A small head, a slender snout, a dress of ashen grey sprinkled with brown, flat wing-cases, a squat thick-set figure, with two large black dots on the flat of the tail: there you have a rough sketch of my visitor. The vanguard arrives by the end of the first fortnight in May.
The Weevils settle on the flowers, which are like so many white Butterflies’ wings: I see some installed at the foot of the upper petal, I see some hidden in the casket of the keel. Others, more numerous these, explore the blossoms and take possession of them. The laying-time has not yet come. It is a mild morning; the sun is hot without being oppressive. This is the moment for nuptial exploits and for raptures amid the splendour of the light. Life therefore is enjoyed for a little while. Couples form, soon part and soon come together again. When the heat grows too [[189]]great, towards the middle of the day, each Jack and Jill retire into the shade, in a fold of the flower whose secret recesses they know so well. To-morrow they will resume the festival and the next day too, until the pod, splitting the sheath of its keel, appears outside, more and more swollen from day to day.
A few pregnant mothers, harder-pressed than the rest, confide their eggs to the growing pod, as it issues flat and tiny from its floral scabbard. These eggs laid prematurely, pushed out perhaps through the exigencies of an ovary which can wait no longer, seem to me in serious danger. The seed in which the grub is to make its home is as yet but a feeble granule, without substance and without floury contents. No Weevil-larva would ever find an adequate meal there, unless by biding its time until the seed ripened.
But is the grub, once hatched, capable of long fasting? It is doubtful. The little that I have seen tells me that the new-born larva begins eating with all speed and, if it cannot do so, dies. I therefore regard as lost the eggs laid upon immature pods. The prosperity of the race will hardly suffer, thanks to the Weevil’s fertility. Moreover, we shall see presently with what reckless prodigality she scatters her germs, most of which are doomed to perish.
The bulk of the mother’s work is finished by the end of May, when the pods begin to bulge [[190]]with protuberances revealing the pressure of the peas, which have now attained their final size, or very nearly. I was anxious to see the Bruchus at work, in her quality of a Curculio, which is how she is classified.[4] The other Weevils are Rhynchophoræ, beak-wearers, armed with a rod that prepares the hollow in which the egg is laid. Our friend possesses only a short snout, which does capitally for sipping a few sweet mouthfuls, but which is of no value as a boring-tool.
Therefore the method of installing the family is quite different. Here we see no ingenious preparations, such as the Balanini, the Larini and the Rhynchites showed us. Having no probe among her tools, the mother scatters her eggs in the open, with no protection against the heat of the sun or the inclemencies of the weather. Nothing could be simpler and nothing more dangerous to the germs, in the absence of a special constitution made to withstand the alternate trials of heat and cold, drought and wet.
In the mild sunshine of ten o’clock in the morning, the mother, with a jerky, capricious, unmethodical step, runs up and down the chosen pod, first on one and then on the other surface. She protrudes at every instant a short oviscapt, which swings [[191]]right and left as though to scrape the skin. An egg follows and is abandoned as soon as laid.
A hasty touch of the oviscapt, first here, then there, on the green skin of the pea-pod; and that is all. The germ is left there, unprotected, right in the sun. Nor is any choice of site made, to assist the coming grub and shorten its quest when it has to make its way unaided into the larder. There are eggs placed on the swellings created by the peas; there are just as many in the barren dividing valleys. It is for the grub to take its bearings accordingly. In short, the Bruchus’ eggs are laid anyhow, as though sown on the wing.
A more serious flaw: the number of eggs confided to one pod is not in proportion to that of the peas contained in it. Let us first realize that each grub needs a ration of one pea, an obligatory ration, amply sufficient for the welfare of one larva, but not big enough for several consumers, nor even for two. A pea for each grub, no more and no less, is the invariable rule.
Procreative economy would therefore demand that the mother, familiar with the pod which she has just explored, should, when emitting her germs, more or less limit their number to that of the peas which it contains. Now there is no limit. To a single ration the impetuous ovaries always offer a multiplicity of consumers.