There are many species of Sphex, but for the most part strangers to our
country. As far as I know, the French fauna contains but three—all
lovers of the hot sun in the olive region—namely, Sphex flavipennis, S.
albisecta, and S. occitanica. It is not without keen interest that an
observer notices in all three of these predatory insects a choice of
provender in conformity with the strict laws of entomological
classification. To nourish their larvæ each confines itself to
Orthoptera. The first hunts grasshoppers, the second crickets, and the
third ephippigers.
These prey are so different outwardly that to associate them and seize
their analogies, either the practised eye of the entomologist, or the
not less expert one of the Sphex is needed. Compare the grasshopper
with the cricket: the former has a round, stumpy head; it is short and
thickset, quite black, with red stripes on its hind thighs; the latter
is grayish and slim, with a small conical head, springing suddenly by
unbending its long hind legs, and carrying on this spring with fanlike
wings. Now compare both with the ephippiger, who carries his musical
instrument on his back, two harshly toned cymbals, shaped like hollow
scales, and who drags his obese body heavily along, ringed with pale
green and butter colour, and ending in a long dagger. Place these three
species side by side, and own with me that to be able to choose
creatures so unlike, and yet keep to the same entomological order, the
Sphex must have such an eye as not only a fairly observant person, but
a practised entomologist would not be ashamed of.
In the presence of these singular predilections, which seem to have
limits laid down by some master of classification,—a Latreille for
instance—it becomes interesting to inquire if foreign Sphegidæ hunt
game of the same order. Unfortunately information as to this is scanty
or absolutely nil as regards most species. This regrettable lack is
chiefly caused by the superficial method generally adopted. An insect
is caught, transfixed with a long pin, fastened in a box with a cork
bottom; a ticket with a Latin name is put under its feet, and all is
said. This way of looking at entomological history does not satisfy me.
It is useless to tell me that such a species has so many joints in its
antennæ, so many nerves in its wings, so many hairs on a part of the
abdomen or thorax; I do not really know the creature until I have
learned its manner of life, its instincts and habits. And observe what
a luminous superiority has a description of the latter kind, given in
two or three words over long descriptions, sometimes so hard to
understand. Let us suppose that you want to introduce Sphex occitanica
to me; you describe the number and arrangement of the wing nerves, and
you speak of cubital and recurrent nerves; next follows the written
description of the insect. Here it is black, there rusty red, smoky
brown at the wing tips, at such a spot it is black velvet, at another
silvery down, and at a third smooth. It is all very precise, very
minute—one must grant that much justice to the clear-sighted patience
of him who describes; but it is very long, and besides, not always easy
to follow, to such a degree that one may be excused for being sometimes
a little bewildered, even when not altogether a novice. But add to the
tedious description just this—hunts ephippigers, and with these two
words light shines at once; there can be no mistake about my Sphex,
none other selecting that prey. And to illuminate the subject thus,
what was needed? Real observation, and not to let entomology consist in
rows of impaled insects. But let us pass on and consider such little as
is known as to the manner in which foreign Sphegidæ hunt. I open
Lepeletier de St. Fargeau’s History of Hymenoptera, and find that on
the other side of the Mediterranean, in our Algerian provinces, S.
flavipennis and S. albisecta have the same tastes that characterise
them here. In the land of palms they catch Orthoptera just as they do
in the land of olives. Although separated by the width of the sea,
these sporting fellow citizens of the Kabyle and the Berber hunt the
same game as their relatives in Provence. I see mentioned a fourth
species, S. afra, as hunting crickets round Oran. Moreover, I have a
recollection of having read—I know not where—of a fifth species, which
makes war on crickets upon the steppes in the neighbourhood of the
Caspian Sea. Thus in the lands bordering the Mediterranean we have five
different species whose larvæ all live on Orthoptera.
