour, seeming unable to make up her mind to enter. At
length we withdrew a little way, but still her suspicions were not
entirely allayed; and after a further study of the situation she
dropped, not into her own nest, but into a large cricket hole near
by. Taken aback by this manœuvre, and thinking that perhaps we had a
second individual to deal with, we stealthily approached, and peering
in, could see the cricket inside, the wasp having slipped beyond. It
did not seem possible that the little creature could be endeavoring to
deceive us, and yet what other explanation could be offered for her
conduct? We again took up our distant position, and after ten minutes
more had the satisfaction of seeing the wasp slip out of the false nest
and drop instantly into the true one. After a little she became quite
accustomed to us, and entered her nest without the least delay.
The prey of deserta is held in the mandibles, and while we were
watching her she did not support it with the second legs, even when
flying.
Philanthus punctatus is a pretty little yellow–banded species much
resembling Cerceris in appearance. The nest consists of a main gallery
with pockets leading from it, each pocket being stored with one egg and
enough bees to nourish a single larva. When the wasps emerge from the
cocoon they find themselves in the company of their nearest relatives
and in possession of a dwelling–place, and they all live together for
a time before starting out independently to seek their fortunes. On
the fifth of August we discovered on the island a happy family of this
kind, consisting of three brothers and four sisters, the females, with
their bright yellow faces and mandibles, being handsomer than the
males. They seemed to be on the most amicable terms with each other,
their only trouble being that while they were all fond of looking out,
the doorway was too small to hold more than one at a time. The nest
was opened in the morning at about nine o’clock, and during the next
thirty or forty minutes their comical little faces would appear, one
after another, each wasp enjoying the view for a few minutes with many
twitchings of the head, and then retreating to make way for another,
perhaps in response to some hint from behind. Then one by one they
would come out, circle about the spot, and depart, sometimes leaving
one of their number to keep house all day alone. They usually left the
hole open; but when there was a wasp within, it was soon closed from
below. During this playtime period they did not return until they were
ready to settle down for the night, the first one coming home at half
after two or three o’clock, and the others arriving at intervals, none
of them staying out later than five. Most commonly they found the right
spot without trouble, scratched open the hole, and then either closed
it behind them or stood waiting in the doorway for the next arrival;
but occasionally they had difficulty in locating the nest, and worked
at two or three different places before finding it.
We kept these wasps under close observation, often watching the nest
from the moment it was opened in the morning until it was closed
at night. On the twelfth of August, a week from the time that we
first saw them, one of the females felt the responsibilities of life
settling down upon her. At half after four in the afternoon she began
to enlarge the nest, and worked with a great deal of energy for forty
minutes. After a long disappearance within the hole she would come up
backwards, kicking behind her a quantity of earth which was not only
taken outside, but was then spread out far and wide. She worked with
the front pair of legs, which were curved inward, after the manner
of Bembex; and when a pebble or some such object came in her way she
either dragged it to a distance with her mandibles or pushed it before
her with her head in a way quite peculiar to herself. In distributing
the earth that was taken out, she went five and one half inches
from the nest—a distance which is much greater than is common among
wasps, but which accords well with the habits of punctatus, since she
continues the work of excavation from day to day.
[Illustration: PHILANTHUS PUNCTATUS]
On August thirteenth, at half after eight in the morning, we found
that a second female, perhaps inspired by the example of her sister,
had made a new nest within two inches of the first one, and had flown
away, leaving it open. Presently the other wasps began to appear, one
after the other, in their doorway. Two of the males flew away, and one
of the females, doubtless the one that we had seen digging the night
before, began to work afresh at making the nest larger. Probably she
was excavating a pocket for the reception of an egg, and the amount
of labor required was enormously increased by the great length (about
twenty–two inches) of the main gallery by which the displaced earth
must be carried out. She worked for an hour, and in spreading the dirt
about, inadvertently filled in the opening of the second nest. At
length she flew away.
At ten o’clock a female arrived carrying a bee, and tried to find
nest No. 2. She came to the wrong place, and worked about, here and
there, for some minutes, holding the bee under the thorax, clasped by
the second pair of legs. Being unsuccessful, she dropped her burden,
and flew away for a few minutes. While she was gone we removed a leaf
that had fallen over her nest, and on her return she at once descended
upon the right spot, and began to scratch open the entrance, the bee
being kicked backward with the rejected earth. When the way was clear,
however, she picked it up, brought it toward the hole, dropped it, ran
in and out, brought it nearer, ran in again, and turning around in
the tunnel, seized the bee in her mandibles and pulled it down. This
performance was due to the accidental obstruction of the gallery, for
we afterward found that punctatus ordinarily flies directly into her
nest, or, when it is closed, pauses on the wing to scratch an opening
with the first legs. The bee is pushed backward a little as she goes
in, but does not often project from under her abdomen.
At fifteen minutes after ten the worker from nest No. 1 brought in a
bee, and from that time the two worked industriously. They showed some
individuality in their ways, for No. 2 always closed her door when she
went away, and never circled at all, while No. 1 invariably circled
before leaving, and always left her nest open. To be sure, there was
a female left on guard, so that perhaps she did not feel the need of
caution.
Our wasps had not far to go for their victims. Forty feet away, on
the eastern side of the island, was a steep declivity, and here, in
the soft crumbly soil, was a great Halictus settlement. No prettier
sight can be imagined than is presented by this colony on every sunny
summer day. The whole bank is riddled with nests, and at the entrance
of each stands a female bee, her tiny head exactly filling the opening.
The bees are constantly arriving, laden with pollen, whereupon the
sentinels politely back inward to make way for them. Into this scene of
contented industry descends the ravaging Philanthus, taking guards and
workers alike.
On the afternoon of the fourteenth of August our two wasps were in
the full tide of affairs. No. 1 took in eleven bees within two hours,
but her record was somewhat confused, as two other females were going
in and out at the same time. We felt sure that neither of these was
hunting, but one of them shared in the labor of the nest by helping
with the work of excavation.
No. 2, however, was alone, so that we could keep a definite account of
her comings and goings. We watched her from half past one until five,
at which hour she came home without a load, and at once closed the nest
for the night, after having stored thirteen bees in three hours and
nine minutes. In some cases the capture of the bee occupied only one,
two, or three minutes, while at other times she was gone much longer.
At each return she stayed only an instant—just long enough to deposit
the bee—inside the nest, and then spent a minute in carefully closing
the hole. The wasps that were going in and out of nest No. 1 sometimes
closed it when they went away, but this was done in an untidy fashion,
quite different from the nicety and precision of No. 2.
At half after five o’clock the wasp that had been digging for some
little time at nest No. 1 flew to nest No. 2, opened it, and attempted
to enter, but was quickly driven out by the owner. She then dug a
little in several other places, finally returning to sleep in the
family home. On the next day we found that No. 2 was tolerating in her
nest one of the females that had not yet begun to hunt, but whether it
was the one she had rejected the night before or the fourth member of
the sisterhood, we could not tell. On the eighteenth, three days later,
the wasp had left this temporary home and made a nest for herself four
feet away on the hillside. The males were still living in the first
nest with two females.
When the weather was cold and cloudy punctatus remained closely housed
within the nest, or, at most, came out to do an hour’s digging, and
then disappeared. The warmer the weather, and the more brilliant the
sunshine, the more rapidly they worked. When leaving the nest they
would often creep out and walk around it three or four times before
rising on their wings, and even then would sometimes alight once or
twice before flying away. The males, especially, liked to stand about
for a time, watching their more industrious sisters at their work. The
females usually began the day with digging, and frequently closed it,
toward night, in the same way.
In order to see the method of stinging, we at one time provided
ourselves with a number of bees, and putting one of them into a bottle,
introduced a wasp. She seized it almost immediately, with great vigor,
and stung it once, under the neck, and then dragged it up and down the
bottle by one antenna which was held in the mandibles. After a moment
she shifted it and held it with the second legs in the usual way. We
now put in another bee, which she also caught, stung in the same place,
and then dropped without relaxing her hold of the first one. As she
seemed to have nothing further to show us we released her, and after
circling a little she took into her nest the bee that she was carrying.
In our next experiment we used a larger glass, thinking that with more
space we might see malaxation. The instant that the wasp was introduced
she grasped the bee with one rapid powerful motion, and stung it
just under the neck as before. Then holding it with the second legs
she began to fly about in the glass. We now introduced another bee,
whereupon the first one was relinquished, and the second was treated
in exactly the same way. The stinging was the beginning and the end of
the operation, and when we released her she at once took the bee into
the nest. There was no malaxation outside, and certainly there was none
within, as was shown by the rapidity with which the wasps issued from
the nest after storing the bees. We were successful in getting the
wasps to sting only when we tried the experiment with those that were
hunting. When those that had not yet begun to store their nests were
put into the glass they paid no attention to the bees.
The victim of the sting of punctatus is killed at once. Life is extinct
from the instant that the stroke is given. This is true also of the
honey–bee that is the victim of Fabre’s Philanthus apivorus; but the
explanation that he gives of the action of his wasp in thus dealing
sudden death instead of paralyzing its foe—that the honey must be
sucked out of the bee before it can be safely used as food for the
larva—does not hold good in our case, since the honey that Halictus
carries to mix with the pollen upon which her offspring are fed, is not
removed.
[Illustration: NEST OF PHILANTHUS PUNCTATUS
A–B, 3½ inches; B–C, 5 inches; C–D, 14 inches; D–E, 8 inches]
As time went on we found on the island two other Philanthus colonies,
although that is rather too large a word to apply to them, since one
consisted of four nests and the other of only two. When we came to
excavate the nests of this species we were greatly astonished at the
length of the gallery, and not until then did we properly appreciate
the industry of these little wasps. It is no small undertaking to
follow one of their tunnels for twenty–two inches, even when, as in
this case, the greater part of it is parallel to the surface of the
ground. We did not find distinct pockets, as the soil was very crumbly
and fell in as we worked, but we came upon clumps of bees an inch or so
to one side of the gallery and about three inches apart, with larvæ in
different stages of development. In one nest we found twenty–six bees
in two clumps, some of them half–eaten, and some of them fresh, but
all quite dead. We have no doubt that punctatus completely provisions
one pocket and closes the opening from it into the gallery, before she
starts another, making a series of six or eight independent cells.
The provision for one larva is probably twelve or fourteen bees, the
capture of which, in good weather, would be a fair day’s work.
That the males do not always stay on in their ancestral home is shown
by an observation that we made on the only occasion that we ever saw
this species in our garden. Nothing was stirring at half past three
o’clock in the afternoon, and we had given up work and started for
home, when, in going up an inclined part of the field, we noticed
something in motion within a ragged–edged hole which ran obliquely into
the ground. It seemed strange that a wasp should be beginning its nest
at so late an hour; but a wasp it was, as we could plainly see when we
took an attitude sufficiently humble. It was loosening the earth with
its mandibles, and then pushing it backward with its hind legs and
abdomen. We had scarcely settled down to watching it when a second one
of the same species appeared, and with a good deal of fuss and flutter
began to dig its hole close by. The spot chosen by this second one
proved unsatisfactory, and another beginning was made in a new place.
Again something was wrong, nor was a third choice any better. At last,
however, the work was started in earnest, and might have been carried
to a conclusion if we had not caught the little creature to satisfy a
suspicion that had been growing in our minds. Yes, we were right. The
worker was not a female making a nest for the rearing of her young, but
a male punctatus, preparing a shelter for the night.
In the mean time the first wasp had pushed back such a quantity of
earth that the hole was entirely closed, but every few minutes he came
backing out to clear the way. At the end of half an hour all became
quiet. The door remained closed, and doubtless the wasp was fast
asleep. Putting a blade of grass and then an inverted tumbler over the
nest, we left him for the night.
On removing the glass at half past seven the next morning, we found
the nest open but the wasp not visible. At half past eight the head
appeared just inside the hole, the long antennæ twitching now to this
side, now to that, as if an inspection were being made. Soon the head
came out. The wasp stood for some minutes making a survey, looking
to right and left with lively jerks of the body. Then, apparently
concluding that the day was not far enough advanced, he came out,
whirled around, and ran head–first into the nest. He probably took
another nap, for all was quiet until just before ten o’clock, when the
antennæ appeared again. The survey was taken as before, first from
within and then with the head in view. At last he flew out, and making
three circles, each one wider than the last, about the place, flew
away. He stayed out all day, and had not returned at half past three in
the afternoon; but on going down at half past four we found that he had
gone in and closed the door from below.
It is clear, then, that these males do not construct a new lodging
every night, but return to the same spot to sleep. Other wasps creep
into crevices. We have often found them, in the morning, in the holes
of the posts of our cottage porch; but we are glad to be able to put
it down to the credit of one male that he has sufficient foresight and
industry to provide a sleeping–place, and sufficient intelligence to
return to the spot when the declining sun warns him that evening is
approaching.
While punctatus was in the height of its activity we found another
species, P. ventilabris, taking bees of several genera and species
into a ground nest. She also carried her prey with her second pair of
legs, and whenever she left her nest she closed the door. She was a shy
little thing, and did not approve of our interest in her. At one time,
being startled by some movement on our part, she dropped her load and
flew away. We placed the bee upon the closed nest, and when she came
back with another, she paused and looked at it, took in the one she
was carrying, and then returned for number one. This was placed on the
threshold while she entered and turned around, and was then pulled in.
Some wasps, notably C. ornata and our little tornado, refuse to take
in their prey, even if they have caught it themselves, excepting in a
regular succession of events; and thus the more reasonable conduct of
ventilabris gains in interest.
To the west of Milwaukee, across the valley of the Menominee, rises
a sandy hilltop which is a little insect kingdom by itself. Ants of
course abound, and the gentle little solitary bees, with their loads
of pollen, may be seen everywhere, seeming to melt into the ground, so
quickly and quietly do they open their burrows. Here Oxybelus plys her
trade of fly–catching, and graceful Ammophila dances with her shadow
over the sunny ground, while Cerceris rests in her doorway with an air
of leisurely superiority to the vulgar cares of life; and here, one day
in early July, a sudden access of energy seemed to strike Aphilanthops
frigidus, a wasp which we had found a year before taking in the
wingless queens of ants. All at once they were digging everywhere,
biting and scratching with great energy, and soon disappearing in
the depths of their sandy tunnels. So deep is their primary gallery
that even in this easy medium it takes them the best part of a day to
get it ready for storing; but once finished it doubtless serves as a
home through the season. It has at the entrance a little cup–shaped
vestibule where the wasp drops the ant as she enters, running out of
sight herself, and then, after she has turned around, coming back to
pull it within. This nest is a very difficult one to excavate neatly,
as the sand falls at the slightest touch.
A day or two after we had seen frigidus making her residential
arrangements, we found twenty–five or thirty within a few feet of each
other, working with great ardor at carrying in queens, the doors being
left closed or open according to individual judgment. The steadiest
workers brought one every forty minutes, scarcely pausing inside the
nest, but others made long stays within, leaving the door closed. The
ants were carried under the body with all the legs folded around them,
but they were heavy things, and were often dropped as the wasp flew
across the field, giving opportunities for robbery that were promptly
taken advantage of. We picked up one of these ants and placed it in
the doorway of a wasp that had just gone in. She came up twice, looked
at it, and backed down again; but the third time she first touched
it, then seized it and took it below. From another wasp that was just
entering we took the ant she had dropped and moved it half an inch
away. When she had turned and come up for it, she seemed surprised,
came out and looked about, found it and dropped it in the doorway,
going in herself to turn around as before. We seized this chance to
move it again, and again she came out, found it, took it back, and
dropped it. This was repeated five times, but when she took it in for
the sixth time, after dropping it, she whirled around and picked it up
so quickly that our malice was foiled.
[Illustration: APHILANTHOPS GATHERING ANTS]
We were puzzled by the actions of a wasp that approached her nest
again and again, but always circled away without entering, until
looking closely we saw that she was pursued by two tiny flies. When she
alighted and walked about awhile with her ant tucked under the third
leg on one side, the flies alighted also and walked about behind her.
In the end she evaded them by a sudden drop into her hole.
A wasp now came circling along with an ant in her grasp, and settled
down between two small weeds that grew about four inches apart. She
stood quiet a moment and then began to dig, but had evidently struck
the wrong spot, for after a moment she moved and tried another place.
Not finding the entrance, she rose and flew close under one of the
plants and began to scratch again, but still in vain. For ten minutes
she persisted, keeping within a few inches of the spot, and holding on
to the ant all the time, although it was dreadfully in her way as she
walked about. Then she dropped it and began to dig more vigorously,
dividing her attention between the two spots she had attempted at
first. She seemed troubled at having to leave the ant, and often picked
it up and tried to hold it while she worked. Once in a while she would
take it with her, and after circling about the spot would disappear,
but in a few minutes she would return. It seemed to us that two little
plants growing near together must have been her landmarks, and that
probably she had been deceived by the likeness that those before us
bore to the ones near her nest. Again and again she seemed to hesitate
and think the matter over, but gradually one of the holes absorbed her
more and more. At the end of an hour she was out of sight in it, and
had carried her ant down, although she was still kicking out sand. It
was evident that her memory had played her false, and that she had
either covered her hole so neatly that she could not find the spot
herself, or had missed the place entirely. She had accommodated herself
to circumstances pretty well, although she ought to have realized
earlier that it would be easier to dig one nest than two.
We now tried to excavate a nest, but could not follow the tunnel,
although we found clumps of ants at different levels, some with larvæ
feeding on them. The deepest were eighteen inches down. Hoping to
secure a guide, we borrowed an ant as it was dropped in the doorway
and tied a thread to it. The wasp pulled it in and took it part way
down with this attachment; but before any great depth was reached, the
thread was seemingly bitten off, as we found the free end without the
ant. A second attempt brought no better results.
So long as we were quiet the wasps did not notice us, but after
being disturbed they became shy and circled about a good deal before
entering. Some of the ants were completely paralyzed, while others
moved their abdomens, legs, and mouth parts. All through the morning,
the whole place was in a bustle, but when we came back, after eating
our luncheon in a shady spot, quiet reigned; the colony seemed asleep,
and although we waited for an hour not a wasp showed herself.
