ADVANCED THEORIES

There are many species of Sphex, but for the most part strangers to our country. As far as I know, the French fauna contains but three—all lovers of the hot sun in the olive region—namely, Sphex flavipennis, S. albisecta, and S. occitanica. It is not without keen interest that an observer notices in all three of these predatory insects a choice of provender in conformity with the strict laws of entomological classification. To nourish their larvæ each confines itself to Orthoptera. The first hunts grasshoppers, the second crickets, and the third ephippigers.

These prey are so different outwardly that to associate them and seize their analogies, either the practised eye of the entomologist, or the not less expert one of the Sphex is needed. Compare the grasshopper with the cricket: the former has a round, stumpy head; it is short and thickset, quite black, with red stripes on its hind thighs; the latter is grayish and slim, with a small conical head, springing suddenly by unbending its long hind legs, and carrying on this spring with fanlike wings. Now compare both with the ephippiger, who carries his musical instrument on his back, two harshly toned cymbals, shaped like hollow scales, and who drags his obese body heavily along, ringed with pale green and butter colour, and ending in a long dagger. Place these three species side by side, and own with me that to be able to choose creatures so unlike, and yet keep to the same entomological order, the Sphex must have such an eye as not only a fairly observant person, but a practised entomologist would not be ashamed of.

In the presence of these singular predilections, which seem to have limits laid down by some master of classification,—a Latreille for instance—it becomes interesting to inquire if foreign Sphegidæ hunt game of the same order. Unfortunately information as to this is scanty or absolutely nil as regards most species. This regrettable lack is chiefly caused by the superficial method generally adopted. An insect is caught, transfixed with a long pin, fastened in a box with a cork bottom; a ticket with a Latin name is put under its feet, and all is said. This way of looking at entomological history does not satisfy me. It is useless to tell me that such a species has so many joints in its antennæ, so many nerves in its wings, so many hairs on a part of the abdomen or thorax; I do not really know the creature until I have learned its manner of life, its instincts and habits. And observe what a luminous superiority has a description of the latter kind, given in two or three words over long descriptions, sometimes so hard to understand. Let us suppose that you want to introduce Sphex occitanica to me; [118]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 [119]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 [120]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.

SPHEX FLAVIPENNIS ABOUT TO SEIZE GRASSHOPPER

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; [121]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 [122]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 [123]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,1 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, [124]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 [125]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, [126]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 [127]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 [128]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 [129]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 [130]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 [131]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!