Now let us cross the equator, and descend in the other hemisphere to
the Mauritius and Réunion Islands, and we shall find, not a Sphex but a
Hymenopteron, nearly allied, of the same tribe, Chlorion or Ampulex,
chasing the horrid kakerlacs, the curse of merchandise in ships and
colonial ports. These kakerlacs are none other than cockroaches, one
species of which haunts our houses. Who does not know this stinking
insect, which, thanks to its flat shape, like that of an enormous bug,
insinuates itself into gaps in furniture and partitions, and swarms
everywhere that there is food to devour. Such is the cockroach of our
houses—a disgusting likeness of the not less disgusting prey beloved by
the Chlorion. Why does a near relation of our Sphex select the kakerlac
as prey. The reason is simple: With its buglike form the kakerlac is an
Orthopteron by the same rights as the grasshopper, ephippiger, and
cricket. From these six examples, the only ones known to me, and from
such widely distant localities, may we not conclude that all Sphegidæ
hunt Orthoptera? Without adopting so sweeping a conclusion, one at
least sees what the usual food of their larvæ must be.
There is a reason for this surprising choice. What is it? What motives
fix a diet which in the strict limits of one and the same entomological
order is now composed of ill-smelling kakerlacs, now of dry, but
well-flavoured crickets, and in yet another of plump grasshoppers, or
corpulent ephippigers? I confess that to me it is incomprehensible, and
I leave the problem to others. Observe, however, that the Orthoptera
rank among insects as the ruminants do among mammalia. Endowed with a
mighty paunch and a placid character, they feed on herbage, and easily
get corpulent. They are numerous and met with everywhere, slow of gait,
and thus easy to catch, and, moreover, of a size just right for prey.
Who can say if the Sphegidæ—vigorous hunters which require a large
prey—do not find in these ruminants among insects what we find in our
domestic ruminants—the sheep and ox, peaceful victims rich in flesh?
This is, however, a mere supposition.
I have more than a supposition in another case, equally important. Do
the consumers of Orthoptera ever vary their diet? Should their
favourite game fail, can they do with another? Does S. occitanica think
that except a fat ephippiger, there is nothing in the wide world worth
eating. Does S. albisecta admit nothing but crickets to her table, and
S. flavipennis only grasshoppers? Or according to time, place, and
circumstance, does each replace the favourite food by some equivalent?
It would be of the highest importance to bring forward such facts if
they exist, as they would tell us whether the suggestions of instinct
are absolute and immutable, or if they vary, and within what limits. It
is true that in the cell of a Cerceris are buried most varied species
of Buprestids or of the Weevil group, which shows that she has a great
latitude of choice; but such an extension of hunting ground cannot be
supposed for the Sphex, which I have found so faithful to one exclusive
prey, invariable for each species, and which, moreover, finds among the
Orthoptera kinds of very different shapes. I have, however, had the
good fortune to meet with one case—only one—of complete change in the
larva’s food, and I mention it the more willingly in the archives of
the Sphegidæ because such facts, scrupulously observed, will one day be
corner-stones for him who may desire to build the psychology of
instinct on solid foundations.
This is my fact. The scene is on a jetty by the Rhône. On one side is
the great river, with its thunder of waters, on the other, a dense
thicket of osiers, willows, and reeds, and between the two a narrow
path with a bed of fine sand. A yellow-winged Sphex appears, hopping
and dragging its prey along. What do I see! It is no grasshopper, but a
common Acridian! And yet the Hymenopteron really is the Sphex so well
known to me (S. flavipennis), the energetic huntress of grasshoppers! I
can hardly believe my eyes. The burrow is not far off; she enters and
stores her booty. I seat myself, determined to await a new
expedition—wait hours if need be to see if so extraordinary a capture
is repeated. Seated there I occupy the whole width of the path. Two
simple conscripts come up, new-clipped, with that incomparable,
automaton-look conferred by the first days of barrack life. They are
chattering together—no doubt talking of their homes and the girls they
left behind them; each is peeling a willow switch with a knife. A fear
seizes me; ah! it is not easy to try an experiment on the public way,
where, when some fact watched for during long years does present
itself, a passer-by may disturb or annihilate chances which may never
occur again! I rise anxiously to make way for the conscripts; I
withdraw into the osier bed, and leave the narrow way free. To do more
was not prudent; to say, “My good fellows, do not go that way,” would
have made bad worse. They would have supposed some snare hidden in the
sand, and questions would have arisen to which no reply that would
satisfy them could have been given. My request, moreover, would have
turned these idlers into lookers-on, very embarrassing company in such
studies, so I resolved to say nothing, and trust to my luck. Alas!
alas! my star betrayed me. The heavy regulation boot was planted
exactly on the Sphex’s roof. A shudder ran through me as though I had
myself received the impress of the iron heel.
