Insect life: Souvenirs of a naturalist

by Jean-Henri Fabre

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! [[132]]