What will the Sphex do to obtain this result? Man, and even a learned man, would hesitate, bewilder himself with vain attempts, and perhaps despair of success. Let him come and take a lesson [[153]]from the Sphex, who, without having learned, without ever seeing any one else at work, is thoroughly up in her profession of operator. She knows that under her victim’s skull lies a circlet of nerve-knots, somewhat analogous to the brain of higher animals. She knows too that this chief nerve centre directs the action of the mouth-parts, and, moreover, is the seat of will, without whose command no muscle acts; finally, she is aware that if this kind of brain be injured, all resistance will cease, the insect no longer possessing will-power. As for the method of operation, it is the easiest thing possible for her, and when we have studied at her school we may try in our turn. The sting is no longer employed; in her wisdom the Sphex decides compression to be preferable to the poisoned sting. Let us bow to her decision, for we shall presently see how prudent it is to be convinced of our ignorance compared with the animal’s knowledge. Lest by re-writing my account I fail to do justice to the sublime talent of this masterly operation, I transcribe my notes written on the spot directly after witnessing the exciting spectacle.
The Sphex, finding that her prey resists too much, hooking itself here and there to blades of grass, pauses to perform the singular operation about to be described—a kind of coup de grâce. The Hymenopteron, still astride her victim, makes the articulation in the upper part of the neck, at the nape, to open wide. Then she seizes the neck with her mandibles, groping as far forward as possible under the skull, but making no outward wound, grasps and chews repeatedly the nerve-centres of the head. This renders her victim quite motionless, and incapable [[154]]of the least resistance, whereas previously the feet, though unable to move in the manner necessary for walking, vigorously resisted being dragged along. This is the fact in all its eloquence. While leaving intact the thin, supple membrane of the neck, the insect finds a way into the skull with the point of its mandibles, and bruises the brain. There is neither effusion of blood nor wound, but merely external compression. Of course I kept the paralysed ephippiger under inspection in order to watch the consequences of the operation at my leisure, and equally of course I hastened to repeat on living specimens what the Sphex had taught me. I will now compare my results with hers.
Two ephippigers, whose cervical ganglia I compressed with pincers, fell quickly into a state like that of her victims, only they sounded their harsh cymbals if irritated by the point of a needle, and their feet made some irregular languid movements. The difference in the results obtained doubtless arises from the fact that my victim had not been previously stung in the thoracic ganglia, as those had been which the Sphex had struck in the breast. Allowing for this important point, it will be seen that I made no bad pupil, and imitated my teacher in physiology, the Sphex, not ill. I own that it was not without a certain satisfaction that I found I had done almost as well as the insect does.
As well! What have I just said? Wait a little, and it will be seen that I had to attend the Sphex’s school for many another day. For my two ephippigers speedily died—died outright, and after three or four days I had only decaying bodies under my eyes. [[155]]But the ephippiger of the Sphex? Need I say that ten days after the operation this was perfectly fresh, as it has to be for the larva whose destined prey it is. Yet more, a few hours after the operation under the skull, there reappeared as if nothing had happened movements of an irregular kind in feet, antennæ, palpi, ovipositor, and mandibles—in short, the creature was again in the same state as before the Sphex bit its brain. And the movements went on, only feebler each day. The Sphex had only benumbed her victim for a period amply sufficient to enable her to get it home without resistance, while I, who thought myself her rival, was but a clumsy, barbarous butcher, and killed mine. She, with her inimitable dexterity, compressed the brain scientifically to cause a lethargy of a few hours; I, brutal through ignorance, perhaps crushed this delicate organ, primal source of life, with my pincers. If anything could prevent my blushing at my defeat, it would be that few if any could rival the Sphex in skill.
Ah! now I comprehend why she did not use her sting to injure the ganglia of the neck. A drop of poison instilled here, at the centre of vital force, would annihilate all nerve power, and death would soon follow. But the Sphex does not at all desire death. Dead food by no means suits the larvæ, and still less a body smelling of decay. All that is needed is lethargy, a passing torpor, hindering resistance while the victim is carted along—resistance difficult to overcome and dangerous to the Sphex. This torpor is obtained by the proceeding known in laboratories of experimental science as compression [[156]]of the brain. The Sphex acts like a Flourens who, baring an animal’s brain and pressing on the cerebrum, abolishes at once sensibility, will, intelligence, and motion. The pressure ceases and all reappears. So reappear the remains of life in the ephippiger as the lethargic effects of a skilful pressure go off. The ganglia of the skull, squeezed by the mandibles, but without mortal contusions, gradually recover activity, and put an end to the general torpor. It is alarmingly scientific!
