More Beetles

by Jean-Henri Fabre

In May, I procure four recent pears, containing the egg in the chamber of the terminal nipple. By making an equatorial section, I cut off the hinder half, in the shape of a large spherical cap; the other half, surmounted by its neck, I retain; and I place the four egg-bearing portions in as many small jars, in which there is no danger of either desiccation or excessive damp.

With these provisions decreased by half, development takes place as usual; then two of the grubs die, apparently the victims of defective hygiene: my jars are not equal to the burrows, with their pleasant moisture. The two others are still in good condition, ever ready to plug with dung the window which I cut through the wall of the cell when I wish to inspect them. At the end of the active period, I find them remarkably small in comparison with those of their fellows who have been left in possession of the whole pear. The effect of insufficient food is already manifest. What will it be in the perfect insect?

In September there emerge from the shells [[245]]adults such as my hunts in the meadows never yielded, dwarfs, hardly larger than a thumbnail, but correctly shaped in every other respect.

Let me quote some exact figures. Each of them measures nineteen millimetres[3] from the edge of the clypeus to the tip of the abdomen. The smallest specimen in my boxes, as the freedom of the fields made him, measures twenty-six.[4] The products of my experiments, fed upon half rations, are therefore only half the bulk of the normal Beetle chosen from among the smallest. This is also approximately the ratio between the full and the reduced diet. The extensible mould of the organism has reproduced the proportion of the substance at its disposal.

My intervention has just created dwarfs; treatment by starvation has given me abortions. I am not excessively proud of it, though I am glad to have learned by experiment that dwarfishness, at all events in the insects, is not a matter of predisposition and heredity but a mere accident caused by deficient nourishment.

What then had happened to the little Minotaur [[246]]who suggested these experiments in starvation? Assuredly a deficiency of food. Though expert in the art of rationing, the mother was unable to complete the sausage over the egg, perhaps because the materials were lacking, or because some inopportune incident interrupted her work; and the grub, scantily fed, though strong enough to withstand a not too rigorous diet, was unable to acquire the wherewithal to provide the adult with the amount of substance needed for the normal size. This seems to be the whole secret of the tiny Minotaur. He was a child of poverty.

While privation reduces the size, it does not follow that unlimited abundance is able to increase it very notably. In vain do I provide the grubs of the Sacred Beetle with an extra allowance of food that doubles or trebles the ration supplied by the mother. My boarders do not attain a growth worth mentioning. As they leave the maternal pears, so do they leave the plentiful messes which my spatula has mixed for them. And this must be so: the appetite has its limits, which, once reached, leave the consumer indifferent to the luxuries of the table. It is not in our power to make giants by means of [[247]]an excess of food. When the grub has gorged to the required degree, it ceases to eat.

There are nevertheless giants among the Sacred Beetles. I have some that came from Ajaccio and Algeria and measure thirty-four millimetres[5] in length. By comparing this figure with those already given, we see that, if the size of the dwarfs obtained by fasting is represented by the figure 1, that of the Sacred Beetle of the Sérignan district is expressed by 2 and that of the Corsican and African Beetles by 5.

To produce these latter, these giants, it is evident that a more generous diet is needed. Whence comes this increase of appetite? We whet ours with condiments. The insect may well have condiments of its own, for instance, as regards the Sacred Beetle, the pepper of the sea-breezes and the mustard of a generous sun. Such, it seems to me, are the causes which augment the dimensions of the African Scarabæus and reduce those of his Sérignan kinsman. As I have not these two appetizers, the sea and the sun, at my disposal, I give up the idea of making giants by an excess of victuals. [[248]]

Let us now try the larvæ which, not being rationed by the mother, have unlimited abundance at their disposal. Among them are the larvæ of Cetonia floricola, Herbst, living in heaps of decomposing leaves. I shall certainly never obtain giants from these by resorting to the artifice of a copious diet! In a corner of my garden they swarm in a heap of rotten leaves, where they find the wherewithal to satisfy their gluttonous appetites to the full, without having to hunt for it; and yet I never find an adult whose dimensions are ever so little exaggerated. To make him exceed the usual proportions it is probable that better climatic conditions are necessary, as in the case of the Sacred Beetle, conditions of which I know nothing and which, moreover, I should be unable to realize. Only one experiment lies within my power, that of starvation.