The proof is furnished by certain specimens, by no means rare in the Golden Cryptocephalus, in which the customary brown is replaced by an unmistakable green, the sign of a vegetable pulp. In course of time, these green eggs turn brown and become like the others, no doubt by reason of an oxidization which alters the natural qualities of the digestive product still further. The egg, entering the cloaca in a soft and utterly naked state, receives an artistic coat of the intestinal dross, even as the Hen's egg is covered by a shell formed of the chalky secretions.
Materiem superabat opus, nam Mulciber illic
Æquora celerat,
said Ovid, in his description of the Palace of the Sun. The poet had precious metals and gems wherewith to build his imaginary marvel. What has the Clythra wherewith to achieve its ideal jewel? It has the shameful material whose name is banished from decent speech. And which is the Mulciber, the Vulcan, the artist-engraver that engraves the covering of the egg so prettily? It is the terminal sewer. The cloaca rolls the material, flutes it, twists it into spirals, decks it with chains of little pits and makes it up into a scaly suit of armour, showing how nature laughs at our paltry standards of value and how well able she is to convert the sordid into the beautiful.
In the bird, the egg-shell is a temporary defensive cell which at hatching-time is broken and abandoned and is henceforth useless. Made of horny matter or stercoral paste, the shell of the Clythra and the Cryptocephalus is, on the contrary, a permanent refuge, which the insect will never leave so long as it remains a larva. Here the grub is born with a ready-made garment, of rare elegance and an exact fit, a garment which it only has to enlarge, little by little, in the original manner described above. The shell, shaped like a little barrel or thimble, is open in front. There is nothing therefore to break, nothing to cast aside at the moment of hatching, except perhaps the actual envelope of the egg. Directly this membrane is burst, the tiny creature is free, with a handsome carved jacket, a legacy from its mother.
Let us indulge in a crazy dream and imagine young birds which keep the egg-shell intact, save for an opening through which they pass their head, and which, all their lives long, remain clad in this shell, on condition that they themselves enlarge it as they grow. This absurd dream is realized by our grub: it is dressed in the shell of its egg, expanded by degrees as the grub itself grows bigger.
In July all my collection of eggs are hatched, each isolated in a large cup covered with a slip of glass which will moderate the evaporation. What an interesting family! My vermin are swarming amid the miscellaneous vegetable refuse with which I have furnished the premises. They all move along with tiny steps, dragging their shells, which they carry lifted on a slant; they come halfway out and suddenly pop in again; they tumble over if they merely attempt to scale a sprig of moss, pick themselves up again, forge ahead and cast about at random.
Hunger, we can no longer doubt, is the cause of this agitation. What shall I give my famished nurselings? They are vegetarians: there can be no doubt whatever about that; but this is not enough to settle the bill of fare. What would happen under the natural conditions? Rearing the insects in cages, I find the eggs scattered at random on the ground. The mother drops them carelessly, here and there, from the top of the bough where she is refreshing herself by soberly notching some tender leaf. The Taxicorn Clythra fits a long stalk to her eggs and fixes them in clusters on the foliage. While I cannot yet make up my mind, in the absence of direct observation, whether the new-born larva cuts the suspension-thread itself, or whether the thread is broken merely as a result of drying up, sooner or later these eggs are lying on the ground, like the others.
The same thing must happen outside my cages: the eggs of the Clythræ and the Cryptocephali are scattered over the ground beneath the tree or plant on which the adult feeds.
Now what do we find under the shelter of the oak? Turf, dead leaves, more or less pickled by decay, dry twigs cased in lichens, broken stones with cushions of moss and, lastly, mould, the final residue of vegetable matters wrought upon by time. Under the tufts of the centaury on which the Golden Cryptocephalus browses lies a black bed of the miscellaneous refuse of the plant.