ADVANCED THEORIES
The species of the genus Sphex are fairly numerous, but are for the
most part strangers to my country. As far as I know, the French fauna
numbers only three, all lovers of the hot sun of the olive district,
namely, the Yellow-winged Sphex (Sphex flavipennis), the White-edged
Sphex (S. albisecta), and the Languedocian Sphex (S. occitanica). Now
it is not without a lively interest that the observer notices in the
case of these three freebooters a choice of provisions which is in
strict accordance with the rigid laws of entomological classification.
To feed their grubs, all three choose solely Orthoptera. [25] The first
hunts Crickets, the second Locusts, the third Ephippigers.
The prey selected have such great outward differences one from the
other that to associate them and grasp their similarity calls for the
practised eye of the entomologist or the no less experienced eye of the
Sphex. Pray compare the Cricket with the Locust: the first has a large,
round, stumpy head, is short and thickset and black all over, with red
stripes on his hinder thighs; the second is greyish in colour, long and
slim, with a small, tapering head, leaps forward by suddenly unbending
his long hind-legs and continues this flight with wings furled like a
fan. Next compare both of these with the Ephippiger, who carries his
musical instrument, two shrill cymbals shaped like concave scales, on
his back and who waddles along with his pendulous belly, ringed
pale-green and buttercup-yellow and armed with a long dirk. Place the
three side by side and you will agree with me that, to guide her in
choosing between such dissimilar species, while still keeping to the
same entomological order, the Sphex must have an eye so expert that no
man—not your ordinary layman, but a man of science—need be ashamed to
own it.
In the face of these singular predilections, which seem to have had
their limits laid down for them by some master of classification, by a
Latreille, for instance, it becomes interesting to investigate whether
the Sphex-wasps that are not natives of our country hunt game of the
same order. Unfortunately, information on this point is scanty and, in
the case of most of the species, is lacking altogether. The chief cause
of this regrettable lacuna is the superficial method generally adopted.
People catch an insect, stick a long pin through it, fix it in the
cork-bottomed box, gum a label with a Latin name underneath its feet,
and let its history end there. It is not thus that I understand the
duties of an entomological biographer. It is no use telling me that
this or that species has so many joints to its antennæ, so many
nervures to its wings, so many hairs on a region of the belly or
thorax; I do not really know the insect until I am acquainted with its
manner of life, its instincts and its habits.
And see the immense and luminous advantage which a description of this
kind, told in two or three words, would possess over those long
descriptive details, sometimes so hard to grasp. Suppose that you wish
to make the Languedocian Sphex known to me and you begin by describing
the number and distribution of the nervures of the wings; you speak to
me of cubital nervures and recurrent nervures. Next comes the insect’s
pen-portrait. Black here, rusty red there, smoky brown at the tips of
the wings; black velvet in this part, silvery down in that, a smooth
surface in a third. It is all very definite and minute: we must do this
much justice to the precision and patience of the narrator; but it is
very long and also it is by no means always clear, so much so that we
may be excused if we are not quite able to follow it, even when we are
not altogether new to the business. But add to the tedious description
merely this: ‘Hunts Ephippigers’; and these two words at once shed
light: there is no possibility of my now mistaking my Sphex, for she
alone possesses the monopoly of that particular prey. To give this
illuminating note, what would be needed? The habit of really observing
and of not making entomology consist of so many series of impaled
insects.
But let us pass on and examine the little that is known about the
hunting methods of the foreign Sphex-wasps. I open Lepeletier de
Saint-Fargeau’s [26] Natural History of Hymenoptera and find that, on
the other side of the Mediterranean, in our Algerian provinces, the
Yellow-winged Sphex and the White-edged Sphex retain the same habits
that characterize them here. They capture Orthoptera in the land of
palm-trees even as they do in the land of olive-trees. Though separated
from the others by the vast width of the sea, the hunting compatriots
of the Kabyles and the Berbers pursue the same game as their kindred in
Provence. I also see that a fourth species, the African Sphex (S.
afra), is the scourge of the Locusts in the neighbourhood of Oran.
Lastly, I remember reading, I forget where, of a fifth species which
also wages war on Locusts in the steppes near the Caspian. Thus, on the
borders of the Mediterranean, we have five different species of Sphex,
whose larvæ all live on a diet of Orthoptera.