The ants that these wasps were bringing all had wings. The European
genus Fertonius takes worker ants which can be picked up anywhere; but
so far as we know, these queens leave the nest only at the time of
their nuptial flight, after which the wings are lost. How then are
they captured? Can it be that the wasps, though not much larger than
their prey, descend into the home of the ants, bearding the lions in
their den, and carrying off their young queens by force of arms? This
smacks of heroism.
Much interested in the matter, we carefully examined the ant–hills
of the neighborhood. Those on top of the hill had openings too small
to admit frigidus, supposing she had wanted to enter, but down on
the roadside below we found some larger doorways and sat down beside
them. We had scarcely arrived when a frigidus appeared on the scene,
alighting six feet away. That she should have come hunting so soon
seemed almost too good to be true, but she certainly was not doing
anything else. She did not dig, nor feed on the clover, nor circle
about as though looking for her nest, but began to clean and brush
herself assiduously. Then she climbed a tall grass blade, and swinging
at the top went through some curious gymnastic performances. Then she
brushed herself again, drawing her third legs over the sides of her
abdomen. This went on from moment to moment, until half an hour had
passed, and more than once the painful suspicion crossed our minds that
this was some trifling male putting in the hours between breakfast
and luncheon. One encouraging fact cheered us: aimless as the wasp
appeared she was slowly drawing nearer and nearer to the nest; and at
last, alighting on the top of a weed close by, she crouched there in
a most peculiar attitude, and gazed intently at the opening. Absorbed
and tense, she looked about to leap upon her prey; but after a time
she relaxed and moved about a little. Presently she came close to
the entrance and seemed on the point of going in; but the ants were
swarming up and down, and we thought that perhaps that step required
more courage than she possessed. At any rate, she did not enter, but
hung about for some minutes and then flew away.
Was this a young wasp out on her first hunt? What strange antiphonal
desires must have stirred at the sight of the nest, and how mysterious
was the power that drew her to it! Was there in her brain any image
of the queen she must seek and sting and carry away from among her
guards and subjects? Or had she perhaps already achieved the adventure,
and did the memory of the bitter nips that little ant jaws can give
make it a harder task than it was the first time, when she risked
the ills she knew not of? That she hesitated and carried on the work
reluctantly seemed to show that her flesh was weak and needed the prick
of conscience to drive it on. Had we here then the small beginnings
of moral sense and perception of duty? Can it be that of such humble
origin is the power that “doth preserve the stars from wrong”?
We went on with these meditations for several days while lingering,
with gradually diminishing hopefulness, over one ant–hill after
another. The wasps were carrying in winged queens by the score, but
they did not come our way to find them; and although we ranged about
widely, we failed to see the capture. Occasionally we met a frigidus
hunting, running about on the ground and poking her head, not only into
ant holes, but into holes of all sorts, and as we sometimes saw young
queens (wingless however) starting to dig their nests, we thought these
might be the object of the search. The weather was cold and windy, most
unpropitious for swarming, and yet frigidus was working as briskly as
ever; so that we began to feel sure that she could not depend upon
meeting the queens outside the nest, but must enter to get them. Just
as this point we received a letter from Mr. William M. Wheeler, well
known as an authority on ants, saying that he felt very sure that the
wasp could not extract the queens from the nest, but must find them
running on the ground, just after the nuptial flight, before they dug
their holes and started their colonies. Respecting this opinion, but
still feeling unconvinced, we caught a wasp in a glass, and carrying
it to an ant–hill, inverted it so that she was confined just over
the entrance. After buzzing up and down for a moment, she alighted
and walked calmly into the hole; but a fraction of a second later
she came rushing madly out again, pursued by the most furious lot of
ants that ever defended the home city against invasion. Down tumbled
our air castles about courage and duty, for however frigidus gets her
queens, it is not in that way. We have not yet seen the meeting and the
capture, but hope that sometime we may be lucky enough to be on the
right spot at the right time.
Chapter VIII
THE WOOD–BORERS
OUR two species of Trypoxylon are both slender–waisted black wasps,
albopilosum having bunches of snowy white hairs on the first legs, and
measuring three quarters of an inch in length, while rubrocinctum is a
little smaller, and, as the name implies, wears a red girdle.
Although these wasps are called wood–borers, they will use convenient
cavities in any material. When we went out to our summer cottage, in
the last days of June, 1895, we found many little wasps of the species
Trypoxylon rubrocinctum busily working about a brick smoke–house on the
place. Closer examination showed that in the mortar between the bricks
were many little openings leading back for a considerable distance,
which were occupied by the wasps. It would seem that these holes were
excavated by some other agency than the wasps themselves, as they were
so much too deep for their purposes that before using them they built
a mud partition across the opening about an inch from the outside of
the wall. Later we found nests of the same species in the posts which
support an upper balcony of the cottage; and here, too, the wasps made
use of holes which were already excavated.
In the following summer we found large numbers of these wasps at work
in a straw–stack. The stack had been cut off perfectly smooth on one
side, so that many thousands of the cut ends of the straws were exposed
to view, and these proved very attractive to rubrocinctum. This species
is very cosmopolitan in its tastes, for we found it utilizing the
small holes in the sticks of a woodpile. The straws made the daintiest
nesting–places, however, and were well adapted to our purposes, since
they could be drawn out of the stack and split lengthwise so that the
contents could be easily studied. The two halves could then be brought
together again without injuring the inhabitants, and thus we often
kept several sets under observation long enough to watch the changes
from the egg to the pupa. We found Trypoxylon albopilosum nesting in
holes made by beetles in posts and trees, but never in straws. A third
species, bidentatum, was very common, nesting in the stems of plants.
During the month of August we saw many individuals of this species
hunting for spiders on the blackberry bushes; but at this time we were
so much absorbed in Crabro stirpicola that we never followed them to
their homes.
Rubrocinctum was more conveniently studied, and through July and August
we watched the comings and goings of these little wasps. They were very
good–tempered, never resenting our close proximity nor our interference
with their housekeeping. By working hard they could prepare a nest,
store it with spiders, and seal it up all in the same day. This we have
seen them do in several instances. In other cases the same operation
takes three or four days. In the second summer that we worked with them
we found one very energetic mother that stored four nests in one day.
It had rained hard on the twenty–sixth of July, and no wasp works in
such weather. On the afternoon of the twenty–seventh we took a straw
just as the little mother was bringing in a spider. We opened it and
found that the innermost cell contained eight Epeirids, with an egg on
the abdomen of the last one taken in; the second cell was provisioned
with ten spiders, with the egg on the seventh, so that three had been
brought in after it was laid; the third cell had the egg on the last
spider, as did also the fourth. All of these eggs hatched on the
twenty–ninth,—the two outer ones, that were laid last, between eight
and nine o’clock in the morning, and the two that were laid earlier
between two and three in the afternoon. This was the biggest day’s
hunting that we have ever recorded for any of our wasps.
With both species (T. rubrocinctum and T. albopilosum), when the
preliminary work of clearing the nest and erecting the inner partition
has been performed by the female, the male takes up his station inside
the cell, facing outward, his little head just filling the opening.
Here he stands on guard for the greater part of the time until the nest
is provisioned and sealed up, occasionally varying the monotony of his
task by a short flight. As a usual thing all the work is performed by
the female, who applies herself to her duties with greater or with less
industry according to her individual character; but the male doubtless
discharges an important office in protecting the nest from parasites.
We have frequently seen him drive away the brilliant green Chrysis fly,
which is always waiting about for a chance to enter an unguarded nest.
On these occasions the defense is carried on with great vigor, the fly
being pursued for some distance into the air. There are usually two
or three unmated males flying about in the neighborhood of the nests,
poking their heads into unused holes, and occasionally trying to enter
one that is occupied, but never, so far as we have seen, with any
success, the male in charge being always quite ready and able to take
care of his rights. The males, however, made no objection when strange
females entered the nest, as they sometimes did by mistake, nor did the
females object to the entrance of a strange male when the one belonging
to the nest happened to be away; but in such cases the rightful owner,
on his return, quickly ejected the intruder. We often amused ourselves,
while we were watching the nests, by approaching the little male, as
he stood in his doorway, with a blade of grass. He always attacked it
valiantly, and sometimes grasped it so tightly in his mandibles that he
could be drawn out of the nest with it.
When the female returns to the nest with a spider the male flies out to
make way for her, and then as she goes in he alights on her back and
enters with her. When she comes out again she brings him with her, but
he at once reënters, and then, after a moment, comes out and backs in,
so that he faces outward as before.
In one instance, with rubrocinctum, where the work of storing the nest
had been delayed by rainy weather, we saw the male assisting by taking
the spiders from the female as she brought them and packing them into
the nest, leaving her free to hunt for more. This was an especially
attentive little fellow, as he guarded the nest almost continuously
for four days, the female sometimes being gone for hours at a time. On
the last day he even revisited the nest three or four times after it
had been sealed up.
It is upon the female that the heaviest part of the work devolves.
As soon as she has put the nest in order she begins the arduous task
of catching spiders wherewith to store it. It usually takes her from
ten to twenty minutes to find a spider and bring it home, but she is
sometimes absent for a much longer time. When the spider has been
carried to the nest the process of packing it in begins. This occupies
some time, and apparently a good deal of strength,—the female pushing
it into place with her head, totally disregarding its comfort, all
the spiders that are caught being pressed and jammed together into a
compact mass. While she is busied in this way she makes a loud cheerful
humming noise. The number of spiders brought seems to depend upon
their size, in which quality they vary greatly, the largest ones being
six or eight times as large as the smallest. Rubrocinctum fills her
nest with from seven to fourteen, while the larger albopilosum brings
as many as twenty–five or thirty. Those that we examined represented
many different genera, and even different families, although they were
usually orb–weavers.
In a number of cases, during the first summer, after several spiders
had been stored, we gently drew them out with a bent wire. In one nest
in which there were five spiders, we found, two hours after they had
been stored, that three were alive and two were dead. In another, which
the wasp had just begun to seal up, were ten spiders. Three of these
were injured in being drawn out. Of the remainder four were alive and
three dead. On the anterior part of the dorsum of one of the living
spiders was the egg. It had probably been fertilized as the female
carried the male into the nest on her back.
When we discovered rubrocinctum in the straw–stack, we made many
observations as to the position of the egg and the number and condition
of the spiders. We found that the egg was always placed either on the
side or the back of the anterior part of the abdomen. The number of
spiders stored was, as we have already stated, from seven to fourteen.
A fact that interested us greatly was the remarkable accuracy shown by
the wasp in never selecting too large a spider for the calibre of the
straw. Oftentimes it was an extremely close fit, but it could always
be squeezed down. When they nested in posts they used at times much
larger prey. Unfortunately we never saw this species capture its prey,
nor could we prevail upon it to sting in captivity, but the number
of spiders that we found in straws was so large as to afford abundant
evidence concerning the degree of surgical skill possessed by the
wasps. P. marginatus and P. scelestus, in overpowering their large
fierce Lycosids, must sting when and where they can, but most of the
spiders taken by rubrocinctum are inoffensive creatures, and there is
so little need to be careful or adroit in dealing with them that she
has time and opportunity to sting the exact spot that will give the
best results.
[Illustration: TRYPOXYLON RUBROCINCTUM]
The concentration of the nervous system in the Arachnida would seem
to conduce very strongly to uniform results from the stinging of the
wasps. Unlike the larva used by Ammophila, with its chain of ganglia,
in the Araneidæ the whole central nervous system, including the brain
and the ventral cord, forms a single mass, pierced by the œsophagus.
The greater part of this mass, which lies behind the œsophagus,
represents the fused ventral cord from which the nerves radiate. It is
evident that a thrust given in almost any part of the ventral face of
the cephalothorax, or even on either side of the anterior half of its
edges, would reach the nervous centre. With these facts before us let
us turn to the notes made upon the condition of the spiders that had
been stung and stored up in the nests of the straw–stack. By the “first
cell” we mean the last one stored, which was naturally the first one
opened.
July 11. Opened a nest of _rubrocinctum_. The first cell contained
fourteen live spiders with a newly laid egg. Some of the spiders were
very lively, moving spontaneously. Second cell, ten spiders, one dead,
others alive, and an egg. Third cell, eight spiders, three dead and five
alive, and the egg.
July 12. In each of the first and second cells one spider has died since
yesterday, while in the third there is no change in their condition. The
egg in the third cell hatched at nine in the morning, and the one in the
second cell at three in the afternoon.
July 13. In the first cell all the spiders are dead but one, and in the
second, all but four, while in the third none are alive.
July 15. All the spiders in the second cell are dead.
July 16. The one spider in the first cell has outlived all the others,
but that, too, died to–day.
The record of another set of nests is as follows: On July eighth we
took a straw with a wasp as she went in with her spider. The cell was
not sealed up. It contained fourteen specimens of three species of
orb–weavers, and the egg was apparently just laid. The spiders were
pushed in very tightly, and the legs and abdomens were, in many cases,
bent to one side. All were limp, but alive. By July tenth, four were
dead; on July eleventh the egg hatched. By July thirteenth all of the
spiders were dead.
It is unnecessary to give the history of other nests in detail, since
these facts make it clear that there is a great variation in the degree
of severity with which the spiders are stung, so that while with some
the paralysis is complete, with others it is only partial. Some were
killed outright, others lived two or three days, while still others
survived for two weeks. Compared with the work of the Pelopæi it would
seem that a smaller number of the spiders are killed at once, while a
larger number die after the lapse of a few days. None of the victims
of Trypoxylon live so long as the most perfectly paralyzed spiders of
the mud–daubers. Two of them lived ten and fifteen days respectively,
while with Pelopæus one survived until the thirty–eighth and one until
the fortieth day.
The egg requires from forty to sixty hours for its development, and the
larva feeds for seven or eight days before spinning its cocoon. Those
that we watched usually disposed first of the abdomen and then of the
cephalothorax; sometimes they would consume several abdomens before
attacking the other parts. After the body was devoured the legs were
picked up and eaten. When the supply of food was generous, portions of
the spiders were sometimes left untouched. The cocoons resembled in
general appearance and structure those of Pelopæus.
When a female returns with her load she usually hunts about for a few
moments before finding her nest, sometimes entering, first, two or
three that are empty or are occupied by other wasps; but we do not
wish to cast any reflection upon the sense of locality of a creature
that is able to find one particular straw out of the many thousands in
an expanse of stack twenty feet high by twelve wide. We ourselves can
testify, from experience, to the extreme difficulty of the task.
After the storing process is completed the female seals up the nest
with mud. In the case of one rubrocinctum that we were watching, she
began to close the opening at four in the afternoon and finished her
work just thirty minutes later. In this time she made ten journeys for
mud, bringing it in pellets in her mandibles. In another case, also a
rubrocinctum, the female, after bringing so many spiders that the cell
was full up to the very door (which we saw in no other case), went away
without closing it, and never returned. The male seemed uneasy at her
conduct, and several times flew away, staying an hour or two and then
returning; but after a time he too deserted the nest. Whether some evil
fate overtook the female or whether there was some failure of instinct
on her part, can only be conjectured; but the latter hypothesis is not
untenable, since out of seventy–six nests that we had under observation
seven were cleaned out and prepared and were then sealed up empty. We
have often found similar cases among the nests of the blue mud–dauber
wasps, where it is not a very uncommon thing for the absent–minded
females to build their pretty little cylindrical nests with infinite
care and patience, and then to seal them up without putting anything
inside.
Cocoons of rubrocinctum that were gathered in the month of August
remained over the winter and hatched in May and June.
Almost as interesting as rubrocinctum is the slightly larger species,
T. albopilosum. This wasp has a great liking for the posts that support
the balcony of our cottage, a preference that is very convenient for
us, as it enables us to sit in the shade and watch their doings at our
ease.
One afternoon as we sat, literally, at our posts, a female of
albopilosum came humming along, looking very important and energetic,
as though she had planned beforehand exactly what to do. She entered an
empty hole, head first, and at once began to gnaw at the wood, kicking
it out backwards with considerable violence. After a few minutes she
changed her method of work, and began to carry out loads of wood dust
in her mandibles, dropping it in little showers just outside the nest,
and then hastening back. In forty minutes she carried out, in this way,
upwards of fifty loads. She then flew away, but returned in ten minutes
with a male. She alighted, he took his place on her back, and they went
in together.
After a time they came out and both flew away, but the next morning
they came back and the nest was stored.
[Illustration: MALE TRYPOXYLON AWAITING THE FEMALE]
In this species the male does not always come out of the nest when
the female brings a spider, the nest being enough larger than in
rubrocinctum to accommodate them both comfortably. As a usual thing,
however, he enters on the back of the female. The spiders brought by
albopilosum are larger than those used by rubrocinctum. They sometimes
bring such heavy specimens of Epeira insularis that they are carried
with difficulty, the wasp alighting and dragging the spider into the
hole instead of flying directly in as usual.
We watched a number of albopilosum nests during the second summer,
finding them in several instances through the loud humming of the
female while she was pushing the spiders into her hole. From our not
very extensive study of the spiders taken by this species we are of the
opinion that some are killed at the moment of capture, while others
that are only paralyzed die in the nest from day to day.
Mr. W. H. Ashmead has noted that albopilosum stores its nest with
aphides, but in the cases that we observed they used only spiders.
There can be no mistake on this point, as we more than once took the
spider from the wasp as she was entering the nest. In a recent letter
Mr. Ashmead says that his notes were made in the field, and that he
probably mistook some closely allied species for this one.
We are not as familiar with the habits of T. bidentatum as with those
of the other two, but we have a few notes relating to the female. This
little worker is the smallest of the three, and like her sisters is a
confirmed spider–hunter. Once, when out among the raspberry bushes, we
had the good fortune to witness a capture. The wasp seized the spider,
as it rested on a leaf, by the top of the cephalothorax, and, holding
it firmly, curved her abdomen under and stabbed the ventral face of
the cephalothorax. All her motions were deliberate, and after the
operation she delayed a moment before picking it up by a leg and flying
off. We often found raspberry stems which had been filled with spiders
by this wasp, but we do not know the length of time required for the
development of the egg, nor how long the larva eats before pupation.