[To face p. 156.
THE SPHEX OF LANGUEDOC DRAGGING TO ITS BURROW AN EPHIPPIGER OF THE VINE
Fortune has her entomological caprices; you run after her and do not come up with her; you forget her, and lo, here she is tapping at your door! How many useless excursions, how many fruitless plans, you made to try to see Sphex occitanica sacrifice her victim! Twenty years go by; these pages are already in the printer’s hands, when, in the first days of this month (August 8, 1878), my son Emile darts into my study. “Quick! quick!” he cries, “a Sphex is dragging along her prey under the plane trees, before the door of the court!” Emile, initiated into the affair by what I had told him, and, better still, by like facts seen in our out-of-door life, was quite right. I hurried away, and saw a splendid S. occitanica dragging a paralysed ephippiger by the antennæ. She moved toward the poultry yard, seemingly desirous of scaling the wall, to make her burrow under some roof tile. Some years before I had seen a similar Sphex accomplish the ascent with her game, and choose her domicile under the arch of an ill-joined tile. Perhaps this new one was descended from her whose difficult ascent I have chronicled. A like feat is probably about to be [[157]]repeated, and this time before numerous witnesses, for all the household working under the shade of the plane trees formed a circle round the Sphex. They wonder at the audacious tameness of the insect, noways disturbed by the gallery of interested spectators. All are struck by her proud and robust bearing, as, with raised head and the victim’s antennæ well grasped by her mandibles, she drags after her the enormous burden. I alone among the spectators feel some regret. “Ah, had I but some live ephippigers!” I could not help saying, without the least hope of seeing my wish realised. “Live ephippigers!” replied Emile; “why, I have some quite fresh, caught this morning.” Four steps at a time he flew upstairs to his little study, where barricades of dictionaries enclosed a park wherein was brought up a fine caterpillar of Sphinx euphorbiæ. He brought back three ephippigers as good as heart could wish—two females and one male. How came these insects at hand just at the right moment for an experiment vainly tried twenty years before? This is another story. A southern shrike had nested on one of the tall plane trees in the avenue. Some days before the Mistral, the rude wind of our parts, had blown so violently that branches bent as well as reeds, and the nest overturned by the undulations of its branch let fall the four nestlings it contained. The next day I found the brood on the ground—three killed by the fall, the fourth still alive. The survivor was entrusted to Emile, who thrice a day went cricket-hunting on the turf in the neighbourhood to feed his charge. But crickets are not very large, while the nestling’s appetite was. Something [[158]]else was preferred—ephippigers, collected from time to time on the dry stalks and prickly leaves of the Eryngium. The three insects brought me by Emile came from the shrike’s larder. My pity for the fallen nestlings had brought me this unhoped-for good luck.
Having made the circle of spectators draw back and leave free passage for the Sphex, I took away her prey with my pincers, giving her immediately in exchange one of my ephippigers with an ovipositor like that of the one abstracted. Stamping was the only sign of impatience shown by the bereaved Hymenopteron. She ran at the new prey, too corpulent to try to avoid pursuit, seized it with her mandibles by the saddle-shaped corslet, got astride, and curving her abdomen, passed its end under the ephippiger’s thorax. There doubtless the stings are given, but the difficulty of observation prevents me from telling how many. The ephippiger—gentle victim—lets itself be operated on unresistingly, like the dull sheep of our slaughter-houses. The Sphex takes her time and manœuvres her lancet with a deliberation favourable to the observer; but the prey touches the ground with the whole lower part of its body, and what happens there cannot be seen. As for interfering and lifting the ephippiger a little so as to see better, it is not to be thought of; the murderess would sheath her weapon and retire. The next act is easy to observe. After having stabbed the thorax, the end of the abdomen appears under the neck, which she forces widely open by pressing the nape. Here the sting enters with marked persistence, as if more effective than elsewhere. One [[159]]might suppose that the nerve centre struck was the lower part of the œsophagean collar, but the persistence of movement in the mouthpieces, mandibles, jaws, and palpi, animated by this source of nerve power, shows that this is not so. Through the neck the Sphex simply reaches the thoracic ganglia, or at least the first, more easily attainable through the thin skin of the neck than through the integuments of the chest.