“And then what happens?” Emile inquired.
“The ichneumon gone, the pricked caterpillars soon recover their composure and resume their eating. The prick, not being poisoned with venom, causes very little pain; besides, it would take a good deal more than that to affect their appetites. All goes well for a few days, as long as the eggs are unhatched.”
“Do those eggs hatch in the caterpillar’s body?”
“Yes.”
“And as soon as they have hatched do the little larvæ set to work devouring the caterpillar’s inside?”
“That’s the way of it.”
“What an awful stomach-ache for the poor caterpillars!”
“Nevertheless, even with such pain as may result from the gradual consumption of their flesh, the caterpillars continue to eat as if nothing had happened, the satisfaction of their appetite making them forget their sufferings, so imperious is their need of food. And furthermore, for a reason that I will [[355]]explain, the parasitic worms observe a certain caution in their ravages.
“In the body of every animal are certain organs more indispensable than others for the maintenance of life, and if they are injured, even though slightly, death follows. Such are the heart and brain in the higher animals. In a caterpillar’s body there are, it is true, no heart or brain like those of animals higher in the scale; but there are analogous organs just as necessary to the ongoing of the vital functions. If the ichneumon’s larvæ, in eating their victim’s flesh, were to injure these vital organs, the caterpillar would quickly die, and the larvæ would perish too, for they must have fresh meat, not decayed flesh. It is a question of life or death to them whether the grubs avoid biting in the wrong place or not. The caterpillar must live in order that they may live; it must prolong its miserable existence until they are ready for their metamorphosis. So the little parasites scrupulously respect any organ indispensable to the maintenance of life and feed on the rest; guided by instinct, they distinguish admirably between what they may attack and what they must let alone. A time comes, however, when because of their approaching transformation they do not need to exercise further self-restraint, and they accordingly devour the parts until then left intact. Thereupon the caterpillar dies, being reduced to an empty skin which the larvæ promptly abandon in order to spin their cocoons and turn into nymphs and finally into ichneumons. [[356]]
“Sometimes the caterpillar is spared until it has shut itself up in a case and turned into a chrysalis, with the result that the larvæ inhabiting the caterpillar find themselves, without any labor on their part, provided with snug quarters for the winter. Out of every such wormy chrysalis, consumed to the skin, there emerges in the spring, not a butterfly, but a swarm of ichneumons.”