The cocoon is very different in appearance from those of rubrocinctum
and albopilosum, being exceedingly long, slender, and almost white,
instead of short, wide, and brown. The perfect insects come out in
September, and the last cocoon formed is the first one to hatch. This
was also true of the cocoons of rubrocinctum formed in straws.
Years ago, when we found that many of the orb–weavers laid enormous
numbers of eggs (A. cophinaria from 500 to 2000), we wondered what
became of the thousands of spiderlings. An acquaintance with
Trypoxylon has shown us their fate, and has given us an illustration of
how closely the two groups are related. To make a very modest estimate
there must have been twenty wasps at work in our straw–stack. During
the six weeks which make the busiest part of their working season each
of these must have stored, at the very least, thirty cells, putting
an average of ten spiders into a cell. It may then be considered
certain that the straw–stack, with its working surface of twelve by
twenty feet, was the mausoleum of six thousand spiders, and it is very
probable that twice as many were interred within its depths. It must
be remembered, too, that before the spiders have grown large enough to
be interesting to rubrocinctum, bidentatum has had her turn at them,
and that those that are allowed to grow too large for rubrocinctum are
preyed upon grade after grade, first by albopilosum and finally by
Pelopæus, Pompilus, and other genera.
The wasps of this genus lose their interest in family affairs about the
second week in August, though after this time they may still be seen
taking their well–earned holiday on the blossoms of the aster and the
golden–rod.
Chapter IX
THE SPIDER–HUNTERS
WHILE Ammophila provides caterpillars for her larva, and Bembex, after
the manner of the social wasps, feeds her young from day to day on
dead flies, the Pompilidæ, so far as their habits are known, all prey
upon spiders. The family is a large one in the United States, one
hundred and twenty–seven species having been described. The members of
the group differ in size, color, and habits, and the individuals of
the same species show the very considerable amount of variation which
seems common to all those groups of animals which have been carefully
studied. Happily the old notion that habits and instincts, unlike
structural peculiarities, are always uniform, is no longer insisted
upon, and there is ample evidence for the opinion that functional
variations are as common as morphological. We have studied five species
of this family, and have found their respective rôles of great interest.
According to Fabre, the French members of this genus, although they do
not make their own nests, still exercise some foresight in the matter
by selecting a suitable crevice before catching their prey. Among the
species that we have studied, quinquenotatus, biguttatus, fuscipennis,
marginatus, and interruptus first catch the spider and then make the
nest; while calipterus and scelestus prepare the nest before capturing
their prey.
[Illustration: TORNADO WASP (POMPILUS QUINQUENOTATUS) DIGGING NEST]
Quinquenotatus is usually rather less than half an inch in length and
is black, the abdomen having a variable number of white bands and a
white tip.
It was on the last day of July that, as we were walking through the
bean field, we saw a cloud of fine dust which came spurting up out of
the ground like water in a fountain. By watching intently we saw that
the cause of the commotion was the rapid action of the legs of some
little creature that was almost hidden in the earth, and this proved to
be our first example of P. quinquenotatus.
She was working away as furiously as though she had studied the poets
and knew her _carpe diem_ by heart. Faster and faster went the slender
little legs; higher and higher rose the jet of dust above her. Then
suddenly there was a pause. The burrower had met with some obstacle. A
moment more and she came backing out of the hole, her feet slipping on
its crumbling edges. In her mandibles she carried a pebble, which was
taken to a distance of four or five inches. Then, moving quickly, she
swept away the dust that had accumulated near the mouth of the nest,
reëntered the hole, and resumed the labor of excavation.
We thought that the rate at which she worked was too violent to be kept
up very long; and sure enough, before ten minutes had passed the nest
was deep enough for her purposes, and we afterward learned, to our
chagrin, that it was too deep for ours. The wasp came out, circled
round the spot three or four times, and then flew off like a hurricane.
Never have we seen a creature so fiery, tempestuous, cyclonic. Before
we knew her proper title we took to calling her the tornado wasp, and
by that name we shall always think of her.
[Illustration: POMPILUS QUINQUENOTATUS]
Her flight was too rapid to follow, but in a minute we saw her
returning. She was carrying a spider, a good–sized specimen of Epeira
strix, which she had evidently deposited somewhere in the neighborhood
before beginning to dig. Alighting near by, she left the spider lying
on the ground, while she ran to her nest and kicked out a little more
earth. Then seizing it by one leg, she dragged it, going backward
herself, into the nest. She remained hidden for about two minutes, then
reappeared, and, seeming to be in as great a hurry as ever, filled the
hole with dirt. To disguise the spot and render it indistinguishable
from the rest of the field was her next care. Hither and thither she
rushed, now bringing little pellets of earth and placing them above
the nest, now sweeping away the loose dust which might suggest the
presence of the _cache_, and now tugging frantically at a stone which
she wanted to place over the hidden treasure, but which was too deeply
embedded in the earth to yield to her efforts. She did her work
faithfully, although with such eager haste that all was completed at
the end of twenty minutes from the time we saw her first. So well was
the place hidden that it was only by careful orientation that we could
be certain of its exact locality.
Her task accomplished, away flew our little tornado as though she
were pursued by the avenging spirits of all the spiders that she had
murdered, although more probably she was off in quest of another of
those meek and helpless victims.
“Now,” we said, “we will trace out the nest and make a drawing of it.
We will take the spider home and note its condition from day to day,
watching at the same time the development of the larva.”
Enjoying this little air–castle, we began to excavate. Having had
experience with the nests of Ammophila and Diodontus, and knowing that
the task might not be so easy as it looked, we went to work with all
possible care. It seemed, however, that some magician’s trick—some
deception of the senses—had been played upon us. We saw the spider
interred; we at once dug up the place and found nothing. Slowly and
carefully we enlarged our circle. We went down deeper until the opening
was large enough to hold a thousand spiders,—still nothing. Then we
tried another plan. Gathering all the earth that we had taken out, we
sifted it through our hands—in vain. At last we acknowledged ourselves
beaten, and trudged home empty–handed.
Our pride was destined to be still further humbled. Three times within
that same week we saw the tornado wasp bury her spider, and three
times we failed, just as incredibly, to find it. On the last of these
occasions we did not let her fill the nest, attempting to follow the
tunnel and get out the spider as soon as the egg was laid, but the
loose, unstable character of the soil defeated us.
Our fifth example, however, dug her nest, not among the beans but lower
down in the potato field, where the ground was firmer; and here we made
our first successful excavation,—successful only up to a certain point,
since in getting out the spider we dislodged the egg, and although it
was at once replaced it never developed. The spider was placed three
inches below the surface, but we could not trace the tunnel. At our
next opportunity, wishing to make good this failure, we placed a blade
of grass in the opening just after the wasp began to fill it. On being
disturbed she assumed the most comically threatening aspect, whirling
around, lifting her wings, and then circling about us. As soon as we
moved back she dashed at the grass–blade and pulled it out with great
energy. A few minutes later we made a similar attempt, and again she
frustrated our plan; but when we inserted the grass–blade for the third
time, the nest being now half filled, she let it remain. Some hours
later, with this to guide us, we succeeded in tracing the nest, but
much to our disappointment found it transformed into a banqueting hall.
Scores of tiny red ants had discovered this rich store of food. They
had eaten the egg and were rapidly finishing the spider.
Twice afterward, in opening these nests, we found the same ants in
possession before us. It is probable that they are a formidable enemy
to this and other species of Pompilus; but they seem to find the spider
by burrowing beneath the surface, so that the elaborate hiding of the
nest from above cannot be meant as a protection from them.
[Illustration: EXAMPLE OF EPEIRA STRIX THAT HAS BEEN PARALYZED AND HUNG
UP ON BEAN PLANT BY POMPILUS QUINQUENOTATUS, THAT IT MAY BE OUT OF THE
WAY OF ANTS WHILE SHE DIGS HER NEST]
Pompilus quinquenotatus has a decided preference as to the spider that
she takes. While Pelopæus and Trypoxylon are entirely indifferent
both as to size and species, and the more nearly related Pompilus
marginatus takes Thomisus, Drassus, Attus, Agalena or Lycosa, this more
fastidious wasp will not be tempted from the spider of her choice.
In more than fifty examples the victim in the play was invariably
Epeira strix. If she must confine herself to one species she has made
a fortunate selection, since there is no other spider so common in
our neighborhood, not only in the woods, but around the barns and
outbuildings. Most frequently it was the female that was taken, but
this does not imply a preference for that sex, since the females are
more abundant than the males. We have never seen the spider captured
and do not know where the sting is given, but certainly this wasp
wounds her prey very severely. The spiders that we took from her were
either dead, or so completely paralyzed that it required great care and
the use of a magnifying glass to determine that they were alive.
The next stage of her proceedings we are familiar with, as we have
frequently seen the wasp carry the spider. Unlike her sister,
marginatus, she usually flies with it, and seems not at all encumbered
by its weight. In many cases, however, she drags it, holding it by one
leg and running rapidly backward.
A suitable place for the nest being found, the spider is very prettily
taken care of while the work is in progress. A plant, usually a bean or
a sorrel, is chosen, and the strix is hung in the crotch of a branching
stem, where it will be safe from the depredations of ants. This
precaution is not always taken. We have many times seen the spider left
on the ground, although there were plenty of plants at hand.
The next point is to decide upon the precise spot for the nest,
and here our wasp shows herself very uncertain and hard to please.
Never have we seen one settle down and complete her work in the spot
first chosen. She dashes at a place and scratches and digs away with
furious energy for a few minutes, and then, starting up, she darts
wildly hither and thither until a new place, near by, is fixed upon
and another beginning made. In one instance eight nests were started
and some of them nearly finished, the little worker seeming to be
beside herself with excitement. After the decision is finally made the
tunneling is a rapid process. In one case it took the wasp a whole hour
to complete the work, but out of the thirty nests that we saw made,
nineteen were finished in from twenty to twenty–five minutes. Like
Fabre’s Sphex the wasp interrupts herself three or four times to visit
her spider and make sure that it is safe. When all is done she brings
the strix to within a foot or two of the opening, runs to the nest to
take a final look, and then, going backward herself, pulls it inside.
In two instances we saw the fidgety little creature go through a most
comical performance, which again recalls the Sphex of Fabre. Leaving
her treasure on the ground, she ran to the nest and kicked out a little
more earth; hastening back she dragged it an inch nearer; then away she
went to the nest again for more digging, and so on, dropping her spider
half a dozen times before she at last brought it home. In two other
cases in which there was no such anxiety about the size of the nest,
there was, in reality, more reason for it. Indeed, in one instance the
opening had to be enlarged before the spider could be taken in. There
is a wide–winged parasitic fly that, having nothing else to do, lays
prodigious numbers of eggs, not in any particular nest, but at the
edge of holes wherever it may chance to see them. It hovers about over
the ground until it comes to an opening, dips down twice or thrice,
ovipositing each time, and then passes along. The habit of scratching
out a little dirt at the threshold, just before the prey is brought in,
seemingly from a desire to enlarge the nest, or in other cases from
mere nervousness, is perhaps of use in destroying these eggs, which
might otherwise adhere to the spider or caterpillar as it is dragged
over them.
The laying of the egg takes only two or three minutes, and then the
hole is filled up. In this part of her work quinquenotatus shows a
great deal of variation, sometimes coming out of the hole and sweeping
in the dirt with her first legs and sometimes standing in the tunnel
while she draws the earth in with her mandibles and then jams it down
with the end of her abdomen. The former plan was in vogue in the
garden, while the latter was more common with the wasps on the island.
After the hole is filled the spot is covered with pellets of earth
and pebbles brought from a little distance, very much as is done by
Ammophila.
When we found that quinquenotatus was a very common species, and that
nearly every day brought us a fresh example, we thought that we had
the question of its stinging habits in our own hands. What could be
easier than to carry a strix about with us and to exchange it, when
opportunity offered, for the paralyzed spider of the wasp? The good
results obtained by Fabre and Marchal from this manœuvre made us
confident of success. We did not doubt that when the wasp came for her
spider and found it livelier than it ought to be, she would repeat the
stinging operation before our eyes.
Accordingly, the next time that we saw quinquenotatus digging we made a
diligent search for her spider, and soon found it on a bean plant five
feet away. Just as we discovered it, however, the wasp swooped down and
carried it to some purslain, close to the hole, where she hung it up
again, while she went to make her final preparations at the nest. We
seized our chance, and quickly substituted a fresh strix for the one
that had been paralyzed. According to the habit of its species when
danger threatens, it kept perfectly quiet, and when the wasp returned
it was hanging there as motionless as a piece of dead matter. How she
knew the difference was a mystery, but she would not touch it. She
seemed to think that she had made a mistake in the locality and that
her own spider must be hanging somewhere close by, for she hunted all
over that plant and then over several others near to it, returning
continually to look again in the right spot. After five minutes she
gave it up, circled about three or four times, and flew off in the
direction of the woods to catch another spider.
Why did she go to the woods? When she realized that the strix she had
stung was gone and that she must have another, why did she not take
the one that hung there in plain view? Our failure could not have been
due to the fact that we had handled the spider, since, when on other
occasions we took one that had been paralyzed, examined it and then
returned it to the wasp, she accepted it without hesitation.
Disappointed though we were at the irrational conduct of our wasp, we
resolved to await her return and to try again. In forty minutes she
came back with another spider, but instead of taking it into the nest
she hung it upon a bean plant near by and then proceeded to dig a new
hole a few inches distant from the first. Foolish little wasp, what
a waste of labor! Truly, if you are endowed with energy beyond your
fellows you are but meagrely furnished with reason.
Again we availed ourselves of our opportunity, and substituted our
spider for hers. This time it had grown weary of playing its motionless
rôle, and frequent readjustments were necessary in order to keep it in
position. At the moment that the wasp came back to take it, the spider
scrambled from its place and began to make its way along the stem. The
wasp evidently saw it, for she hovered over it a moment. She then flew
to the next plant, where she hunted about over the leaves and branches
in search of her lost treasure. After a time she returned. The spider
had now come to a standstill, and the wasp examined it attentively,
although without touching it. She then flew away without circling at
all, which might, perhaps, be taken as an indication that she had no
intention of returning to a place where she had fared so badly.
Just at this moment we chanced to see another paralyzed strix hanging
near by. Again the exchange of our specimen was accomplished; but
when the second wasp came to find her spider she gave us no more
satisfaction than the first. The substitute hung there quietly enough.
We ourselves could not have distinguished it from the original, but
quinquenotatus took a good look at it, decided that something was
wrong, hunted about a little for her own spider, and then flew away.
We had then, as the fruit of our morning’s work, gained nothing in
regard to a knowledge of the stinging habits of our wasp, but at
least we had secured three freshly paralyzed spiders to add to our
laboratory collection. As to the strix that had so kindly assisted us
in our experiments, we placed it on a bush in the pleasantest and most
secluded corner of the garden and left it there, wishing it a long and
happy life.
Later on in the season we tried the same experiment. Taking her spider
from quinquenotatus as she was dragging it to her nest, we offered her
a very lively strix in its place. She would not notice it at all, and
soon flew away. Half an hour later she reappeared, and seemed to be
looking for a place to dig. As she ran about on the ground we offered
her another spider, dropping it on the ground in front of her. This one
behaved admirably, drawing up its legs and keeping perfectly still, not
moving even when she felt of it and turned it over, but it was left
without any display of interest or emotion.
One day we saw a quinquenotatus finish her nest and go after her
spider. She was absent for some time, and when an ant passed by,
dragging a paralyzed strix that had evidently been stolen from some
wasp, we thought that the one we were watching had been robbed, and
rescuing the spider, placed it in the doorway of the nest. We had
judged wrongly, for a moment later our wasp came back bringing her
own spider, and dropping it near by, ran to look at her nest. She was
disturbed at finding the way blocked, and dug out a little earth to
one side of the strix. Then she flew to some holes in the ground not
far away and dug a little, first in one and then in the other. After
this she took a look at her spider, and then went back and dug a little
more at her own nest. Finally she seized the impeding strix by a leg,
dragged it out of the way and paid no further attention to it, storing
her own spider and departing, although the one she had rejected might
have saved a hunting expedition.
At another time we saw two wasps digging their nests two or three feet
apart. One of them finished before the other, and being unable to find
her own spider (probably it had been carried away by the ants), she
seized that of her neighbor and bore it away. The rightful owner saw
from a distance what was happening, and ran to the rescue. A violent
scrimmage ensued, the two wasps clinching and rolling over and over
together. The robber escaped and made off, but was followed and caught
again. She fought so well for her ill–gotten treasure, however, that
she finally conquered the other and hurried off with her prize. She
showed by her manner that she felt the need of haste, for instead of
laying the spider down and looking at the nest, she dragged it directly
in, as though she feared another attack. This was the first time that
we had ever seen these wasps fighting over their prey, and we were
surprised to find that they would take spiders which they had not
captured themselves, since when we had tried to exchange with them they
had refused to carry out our scheme. This was clearly an intelligent
act, and could not be an affair of instinct.
Once again we witnessed a similar struggle. One of these wasps was
laboriously dragging her strix up a steep hillside, when a much bigger
one of the same species descended upon her and seized the spider. She
was loath to give it up, and they both pulled until it seemed as though
the poor creature would be dismembered. The highway robber came off
victorious, and after flying to a distance hung the spider up while she
finished a partly made nest, and then stored it away. It may be said in
extenuation of her conduct that since she had a nest started she had
probably been robbed herself, and therefore felt that she was entitled
to a spider.
The nests of quinquenotatus vary considerably according to the kind
of soil in which they are made, the firm clay of the garden giving a
result quite different from the fine dry earth of the island, in which
they are usually much larger, and scarcely to be distinguished from
the holes of Bembex spinolæ. In both localities, however, the nest
consisted of a short tunnel, running obliquely downward, with a slight
enlargement at the end, but with no change in the direction of the
gallery.
[Illustration: NEST OF P. QUINQUENOTATUS]
In the loose sand of a steep hillside we found that the wasps had a
different method. Their tunnels in this place filled up nearly as
fast as they could dig them, and when they had reached a depth of
half an inch they turned off at a right angle, and excavated in an
entirely new direction. They probably derived some advantage from this
variation, for we saw four in succession follow the same plan, which
certainly appeared to be an intelligent adaptation of means to ends.
