Fabre, Poet of Science

by Georges Victor Legros

Like nearly all insects, the young wasp is born in the larval state, and from the moment of its hatching to the end of its growth--that is to say, for a period of many days--the grub enclosed in its cell can look for no help from without.

Here then is a fascinating problem: either the victims deposited by the mother are dead, and desiccation or putrefaction attacks them promptly, or else they are living, as indeed the larvae require; but then "what will become of this fragile creature, which a mere nothing will destroy, shut in the narrow chamber of the burrow among vigorous beetles, for weeks on end working their long spurred legs; or at grips with a monstrous caterpillar making play with its flanks and mandibles, rolling and unrolling its tortuous folds?"

Such is the thrilling mystery of which Fabre discovered the key.

With inconceivable ingenuity, the victim is seized and thrown to the ground, and the wasp plunges her sting, not at random into the body, which would involve the risk of death, but at determined points, exactly into the seat of those invisible nervous ganglions whose mechanism commands the various movements of the creature.

Immediately after these subtle wounds the prey is paralysed throughout its body; its members appear to be disarticulated, "as though all the springs were broken"; the true corpse is not more motionless.

But the wound is not mortal; not only does the insect continue to live, but it has acquired the strange prerogative of being able to live for a very long period without taking any nourishment, thanks precisely to the condition of immobility, in some sort vegetative, which paralysis confers upon it.

When the hour strikes the hungry larva will find its favourite meat served to its liking; and it will attack this defenceless prey with all the circumspection of a refined eater; "with an exquisitely delicate art, nibbling the viscera of its victim little by little, with an infallible method; the less essential parts first of all, and only in the last instance those which are necessary to life. Here then is an incomprehensible spectacle; the spectacle of an animal which, eaten alive, mouthful by mouthful, during nearly a fortnight, is hollowed out, grows less and less, and finally collapses," while retaining to the end its succulence and its freshness.

The fact is that the mother has taken care to deposit her egg "at a point always the same" in the region which her sting has rendered insensible, so that the first mouthfuls are only feebly resented. But as the enemy goes deeper and deeper "it sometimes happens that the cricket, bitten to the quick, attempts to retaliate; but it only succeeds in opening and closing the pincers of its mandibles on the empty air, or in uselessly waving its antennae." Vain efforts: "for now the voracious beast has bitten deep into the spot, and can with impunity ransack the entrails." What a slow and horrible agony for the paralysed victim, should some glimmer of consciousness still linger in its puny brain! What a terrible nightmare for the little field-cricket, suddenly plunged into the den of the Sphex, so far from the sunlit tuft of thyme which sheltered its retreat!

To paralyse without killing, "to deliver the prey to the larvae inert but living": that is the end to be attained; only the method varies according to the species of the hunter and the structure of the prey; thus the Cerceris, which attacks the coleoptera, and the Scolia, which preys upon the larvae of the rose-beetle, sting them only once and in a single place, because there is concentrated the mass of the motor ganglions.

The Pompilus, which selects a spider for its victim, no less than the redoubtable Tarantula, knows that its quarry "has two nervous centres which animate respectively the movements of the limbs and those of the terrible fangs; hence the two stabs of the sting." [(7/36.)]