The conscripts gone I proceeded to the salvage of the contents of the
ruined burrow. There was the Sphex mutilated by the pressure, and there
were not only the cricket which I saw carried down, but two
others—three crickets in all instead of the usual grasshoppers. What
was the reason of this strange variation? Were there no grasshoppers
near the burrow, and did the distressed Hymenopteron do the best she
could with Acridians—contenting herself as it were with blackbirds for
want of thrushes, as the proverb says? I hesitate to believe it, for
there was nothing in the neighbourhood to denote absence of her
favourite game. Some happier means may unriddle this new problem. In
any case S. flavipennis, either from imperious necessity, or from
motives unknown to me, sometimes replaces her favourite prey, the
grasshopper, by another, the Acridian, altogether unlike outwardly to
the former, but still an Orthopteron.
The observer on whose authority Lepeletier de St. Fargeau speaks of
this Sphex’s habits witnessed in Africa, near Oran, a similar storing
of Acridians. S. flavipennis was surprised by him dragging along an
Acridian. Was it an accidental case, like the one seen by me on the
banks of the Rhône? Was it the exception, or was it the rule? Were
grasshoppers wanting around Oran, and did the Hymenopteron replace them
by Acridians? Circumstances compel me to ask the question without
finding a reply.
Here should be interpolated a certain passage from Lacordaire’s
Introduction to Entomology, [6] against which I long to raise my voice
in protest. Here it is: “Darwin, who has written a book on purpose to
prove the identity of the intellectual principle which produces action
in man and animals, walking one day in his garden noticed on the ground
in a shady walk a Sphex which had just caught a fly nearly as big as
itself. He saw it cut off with its mandibles the victim’s head and
abdomen, keeping only the thorax, to which the wings remained attached.
It then flew away, but a breath of wind striking the fly’s wings
twirled the Sphex round, and hindered its progress. Thereupon it lit
again on the walk, cut off first one wing and then the other from the
fly, and having thus removed the cause of its difficulties, flew off
with the remainder of its prey. This fact indicates manifest signs of
reasoning. Instinct might have induced the Sphex to cut off the wings
of its victim before transporting it to the nest, as do some species of
the same genus, but here were consecutive ideas and results of those
ideas quite inexplicable, unless one admits the intervention of
reason.”
This little story, which so lightly bestows reason on an insect, is
wanting not only in truth but in mere probability—not in the act
itself, which I do not question at all, but in its motives. Darwin saw
what he relates, but he was mistaken as to the hero of the drama; as to
the drama itself, and as to its meaning—profoundly mistaken, and I can
prove it.
First and foremost the old English savant ought to have known enough
about the creatures which he so freely ennobles to call things by their
right name. Let us therefore take the word Sphex in its strictly
scientific sense. Then by what strange aberration does this English
Sphex, if English ones there are, choose a fly as its prey when its
fellows hunt such different game—namely, Orthoptera? And even if we
grant, what I consider inadmissible, a Sphex catching flies, other
difficulties crowd in. It is now proved on evidence that the burrowing
Hymenoptera do not carry dead bodies to their larvæ, but merely prey
benumbed and paralysed. What, then, is the meaning of this prey whose
head, abdomen, and wings are cut off? The torso carried away is but a
portion of a corpse that would infect the cell and be useless to the
larva, not yet to be hatched for several days. It is perfectly clear
that Darwin’s insect was not a Sphex, strictly speaking. What, then,
did he see? The word fly, by which the captured prey is designated, is
a very vague term which might be applied to the greater part of the
immense order of Diptera, and therefore leaves us uncertain among
thousands of species. Probably the name of Sphex is used equally
vaguely. When Darwin’s book appeared, not only the real Sphegidæ were
so called, but also the Crabronides. Now among these last some provide
their larvæ with Diptera, the prey required for the unknown
Hymenopteron of the English naturalist. Was then Darwin’s Sphex a
Crabro? No, for these hunters of Diptera, like the hunters of any other
game, require prey which will keep fresh and motionless, but half alive
for the fortnight or three weeks needed before the eggs hatch, and for
the complete development of the larvæ. These little ogres require meat
not decayed, nor even high, but fresh. I know no exception to this
rule, and therefore the name Sphex cannot have been used in its old
meaning.
