"Now, to deprive the caterpillar of means of escape, and to render it motionless, will the Hymenopteron [that's the wasp] dart its sting into each of the eight rings provided with feet? Especially will it do so when the prey is small and weak? Certainly not: a single stab will suffice if given in a central spot, whence the torpor produced by the venomous droplet can spread gradually with as little delay as possible into the midst of those segments which bear feet. There can be no doubt which to choose for this single inoculation; it must be the fifth or sixth, which separate the two groups of locomotive rings. The point indicated by rational deduction is also the one adopted by instinct. Finally, let us add that the egg of the Ammophila is invariably laid on the paralyzed ring. There, and there alone, can the young larva bite without inducing dangerous contortions; where a needle prick has no effect, the bite of a grub will have none either, and the prey will remain immovable until the nursling has gained strength and can bite farther on without danger."
But some Ammophilas catch much larger caterpillars than the inch-long, slender, little loopers. Fabre found a wasp dragging to its nest a caterpillar weighing fifteen times the weight of the wasp. Does one stab suffice for such a giant caterpillar? Here is what Fabre saw: An Ammophila was noticed scratching in the ground around the crown of a plant. She was "pulling up little grass roots, and poking her head under the tiny clods which she raised up, and running hurriedly, now here, now there, round the thyme, visiting every crack which gave access under it; yet she was not digging a burrow, but hunting something hidden underground, as was shown by manœuvres like those of a dog trying to get a rabbit out of its hole. And presently, disturbed by what was going on overhead and closely tracked by the Ammophila, a big gray worm made up his mind to quit his abode and come up to daylight. It is all over with him; the hunter is instantly on the spot, gripping the nape of his neck and holding on in spite of his contortions. Settled on the monster's back, the Ammophila bends her abdomen, and, methodically, deliberately—like a surgeon thoroughly familiar with the anatomy of his subject—plunges a lancet into the ventral surface of every segment, from the first to the last. Not one ring is omitted; with or without feet each is stabbed in due order from the front to the back."
This is what the patient, careful observer saw, with all the "leisure and ease required for an irreproachable observation." "The wasp acts," says Fabre, "with a precision of which science might be jealous; it knows what man but rarely knows; it is acquainted with the complex nervous system of its victim, and keeps repeated stabs for those with numerous ganglia. I said 'It knows; is acquainted'; what I ought to say is, 'It acts as if it did.' What it does is suggested to it; the creature obeys, impelled by instinct, without reasoning on what it does. But whence comes this sublime instinct? Can theories of atavism, of selection, of the struggle for life, interpret it reasonably?"
When I had finished reading this to Mary she looked up and said softly: "Of course I don't understand all this that he says about 'avatism and selection' and so on, but I think the wasp knows. Don't you?"
"Mary," I reply promptly, "the word is 'atavism,' not 'avatism,' please remember!"
"I hope I can," said Mary.