We once saw a wasp of this species digging her nest on the Bembex
field. When finished it was a large hole which could not have been
distinguished from those of spinolæ, which were open all about, the
weather being bright and sunny. She flew off, and soon reappeared
with her spider, which was dropped three feet away while she ran to
make sure that all was right; and now followed something that we had
never seen before—she could not find her nest. She flew, she ran,
she scurried here and there, but she had utterly lost track of it.
She approached it several times, but there are no landmarks on the
Bembex field. We have often wondered how they find their own places.
After five minutes our wasp flew back to look at her spider, and then
returned to her search. She now began to run into the Bembex holes,
but soon came out again, even when not chased out by the proprietor.
Suddenly it seemed to strike her that this was going to be a prolonged
affair, and that her treasure was exposed to danger; and hurrying back
she dragged it into the grass at the edge of the field, where it was
hidden. Again she resumed the hunt, flying wildly now all over the
field, running into wrong holes and even kicking out earth as though
she thought of appropriating them, but soon passing on. Once more she
became anxious about the spider, and carrying it up on to a plant
suspended it there. Now she seemed determined to take possession of
every hole that she went into, digging quite persistently in each, but
then giving it up. On one that seemed to be unoccupied she labored at
enlarging the entrance, until we thought that she had mistaken it for
her own, or at least had determined to use it. At last, however, she
made up her mind that all further search was hopeless and that she must
start afresh; and forty minutes from the time that we saw her first she
began a new nest close to the spider, as though she would run no more
risks. This nest was successfully completed, and the spider was stored
away without further misadventure.
The egg of quinquenotatus can be but lightly attached to the spider,
for only once, out of many attempts, did we succeed in getting it
out without displacing it. In this case three days elapsed before it
hatched. The larva ate for a day or two, but then pined away and died.
Another nest was opened on the tenth day after the egg was laid, and
in this the spider had been entirely eaten and the larva was just
spinning its cocoon; so that the larval stage probably occupies about a
week.
A summary of our notes shows a very wide variation in the condition of
the spiders stored by this wasp. Out of eleven that were stung three
were killed at once, two lived four days, one five, one eleven, one
twenty–three, one twenty–five, one thirty–one, and one at least forty
days and probably longer.
We look back with much pleasure upon our acquaintance with this gay,
excitable little wasp. She was so full of breezy energy that it was
always delightful to meet her, and she showed so wide a variation
in individual character that we seldom watched her without learning
something new.
Pompilus fuscipennis, a little smaller than P. quinquenotatus, is
black, with the red girdle that appears so frequently among the
solitary wasps. The first time that we ever saw this wasp she was
running rapidly backward over the bare ground, the brilliant red of her
body flashing in the sunlight as she dragged along a little spider of
the genus Thomisus. Presently she carried it up on to a leaf and began
to bite at it, but being disturbed by an ant, hurried on with a much
agitated manner. Soon she stopped again and resumed her attack, biting
savagely at the legs near their junction with the body, and now,
looking closely, we saw that two of them had been completely cut off.
While occupied in this way the wasp was evidently intensely excited.
She lay on one side with the abdomen bent under, turning the spider
over and over as she worked. After a time she carried it onward to the
potato–field, where the plants afforded some shelter, and placing it
upon a leaf, well above the ground, began to dig near by. She worked
almost entirely with her mandibles, lying sometimes on her side and
sometimes on her back as she cut away the earth, which was pushed
out with the end of her abdomen. When she had worked for ten minutes
and had gone in the length of her body, she picked up the spider and
rapidly made off with it, several times rising on her wings and flying
backward for a few inches. A little further along she again deposited
it on a leaf and began to dig in a fresh place. At the end of twenty
minutes the nest was ready, but in bringing the spider she missed her
direction and carried it to one side. Dropping it on the ground, she
began to hunt about for her hole, but was distracted with excitement
and ran so far afield that we feared she would never find it. At last,
however, she came to the place, ran in for a moment, brought the spider
nearer, dropped it and ran to the nest once more, caught it up again,
and tried to back in with it. She was holding it by the under side of
the body, the venter being toward the hole, and the legs spread out and
stopped its entrance. A moment’s tugging convinced her that this would
not do, and she then turned the spider over, holding it by the back,
whereupon the legs at once folded themselves across the underside of
the thorax, and it was drawn out of sight.
After the egg was laid the wasp came up to the edge of the hole, and
drawing in some earth with her mandibles began to dance up and down
upon it, jamming it into place with her abdomen. Afterwards she came
up higher and drew the dirt in with her first legs, not getting out
of the hole until it was entirely filled up. Then began a remarkable
performance. Bracing herself firmly on her legs she used the end of her
abdomen as an instrument, and with it she now pounded the earth, now
_rubbed_ it, like a pestle in a mortar, and now used it as a brush to
sweep away loose dust. Sometimes she would throw a little earth back
under her body with her mandibles and rub it down with her abdomen.
This part of the work being finished, she spent a few minutes in
sweeping the ground with her first legs, and then brought a quantity
of small objects and placed them over the nest,—a little stick, the
petal of a faded flower, a scrap of dead leaf, and so on, until ten
or twelve things had been collected. This artistic finishing up of
her duties recalled Ammophila; but among our subsequent examples of
fuscipennis we never saw one do her work with such nicety. They were
usually contented to fill in the nest more or less compactly, sometimes
doing much of the work from the outside, to brush off the surface
without any rubbing or pounding, and then to bring two or three little
pebbles or lumps of earth to place over the spot.
So far as we were concerned this was one of the most fearless of the
wasps, not even interrupting her work when we once placed a glass over
her as she was filling her nest; but the approach of an ant would throw
her into a perfect panic, and seizing her spider she would make off
with every sign of terror. It is difficult to understand why wasps of
this species, as well as of biguttatus, never offer combat to the ants
that rob them right and left, but invariably seek safety in retreat.
Their attitude toward other robbers is quite different. We once saw a
fuscipennis that was dragging a Lycosid attacked by a bigger wasp of
the same species. Number One left her spider on the ground and chased
Number Two to a distance; but no sooner had she returned and taken it
up than Number Two, bold and unashamed, was at her heels again, and
the scene was repeated. The object of the robber was to seize a leg
of the spider, and whenever she succeeded in doing this she jerked it
free, and made off with it very rapidly; but when the owner pursued
and caught up with her she relinquished the prize without a struggle.
Why did she? She was the bigger and the stronger, and possession is
nine points of the law in Waspland as elsewhere; but conscience made
a coward of her, while the other was strong in her righteous cause.
After a time we captured the little pirate; but now the nerves of the
rightful owner were completely upset, and she flew away, deserting the
spider for which she had battled so bravely.
The most interesting thing about fuscipennis is her habit of biting the
legs of her victims. The instinct is very irregularly developed, since
four out of ten spiders had not lost any legs, while the others had
been deprived of one or two. No one who has watched the wasp can doubt
that the habit is related to the fact that she makes a very small nest
in comparison to the size of her prey. The spider never went in easily,
always requiring to be shifted and turned and tugged at. There was an
especial tendency to bite at the legs at this point of time, when the
wasp, standing within the tunnel, was trying to drag the spider down.
In one instance she managed to get it past the entrance, but it stuck
in the gallery; and after working at it in that position for a time
she brought it out, subjected the legs to a severe squeezing, and then
tried again. It was still a very bad fit, but by turning it about and
pulling at it she succeeded in getting it in. It may be that the object
of biting the legs is not to remove them, but to render them limber so
that they will bend easily. Whatever the process may be, it is repeated
at intervals from the time the spider is captured. As she carries
it, the wasp pauses again and again, now on bare ground and now in a
sheltered place or on some plant, to renew her efforts at getting the
legs into a satisfactory state.
P. fuscipennis rarely circles about when leaving a place; this is
unfortunate, since her sense of locality seems to be particularly weak.
She nearly always has to hunt for the plant upon which she has placed
her spider, and always loses track of her nest when she tries to bring
the spider to it. We once caught her as she was carrying her spider,
and then released her on the same spot; but she became so much confused
that without our assistance she would never have found it again.
Our acquaintance with Pompilus marginatus began in the middle of July.
She is a small creature, only half an inch long, and is dressed in
black, with a bright orange spot on each side of the anterior part
of the abdomen. We were watching the pretty little Diodonti, as they
filled their holes with aphides, when we saw her going backward,
dragging along a medium–sized spider. Soon she came to an onion flower
that was lying on the ground. Here she stopped and, after a moment’s
hesitation, drew her prey in among the blossoms of the cluster so
that it was hidden from view. It was not long before she came out
and began to fly about near the ground, frequently alighting to poke
her head into cracks and to run again and again into little chance
holes. Never did an insect behave in a more demented manner, and
although there may have been a method in her madness it was difficult
to discover it. No hole nor cranny pleased her, and back she flew to
the onion to see whether her booty were safe. For fifteen minutes she
ran and flew now here, now there, hurry and anxiety in every movement,
returning frequently to reassure herself about the spider. Several
times she entered a hole at the base of a weed, not a made nest, but
an accidental crevice; and this spot was at length chosen either as a
temporary or a final resting place for her spider, since she dragged
it from the onion and deposited it here. We tried to capture the wasp;
but having failed in this, we dug out the spider. It was three inches
down, the hole being deeper than it looked from the outside. There
was no egg upon it. Evidently the work had not been finished, for the
restless creature returned fifteen times within an hour to the broken
nest, either for the purpose of laying her egg or to remove the spider
to another resting–place on her homeward way.
[Illustration: POMPILUS MARGINATUS]
This was our first specimen of marginatus, and a month passed before
we met another. It was while watching some Bembecidæ that we saw the
pretty little orange–spotted worker dragging a small Thomisid across
their nesting–ground. The spider was so small that she held it in her
mandibles well above the ground, and we speak of her as dragging it
only because she walked backward and acted as though she were obliged
to exert herself. Quite often the spiders taken by this species are
too large to be carried, and then it is necessary to drag them; this
habit is so ingrained that when it would be much more convenient to go
straight ahead they stick to the ancient custom, and seem unable to
move in any other way. This little wasp was in a frantic hurry, running
backward into the Bembex holes and then scrambling out again, until
she had crossed the field and had turned to one side, having gone,
since we first saw her, about fifteen feet. Here she dropped the spider
and began to skim over the ground—it could not be called running and
yet it was not flying—until she found a circular hole in the black
earth, which looked as if it ran vertically downward. At the time we
thought that this was a nest that she had made for herself, but we
afterward concluded that it had been excavated by some other creature,
that she had found it and determined to make use of it, and that she
was bringing her prey to the spot with that end in view. Without
entering she rushed back to the spider, but after carrying it a few
inches, dropped it and ran to take another look at the nest. By this
time, however, she was too much excited to know what she was about,
and for five minutes she scurried over the ground without finding it.
During this time she picked up the spider four times, carried it a
little way, and then dropped it. The last time she carried it to the
edge of the grass and stowed it there, this being her first attempt at
concealment. She now found the hole again and brought the spider nearly
to it, but by this time she was perfectly beside herself. The spider
was seized again and again, only to be dropped the next second, while
the wasp rushed back and forth between it and the hole. In time this
method of procedure brought it close to the nest, but it was carried
around the edge once or twice even then. At last, accidentally as it
seemed, it fell in, when the wasp quickly ran in also and pulled it
down. For half an hour she remained inside, and when she came out we
caught her to make sure of her identity. As we set her free immediately
we expected her to go to work at covering her nest, but in this we were
disappointed, for she did not return. We left the place undisturbed
from the thirteenth to the fifteenth of August, when we dug up the
nest. The Thomisid was there, but we could find neither egg nor larva.
The spider was alive, as was shown by a quivering of the legs. This
quivering grew fainter and fainter, until upon the nineteenth it was
scarcely perceptible, and on the twenty–first the spider was dead. Our
first spider had been stung to death at once, while this one lived
seven days and a half after being stored.
On September first, while out in the bean patch, we saw a large Lycosid
running madly, first in one direction and then in another. Hovering
eagerly and excitedly just above was our marginatus, dashing down at
the spider again and again as it came into view for an instant, and
then circling wildly around until it appeared once more. Now she
pounced upon the frightened spider but missed her aim, now she really
grasped it but was shaken off. At last the end came. The wasp descended
upon the doomed spider, and there was a violent struggle, both the
combatants rolling over and over upon the ground, while all that we
could distinguish was the flashing of the red upon the body of the
wasp. In an instant it was over, and the wasp rose, leaving the spider
limp and motionless upon its back. In our other examples of marginatus
the spider taken had been so small that the wasp might easily have
held it and thrust her sting into any spot that she pleased, but this
Lycosid was a different antagonist. Where the two were so nearly
matched, there could have been but slight opportunity for skillful
surgery. In point of strength the wasp was at a disadvantage, and she
must have come off victor by the quick use of her sting. Under these
circumstances she must have struck when and where she could, without
selecting any particular spot. That she quite realized the power of
her foe was shown by her next action. With the utmost circumspection
she settled down upon the spider and made a prolonged and careful
examination of the mouth parts. The investigation was satisfactory,
and without any further stinging she seized the spider by one leg,
and this time really dragged it off. It was a good load for her, and
it evidently required all of her strength to pull it along. Not far
away was a lump of earth, under which the treasure was stowed; and
then began the usual hunting performance, which soon resulted in the
discovery of another cavity which had a very small opening.
She crept in, remained a minute, and then came out and brought her
spider to this new hiding–place. The head went in easily, but it took
a great deal of tugging to get the rest to follow. At last both spider
and wasp were out of sight, and everything remained quiet for so long
that we began to think that this time we were really to see the final
act in the play. But no; when the little wasp came creeping out it was
only to start off on another extended tour, in which we did not attempt
to follow her. She doubtless selected another halting–place, for when
she returned it was to try to get the spider out of the hole by pulling
at one of its hind legs. The task, however, was not an easy one. She
exerted all her strength, so that we expected to see the victim torn to
pieces before our eyes, and still it did not come. At last she seemed
to realize that there was more than one way to accomplish her end, and
turned her attention to cutting away the earth to make the opening
larger. After a few moments’ work she tried again, and although the
passage was still much too small for convenience the spider was at
length dragged forth, looking much the worse for wear. As she moved
away we alarmed her by lifting some vines that prevented our keeping
her in view, and she flew up, leaving the spider on the ground. We
seized the opportunity to bend and twist the plants this way and that
so that the ground might be left uncovered. The changes that we made
probably disconcerted her, for she seemed to lose track of her prey.
For over half an hour she hunted about, circling above the place and
running around and around over the ground. She often came so close to
the spider that we could not understand why she did not see it. At last
it was recovered, and again she started off. We tried to follow her,
but the vines were so thick that, in spite of our efforts, she soon
disappeared into the undiscovered country which we had thus far been
unable to penetrate.
Up to this time we had been entirely unable to understand the actions
of marginatus, and each new example added to our confusion instead of
clearing it away. We were inclined to think that she never made a nest
for herself, but caught her spider and then hurried about for a good
place to store it, and that her absurd conduct was the result of an
indecision of character which made it extremely difficult for her to
choose a place and be contented with it. The last part of this judgment
holds true, even now when we know her whole history, but we have at
last learned that she does dig her own nest.
We had watched a wasp for some time as she carried her spider from
place to place, and finally saw her take it into a crevice among some
rough lumps of earth which she had previously examined. We expected one
of the long spells of eventless waiting to which she had accustomed us,
but on lying down and peering into the hole we found that there was
an opening on the further side, for a ray of light feebly penetrated
the interior. Moving about in this dim illumination was our wasp, and
after a little, we could see, quite distinctly, that she was digging a
hole. This then is her method—to find some sheltered hiding–place where
she may secretly make her nest, that no creature may know where her
treasure is hidden.
We have twice seen a marginatus pick up her spider and fly with it
backward for a long distance—as much as four or five feet. This recalls
the wasp which is said to fly backward before a moving horse and catch
the flies that are hovering over it.
P. marginatus is not troubled by any notion as to the family
connections of the spider that she takes. Anything will do provided she
is strong enough to overcome it and carry it to her nest. The effect of
her sting is quite variable, since in some cases the victim was killed
at once, while in others it was but little affected in the beginning
and lived for eighteen or twenty days.
At eleven o’clock on the morning of a warm day in mid–August we saw the
steel–blue Pompilus scelestus dragging a big Lycosid across a field.
The spider was sixteen millimeters long and wide in proportion, while
the wasp was but thirteen millimeters long and very slender, so that
the weight of the spider was at least three times that of its captor.
The necessity for going backward was evident in this case, but the wasp
moved rapidly considering the load that she was dragging. As she worked
her way along she made frequent pauses, stopping for two or three
minutes at a time in some little hollow, or under leaves or weeds. She
spent a good deal of time, during these pauses, in cleaning herself,
and a good deal of time also in doing something to the spider which we
could not understand. She seemed to be biting the legs, near the body,
beginning with an anterior leg on one side and working backward, and
then repeating the operation on the other side. She went through this
squeezing process again and again, and to us it looked as though she
might be trying to force back the juices from the legs into the body
preparatory to cutting them off; but after a time she would seize her
prey and start on again. She had made her way along in this fashion
for some ten feet, when a second wasp appeared and alighted on a weed
near by. This interloper was a trifle smaller than the other, and from
her actions was evidently greatly interested in the paralyzed spider.
When the Pompilus stopped for a moment the other moved from stem to
stem in a stealthy manner just as a cat stalks a bird. The rightful
owner of the prey was disturbed and dashed at her, driving her away
again and again, but she flew only a short distance and was soon
back, always creeping nearer and nearer to the spider. We, too, were
watching with closest attention, but our desire was to see the speedy
homecoming of Pompilus and to learn whether she cut off the legs of her
victim; and so, interesting as was the contest between the wasp and the
wasp–inquiline, we decided to interfere and remove the intruder. This
was very easily accomplished, since the little insect was so intent
upon following the spider that she was oblivious to our presence, and
allowed us to place a bottle over her as she stood eagerly looking
for a chance to advance. Her removal gave great relief to the other
wasp, as was manifested by an entire change of manner. Before, she
had been constantly on the lookout, moving only with the greatest
circumspection, but now she relaxed her vigilance. With the Ceropales
in our vial we, too, felt relieved, and now the path of discovery
seemed clear before us; but scarcely had things assumed their old
status when a second enemy, a much larger and bolder Ceropales, threw
both the Pompilus and ourselves into consternation. Again we took the
side of our wasp and drove the other one off, but only to see it return
a few moments later. The Pompilus now flew at it in a most gallant
fashion and pursued it far afield, but when she came back the enemy was
but a few seconds behind her. Here we again interposed and removed the
second Ceropales from the field of action.