Now let us cross the equator and go right down to the southern
hemisphere, to the islands of Mauritius and Réunion: we shall here find
not a Sphex, but a closely-allied Wasp of the same tribe, the
Compressed Chlorion, hunting the horrible Kakerlak, that ravager of the
foodstuffs in the ships and harbours of the colonies. These Kakerlaks
are none other than Cockroaches, whereof one species haunts our
dwellings. Who does not know the evil-smelling insect, which, thanks to
its flat body, like that of a huge Bug, slips at night through the gaps
in furniture and the crannies of partitions and invades any place
containing provisions to be devoured? This is the Black-beetle of our
houses, a disgusting counterpart of the no less disgusting prey beloved
of the Chlorion. What is there about the Kakerlak to cause him to be
selected as a prey by a near cousin of our Sphex-wasps? It is quite
simple: with his Bug shape, the Kakerlak also is an Orthopteron, just
as much as the Cricket, the Ephippiger or the Locust. From these six
examples, the only ones known to me and of such different origins, we
might perhaps deduce that all the Sphex hunt Orthoptera. At any rate,
without adopting so general a conclusion, we see what the food of their
larvæ must be in most cases.
There is a reason for this surprising choice. What is it? What are the
grounds for a diet which, within the strict limits of one entomological
order, is composed here of stinking Kakerlaks, there of somewhat dry,
but highly-flavoured Locusts, elsewhere again of plump Crickets or fat
Ephippigers? I confess that I cannot tell, that I am absolutely in the
dark; and I leave the problem to others. At the same time, we may
observe that the Orthoptera are among insects what the Ruminants are
among mammals. Endowed with a mighty paunch and a placid temperament,
they graze contentedly and soon put on flesh. They are numerous, widely
distributed and slow in movement, which renders them easy to catch;
moreover, they are of a large size, making fine heads of game. Who can
say if the Sphex-wasps, powerful huntresses, requiring big prey, do not
find in these Ruminants of the insect world what we ourselves find in
our domestic Ruminants, the Sheep and the Ox, peaceable victims
yielding plenty of flesh? It is just a possibility, but no more.
I have something better than a possibility to offer in reply to another
and no less important question. Do the Orthopteron-eaters ever vary
their diet? Should the favourite type of game fall short, can they not
accept a different one? Does the Languedocian Sphex consider that there
is nothing in the world worth having but fat Ephippigers? Does the
White-edged Sphex allow none but Locusts to figure on her table; and
the Yellow-winged Sphex none but Crickets? Or, according to time, place
and circumstances, does each make up for the lack of her favourite
victuals by others more or less equivalent? To ascertain such facts, if
they exist, would be of the greatest importance, for they would tell us
if the inspirations of instinct are absolute and unchangeable, or if
they vary and within what limits. It is true that the cells of one and
the same Cerceris contain the most varied species of either the
Buprestis or the Weevil group, which shows that the huntress has a
great latitude of choice; but this extension of the hunting-fields
cannot be presumed in the case of the Sphex-wasps, whom I have seen so
faithful to an exclusive victim, always the same for each of them, and
who moreover find, among the Orthoptera, groups that differ very widely
in shape. Nevertheless, I have had the good fortune to come upon one
case, one only, of complete change in the larva’s nourishment; and I
record it the more willingly in the Sphegian archives inasmuch as such
facts, scrupulously observed, will one day form foundation-stones for
any one who cares to build up the psychology of instinct on a solid
basis.
Here are the facts. The scene is enacted on a towing-path along the
Rhône. On one side is the mighty stream, with its roaring waters; on
the other is a thick hedge of osiers, willows, and reeds; between the
two runs a narrow walk, with a carpet of fine sand. A Yellow-winged
Sphex appears, hopping along, dragging her prey. What do I see! The
prey is not a Cricket, but a common Acridian, a Locust! And yet the
Wasp is really the Sphex with whom I am so familiar, the Yellow-winged
Sphex, the keen Cricket-huntress. I can hardly believe the evidence of
my own eyes.
The burrow is not far off: the insect enters it and stores away the
booty. I sit down, determined to wait for a new expedition, to wait
hours if necessary, so that I may see if the extraordinary capture is
repeated. My sitting attitude makes me take up the whole width of the
path. Two raw conscripts heave in sight, their hair newly cut, wearing
that inimitable automaton look which the first days of barrack-life
bestow. They are chatting together, talking no doubt of home and the
girl they left behind them; and each is innocently whittling a
willow-switch with his knife. I am seized with a sudden apprehension.
Ah, it is no easy matter to experiment on the public road, where, when
the long-awaited event occurs at last, the arrival of a wayfarer is
likely to disturb or ruin opportunities that may never return! I rise,
anxiously, to make way for the conscripts; I stand back in the
osier-bed and leave the narrow passage free. To do more would have been
unwise. To say, ‘Don’t go this way, my good lads,’ would have made bad
worse. They would have suspected some trap hidden under the sand,
giving rise to questions to which no reply that I could have made would
have sounded satisfactory. Besides, my request would have turned those
idlers into lookers-on, very embarrassing company in such studies. I
therefore got up without speaking and trusted to my lucky star. Alas
and alack, my star betrayed me: the heavy regulation boot came straight
down upon the ceiling of the Sphex! A shudder ran through me as though
I myself had received the impress of the hobnailed sole.
