The Life and Love of the Insect

by Jean-Henri Fabre

“We must pluck the leaf, let it fall to the earth, and manipulate it on the ground when it is rightly withered.” [[187]]

The Curculionid is cleverer than we at this sort of business and does not share our opinion. What she says to herself is:

“On the ground, amid the obstruction of the grass, my labours would be impracticable. I want elbow-room; I want the thing to hang in the air, where there are no obstacles of any kind. And there is a more serious consideration: my grub would refuse a rank, dried-up sausage; it insists on food that retains a certain freshness. The scroll which I intend for its consumption must be not a dead leaf, but an impaired leaf, not altogether deprived of the juices with which the tree supplies it. I must wean my joint, but not kill it outright, so that the dying leaf may remain in its place for the few days during which the extreme youth of the worm lasts.”

The mother, therefore, having made her selection, takes up her stand on the stalk of the leaf and there patiently drives in her rostrum, turning it with a persistency that denotes the great importance of this thrust of the bodkin. A little wound opens, a fairly deep wound, which soon becomes a point of mortification.

It is done: the sap-conduits are cut and allow only a scanty proportion to ooze through to the edge. At the injured point, the leaf gives way under the weight; it bends vertically, withers a little and soon acquires the requisite flexibility. The moment has come to work it.

That bodkin-thrust represents, although much less scientifically, the prick of the hunting Hymenopteron’s sting. The latter wants for her offspring a prey now dead, now paralyzed; she knows, with the thoroughness of a consummate anatomist, at what points it behoves her to insert the sting to obtain either sudden [[188]]death or merely a cessation of movement. The Rhynchites requires for her young a leaf rendered flexible ad hoc, half-alive, paralyzed in a fashion, a leaf that can easily be shaped into a scroll; she is wonderfully familiar with the little leaf-stalk, the petiole, in which the vessels that dispense the foliaceous energy are collected in a tiny bundle; and she inserts her drill there, there only and never any elsewhere. Thus, at one blow, without much trouble, she effects the ruin of the aqueduct. Where can the beaked insect have learnt her astute trade as a drier-up of wells?

The leaf of the poplar is an irregular rhombus, a spear-head whose sides widen into pointed pinions. The manufacture of the scroll begins with one of those two lateral corners, the right or left indifferently. Notwithstanding the hanging posture of the leaf, which makes the upper or lower surface equally easy of access, the insect never fails to take its position on the upper side. It has its reasons, dictated by the laws of mechanics. The upper surface of the piece, which is smoother and more flexible, has to form the inside of the scroll; the lower surface, which has greater elasticity because of its powerful veins, must occupy the outside. The statics of the small-brained Weevil agree with those of the scientists.

See her at work. She stands on the rolling-line, with three of her legs on the part already rolled and the three opposite on the part still free. Solidly fixed, on both sides, with her claws and tufts, she obtains a purchase with the legs on the one side, while making her effort with the legs on the other. The two halves of the machine alternate like motors, so that, at one time, the formed cylinder rolls over the free blade and, at another, the free blade moves and is laid upon the scroll already made. [[189]]

There is nothing regular, however, about these alternations, which depend upon circumstances known to the animal alone. Perhaps they merely afford a means of resting for a little while without stopping a work that does not allow of interruption. In the same way, our two hands mutually relieve each other by taking it in turns to carry the burden.

It is impossible to form an exact image of the difficulty overcome, without watching, for hours on end, the obstinate straining of the legs, which tremble with exhaustion and threaten to spoil everything if one of them let go at the wrong moment, or without seeing with what prudence the roller never releases one claw until the five others are firmly fixed. On the one side are three points of support, on the other three points of traction; and the six are shifted, one by one, little by little, without for a moment allowing their connected mechanical system to flag. A single instant of forgetfulness or weariness would cause the rebellious piece to unroll its scroll and escape from the manipulator’s grasp.