All cause for anxiety being over, the wasp now resumed her journey.
Before long she came to a shallow depression in the ground which was
partly sheltered by an overhanging lump of earth, and under this
covering she dropped the spider and again began to squeeze its legs.
After a moment she removed it to the other side of the depression,
where it was subjected to further manipulation. Next, her toilet was
attended to, and then the spider was carried back and placed again
under the lump of earth. At least ten times was that limp and helpless
creature dragged from one side to the other of the little depression, a
distance of about two inches, the time between being filled in by the
wasp with cleaning herself and squeezing the legs of her victim. After
forty minutes of this tedious delay the moment came when she picked
up her burden with renewed determination and started rapidly on her
way. We kept very close to her, but she did not allow our presence to
interrupt her work, and, indeed, paid no attention to it. After she had
gone along for a distance of about eight feet there was another pause,
of only five minutes this time, and when she resumed her onward march
it was in a new direction. Thus far she had gone almost due south,
but now she turned and went six feet toward the west. Suddenly the
spider was dropped. There was no hole in sight, but the wasp seemed
to feel that some important crisis had arrived. Her whole manner was
excited and flurried, and we thought that surely we had reached the
neighborhood of the nest. How little we understood her! Her nest was
still far away, and it may be that she had just begun to realize that
the task she had undertaken was too heavy for her accomplishment—that
at her present rate of progress her strength would be exhausted before
she could reach her goal. At any rate, something was wrong. The
spider was left unprotected on the ground while she made a number of
long excursions without it, sometimes being gone as much as fifteen
minutes. On coming back from these trips she would return to the task
of squeezing the legs with such energy and persistence that we expected
to see them drop off. Then she would run over the ground in all
directions, looking under lumps of earth and stones and poking her head
into every little hole. Was she trying to find some suitable spot near
at hand to take the place of the one which she had prepared or selected
at a distance?
One hour from the time of her arrival at this place, and two hours from
the time that we began to watch her, she flew away and was gone for an
unusually long time. We can only suppose that when she absented herself
in this way she was visiting the spot to which she wished to convey her
booty. On her return she seemed to be filled with a new idea, for after
climbing to the top of a tall stout weed that grew near by, she came
down, seized the spider, and tried to drag it up the stem. Perhaps she
meant to lift it to such an elevation that she could fly with it, but
it was too heavy for her and fell after she had raised it to a height
of three inches. She then flew away again, and on her return we caught
her, fearing that she was becoming discouraged and that she might
presently depart to be seen no more. Had there been any prospect of her
solving the difficulty that beset her our patience might have held out
to the end, but this was evidently a case in which there was a failure
of instinct, or intelligence, or whatever faculty was concerned.
More than a year passed before we had another opportunity of solving
this problem of scelestus, and the pleasure with which we hailed her
second appearance in our garden may be easily imagined. This time the
wasp had made her nest, but was not ready to fill it, and when we first
saw her she was running about without any particular aim in view,
although at the time we supposed her to be hunting. Before long she
went and took a look at the neat round hole which she had made near the
fence that separates the garden from the woods. The earth that had been
taken out either had been carried to a distance or had been swept away
after the digging was completed, for there was no pile to be seen. This
was at two o’clock of a cloudy afternoon. It may be that she needed the
stimulus of sunshine to make her hunt, or perhaps she realized that
what was left of the day would not give her sufficient time to capture
her spider and bring it home. At any rate, she spent the remainder of
the afternoon in making short excursions around her nest, attended, at
a little distance, by a smaller blue wasp, Pompilus subviolaceus, whose
presence she did not seem to notice. These trips took her from ten to
twenty feet from the nest, each occupying from fifteen minutes to half
an hour. At every return to the nest she flattened herself out on the
ground and wriggled in the dust, and then dragged herself all around
it in the strangest manner. Perhaps these actions were indications of
pleasurable emotion. We had seen them once before, in Priononyx atrata
just before she carried a locust into her nest.
At a little after four o’clock she began to investigate, very
carefully, the plants and grasses that immediately surrounded her hole,
showing an especial interest in one bunch of clover that grew four
inches away. Into this she finally vanished, and peering curiously
among the greenery, we discovered her hanging to a leaf, which was
sheltered by thick foliage on all sides. Here she remained motionless
and probably fast asleep until sundown, when we left her for the night.
When we went to the garden at eight o’clock on the following morning,
subviolaceus was on hand, but scelestus was still sound asleep in her
leafy bower. We thought it best to awaken her, for a large spider
had spread its web just below, and if the wasp should drop upon it
nothing could save her. We therefore aroused her gently, whereupon she
crept slowly up the stem and, taking her stand on the highest point,
surveyed the world. Then, after stretching herself sleepily, she made
her toilet, cleaning off her wings and legs, and washing her face with
her feet like a cat. When these duties were finished she walked slowly
about for an hour, visiting her nest every now and then. Suddenly, at
half past nine o’clock, her whole manner changed, and seeming very much
excited she ran rapidly along, parallel with the fence, for fifteen
or twenty feet, and then, rising on her wings, flew far away into the
woods. She had evidently gone hunting at last, and we watched eagerly
for her return. She was not successful at once, however, for at half
past ten she came back without anything, stayed at the nest for a
few minutes, and then flew to the woods again with the same excited
manner as before. Perhaps she had already caught her spider at some far
distant spot, and was getting her bearings preparatory to bringing it
home; but it was half past one when she suddenly appeared, five or six
inches from the nest, coming backward through the fence, and dragging a
large Lycosid. This she laid down close by, and began to bite at the
legs quite after the manner of the wasp we had seen the year before.
Her movements were full of nervous excitement, in marked contrast to
those of the previous day. Presently she went to look at her nest, and
seemed to be struck with a thought that had already occurred to us—that
it was decidedly too small to hold the spider. Back she went for
another survey of her bulky victim, measured it with her eye, without
touching it, drew her conclusions, and at once returned to the nest
and began to make it larger. We have several times seen wasps enlarge
their holes when a trial had demonstrated that the spider would not go
in, but this seemed a remarkably intelligent use of the comparative
faculty. Her method of work was peculiar. Standing in the tunnel with
her head down and her abdomen curved under, she bit the earth loose
with her mandibles and pushed it under her body and beyond the tip of
the abdomen. When a little had accumulated she backed out, holding it
in this way.
While she was thus employed the spider was attacked by a very tiny
red ant, that could not by any possibility have stirred it. When the
wasp caught sight of this insignificant marauder she fell into a fit
of wild fury, and bending her abdomen under, seized the ant again and
again in her mandibles, and flung it backward against the tip of her
sting. The little creature finally escaped, seeming none the worse for
the rough handling to which it had been subjected, while the wasp,
still trembling with excitement, grasped her spider and rushed off to
a distance of several feet, carrying it up on a weed and depositing
it there. The labor of excavation was then resumed, and after a
half–hour’s work the nest was completed to her satisfaction.
Coming up head first, she flattened herself out on the ground, and
sprawling thus, dragged herself all around it. The spider was now
brought to the nest, being left once on the way while she ran in and
out again, and was taken in after a new and original fashion. Backing
in herself, she seized it by the tip of the abdomen and dragged it down
without any trouble, since the legs were gently pushed up over the head
and made no resistance.
In two minutes she emerged from the opening, and standing on the four
posterior legs, with her abdomen hanging down into the hole, scratched
the earth backward with the front legs and mandibles. As it fell in
she pushed it down with the abdomen, and as the hole filled she raised
herself higher and higher on her legs, still using the tip of the
abdomen to work the material into place.
When the filling of the nest was nearly completed, we caught the
wasp, and after taking the spider, threw back the earth into the
hole. Subviolaceus, who had watched the homecoming from a respectful
distance, now felt that her turn had come, and descending upon the spot
began to dig. Not finding anything, she shifted her position several
times, and worked industriously, even returning after we had frightened
her away. Sharp says that a Ceropales has been observed to oviposit
on a spider, not while it was being carried in, but subsequently by
entering the nest for the purpose; and the actions of subviolaceus
pointed to similar intentions on her part. We have watched her for
an hour at a time running into the open nests on the Bembex field,
sometimes coming out again directly and sometimes remaining inside
for several minutes. It is not likely that she would utilize the
flies of Bembex, but it may be that she was looking for the Pompelid
nests that are often made in the same locality. Scelestus did not
notice subviolaceus, and it is difficult to see why a wasp should be
disturbed by the presence of a parasite. In making and storing her
nest she is the blind instrument of an impelling power; she knows
what she must do, but not why she does it. Her descendants are in
most cases as completely outside of her experience as her ancestors,
and how should she guess that the presence of a certain fly or wasp
means danger to her race? Of what happens to her egg after she leaves
it she is so absolutely ignorant that she might easily look on with
serene indifference at the destruction of her own larva by that of the
intruder. In Astata we see, as might be expected, a calm tolerance of
the visits of the Chrysis fly, but the uneasiness of scelestus herself
at the sight of Ceropales and the valorous defense of Trypoxylon
show more highly developed instincts. Bembex, too, deeply resents
the presence of parasites, although after the deed is done she feeds
their young without questioning their right to her care. Among bees,
Andrena, and Nomada, which is parasitic upon it, are said to live on
most friendly terms; but in other genera there is a deep–seated enmity
between host and parasite.
[Illustration: THE HOME–COMING OF SCELESTUS]
In the literature of the Hymenoptera references have been made from
time to time to certain wasps that cut off the legs of spiders or other
creatures before storing them away; but observations on the subject
have been rare and not very definite. Brehm, in the “Thierleben,”
says that Agenia punctata builds nests of mud, and places in each
cell one moderately large spider from which she has first removed all
the legs. The most interesting notes on the subject have been made
by M. Goureau, who gives an account of finding two spiders that had
been mutilated by wasps, one of them having had all of the legs cut
off, and the other all but the first pair. At another time a wasp that
was flying near him let fall a spider, which he captured before it
could be recovered by the owner. The wasp escaped, so that he could
not determine the species, but the spider’s legs had been removed. He
concluded that instead of stinging the spiders the wasps had mutilated
them so that they could not run away. He does not seem to realize that
death would certainly result from such an operation.
[Illustration: NEST OF AGENIA BOMBYCINA]
Vespa germanica often cuts off the wings of a dead wasp, or even cuts
its body into two parts, before flying away with it, but this is only
when the captured insect is too large to be handled in any other way;
and Pompilus fuscipennis sometimes cuts off one or more legs from her
spider, although without any regular method of procedure.
Agenia bombycina finds a nesting–place to her liking on our
smoke–house, in the crevice between the bricks and the wooden
door–frame, where she makes clusters of little mud cells, putting one
mutilated spider into each, and storing about one a day. Her locality
sense is unusually poor, owing apparently to her intense nervousness
and excitability, but some individuals are better endowed than others
in this respect.
[Illustration: LYCOSA KOCHII, FOUND IN NEST OF AGENIA BOMBYCINA]
On a bright morning in the middle of August we stationed ourselves by
the smoke–house at eight o’clock, and half an hour later an Agenia
began to bring lumps of earth, working out of sight under the door
frame. She kept at it steadily, spending three or four minutes in
getting a load and one or two in placing it. At twelve o’clock, her
nest being ready, she flew away to hunt for a spider. So long as a wasp
comes and goes at frequent intervals time slips away rapidly, but to
keep one’s attention unflagging through hours of watching is weariness
to the flesh. We saw no more of our Agenia until three, when she
appeared, half walking, half flying through the grass, going forward.
Her spider was held by the spinnerets, and being larger than she was it
trailed behind her. On reaching the wall she began to climb; but the
weight of the spider made her fall again and again, and forty minutes
passed in wearisome toil before it was safely put away. The egg having
been laid, she began to bring earth for closing, and we felt thankful
that our task as well as hers was nearly over. She worked slowly
now, taking ten or fifteen minutes for a trip; but after bringing in
the sixth pellet she took on a livelier air, and before long we were
convinced that she had begun to build a new cell. For two hours longer
we watched her unremitting labor, and when we left her at six o’clock
she was flying back and forth as briskly as ever.
Another Agenia, less ambitious, brought her spider at three o’clock
and then went to bed in an empty cell, head in, tail sticking out. We
cut away a section of the door–frame that covered the spot without
disturbing her slumber. This one could never remember where her nest
was, but had a long hunt for it every time she brought a pellet; and
when she had caught the spider she lost herself completely on the brick
wall, going to the very top, and even around the corner on to the side
of the building. Every little while she would fly back to the grass at
the threshold and start up afresh, and in this way she finally stumbled
on the right spot by accident. This seemed very stupid of her, as she
made many locality studies. Her behavior was in striking contrast to
little Rhopalum’s unerring choice of one tiny pin–hole among hundreds
just like it.
The larva of bombycina cocoons nine days after the egg is laid. The
spiders that we found in the cells were dead even when taken on the
day of storing. There was no rule about the degree of mutilation, one
having seven legs left, two five, one two, and four none. We have no
doubt that the object of this curious habit is to save room in the
nest.
Chapter X
THE ENEMIES OF THE GRASSHOPPER
EARLY in September a little black Tachytes suddenly became very common
in the garden. The first one that we saw was going forwards in a series
of long jumps, carrying a small grasshopper which was held by the base
of the antennæ. She soon doubled on her tracks, and it became evident
that she did not know her way; but after going about in circles for
two minutes she ran into her nest. When she came out she spent a long
time in circling around, flying close to the ground in wavy, snaky
lines, occasionally alighting to run a few steps; but in spite of this
locality study, ten minutes later, when she came jumping along with her
second grasshopper, she had lost her nest again and hunted about just
as before, twice going directly over it without seeing it. While she
was thus occupied another wasp of the same species attacked her and
tried to get possession of the grasshopper, but the rightful owner was
able to defend it. At last it was stored away, and she proceeded to
fill the nest, scratching the earth in with her first legs and working
it down with the tip of the abdomen. She worked quietly but steadily
for ten minutes, closing the place neatly, and then brought bits of
leaf and pieces of earth to cover it all over.
[Illustration: TACHYTES]
On the same afternoon we saw another of these wasps digging her nest,
but she was so much disturbed when we came anywhere near her that we
were obliged to retire. On the next day we saw her astride of a small
grasshopper, jumping along like the one of the day before. She too had
great trouble in finding her way. When she reached the nest she laid
her prey down while she went inside for a moment, and then, coming
out, seized it by the antennæ and backed in with it, instead of taking
it in forwards as was done in the other case.
Another wasp of this species carried a much larger grasshopper, which
was so heavy that she could not jump with it, but was obliged to keep
to the ground. In this case only one was used instead of two, which is
the usual number. This wasp was first seen at a distance of twenty feet
from her nest, and yet she went straight to the right spot without the
least confusion, showing that some individuals of the species have a
better idea of locality than others.
The nest is a short, shallow tunnel with an enlargement at the end,
within which are placed the grasshoppers, on their backs, with their
heads in. Earth is packed solidly into the tunnel, but not into the
cavity at the end.
We took two eggs of this species. Each was placed across the thorax
of the grasshopper at the base of the neck, on the ventral side. Both
hatched at the end of thirty–six hours from the time they were laid,
ate for three days, and then spun their cocoons. One of them ate only
one small grasshopper, leaving a second one untouched, while the other
finished the large grasshopper that formed her sole provision.
The grasshoppers taken from the nests, five in number, were in all
cases alive, there being a quivering of the mouth parts, and in some
cases of the legs also, without any stimulation. This condition lasted
for twenty–four hours from the time the poison was injected. After that
they became quiet, but remained alive until they were destroyed by the
larvæ.
[Illustration: NEST OF TACHYTES]
It is a curious thing that in these wasps is found the perfection of
that method of paralyzing the prey which is so much dwelt upon by
Fabre, although from their habits this fine workmanship is not of the
slightest use to them. They entomb their victims underground, where the
conditions are favorable to their preservation, and the extremely short
period that elapses between the laying of the egg and the spinning of
the cocoon makes it a matter of indifference whether the grasshopper is
alive or dead, since in any case it would be eaten before decomposition
set in.
We deserve no credit for discovering a second species, Tachytes
peptonica, for by her loud buzzing, slow flight, and persistent
hovering over the nest she gave us every assistance in her power.
She looks and acts like one of the large leaf–cutting bees, and this
resemblance is heightened by the fact that the grasshopper which
she carries is frequently of a leaf–green color. Her nest, which
is sometimes on the bare ground and sometimes in the grass, has no
external sign to mark it, and when with a great deal of fuss and
buzzing she descends and burrows, it closes behind her and disappears
from view, so that unless one marks the exact spot there is no way of
detecting it afterward. On her exit a very slight amount of scratching
closes the hole and leaves it looking exactly like the surrounding
surface; so that in comparing her work with the protracted labor of
Ammophila and some species of Pompilus in disguising the locality of
the nest, we were struck by the success to which she attained with a
very trifling amount of effort.
It takes peptonica thirty or forty minutes to catch a grasshopper, and
at each visit she remains for ten or fifteen minutes inside the nest.
The grasshopper is carried in the mandibles, supported by the second
and third pairs of legs. We never succeeded in opening a nest of this
species, but a grasshopper taken as the wasp was bringing it home did
not die until the sixth day.
In our summer work we often found ourselves wishing that we could
be in half a dozen places at once and could chase several wasps at
the same time. Never did we feel these desires more keenly than on
the twenty–ninth of July, when, after spending the best part of an
hour in watching the hunting of an Ammophila, we were obliged to
choose between following her to a possible conclusion, and giving our
attention to a little jet–black wasp, Lyroda subita, which we now saw
for the first time. This wasp was running around a bunch of clover in
a nervous, agitated manner, as though she were oppressed by some great
anxiety. The chance of discovering something entirely new decided us to
relinquish our Ammophiline hopes, and we sat down at the feet of our
new teacher.