When the conscripts had passed, I proceeded to save what I could of the
ruined burrow’s contents. The Sphex was there, crushed and mangled; and
with her not only the Locust whom I had seen carried down, but two
others as well, making three Locusts in all instead of the usual
Crickets. What was the reason of this curious change? Were there no
Crickets in the neighbourhood of the burrow and was the distressed Wasp
making up for them with Locusts: a case of Hobson’s choice, in fact? I
hesitate to believe it, for there was nothing about the neighbourhood
to warrant the supposition that the favourite game was absent. Another,
luckier than I, will unriddle this new and unknown mystery. The fact
remains that the Yellow-winged Sphex, either from imperious necessity
or for some reason that escapes me, sometimes replaces her chosen prey,
the Cricket, with another prey, the Locust, presenting no external
resemblance to the first, but itself also an Orthopteron.
The observer on whose authority Lepeletier de Saint-Fargeau says a word
or two touching the habits of this same Sphex witnessed a similar
storing away of Locusts in Africa, near Oran. He surprised a
Yellow-winged Sphex dragging an Acridian along. Was it an accidental
case, like that which I witnessed on the banks of the Rhône? Was it an
exception or the rule? Can there be a lack of Crickets in the country
around Oran and does the Wasp fill their place with Acridians? The
force of circumstances compels me to put the question without finding a
reply.
This is the place to interpolate a certain passage from Lacordaire’s
[27] Introduction to Entomology against which I am eager to protest.
Here it is:
‘Darwin, [28] who wrote a book on purpose to prove the identity of
the intellectual principle actuating men and animals, was walking
one day in his garden when he saw on the path a Sphex who had just
possessed herself of a Fly almost as large as herself. He saw her
cut off the victim’s head and abdomen with her mandibles, keeping
only the thorax, to which the wings remained attached, after which
she flew away; but a breath of wind, striking the Fly’s wings, made
the Sphex spin round and prevented her progress; hereupon she
alighted again on the path, cut off one of the Fly’s wings and then
the other, and, after thus destroying the cause of her
difficulties, resumed her flight with what remained of her prey.
This fact carries with it manifest signs of reasoning power.
Instinct might have led this Sphex to cut off her victim’s wings
before carrying it to her nest, as do some species of the same
genus; but here there was a sequence of ideas and results from
those ideas, which are quite inexplicable unless we allow the
intervention of reason.’
This little story, which so lightly grants reason to an insect, lacks I
will not say truth, but even mere likelihood, not in the act itself,
which I accept without reserve, but in the motives for the act. Darwin
saw what he tells us; only, he was mistaken as to the heroine of the
drama, the drama itself and its significance. He was profoundly
mistaken; and I will prove it.
First of all, the old English scientist was bound to know enough about
the creatures to which he gives these high dignities to call things by
their right names. Let us therefore take the word Sphex in its strict
scientific meaning. Under this assumption, by what strange aberration
was this English Sphex, if any such there be, choosing a Fly for her
prey, when her kinswomen hunt such different game, Orthoptera? Even
admitting what I consider to be inadmissible, a Fly to form the quarry
of a Sphex, other difficulties come crowding up. It is now duly proved
that the Burrowing Wasps do not take dead bodies to their larvæ, but a
victim merely numbed, paralysed. Then what is the meaning of this prey
of which the Sphex cuts off the head, the abdomen, the wings? The stump
carried away is no more than a fragment of a corpse, which would infect
the cell with its rottenness, without being of any use to the larva,
whose hatching is not due for some days yet. It is as clear as
daylight: when making his observation, Darwin did not have before him a
Sphex in the strict sense of the word. Then what did he see?
The term Fly, by which the captured prey is designated, is a very
elastic word, which can be applied to the immense order of Diptera and
which therefore leaves us undecided among thousands of species. The
expression Sphex is most likely also employed in an equally indefinite
sense. At the end of the eighteenth century, when Darwin’s book
appeared, this expression was used to denote not only the Sphegidæ
proper, but particularly the Crabronidæ. Now, among the latter, some,
when storing provisions for their larvæ, hunt Diptera, Flies, the prey
required by the unknown Hymenopteron of the English naturalist. Then
was Darwin’s Sphex a Crabro? No; for these Dipteron-hunters, like the
hunters of any other prey, want game that keeps fresh, motionless but
half-alive, for the fortnight or three weeks required for the hatching
of the eggs and the complete development of the larvæ. All these little
ogres need meat killed that day and not gone bad or even a little high.