Instead of dealing with a precise fact, really worthy of science, we
have an enigma to find out. Let us continue to examine it. Several of
the Crabronides are so like wasps in figure and form and shape and
their yellow and black livery, that they might deceive any eye
unpractised in the delicate distinctions of entomology. In the eyes of
every one who has not made a special study of the subject, a Crabro is
a wasp. Is it not possible that the English observer, regarding things
from a lofty height, and considering unworthy of close examination the
petty fact, which, however, was to serve to corroborate his
transcendent views and grant reason to animals, may have in his turn
committed an error, conversely and very excusably, by taking a wasp for
one of the Crabronides? I could almost declare it is so, and for the
following reasons. Wasps, if not always at any rate frequently, bring
up their family on animal food, but instead of provisioning each cell
they distribute nourishment singly to the larvæ, and several times in
the day; feeding them from their mouths with soft pap, as the father
and mother do young birds. This pap consists of mashed insects, ground
down in the jaws of the nursing wasp; the insects preferred for it are
Diptera, especially the common fly; if fresh meat offers itself it is
largely used. Who has not seen wasps penetrate into our kitchens, or
dart on the joints in a butcher’s shop, cut off some scrap of flesh
which suits them, and carry away a tiny spoil for the use of their
larvæ? When half-closed shutters allow a ray of light to fall on the
floor of a room where the house-fly is taking a comfortable nap, or
brushing its wings, who has not seen a wasp suddenly enter, pounce upon
it, crush it in its jaws, and flee with the booty? This again is a
dainty meal for the carnivorous nurslings. Sometimes the prey is at
once dismembered, sometimes on the way, sometimes at the nest. The
wings, in which there is no nourishment, are cut off and rejected; the
feet, poor in juices, are also sometimes disdained. There remains a
mutilated corpse, head, thorax, abdomen, or part thereof, which the
wasp chews repeatedly to reduce into a pap for the larvæ to feast on. I
have tried to bring up larvæ myself on fly-paste. The experiment was
tried on a nest of Polistes gallica, the wasp which fixes her little
rose-shaped nest of gray paper cells on the bough of some shrub. My
kitchen apparatus was a piece of marble slab, on which I crushed up the
fly-paste after cleaning my game—in other words, having taken away the
parts which were too tough—wings and feet; and the feeding-spoon was a
slender straw, at the end of which, going from cell to cell, I handed
the food to larvæ, which opened their mouths just like young birds in a
nest. I did just the same and succeeded just as well in the days when I
used to bring up broods of sparrows—that joy of childhood! All went on
as well as heart could wish as long as my patience held out against the
trials of a bringing up so absorbing and full of small cares.
The obscurity of the enigma is replaced by the full light of truth,
thanks to the following observation, made with all the leisure that a
strict precision demands. In the first days of October two great clumps
of blossoming asters at the door of my study became the rendezvous of a
quantity of insects, among which the hive bee and Eristalis tenax were
the most numerous. A gentle murmur arose from them, like that of which
Virgil wrote, “Sæpe levi somnum suadebit inire susurro.” But if the
poet finds in it only an invitation to slumber, the naturalist finds a
subject for study; these small folk luxuriating on the last flowers of
the year may perhaps afford him some new information. So I am on the
watch before the two clumps with their countless lilac corollas.
The air is perfectly still; the sun burns, the air is heavy—all signs
of a coming storm; but these are conditions eminently favourable to the
labours of the Hymenoptera, which seem to foresee to-morrow’s rain, and
redouble their activity in turning the present hour to profit. The bees
work ardently; the Eristalis fly clumsily from flower to flower. Now
and then, into the midst of the peaceable throng who are swilling
nectar, bursts a wasp, insect of rapine, attracted there by prey, not
honey.