We could not see anything remarkable about that bunch of clover, but
certainly the spot had some strong attraction for the uneasy little
wasp. She ran off first in one direction and then in another. She
circled about and made short flights now this way and now that, but
always returned. At last she betrayed the secret of her interest by
descending to the ground and picking up a small black cricket which had
been lying close by all the time. She flew up into the air with it, but
even now did not leave the neighborhood, continuing to fly about from
place to place, alighting now and again on the bean plants.
After this performance had lasted for five minutes she brought her
burden back to the same spot that it had occupied before, laid it down,
and without vouchsafing to us any explanation of her conduct, began
to burrow into the soft earth. She went down head first, backing out
with the dirt, which she carried with the front legs. While she was
thus occupied we defended her booty against two hunting parties of
ants which, at different times, fell upon it and would certainly have
carried it off if we had not been at hand.
It took the wasp twenty minutes to open the burrow, although, as we
afterward learned, it had been excavated before. At the end of that
time she turned around inside, came out head first, and dragged the
cricket within.
We at once opened the nest, but found it impossible to follow the
tunnel on account of the crumbling of the earth. Indeed, we almost
concluded that we were doomed to complete failure, for it was not
until we had gone down between six and seven inches that we found, in
a little pocket, our wasp in company with three crickets, upon one of
which was a larva a day or two old. At the time we knew nothing of the
habits of Bembex spinolæ, and we were much astonished to find a wasp
which evidently fed her young from day to day.
The contents of the nest were carefully conveyed to our wasp–nursery
at the cottage. The cricket that we had seen taken in was dead, as was
also the one upon which the larva was feeding. The third one was alive,
as was shown by a rhythmic movement of the palp on the right side. By
the next day, however, this one also was dead.
On the morning of the third day, July thirty–first, the larva had eaten
all of the first cricket and the greater part of one of the others,
leaving only the large hind legs. Supplying the place of the mother,
we killed two more and put them into the tube. One of these was eight
millimeters long, this being about the size of those which the wasp
herself had caught, while the other was of another species and much
larger, being thirty millimeters long. Its size and kind, however, made
no difference to the larva, which attacked this one next, although
there were two small ones yet untouched. It ate only half of this
big one, however, and then passed on. On August second we gave it two
more small crickets, and for that day and the one following its good
appetite continued, but on August fourth it stopped eating. We thought
that its larval life must be completed, and expected to see it spin its
cocoon, but something was lacking which we were too ignorant to supply,
and on August fifth it died. It had eaten six small crickets and half
of the large one, which was equal to about two more. Thus ended our
only acquaintance with this interesting little wasp.
The second week of August furnished such good play in our garden that
island life was neglected; but one brilliant morning we rowed over to
the home of Bembex and Philanthus, hoping that something new was in
store for us. We were not disappointed, for as we climbed the crest we
met a splendid Chlorion cœruleum dressed in shining blue, cricket in
mouth, plunging down the hillside through the long grass. Twenty–five
feet below, she reached her underground home, vanished for two or
three minutes, and then, coming to the entrance, turned her head from
side to side as though listening. Some indiscreet insect was chirping
loudly not far away, and before long the wasp ran out into the grass,
flew to a stump, dropped to the ground, flew to the top of a tall
weed, dropped again, and ran into a hole. A moment later she came out,
dragging a very limp cricket. An ant that crossed her path was chased
vindictively, and then the cricket was placed on its back and scraped
from head to foot four or five times with the mandibles. She then ran a
little farther, laid it down again, and repeated the operation, after
which it was taken into the nest.
[Illustration: CHLORION AND THE INDISCREET CRICKET]
To find ourselves on the track of a lively wasp at the beginning of her
day’s work was great good luck, and as Madam Cœruleum was perfectly
fearless and did her hunting on foot, instead of disconcerting us with
the long flights by which many of our wasps made the chase hopeless, we
had every chance to learn her ways.
It was a fatal day for the crickets. Between nine o’clock and one,
sixteen had been packed away, enough to provision three cells, as we
knew from former observations. Her manner was brisk and energetic, as
she ran about poking her head into every likely hole. At one time we
saw her dislodge a cricket which tried to escape by hiding under some
brush. She pursued, there was a lively scrimmage, and it was pulled
out quite limp and was then held in the mandibles, back up, while she
gave it a prolonged sting under the neck, after which it was carried
home without further manipulation. At another time she paused in
her homecoming to give the victim one long squeeze at the neck. The
crickets were placed in pockets, neatly arranged on their backs with
their heads inward and their long legs projecting into the main tunnel.
They were alive when taken, but died from day to day in the laboratory,
the larvæ eating them in this state without criticism.
While we were watching we noticed a much smaller wasp hovering about,
and presently she slipped into the nest. When the owner returned and
found her, there was a slight commotion in the passage–way, and then
the inquiline appeared, shaking her wings in a flippant manner, as
though she cared nothing for an encounter with the Big Blue. Instead of
coming out immediately as usual, cœruleum stayed inside for twenty–five
minutes. We should like to think that she was occupied in finding and
destroying the egg of the parasite, but we have no reason to suppose
that she could recognize that menace to her fortunes.
Cœruleum lives in her nest and enlarges it from day to day to fit her
necessities. On going over to the island one morning we found a cricket
sleeping calmly in the entrance way, little guessing how dangerous
was its position. It did not budge until the wasp came creeping up
from below, when it jumped away to a place of safety. Before the day’s
hunting began, a long study of the locality was made on foot, tufts of
grass, weeds and stones being carefully noted, and this accounts for
the ease with which the nest is afterward found.
One July afternoon we saw a little red Tachysphex tarsata on the Bembex
field of the island. She had a very anxious air, and was running
about wildly and rapidly, holding a small grasshopper with the third
pair of legs. She let it drop four or five times, and when she picked
it up again she seemed to sting it, but of this we were not quite
certain. At last she left it and began to rush about, investigating
the Bembex holes, entering one of them and perhaps throwing out a
little dirt as though she intended to use it, and then hurrying off
to another. We have no doubt that her confusion was the result of her
having lost track of a hole that she had made, as was the case with P.
quinquenotatus in one of our earlier observations. The Pompilus, after
a long search, resigned herself to the necessities of the case and made
a new nest; but this little wasp could not adjust herself to a break
in the system of her instinctive activities, and at last deserted her
prey and disappeared. We waited for an hour; and then, as she did not
return, we took possession of the grasshopper. It gave no response to
stimulation and never revived, a very careful examination later showing
that it was quite dead.
On the next morning we again saw this wasp on the Bembex field. She was
looking for a nesting–place, and when she had selected one she began
to work; the weather was warm and sunny, so that the Bembecids were in
the full swing of their obstreperous activity, and perhaps resenting
the presence of the little red wasp, or perhaps in a spirit of teasing,
they kept snatching her up and carrying her off to a distance of two
or three feet. She took these interruptions with the most philosophic
composure, hurrying back to her work as soon as she was released,
without any display of resentment. When the nest was finished, she
made a careful locality study both on foot and on the wing and then
flew away. In twenty minutes she came back, apparently to refresh
her memory, for she again made careful notes of all the points that
could help her to identify the place. She dug a little more and then
departed, to return five minutes later, on foot, with a grasshopper.
In spite of all the precautions she had taken, at this exciting moment
she was unable to remember just where her nest was, and spent some time
in running wildly about, but when she did find it she went in without
delay. We caught her as she came out, and dug up the grasshopper,
but found no egg, so that she probably would have brought in a second
victim had we let her go. The tunnel ran in obliquely for an inch and a
half, the pocket at the end being two inches below the surface.
A few days later we saw Larra quebecensis, another little grasshopper
wasp, with the same red abdomen as tarsata, going to and fro about her
nest, occasionally throwing out a little sand. She ran about near by
all through the afternoon, but was not in a mood for work. On the next
morning at ten o’clock, we found her touching up the nest a little,
after which she left it open and flew away. In an hour she came leaping
along like Tachytes, holding a small grasshopper in the third legs.
This was placed inside the door while she turned around, and was then
pulled in. She came out immediately, and in twenty minutes brought a
second, and in ten more a third grasshopper, staying within this time
for some minutes, after which she closed the nest. We took out the
grasshoppers, one of which bore an egg underneath, in the middle, in
front of the first pair of legs. The grasshoppers lived for five, six,
and seven days, but the egg did not develop. We once saw a quebecensis
that had laid down her grasshopper while she hunted for her nest. She
was moving in sinuous lines up and down the face of a cliff, with
incredible rapidity; we could not distinguish her, but could see only
a black streak with an occasional flash of crimson. When she rises on
her wings, too, she is wonderfully quick, disappearing as if by magic,
it being quite impossible to even guess at the direction she is taking.
Chapter XI
WORKERS IN CLAY
THE nests of Pelopæus cœruleus and Pelopæus cementarius, our two
mud–daubers, are common under eaves and in other sheltered places,
and many a country boy on opening them has been astonished to find
that they do not contain wasps, but are crammed with spiders. Let them
alone, however, and the wasps will arrive, for somewhere in the mass is
an egg; and when it hatches the spiders will serve as breakfast, dinner
and tea for the larva, until the change from the Arachnida to the
Hymenoptera has been accomplished. Poor spiders! it is a wonder that
there are any left, such thousands and tens of thousands are destroyed
by these tremendously energetic enemies.
Of what is Pelopæus thinking as, humming loudly, she jams her paralyzed
and benumbed victims into her little cylindrical tubes? If only we
could get inside of that little head! If only we could be wasps for a
day, and then come back and tell about it, how much vain speculation
would be saved! We can understand her when she soars gayly into the
blue, the sunshine flashing from her brilliant wings; we too have felt
the delight of health and freedom. She is still comprehensible when,
at the close of day, she and her sisters quarrel for the favorite
sleeping–places among the carvings of the porch pillars; but we
cannot follow her mental processes when, at the moment of building,
she surrenders herself to the mysterious sway of instinct, doing she
knows not what, but doing it joyously, and preserving through it all
the precious possession of her own individuality. Every aspect speaks
of pleasure as these wasps gather at well or spring, and, singing
contentedly, stand on their heads to gather their loads of mud. Briskly
and gayly they fly back and forth, pausing at the nest long enough to
pat the soft building material into shape. A single load makes half a
ring at the larger part of the nest or a whole one at the bottom; and
since one dries before the next is put on, the contour of each ring is
visible when the tube is done, giving a very artistic effect. This is
only accident, however; the wasp cares nothing about the beauty of the
structure, for her next step is to daub the whole with lumps of mud,
the walls being thus thickened and strengthened. About forty loads are
necessary for each cell, and to build and provision one is a good day’s
work.
It is strange enough that with no one to teach her Pelopæus knew how
to make her cell; but now she must do her hunting, and it is stranger
still that she should be impelled to catch nothing but spiders. How
does she know a spider from a fly, and why should she prefer one to the
other? Not so unreasonable as some wasps, however, she demands nothing
further than that her prey shall belong to this great group, and passes
lightly over differences of species and genera. Her powerful sting fits
her to cope with anything she may meet; but as the size of the cell
must be taken into consideration, and the victim must be carried home
on the wing, she is on the lookout for something not too large. Here
then she ceases to be an automaton, and to some extent makes use of her
wits.
How does Pelopæus seize her spider? When and how many times is it
stung? Is the wound given with discrimination, a certain point in the
ganglion being pricked, so that the spider may be paralyzed, but not
killed? Is there any malaxation?
These were important questions to us, and we were therefore greatly
excited over our first hunt. One of the blue wasps came flying along,
alighted on our cottage wall, and began her search, creeping into
corners and cracks and investigating cottony lumps of web. In a few
moments a small Epeira strix (the only species to be found on the
cottage) was dislodged, and at once dropped to the floor of the porch.
The wasp paid no further attention to it, but went on with her search.
Three more spiders, one after the other, were disturbed and dropped to
the floor without being followed. The fifth one discovered was a little
larger than the others, and was seized by the jaws and first legs of
the wasp before it had time to escape. It was then rolled into a ball,
or at least so it appeared, and stung, then rolled a little more and
stung again, and then carried off. We had scarcely drawn breath after
this performance when a second wasp appeared. This one dislodged two
spiders, and then caught a third, which was seized and stung without
any rolling, and then instantly borne away. A third wasp seized the
first spider that she found, and started on her flight at the same
moment, stinging it on the wing.
So the game went on, while we waxed warm with the excitement and
fascination of the chase. As the hours went by some of the yellow
mud–daubers appeared, adding to the interest of the scene, although
we could not see that their method differed in the least from that of
cœruleus.
Rarely did they succeed in catching a spider until they had dislodged
two or three. Sometimes the spiders were followed as they dropped, and
were caught on the floor, but oftener the wasp let them escape and
continued her search on the wall. At the moment of capture we could see
that she bent her abdomen under and inflicted a sting, but although we
concentrated our attention on the point we could not be sure as to just
what part was touched. It is our impression that this first sting was
given anywhere, at random, with the object of producing a condition of
temporary quiet in the victim, so that the next part of the operation
could be carried on with deliberation.
The second step in the procedure was commonly for the wasp to alight
upon some neighboring object, usually the branch of a bush or tree, and
sting the spider a second time, being evidently in no haste; but the
difficulty of following her as she flew, and her habit of alighting
above our range of vision, made it almost impossible to see just what
she did. She certainly remained on the branch for some moments, either
resting quietly or rolling the spider around and around, and had every
opportunity to sting it as carefully as she wished; but we afterward
found that she followed no exact method, since two thirds of the
spiders were killed at the moment of capture, and most of the others
died within a week, while a few lived for thirty–five or forty days. In
this study we opened five hundred and seventy–three cells and handled
over two thousand spiders, watching over them from day to day with a
magnifying glass, that no sign of life might be neglected.
When Pelopæus has filled her cell, she seals it up and makes another
close to it, clusters of from six to twenty being found in one spot.
Any especially desirable place is used by great numbers; and they make
a lively scene, working eagerly at their nests, dashing off for more
mud or bringing in their victims. All animated by the same compelling
instinct, they are still individuals, and the character of each enters
into her work. One picks up the first spider she sees, no matter how
tiny it may be, and makes twenty–five or thirty journeys before her
cell is filled, while another seems to have a calculating turn of mind,
using four or five big spiders instead of a quantity of small ones.
Has she made a note of the calibre of her cell, and determined to save
herself trouble by looking farther and selecting the largest ones that
will go in?
[Illustration: HORIZONTAL CELLS OF THE MUD–DAUBER]
Most of them place their cells vertically; but a few prefer the
horizontal position, while still others, undecided as to the matter
of direction, make clusters in which some are horizontal and
others upright. Occasionally there is a remarkable innovation in
building–material, as where in a group of fifteen, four cells in the
centre were constructed of pure white plaster, forming a striking
contrast to the surrounding mud color. One wasp built an entire cluster
after an original fashion, following the beaten track until the cell
was completed, and even bringing mud enough to daub it over, as her
sisters were doing, but sticking it all in one spot, so that when
the group was complete irregular lumps were attached here and there,
leaving visible the elegant architecture of the individual cells. Did
she think they were too pretty to spoil? or was she merely one of those
radical spirits that rebel against conventionality and demand change
for the sake of change? It is these variations that furnish Natural
Selection with its materials; but rigid as may be the rules regarding
the non–survival of the unfit, we find that the race of Pelopæus
still produces many absent–minded wasps, that after spending hours in
carefully constructing their nests, seal them up empty, forgetting to
put in the spiders or to lay the egg.
When a cell is sealed, the mother wasp ceases to take an interest
in it, but she has done all that is necessary. In two or three days
the egg hatches, after which the larva spends ten or fifteen days in
eating, and then spins its cocoon. Here it remains, perhaps for only
a few weeks,—for there are two or three generations in one season,—or
perhaps through the long months of winter.
Fabre gives a most entertaining account of a French species of Pelopæus
which nests in the wide–mouthed chimneys of the peasant. Undisturbed
by the steam of washing day or the bustle of dinner–getting, the wasp
enters the open door, passes unconcerned among the human inhabitants,
and makes her cells against the smoky bricks, out of reach of the
flames. This species kills her prey at the moment of capture, by which
act she falls in the estimation of Fabre, who respects a wasp in
proportion to the nicety with which she delivers her sting. He says,
however, that at least she follows a logical method in turning to
account these spiders, menaced with early decay. In the first place
the prey is multiplied in each cell. The piece actually attacked by
the larva is soon a disorganized mass, likely to decay speedily; but
it is small and is consumed before decomposition can advance, for when
a larva once attacks a spider it does not leave it for another. The
others then remain intact, which is enough to keep them fresh during
the short period of larval life. When, on the contrary, the prey
consists of a single large piece, it is necessary that the organic life
should be maintained, and a special art must also be observed in eating
it. It is well then that Pelopæus is inspired to take numerous small
pieces. The egg, moreover, is always placed on the first spider brought
in, whether the storing of the nest is completed within a few hours, or
whether, as in some cases, it occupies several days; and this M. Fabre
considers a very happy arrangement.
The French Pelopæi differ from ours at nearly every point. Ours kill
only about two thirds of their victims, many of the others being
paralyzed so perfectly that they live for two or three weeks. Again,
ours, instead of placing the egg upon the first spider, almost
invariably lay it upon the last one brought in. Another point of
difference is that our larvæ frequently start in by eating up the
soft abdomens, like children who first devour the plums in their
pudding, returning later to the tough parts that are left, a rash and
reprehensible course of action of which their better–taught French
cousins are never guilty. When one comes to compare the two sets of
facts furnished by the two groups of species, the deductions which
Fabre has drawn as to the importance of the instincts of the French
group are seen to be unfounded. The American species violate nearly
every principle which he considers necessary to their existence, and
yet they flourish and multiply. For our part we find nothing in the
actions of Pelopæus that needs to be explained—nothing that is not well
adapted to the conditions under which each species works. The measure
of praise or blame which we mete out to these depredators is merely a
way of saying whether we would or would not follow their methods in
provisioning our houses and rearing our children. Perhaps we would
always use large spiders and would always have them fresh; but it is
evident that tastes differ, and the matter is so purely a subjective
affair that it will have to go unsettled. In any event, whether her
victims be strong or feeble, old or young, big or little, fresh or dry,
they certainly serve admirably in enabling Pelopæus to rear brood after
brood, and to people the different parts of the earth with abundant
representatives of her kind.