This is a rule to which I know of no exception. The word Sphex cannot
be accepted therefore, even with its old meaning.
Instead of a precise fact, really worthy of science, we have a riddle
to read. Let us continue to examine the riddle. Different species of
the Crabro family are so like the Social Wasps in size, in shape and in
their black-and-yellow livery as to deceive any eye unversed in the
delicate distinctions of entomology. To any one who has not made a
special study of such subjects a Crabro is a Common Wasp. May it not
have happened that the English observer, looking at things from a
height and thinking unworthy of strict investigation the tiny fact
which nevertheless was to corroborate his transcendental theories and
help to bestow reason upon an animal, made a mistake in his turn, but
one in the other direction and quite pardonable, by taking a Wasp for a
Crabro? I would almost dare swear so; and here are my reasons.
Wasps, if not always, at least often bring up their family on animal
food; but, instead of accumulating a provision of game in each cell
beforehand, they distribute the food to the larvæ, one by one and
several times a day; they feed them with their mouths, as the father
and mother feed young birds with their beaks. And the mouthful consists
of a fine mash of chewed insects, ground between the mandibles of the
Wasp nurse. The favourite insects for the preparation of this infants’
food are Diptera, especially Common Flies; when fresh meat can be had,
it is a windfall eagerly turned to account. Who has not seen Wasps
boldly enter our kitchens or pounce upon the meat hanging in the
butchers’ shops, to cut off a scrap that suits them and carry it away
forthwith, as spolia opima for the use of the grubs? When the
half-closed shutters admit a streak of sunlight to the floor of a room,
where the Housefly is taking a luxurious nap or polishing her wings,
who has not seen the Wasp rush in, swoop down upon the Fly, crush her
in her mandibles and make off with the booty? Once again, a morsel
reserved for the carnivorous nurselings.
The prey is dismembered now on the spot where captured, now on the way,
now at the nest. The wings, which possess no nutritive value, are cut
off and rejected; the legs, which are poor in juices, are also
sometimes disdained. There remains a mutilated corpse, head, thorax,
abdomen, united or separated, which the Wasp chews and rechews to
reduce it to the pap beloved of the larvæ. I have tried to take the
place of the nurses in this method of rearing grubs on Fly-soup. The
subject of my experiment was a nest of Polistes gallica, the Wasp who
fastens her little rosette of brown-paper cells to the roots of a
shrub. My kitchen-table was a flat piece of marble on which I crushed
the Fly-pap after cleaning the heads of game, that is to say, after
removing the parts that were too tough, the wings and legs; lastly, the
feeding-spoon was a fine straw, at the tip of which the dish was
served, from cell to cell, to each nurseling, which opened its
mandibles just as the young birds in the nest might do. I used to go to
work in exactly the same way and succeeded no better when bringing up
broods of Sparrows, that joy of my childhood. All went well as long as
my patience did not fail me, tried as it was by the cares of so finikin
and absorbing an education.
The obscurity of the enigma gives way to the full light of truth thanks
to the following observation, made with all the deliberateness which
strict precision calls for. In the early days of October, two large
clumps of asters in blossom outside the door of my study became the
meeting-place of a host of insects, among which the Hive-bee and an
Eristalis-fly (Eristalis tenax) predominate. A gentle murmur rose from
them, like that of which Virgil sings:
Sæpe levi somnum suadebit inire susurro. [29]
But, where the poet finds but an incitement to the delights of sleep,
the naturalist beholds a subject for study: all this small folk making
holiday on the last flowers of the year will perhaps furnish him with
some fresh data. Behold me then on observation duty before the two
clumps with their thousands of lilac petals.
The air is absolutely still, the sun blazing, the atmosphere heavy:
signs of an approaching storm, but conditions eminently favourable to
the work of the Hymenoptera, who seem to foresee to-morrow’s rain and
redouble their activity to improve the opportunity. And so the Bees
plunder eagerly, while the Eristales fly clumsily from flower to
flower. At times, the peaceable multitude, filling its crop with
nectar, is disturbed by the sudden invasion of the Wasp, a ravening
insect attracted hither by prey, not honey.
