All is over. Without one convulsion or sign of pain the ephippiger is rendered henceforward an inert mass. For the second time I deprived the Sphex of the subject operated on, replacing it by the second female at my disposal. The same manœuvres were followed by the same result. Three times, almost without a pause, the Sphex repeated her skilled surgery, first on her own capture, then on those exchanged by me. Will she do so a fourth time on the male which I still have? It is doubtful, not that she is weary, but because the game does not suit her. I have never seen a Sphex with any but female prey, which, filled as they are with eggs, are the favourite food of the larvæ. My suspicion was well founded. Deprived of her third capture, she obstinately refused the male which I offered her. She ran hither and thither with hurried steps, seeking her lost prey. Three or four times she approached the ephippiger, walked round it, cast a disdainful glance at it, and finally flew away. This was not what her larvæ wanted. Experiment reiterated it after twenty years’ interval.
The three females, two stabbed under my eyes, remained mine. All the feet were quite paralysed, [[160]]Whether in its natural position or on its back or side, the creature retains whichever is given it. Constant oscillations of the antennæ, and, at intervals, some pulsations of the stomach and movements of the mouthpieces, are the only sign of life. Motion is destroyed but not feeling, for at the least prick where the skin is thin, the whole body shudders faintly. Perhaps one day physiology will discover in these victims a subject for fine studies on the functions of the nervous system. The Hymenopteron’s sting, incomparably skilful in reaching a given point and inflicting a wound to affect it alone, will replace, with immense advantage, the brutal scalpel of the experimenter, which disembowels where it should lightly touch. Meanwhile, here are the results obtained from the three victims, but from another point of view.
Only movement of the feet being destroyed, there being no injury save that to the nerve centres, the source of motion, the creature perishes, not from its wound, but from inanition. The experiment was tried thus:
Two uninjured ephippigers found in the fields were imprisoned without food, one in the dark, the other in the light. In four days the latter died of hunger, in five the former. This difference of a day is easily explained. In the light the creature is more eager to recover liberty, and as every movement of the animal machine causes a corresponding expenditure of energy, greater activity used up sooner the reserves of the organisation. With light, more agitation and shorter life; in darkness, less movement and longer life; both insects fasted [[161]]equally. One of the three stabbed was kept in the dark and foodless. In this case there was not only darkness and want of food, but the serious wounds inflicted by the Sphex, and yet for seventeen days it perpetually moved its antennæ. As long as this kind of pendulum oscillates, the clock of life has not stopped. On the eighteenth day the creature ceased to wave its antennæ and died. Thus the seriously wounded insect lived in the same conditions as the uninjured one four times as long. What seems as if it should be a cause of death is really the cause of life.
However paradoxical it may at first appear, this result is perfectly simple. Intact, the creature agitates and spends itself; paralysed, it makes only those feeble, internal movements, inseparable from all organised life, and the waste of substance is in proportion to the amount of action employed. In the first case the animal machine works and spends itself; in the second it is at rest and saves itself up. Nourishment no longer repairing loss, the insect in motion spends in four days its food reserves and dies; the motionless one does not spend them, and lives eighteen. Physiology tells us that life is continual destruction, and the Sphex’s victims are a most elegant demonstration of this fact.
One more remark. Fresh food is absolutely necessary to larvæ of the Hymenopteron. If the prey were stored intact, in four or five days it would be a dead body, given up to decay, and the newly hatched grubs would find no food but a corrupted mass. Touched by the sting it can live two or three weeks—a period more than sufficient for the [[162]]egg to hatch and the grub to develop. The paralysis has thus a double result—immobility, so as not to endanger the life of the delicate larvæ, and long preservation of the flesh to assure wholesome nourishment for them. Even when enlightened by science human logic could find nothing better.
My two other ephippigers, stung by the Sphex, were kept in darkness with food. To feed inert creatures, differing only from dead bodies by the perpetual oscillation of their long antennæ, seems at first an impossibility; however, the play of the mouth organs gave me some hope, and I made the attempt. My success surpassed my expectations. There was no question, of course, of offering them a lettuce leaf or any other green thing on which they might have browsed in their normal condition; they were feeble invalids, to be nourished with a feeding-cup, so to say, and broth. I used sugar and water.
The insect being laid on its back, I put a drop of sugared liquid on its mouth with a straw. Instantly the palpi stirred, mandibles and jaws moved; the drop was consumed with evident satisfaction, especially if the fast had been somewhat prolonged. I renewed the dose till it was refused. The repast took place once or twice a day at irregular intervals, as I could not devote myself very much to a hospital of this kind.
Well, with this meagre diet one of the ephippigers lived twenty-one days. This was little longer than the life of the one which I allowed to die of inanition. It is true that twice the insect had had a bad fall, having dropped from the experiment table to the floor through some awkwardness of mine. [[163]]The bruises consequent may have hastened its end. As for the other, exempt from accidents, it lived six weeks. As the nourishment offered, sugar and water, could not indefinitely replace the natural food, it is very probable that it would have lived longer still had its customary diet been available. Thus the point which I had in view is demonstrated: victims pierced by the sting of the Hymenopteron die from inanition and not of their wound. [[164]]