Equally ardent in carnage, but unequal in strength, two species divide
the chase; the common wasp, Vespa vulgaris, which catches Eristalis,
and the hornet, V. crabro, which hunts hive bees. Both carry on the
chase in the same way. They fly fast backwards and forwards over the
flowers, and suddenly throw themselves on the prey which is on its
guard and flies off, while their impulse carries them headfirst against
the deserted flower. Then the chase is continued in the air, just as a
sparrowhawk hunts a lark. But bee and Eristalis foil the wasp by their
sudden turns, and it goes back to fly above the blossoms. By and by
some insect less swift to escape gets captured. The common wasp
instantly drops on the turf with its Eristalis, and I drop down too at
the same moment, putting aside with both hands the dead leaves and bits
of grass which might hinder my seeing clearly, and this is the drama
which I behold, if proper precautions be taken not to scare the wasp.
First there is a wild struggle among the blades of grass between the
wasp and an Eristalis bigger than itself. The Dipteron is unarmed but
strong, and a shrill hum tells of desperate resistance. The wasp
carries a poignard, but does not know how to use it methodically, and
is ignorant of the vulnerable points so well known to the hunters which
need flesh that must keep good for a considerable time. What its
nurslings want is a paste made of flies newly crushed, so that it
matters little how the game is killed. The sting is used
blindly—anywhere, pointed at the head, sides, thorax, or under part of
the victim, as chance directs while the two wrestle. The Hymenopteron,
paralysing its victim, acts like the surgeon, who directs his scalpel
with a skilled hand; the wasp when slaying acts like a common assassin
stabbing blindly in a struggle. Thus the resistance of the Eristalis is
long, and its death rather the result of being cut up by a pair of
scissors than of stabs with a dagger. These scissors are the wasp’s
mandibles, cutting, disembowelling, and dividing. When the game has
been garroted and is motionless between the feet of its captor, a bite
of the mandibles severs the head from the body; then the wings are
shorn off at the junction with the shoulder; the feet follow, cut off
one by one; then the abdomen is rejected, but emptied of its interior,
which the wasp appears to preserve with her favourite part, the thorax,
which is richer in muscle than the rest of the Eristalis. Without
further delay she flies off, carrying it between her feet. Having
reached the nest she will mash it up and distribute it to the larvæ.
The hornet having seized a bee acts almost in the same way, but it is a
giant of a robber, and the fight cannot last long, despite the sting of
the victim. Upon the very flower where the capture was made, or oftener
on some twig of a neighbouring shrub, the hornet prepares its dish.
First of all the bag of the bee is torn open, and the honey lapped up.
The prize is thus twofold—that of a drop of honey, and the bee itself
for the larvæ to feast on. Sometimes the wings are detached, as well
as the abdomen, but generally the hornet is contented with making a
shapeless mass of the bee which is carried off whole. It is at the nest
that the parts valueless for food are rejected, especially the wings.
Or the paste may be prepared on the spot, the bee being crushed at once
between the hornet’s mandibles, after wings, feet, and sometimes the
abdomen are cut off.
Here, then, in all its details is the fact observed by Darwin. A wasp,
Vespa vulgaris, seizes Eristalis tenax; with her mandibles she cuts off
head, wings, and abdomen of the victim, keeping only the thorax, with
which she flies away. But we need no breath of air to explain why they
were cut off; the scene takes place in perfect shelter, in the grass.
The captor rejects such parts as are useless for the larvæ, and that is
all.
In short, a wasp is certainly the heroine of Darwin’s story. What,
then, becomes of that reasoning which made the creature, in order
better to contend with the wind, deprive its prey of abdomen, head, and
wings, leaving only a thorax? It becomes a very simple fact, whence
flow none of the great consequences that were drawn from it,—the very
trivial fact that a wasp began at once to cut up her prey, and only
considered the trunk worthy of her larvæ. Far from discovering the
least indication of reasoning, I see only an act of instinct so
elementary that it is really not worth consideration.
To abase man and exalt animals in order to establish a point of
contact, then a point of fusion,—such has been the usual system of the
advanced theories now in fashion. Ah! how often do we not find in these
sublime theories that are a sickly craze of our day, proofs
peremptorily asserted, which under the light of experiment would appear
as absurd as the Sphex of the learned Erasmus Darwin!
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