Equally ardent in carnage, but very unequal in strength, two species
divide the hunting between them: the Common Wasp (Vespa vulgaris), who
catches Eristales, and the Hornet (Vespa crabro), who preys on
Hive-bees. The methods are the same in either case. Both bandits
explore the expanse of flowers with an impetuous flight, going
backwards and forwards in a thousand directions, and then make a sudden
rush for the coveted prey, which is on its guard and flies away, while
the kidnapper’s impetus brings her up with a bump against the deserted
flower. Then the pursuit continues in the air, as though a Sparrow-hawk
were chasing a Lark. But the Bee and the Eristalis, by taking brisk
turns, soon baffle the attempts of the Wasp, who resumes her evolutions
above the clustering blossoms. At last, sooner or later, some quarry
less quick at flight is captured. Forthwith, the Common Wasp drops on
to the lawn with her Eristalis; I also instantly lie on the ground,
quietly removing with my hands the dead leaves and bits of grass that
might interfere with my view; and I witness the following tragedy, if I
have taken proper precautions not to scare the huntress.
First, there is a wild struggle in the tangle of the grass between the
Wasp and the Eristalis, who is bigger than her assailant. The Fly is
unarmed, but powerful; a shrill buzz of her wings tells of her
desperate resistance. The Wasp carries a dagger; but she does not
understand the methodical use of it, is unacquainted with the
vulnerable points so well known to the marauders who need a prey that
keeps fresh for long. What her nurselings want is a mess of Flies that
moment reduced to pulp; and, so long as this is achieved, the Wasp
cares little how the game is killed. The sting therefore is used
blindly, without any method. We see it pointed indifferently at the
victim’s back, sides, head, thorax, or belly, according to the chances
of the scuffle. The Hunting Wasp paralysing her victim acts like a
surgeon who directs his scalpel with a skilled hand; the Social Wasp
killing her prey behaves like a common assassin who stabs at random.
For this reason the Eristalis’ resistance is prolonged; and her death
is the result of scissor-cuts rather than dagger-thrusts. When the
victim is duly garrotted, motionless between its ravisher’s legs, the
head falls under a snap of the mandibles; then the wings are cut off at
their juncture with the shoulder; the legs follow, severed one by one;
lastly, the belly is flung aside, but emptied of the entrails, which
the Wasp appears to add to the one favoured portion. This choice morsel
is solely the thorax, which is richer in lean meat than the rest of the
Eristalis’ body. Without further delay the Wasp flies off with it,
carrying it in her legs. On reaching the nest, she will make it into
potted Fly and serve it in mouthfuls to the larvæ.
The Hornet who has caught a Bee acts in much the same manner; but, in
the case of an assailant of her dimensions, the struggle cannot last
long, notwithstanding the victim’s sting. The Hornet may prepare her
dish on the very flower where the capture was effected, or more often
on some twig of an adjacent shrub. The Bee’s crop is first ripped open
and the honey that runs out of it lapped up. The prize is thus a
twofold one: a drop of honey for the huntress to feast upon and the Bee
herself for the larvæ. Sometimes the wings are removed and also the
abdomen; but generally the Hornet is satisfied with reducing the Bee to
a shapeless mass, which she carries off without disdaining anything.
Those parts which have no nutritive value, especially the wings, will
be rejected on arriving at the nest. Lastly, she sometimes prepares the
mash in the actual hunting-field, that is to say, she crushes the Bee
between her mandibles after removing the wings, the legs, and at times
the abdomen as well.
Here then, in all its details, is the incident observed by Darwin. A
Wasp (Vespa vulgaris) catches a big Fly (Eristalis tenax); she cuts off
the victim’s head, wings, abdomen, and legs with her mandibles and
keeps only the thorax, which she carries off flying. But here there is
not the least breath of wind to explain the carving process; besides,
the thing happens in a perfect shelter, in the thick tangle of the
grass. The butcher rejects such parts of her prey as she considers
valueless to her larvæ; and that is all about it.
In short, the heroine of Darwin’s story is certainly a Wasp. Then what
becomes of that rational calculation on the part of the insect which,
the better to contend with the wind, cuts off its prey’s abdomen, head
and wings and keeps only the thorax? It becomes a most simple incident,
leading to none of the mighty consequences which the writer seeks to
deduce from it: the very trivial incident of a Wasp who begins to carve
up her prey on the spot and keeps only the stump, the one part which
she considers fit for her larvæ. Far from seeing the least sign of
reason in this, I look upon it as a mere act of instinct, one so
elementary that it is really not worth expatiating upon.
To disparage man and exalt animals in order to establish a point of
contact, followed by a point of union, has been and still is the
general tendency of the ‘advanced theories’ in fashion in our day. Ah,
how often are these ‘sublime theories,’ that morbid craze of the time,
based upon ‘proofs’ which, if subjected to the light of experiment,
would lead to as ridiculous results as the learned Erasmus Darwin’s
Sphex!