Chapter XII
SENSE OF DIRECTION
WE once made a number of experiments to discover in what way the
social wasps came back to the nest on returning from their hunting
expeditions. Were they endowed with some innate power which made
memory of places unnecessary, and enabled them to fly in a straight
line to any point they wished to reach, or did their return depend
upon the more commonplace method of remembering the appearance of the
country–side?
One morning at half past eight, we placed a wasp cage over the opening
of a yellow–jacket hole that had been closed since the night before,
and caught fifty–five workers, after which the nest was again closed,
one of us taking the cage out on to the lake, while the other remained
to watch for their return.
At seven minutes before nine, twenty of the wasps were liberated an
eighth of a mile from shore near the end of the island. All, without
exception, flew toward the island and away from the nest. Whether they
settled could not be determined. The boat was then moved an eighth of a
mile beyond the island to the north, where, at ten minutes after nine,
the remaining wasps were set free. They seemed a good deal confused,
and flew in all directions. Many returned to the boat and alighted, but
soon flew away again. Two that settled on the boat were knocked into
the water; but they instantly rose and circled up into the air until
out of sight.
Of the fifty–five wasps that we set free, thirty–nine returned to the
nest by ten o’clock, five of them belonging to the lot that flew to the
island, since they soon found their bearings and came directly home,
reaching the nest before the wasps of the second lot were liberated.
Of the thirty–five wasps that were set free at the second point, at
least twenty started in wrong directions. Adding these to the first
twenty, we have left only fifteen that appeared to know where to look
for their home, and yet thirty–nine reached the nest in a little more
than an hour from the time the first wasps were set free.
On another morning we caught thirty–eight workers and took them to a
boat–house on the shore of the lake, in the second story of which was a
large room with two good–sized windows; one looked west over the lake
and away from the nest, the other east toward the nest, and both were
wide open. The west window was the brighter, but the other was light,
the sun being on that side of the house.
We placed the cage in the middle of this room and opened the door,
stationing ourselves well to one side so as not to interfere with the
movements of the wasps. They came out very naturally, pausing a moment
before flying, and followed each other so slowly that we could easily
see which window they went out by. Twenty–two flew through the west
window away from the nest, and sixteen through the east toward the nest.
At another time we took fourteen wasps from the nest of a different
species and carried them seventy–three yards to the southeast. The cage
was opened so that they could fly out in any direction they chose, and
they all started in a straight line for the nest. Later on the same
day, we took forty–five from this nest, and set them free one hundred
and seventy–six yards to the south. Seven flew north toward the nest,
twenty–one south, eight west, and seven east, while the other two
circled around as they rose higher and higher, until they were lost to
view. None in this experiment returned to take a fresh start.
Again, we took twenty–three wasps three hundred yards southeast of the
nest and liberated them in an open field; thirteen flew east or south
away from the nest, seven west or northwest toward the nest, and four
returned to the starting–place and seemed unwilling to venture out
again.
These observations show that the two species of wasps with which we
experimented have no sense of direction in the form of a mysterious
additional sense, nor yet in the form of a power by which they keep a
register of the turns and changes in a journey and are thus able to
retrace their way. Our cage was of wire, and so open that they could
see all about, as we carried them from place to place; yet when they
flew out, they most frequently started in a wrong direction and toward
a point that we had not passed. In many instances, however, these wasps
returned to the nest, and it seems highly probable that as they rose
higher and higher into the air, circling as they went, they discovered
some lofty treetop or other object that had before served them as a
landmark, and that in this way they were able to make their way home.
Bee–keepers know that if young workers which, in strong hives, pass the
first ten or fifteen days of their lives in feeding the larvæ without
going abroad, are taken out and set free only a short distance from
home, they are unable to find their way back, and perish, while those
that have passed beyond the nursing stage and have begun to do outside
work may be carried long distances away and still readily regain the
nest.
With the solitary wasps we attacked the problem from the other end. We
observed what the social wasps did in attempting to return to the nest;
with the solitaries, we watched them when, after making the nest, they
prepared to leave it to go out into the fields or woods in search of
food or prey, thinking that the procedure of different species under
these circumstances would afford a clue to the faculty upon which they
depended to find their way about. If they were furnished with an innate
sense of direction they would not need to make a study of the locality
of the nest in order to find the way back, but if they were without
this sense it would be only common prudence to take a good account of
their bearings before going far afield.
The sight of a bee or a wasp returning to its home from some far
distant spot, without hesitation or uncertainty, is indeed marvelous.
When we saw our first Ammophila perform this feat we were filled
with wonder. How was it possible for her to hunt for hours, in all
directions, far and wide, and then return in a direct line to a nest
which had been so carefully covered over that every trace of its
existence was obliterated?
To say that she is a creature of instinct, however, is not quite
fair to her ladyship’s intelligence, as a better acquaintance with
her would prove. In reading much popular natural history one might
suppose that the insects seen flying about on a summer’s day were a
part of some great throng which is ever moving onward, those that are
here to–day being replaced by a new set on the morrow. Except during
certain seasons the exact opposite of this is true. The flying things
about us abide in the same locality and are the inhabitants of a fairly
restricted area. The garden in which we worked was, to a large extent,
the home of a limited number of certain species of wasps that had
resided there from birth, or having found the place accidentally, had
settled there permanently. To make this matter clear let us suppose
the case of an individual of A. urnaria. In June she spent her time in
sipping nectar from the onion flowers or from the sorrel that grew on
the border of the garden. In July came the days of her courtship and
honeymoon, and these too were passed in going from flower to flower,
from one part of the garden to another. Many a day we have followed
her when she flew from blossom to blossom along a row of bean plants,
turning, when she reached the end, and wending her way leisurely back
along the next row. Then comes a day when we see her running over the
ground and looking carefully under the weeds for a good nesting–place.
At last a spot is selected and she begins to dig; but two or three
times before the work is completed she goes away for a short flight.
When it is done, and covered over, she flies away, but returns again
and again within the next few hours, to look at the spot and, perhaps,
to make some little alteration in her arrangements. From this time on,
until the caterpillars are stored and the egg laid, she visits her nest
several times a day, so that she becomes perfectly familiar with the
neighborhood, and it is not surprising, after all, that she is able
to carry her prey from any point in her territory in a nearly direct
line to her hole—we say nearly direct, for there was almost invariably
some slight mistake in the direction which made a little looking about
necessary before the exact spot was found.
After days passed in flying about the garden—going up Bean Street and
down Onion Avenue, time and time again—one would think that any formal
study of the precise locality of a nest might be omitted; but it was
not so with our wasps. They made repeated and detailed studies of the
surroundings of their nests. Moreover, when their prey was laid down
for a moment on the way home, they felt the necessity of noting the
place carefully before leaving it.
Of the species that catch their prey before making the nest we have
good examples in Pompilus quinquenotatus, the tornado wasp, and
fuscipennis, the Pompilus with the red girdle.
[Illustration: COURSE FOLLOWED BY POMPILUS FUSCIPENNIS IN FINDING HER
SPIDER AND IN RETRACING HER STEPS TO THE NEST[5]]
The tornado wasp may make her nest anywhere from one to ten feet from
the spot on which she has deposited her spider, while fuscipennis never
goes more than fourteen inches away. During the process of excavation
both of these wasps pay several visits to the spider, and frequently
they have difficulty in finding it. As an example of this kind of
trouble we give a diagram of the course followed by an individual of
fuscipennis after she had finished her nest, in trying to find her
spider and in bringing it home. This and the other similar diagrams
that are given are reductions of large tracings that were made on the
spot. Although not absolutely correct they are exact enough for all
practical purposes, since wherever there is an error it is necessarily
in the direction of making the path pursued by the wasp appear shorter
and less complex than it really was. The individual in question had
placed her spider on a cucumber vine which lay on the ground, not
hidden by leaves, but fully exposed to view. The nest was only eight
inches away, but when it was finished and the wasp went to bring the
spider, she found it only after a search of three minutes; and then
when she went back to the nest she at first passed to one side and
went some inches beyond, so that she had to retrace her steps.
Marchal notes that some wasps are very unskillful in finding their way
about, showing by their errors and hesitations not only that they have
no sense of direction, but that they are badly served by their memory
and by what senses they have. He draws this conclusion from his own
observations, one of which had for its subject Pompilus seriaceus,
which nests, conveniently for him, in the walls of the rustic
summer–house which he uses for a laboratory. A wasp of this species,
having caught her spider, had a most wearisome experience in getting
it to the nest, which had been previously excavated near the ground.
She first carried it straight up, not only passing the opening, but
going to the very top of the wall. Realizing that she had gone wrong,
she laid it down, and after a prolonged hunt up and down, to the right
and to the left, found the nest; but on leaving it again to go for the
spider, she started in exactly the wrong direction, down instead of up;
and not until forty minutes had been spent in searching alternately for
spider and for nest did she finally bring the two together.
The best evidence that wasps depend upon a knowledge of the place in
returning to their nests is given by the pains they take to acquire
that knowledge. When Sphex ichneumonea was ready to dig her nest, she
had great difficulty in finding a place that suited her. Many a spot
was merely looked at and passed by, while others that seemed more
attractive were left after they had been excavated for a little way. At
last, the nest dug, she was ready to go out and seek for her store of
provisions; and now came a most thorough and systematic study of the
surroundings. The nests that had been partly made and then deserted
had been left without any circling. Evidently she was conscious of the
difference and meant, now, to take all necessary precautions against
losing her way. She flew in and out among the plants, first in narrow
circles near the surface of the ground, and now in wider and wider ones
as she rose higher in the air, until at last she took a straight line
and disappeared in the distance. Very often, after one thorough study
of the topography of her home has been made, a wasp goes away a second
time with much less circling or with none at all.
If the examination of the objects about the nest makes no impression
upon the wasp, or if it is not remembered, she ought not to be
inconvenienced nor thrown off her track when weeds and stones are
removed and the surface of the ground is smoothed over; but this
is just what happens. Aporus fasciatus entirely lost her way when
we broke off the leaf that covered her nest, but found it, without
trouble, when the missing object was replaced. All of the species of
Cerceris were extremely annoyed if we placed any new object near their
nesting–places. One Ammophila refused to make use of her burrow after
we had drawn some deep lines in the dust before it. The same annoyance
is exhibited when there is any change made near the spot upon which
the prey of the wasp, whatever it may be, is deposited temporarily.
We learned from experience how important it was not to disarrange
the grass or plants on such occasions. The wasps are in many cases
so prudent as to conceal their booty among the leaves; and this made
it very inconvenient to keep our eyes upon the captured prey, as was
quite necessary if we wished to follow it on its travels. To avoid
the discomfort of lying on the ground or of twisting the neck at some
impossible angle for half an hour at a time, we sometimes gently moved
the intercepting objects to one side; but even such a slight change
cost us dear in time and patience, as it threw the wasp out of her
bearings and made it difficult for her to recover her treasure. We
recall one exceedingly warm day in September when we were delayed in
this way for forty minutes, when she would have seized the spider and
gone on her way without a pause had we not interfered.
[Illustration: LOCALITY STUDY OF ASTATA BICOLOR[6]]
Very often the wind would shake the plant so that the spider or
caterpillar would fall to the ground. Under these circumstances
the wasp was not at all disconcerted, but, on not finding her prey
where she had left it, dropped at once to where it was lying. This
is probably only an extension of their ordinary habits. A wasp that
takes spiders learns to follow them as they drop from the web on being
disturbed. In this they are evidently guided by sight, but perhaps
they are also aided by the sense of smell under other conditions,—to
the extent, at least, of recognizing the place upon which their prey
has lain. With so much to build upon, it is easy to see how natural
selection may have perfected the habit. We are delaying a long
time over details, but we feel that to invoke an unknown sense is
permissible only after a careful study of the daily life of the animals
in question has left the problem unsolved.
[Illustration: LOCALITY STUDY OF ASTATA UNICOLOR[7]]
Among the wasps that first make the nest and then provision the larder,
Astata bicolor is one of the most interesting. She makes a permanent
abiding–place, and probably uses it until all of her eggs are laid.
It is evident that since she comes and goes many times during the
several weeks of her occupation, she does not need to make a prolonged
study of the environment at every departure. Her first survey, just
after the nest is completed, is most thorough; and, as a usual thing,
when she first comes out on each succeeding morning, she reviews the
situation more or less carefully. Individuals differ in this respect,
however, some studying their local habitat much more than others. In
this as well as in all other matters our observations are in complete
accord with those of Sir John Lubbock, who says: “Indeed, many of my
experiences seem to show not only a difference of character in the
different species of ants, but that even within the limits of the same
species there are individual differences between ants, just as between
men.”[8]
This little bug–hunting Astata bicolor made her study in a different
way from Sphex ichneumonea. She first flew from the nest to a spot
near by and settled there, returning, after a moment, to the nest, or
else flying to another resting–place. After pausing in a number of
places (in the case of the one followed in the diagram, thirteen),
she finished by a rapid zigzag flight. Another wasp of this genus,
unicolor, differed from bicolor in not returning to the nest from the
different resting–places, and in walking from one to another of them
instead of flying, although the last part of the study was made on the
wing.
[Illustration: SECOND LOCALITY STUDY OF A. UNICOLOR[9]]
Cerceris deserta was one of the wasps that objected strongly to our
presence, and she also made a great deal of fuss about leaving her
nest. Nearly all the species circle before leaving a spot to which
they intend to return, but deserta begins her flight with a series of
short zigzags in the form of a half circle on one side of the nest.
C. nigrescens, too, begins with semicircles, while C. clypeata flies
entirely around and around the opening. The contrast between the
deliberate movements of Astata and the rapid flight of Cerceris is very
striking.
We have now given a sufficient number of instances, from widely
separated genera, to show the care that is taken by wasps to acquaint
themselves with the surroundings of their nests. It has also been shown
that in spite of all this care they frequently have trouble in finding
their way about. All these facts have led us to conclude that wasps are
guided in their movements by their memory of localities. They go from
place to place quite readily because they are familiar with the details
of the landscape in the district they inhabit. Fair eyesight and a
moderately good memory on their part are all that need be assumed in
this simple explanation of the problem.
Chapter XIII
INSTINCT AND INTELLIGENCE
OUR study of the activities of wasps has satisfied us that it is
impracticable to classify them in any simple way. The old notion that
the acts of bees, wasps, and ants were all varying forms of instinct is
no longer tenable, and must give way to a more philosophical view. It
would appear to be quite certain that there are not only instinctive
acts but acts of intelligence as well, and a third variety also—acts
that are probably due to imitation, although whether much or little
intelligence accompanies this imitation is admittedly difficult
to determine. Again, acts that are instinctive in one species may
be intelligent in another, and we may even assert that there is a
considerable variation in the amount of intelligence displayed by
different individuals of the same species. We have met with such
difficulty in our attempts to arrange the activities of wasps in
different groups that we are forced to the conclusion that any scheme
of classification is merely a convenience, useful for purposes of
study or generalization, but not to be taken for an absolutely true
expression of all the facts. This kind of perplexity is well understood
and allowed for in all morphological work, but it has never been fully
realized in the study of habits. The explanation is not far to seek.
The habits of but few animals have been studied in sufficient detail
to bring out the evidence that there is as much variation on the
psychological as on the morphological side, although this field seems
fresh and inviting when compared with the researches of the laboratory.
The necessity of interpreting the actions of animals in terms of our
own consciousness must be always with us. To interpret them at all
we must consider what our own mental states would be under similar
circumstances, our safeguard being to keep always before us the
progressive weakening of the evidence as we apply it to animals whose
structure is less and less like our own.
We arrange the activities of the wasps that we have studied into two
groups, Instincts, and Acts of Intelligence, it being understood that
these classes pass by insensible stages into each other, and that acts
that are purely instinctive when performed for the first time are
probably in some degree modified by individual experience. In this
classification the question of origin is not considered. The facts
are grouped under the two heads, the inferences that they warrant
being left for later consideration. Under the term Instinct we place
all complex acts that are performed previous to experience and in a
similar manner by all members of the same sex and race, leaving out as
non–essential, at this time, the question of whether they are or are
not accompanied by consciousness. Under Intelligence we place those
conscious actions which are more or less modifiable by experience.
It is this power that enables an insect to seek, accept, refuse,
choose,—to decline to make use of this or to turn to account some other
thing. Many writers prefer the term Adaptation for these activities,
and it possesses certain advantages. With these definitions in mind,
let us group the activities of wasps under the two heads.
With the wasps of the genus Pelopæus we were present on several
occasions when the young emerged from the pupa case and gnawed their
way out of the mud cell. They were limp, and their wings had not
perfectly hardened, and yet when we touched them they tried to attack
us, thrusting out the sting and moving the abdomen about in various
directions. These movements were well directed, and, so far as we could
observe, quite as perfect as in the adult wasp. Stinging, then, is an
instinctive act.
The particular method of attack and capture practiced by each species
in securing its prey is instinctive. Ammophila pricks a number of
ganglia along the ventral face of the caterpillar; Pelopæus, we
believe, stabs the spider in the cephalothorax, and probably the
several species of Pompilus do the same. Astata bicolor adopts the same
tactics in capturing her bugs, while it is said of the fly–catchers
that they commonly overcome their victims without using the sting. It
is by instinct, too, that these wasps take their proper food supply,
one worms, another spiders, a third flies, moths, or beetles. So strong
and deeply seated is the preference, that no fly robber ever takes
spiders, nor will the ravisher of the spiders change to beetles or bugs.
