The Life of the Weevil

by Jean-Henri Fabre; Alexander Teixeira de Mattos

A stupendous task for a speck of albumen. But this feeble speck boasts a set of carpenter’s tools; its mandibles, a pair of fine chisels, received the necessary temper while their owner was still in the egg. The grub sets to work immediately. By the following day, through a tiny aperture which would hardly admit the point of a fair-sized needle, it has entered into the promised land and is in possession of the kernel.

Another stroke of luck partly tells me the use of the central cone pierced chimney-fashion. The mother, while sinking the pit in the flesh of the sloe, drinks the juices that ooze out and eats the pulp. This is the most direct manner of getting rid of the refuse without interrupting her work. When she is digging in the surface of the stone, the cup intended to receive the egg, she leaves in place the fine dust resulting from her labours, an excellent material as bedding for the egg but useless as food.

And what does the maggot in its turn do with its sawdust as it deepens the pit in order to reach the kernel? To scatter the rubbish round about is impossible: there is no room; to put it away [[172]]in its stomach is even less feasible: it cannot make its first mouthfuls of this dry flour while waiting for the milk-food of a kernel.

The new-born grub has a better method. With a few heaves of its back, it thrusts the litter of rubbish outside, through the chimney in the cone. I have indeed caught sight of a white, powdery speck at the top of the central cone. This tunnelled cone therefore is a lift which carries away the rubbish of the excavation.

But the use of the curious building cannot be limited to this: the ever-thrifty insect has not gone to the pains of building a tall, hollow obelisk with the sole object of preparing a thoroughfare for the atoms of dust that hamper the grub in its labours. The same result could be obtained with less trouble; and the Weevil is too sensible to construct the complex when the single would suffice. Let us look at things more closely.

Evidently the egg, laid in a cup on the surface of the stone, needs a protecting roof. Moreover, the grub, which will presently be working at the bottom of its cup to reach the kernel, will require a refuse-shoot in its restricted quarters. A small, shallow dome, with a window to get rid of the sweepings, would, it seems, fulfil all the requisite conditions. Then why the luxury of this pyramidal chimney which rises to the topmost level of the pit, as a cone in eruption rises in the centre of a volcanic crater? [[173]]

The craters in the sloes have their lava, that is, their flow of gum, which trickles from the various points injured and then hardens into blocks. This flood stops up every hole at which the insect has merely fed. The large pits with the central cones, on the other hand, have no gum or show only a few scanty drops of it on their walls.

The mother, it is obvious, has taken certain precautions to defend the home of the egg against the inroads of the gum. In the first place, she has enlarged the cavity to keep the egg at a due distance from the treacherous wall oozing with viscidity; she has moreover dug the pulp down to the stone and has thoroughly stripped a perfectly clean surface from which nothing dangerous can now exude.

This is not yet enough: though distant and rising perpendicularly from the stripped area, the walls of the pit still give cause for alarm. In some sloes under certain conditions, they will perhaps yield a superabundance of gum. The only means of averting the danger is to raise above the egg a barricade as high as the brink of the crater and capable of arresting the flow. This is the reason for the central cone. If there is a copious eruption, the gum will fill the ringed space, but at least it will not cover the spot where the egg lies. The tall, insubmersible obelisk is therefore almost ingeniously-contrived defensive structure.

This obelisk is hollow along its axis. We have [[174]]seen it serving as a lift for the rubbish which the young grub throws out when deepening its natal basin and converting it into a passage which gives access to the kernel. But this is a very secondary function; it has another of greater importance.