[Illustration: PARALYZED SPIDER HUNG UP ON SORREL BY QUINQUENOTATUS
WHILE SHE DIGS HER NEST]
The mode of carrying their booty is a true instinct. Pompilus takes
hold of her spider anywhere, but always drags it over the ground,
walking backward; Oxybelus clasps her fly with the hind legs, while
Bembex uses the second pair to hold hers tightly against the under
side of her thorax. Each works after her own fashion, and in a way
that is uniform for each species.
The capturing of the victim and caring for it before the hole is made,
as in the case of P. quinquenotatus, or the reverse method, pursued by
Astata, Ammophila, Bembex, and others, of preparing the nest before
the food supply is secured, is certainly instinctive; as is also the
way in which some of these wasps act after bringing the prey to the
nest. For example, S. ichneumonea places her grasshopper just at the
entrance to the excavation, and then enters to see that all is right
before dragging it in. Under natural conditions this order is never
varied, although the wasp can adapt herself to different circumstances
when occasion demands. Again, we see Oxybelus scratching open her nest
while on the wing, and entering at once with the fly held tightly in
her legs. Each way is characteristic of the species, and would be an
important part of any definition of the animal based upon its habits.
The general style of the nest depends upon instinct. Trypoxylon uses
hollow passages in trees, posts, straws, or brick walls; Diodontus
americanus, a member of the same family, always burrows in the ground,
as do Bembex, Ammophila, and Sphex. In the case of Trypoxylon the
passage may be ready for use or may require more or less preparation;
the instinctive part is the impulse that requires the insect to use
a certain kind of habitation. Any one familiar with T. rubrocinctum
would never look for her nest in standing stems or under stones; to
use Mr. Morgan’s test, he would be willing to bet on the general style
of the dwelling–place. All of these acts are similarly performed by
individuals of the same sex and race, not in circumstantial detail but
quite in the same way in a broad sense. Variation is always present,
but the tendency to depart from a certain type is not excessive. In
Cerceris the burrow is tortuous, this style of work being common to
many species in the genus, and very characteristic. No Sphex nor
Ammophila constructs any such tunnel. The adherence of all the members
of a species to a certain style of architecture is, then, due to
instinct.
The spinning of the cocoon, in those species in which the larva is
protected in this manner, and its shape, are instinctive. We find that
closely allied species in the same genus make very different cocoons,
as is seen in T. rubrocinctum and T. bidentatum. Some wasps spin no
such covering for themselves. It is a well–known fact that silkworms
sometimes omit the spinning of a cocoon; but this does not affect
the argument, since the descendants of these individuals make the
characteristic covering. Such cases are probably due to individual
variation or perhaps to atavism, this throwing back being not uncommon
among forms that are well known.
Not all of the instinctive acts here enumerated are displayed by each
species studied, although they are common to most of them. We have
doubtless overlooked some activities that should come under this head,
as we have not made a thorough study of any sufficient number of
species to make a final settlement of the matter.
As we have seen with Ammophila and Pelopæus, faults of instinct are
not uncommon, but of all our wasps the one that shows the greatest
aberrations is Pompilus biguttatus. The sandy beach of Lake Michigan is
a favorite nesting–ground with this species, and is the scene of many a
bold robbery, since they are unprincipled little wretches and
“... the good old rule
Sufficeth them, the simple plan
That they should take who have the power
And they should keep who can.”
We once found an unusually tiny biguttatus vainly trying to drag a
large Epeirid which her sting had reduced to helplessness. It was as
though a feeble child should try to move the body of an elephant. The
little wasp clasped one of the spider’s legs firmly in her mandibles,
and then with braced feet and the wildest flutter of wings made gallant
but futile attempts to get it started. Now she lost her hold on the
ground, and wings and legs were all whirling desperately in the air.
Now her feet grasped a loose ball of earth, and, feeling that something
was moving, she renewed her efforts. The pellet was drawn nearer and
began to rotate around the wasp, while she seemed to be under the
impression that she was moving forward. After a few minutes of vigorous
exercise, she paused, perhaps to see how she was getting on, and the
bit of earth rolled away; so that when the attack was renewed, it
was under the old discouraging conditions. She was the impersonation
of perseverance and energy; but after half an hour (no one knows how
long she had been at it before we came) she gave it up, and with many
reluctant circlings flew away. It was probably experiences of this kind
that developed in some of her relatives the habit of digging the grave
under the victim, and thus saving the trouble of transportation.
At another time, we saw a biguttatus trying to run backward with a
little bit of a spider, which she had lifted from the ground and was
carrying in her mandibles,—trying to run backward, because it is
the rule with this genus to move in that way when encumbered with
a load, it being easier to drag a heavy spider than to pick it up
and go forward. The wasp in question was drawn in two directions.
Instinct made her go backward, although in this particular case it was
needless, while she felt a constant desire to turn and go straight
ahead. As a result she waltzed slowly over the sand in a series of
overlapping circles, her head turned toward every point of the compass
in succession, a kind of progress most amusing to the lookers–on.
Biguttatus is not strong enough to fly when laden, but it is the habit
of the species to climb backwards to the top of every obstacle in the
path, and from this vantage point to gain time by taking a downward
flight in the direction of the nest. It is only in the case of tall,
smooth–stemmed plants and grasses that the advantage gained is enough
to repay the trouble of climbing, and we have often thought that the
notion costs the wasp more trouble than it is worth,—as was certainly
the case with one comical little creature that carried the idea to the
extreme of folly. Not only did she scale objects in her way, but just
as old Dr. Johnson felt that he had to touch every tree and post as
he walked along, so when this wasp saw, out of the corner of her eye,
a stone or a plant three or four inches to one side, it called upon
her to climb, and climb she did, although she was obliged to leave her
proper path to do it.
It is obviously more difficult to distinguish actions of intelligence
than of instinct. One must be familiar with the normal conditions of
the insects in question before he is able to note those slight changes
in the environment that offer some opportunity for an adaptation of
means to ends, or before he is competent to devise experiments which
will test their powers in this direction.
We find two classes of intelligent actions among the Hymenoptera which
are sufficiently distinct to be considered separately, although, like
all natural groups, they grade into each other. The first of these
includes those actions that are performed by large numbers in a similar
fashion under like conditions, while in the second class each act is
an individual affair,—as where a single wasp, uninfluenced in any way
by the example of those about it, displays unusual intelligence in
grappling with the affairs of life. Examples of the first class are
found in such modifications of instinct as are shown by Pelopæus and
other wasps in the character of their habitations. Pelopæus, instead of
building in hollow trees or under shelving rocks, as was the ancient
custom of the race, now nests in chimneys, or under the eaves of
buildings. We have found T. rubrocinctum taking advantage of the face
of a straw–stack that had been cut off smoothly as the cattle were fed
through the winter. The same power of adaptation is shown by Fabre’s
experiment with Osmia, in which he took two dozen nests in shells from
a quarry, where the bees had been nesting for centuries, and placed
them in his study along with some empty shells and some hollow stems.
When the bees came out, in the spring, nearly all of them selected the
stalks to build in as being better suited to their use than the shells.
All of these changes are intelligent adaptations to new modes of life,
serving to keep the species in harmony with its surroundings. The
same thing may be seen when a number of social wasps work together to
replace the roof of their nest when it has been torn off.
An instance of the second class is seen in one of our examples of
Pompilus marginatus. This species, while searching for a nesting–place,
leaves its spider lying on the ground or hides it under a lump of
earth, in either of which positions the booty is subject to the attacks
of ants; the wasp in question improved upon the custom of her tribe by
carrying the spider up into a plant and hanging it there. We have now
and then seen a queen of Polistes fusca occupy a comb of the previous
year instead of building a new one for herself,—showing a better
mental equipment than her sisters who were not strong–minded enough to
change their ways, and so built new nests alongside of unoccupied old
ones which were in good condition. In Bembex society it is good form to
close the door on leaving home, but sometimes a wasp will save time by
leaving the entrance open. This, however, is a doubtful case, as the
advantage would, perhaps, be more than balanced by the exposure of the
nest to parasites.
Some years after our first experience with Pompilus scelestus we saw
a wasp of this species carrying her spider home. She dropped it close
to the nest, and looked meditatively, first at the hole and then at
the spider. It was unquestionably going to be a very tight fit, but if
she could get it in that would be an advantage; so after a moment she
seized it by the tip of the abdomen and backing down tried to pull it
after. Tug—_tug!_ No, it would not go down, and scelestus pushed it out
and carried it to a place of safety up among some clover blossoms. She
then washed and brushed herself neatly, and took several little walks,
so that it was fully fifteen minutes before she began to enlarge her
nest. All that time she must have carried in her little scrap of a mind
the idea of doing a necessary act which was outside of her ordinary
routine; and we noted with interest that the change when it was made
accomplished exactly what was needed,—the spider went in, but not too
easily.
In an experiment with a French Sphex which has the habit of laying her
cricket down at the threshold, and going inside for an instant before
dragging it in, Fabre took advantage of the moment that the wasp was
out of sight below to move her prey to a little distance, with the
result that when the wasp came up she brought her cricket to the same
spot and left it as before, while she visited the interior of the nest.
Since he repeated this experiment about forty times and always with the
same result, it seemed fair to draw the conclusion that nothing less
than the performance of a certain series of acts in a certain order
would satisfy her impulse. She must place her prey just so close to
the doorway; she must then descend to examine the nest; and after that
she must at once drag it down, any disturbance of this routine causing
her to refuse to proceed. We once found a Sphex ichneumonea at work
storing her nest, and thought it would be interesting to pursue Fabre’s
method and find out whether she were equally persistent in following
her regular routine. We allowed her to carry in one grasshopper to
establish her normal method of procedure, and found that, bringing it
on the wing, she dropped it about six inches away, ran into the nest,
out again and over to the grasshopper, which she straddled and carried
by the head to the entrance. She then ran down head first, turned
around, came up, and seizing it by the head, pulled it within. On the
following day, when she had brought a grasshopper to the entrance of
the nest, and while she was below, we moved it back five or six inches.
When she came out, she carried it to the same spot and went down as
before. We removed it again, with the same result, and the performance
was repeated a third and a fourth time, but the fifth time that she
had found her prey where we had placed it she seized it by the head,
and going backward dragged it down into the nest without pausing.
On the next day the experiment was repeated. After we had moved the
grasshopper away four times, she carried it into the nest, going head
foremost. On the fourth and last day of our experiment, she replaced
the grasshopper at the door of the nest and ran inside seven times, but
then seized it and dragged it in, going backward. How shall this change
in a long–established custom be explained, except by saying that her
intelligence led her to adapt herself to circumstances? She was enough
of a conservative to prefer the old way, but was not such a slave to
custom as to be unable to vary it.
“It hath been an opinion,” says Lord Bacon, “that the French are wiser
than they seem, while the Spaniards seem wiser than they are.” We leave
it to our readers to determine whether the wasps are wiser than they
seem or seem wiser than they are.
INDEX
INDEX
Agenia, mutilation of spiders, 243, 247.
—— bombycina, 244.
Ammophila, 15;
stinging habits of American and French species, 28;
Fabre’s conclusions contrasted with ours, 52;
sleeping habits noted by Banks, 117.
—— gracilis, great distance over which prey is carried, 46;
failure of instinct, 46.
—— polita, 50.
—— urnaria, 18;
sense of locality, 20;
individuality, 22;
using a pebble as a tool, 38.
—— vulgaris, losing her way, 46.
—— yarrowii, Williston’s notes on habits, 40.
Aphilanthops frigidus, 167;
losing her way, 171;
method of capturing queen ants uncertain, 174.
Aporus fasciatus, 80;
habit of filling up partly made nests, 82;
depends upon close packing to keep spider quiet, 83;
contrast between two individuals, 84.
Ashmead, W. H., on European species of Oxybelus, 78.
Astata bicolor, locality study, 288.
—— unicolor, locality study, 290.
Banks, Nathan, observation on sleeping habits of Ammophila, 117.
Bates, H. W., on habits of Monedula signata, 136.
Belt, Thomas, on locality study of Polistes carnifex, 60.
Bembex labiatus, note on locality sense by Bouvier, 124.
—— rostrata, account of habits by Wesenberg, 139;
note on locality sense by Marchand, 125.
—— spinolæ, 119;
less numerous progeny than other wasps, 120;
habit of feeding young from day to day, 120;
quarrelsome habits, 129;
tolerance of parasites, 132;
number of parasitic larvæ found in nests, 133;
experiment to determine number of nests visited by female at one
time, 139;
teasing Tachysphex, 262.
Bouvier, note on locality sense of Bembex labiatus, 124.
Brehm, on mutilation of spiders by Agenia punctata, 243.
Brues, on sleeping habits of Priononyx atrata, 118.
Cerceris clypeata, 147;
locality study, 149;
experiments on stinging habits, 151.
—— deserta, 152;
locality study, 153.
—— fumipennis, 142.
—— nigrescens, 142.
Ceropales, following Pompilus scelestus, 231.
Chlorion cœruleum, 256.
Crabro interruptus, 102;
locality study, 105.
Crabro lentus, 101;
both flies and bugs found in nests, 101.
—— sexmaculatus, 99;
takes both flies and gnats, 101.
—— stirpicola, 106;
contrasted with other wasps as to manner, 106;
works night and day to finish nest, 108.
—— wesmæli, said to take both flies and bugs, 101.
Dunning, S. W., on finding flies alive in nests of Bembex, 135.
Fabre, J. H., on automatically perfect instincts of Ammophila, 52;
on French species of Sphex, 69;
on the habits of Bembex, 134;
on Philanthus apivorus, 162;
on French species of Pelopæus, 273.
Goureau, on mutilation of spiders by wasps, 244.
Larra quebecensis, 263.
Lubbock, Sir John, on individuality in ants, 288.
Lyroda subita, 253;
feeds her young from day to day, 255.
Marchal, Paul, on poor locality sense of Pompilus seriaceus, 284.
Marchand, observation on locality sense of Bembex rostrata, 125.
Monedula signata, locality study noted by Bates, 136.
Mutilation of spiders by wasps, 243.
Odynerus, variation in nesting habits, 95.
—— anormis, position of egg in nest, 91.
—— capra, 94.
—— conformis, position of egg, 91.
—— perennis, 89.
—— reniformis, position of egg, 90.
—— vagus, wariness, 94.
Oxybelus quadrinotatus, 75;
method of carrying fly, 80.
Passolocus annulatus, 87.
Pelopæus, 265;
individuality, 270;
forgetfulness, 271;
difference between French and American species, 273.
Philanthus apivorus, sucks honey from bee, 162.
—— punctatus, 154;
habits of colony, 156;
experiments on stinging habits, 162;
nesting habits of males, 166.
—— ventilabris, 166.
Plenolocus peckhamii, 95;
stalk invaded by bees and other wasps, 96.
Polistes carnifex, locality study noted by Belt, 60.
Pompilus biguttatus, unreasoning conduct, 298.
—— fuscipennis, 216;
afraid of ants, 219;
biting legs of spider, 220;
sense of locality, 221.
—— marginatus, 221;
capturing spider, 225;
method of digging nest, 229.
—— quinquenotatus, 197;
confined to one species of spider, 202;
nest invaded by small ants, 202;
hangs spider on plant while nest is being made, 204;
robs her neighbors, 211;
loses her way, 214.
—— scelestus, 230;
bites legs of spider, 230;
pursued by parasites, 231;
sleeping habits, 236.
—— seriaceus, poor locality sense noted by Marchal, 284.
—— subviolaceus, following scelestus, 236.
Priononyx atrata, note on sleeping habits, 118.
Rhopalum pedicellatum, 73;
strong power of localization, 73.
—— rubrocinctum, 74.
Social wasps, general habits, 3;
color sense, 5;
sense of smell, 8;
affecting plant distribution, 11;
number in one nest, 12.
Solitary wasps, general habits, 15.
Sphex, habits noted by Fabre, 69.
—— ichneumonea, 56;
nests begun and deserted, 56;
locality study, 58;
intelligence, 305.
Tachysphex tarsata, 261.
Tachytes sp. ?, 248.
—— peptonica, 252.
Trypoxylon, immense numbers of spiders destroyed, 195.
—— albopilosum, 190.
—— bidentatum, 194.
—— rubrocinctum, 180;
protection of nest by male, 181;
male sometimes assists in storing nest, 182;
order in which eggs hatch, 180.
Vespa germanica, 13.
—— maculata, 13.
Wesenberg, on habits of Bembex rostrata, 139.
Wheeler, W. M., on capture of ants by Aphilanthops frigidus, 176.
Williston, S. W., on habits of Ammophila yarrowii, 40.
The Riverside Press
_Electrotyped and printed by H. O. Houghton & Co.
Cambridge, Mass., U. S. A._
FOOTNOTES:
[1] _Introduction to Modern Classification of Insects_, ii, 189.
[2] _Naturalist in Nicaragua_, p. 136.
[3] Fabre says that all of the three species of Sphex that he has
studied lay the egg on this identical place. He places immense
importance on this point, which seems to us rather fanciful. He also
noticed the pulsation of the abdomen and the movements of the other
parts.
[4] Sharp, _Insects_, page 130.
[5] The nest being completed, the wasp went skimming over the ground
as indicated by the line, until the spider, which had previously been
stung and placed upon a leaf, was found. She then dragged it some
distance beyond the nest to the point 2, from which place she took it
to the nest.
[6] The wasp flew from nest to 1, paused a moment, then flew back; then
to 2, paused and flew back; then to 3, paused, then to 4, paused and
flew back to nest; flew to 4, 5, 6, 7, 8, and 9, pausing at each spot,
and flew back to nest along 10; flew, successively, along 11, 12 and
13, resting at the spots designated; from 13 she circled around nest in
direction of arrow points and departed.
[7] The continuous line shows the course walked over by the wasp, the
short marks at right angles representing resting–places; the broken
line indicates flight. Line 1 shows the first study, leading back to
the nest, and line 2 the second, ending in flight and departure.
[8] _Ants, Bees, and Wasps_, p. 95.
[9] The continuous line shows the course walked over by the wasp; the
short marks at a right angle indicate resting–places; the broken line
indicates flight.
TRANSCRIBER’S NOTE:
—Obvious print and punctuation errors were corrected.
*** End of this LibraryBlog Digital Book "Wasps - Social and Solitary" ***
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