The Sacred Beetle, and Others

by Jean-Henri Fabre

The surmise rests upon no valid foundation. The Dung-beetle is recent in the general chronology of created beings; he ranks among the last-comers. With him there is no means of going back to the mists of the past, which lends itself to the invention of imaginary precursors. Geological and even lacustrine schists, rich though the latter be in Diptera and Weevils, have hitherto furnished not the slightest relic of the dung-workers. This being so, it is wiser not to claim horned ancestors from the distant past as accounting for those degenerate descendants, the Onthophagi.

Since the past explains nothing, let us turn to the future. If the thoracic horn be not a reminiscence, it may be a promise. It represents a timid attempt, which the ages will harden into a permanent weapon. It lets us assist at the slow and gradual evolution of a new organ; it shows us life in travail of a thing not yet existing on the adult Beetle’s corselet, a thing which will exist one day. We catch the genesis of the species in the act; the present teaches us how the future is prepared.

And what does the Beetle propose to do with this object of his ambition, this spear which he hopes by and by to place upon his spine? At any rate as a dazzling piece of masculine finery the thing is already fashionable among the various foreign Scarabs that feed themselves and their grubs on decaying vegetable matter. [[288]]These giants among the wearers of armoured wing-cases delight in associating their placid corpulence with halberds terrible to gaze upon.

Look at one, Dynastes Hercules by name, a denizen of rotten tree-stumps under the scorching skies of the West Indies. The peaceable colossus well deserves his epithet: he measures three inches long. Of what service can the threatening rapier of the corselet and the toothed lifting-jack of the forehead be to him, unless it be to make him look grand in the presence of his female, herself deprived of these extravagances? Perhaps also they are of use to him in certain operations, even as the trident helps the Minotaurus to crumble his pellets and cart his rubbish. Implements of which we do not know the use always strike us as singular. Having never been intimate with the West-Indian Hercules, I must content myself with suspicions touching the purpose of his fearsome equipment.

Well, one of the subjects in my insect-house would achieve a similar savage finery if he persisted in his attempts. I speak of the Cow Onthophagus (O. vacca). His nymph has on its forehead a big horn, one only, bent backward; on its corselet it possesses a similar horn, jutting forward. The two, approaching their tips, look like some kind of pincers. What does the insect lack in order to acquire, on a smaller scale, the eccentric ornament of the West-Indian Scarab? It lacks perseverance. It matures the appendage of the forehead and allows that of the corselet to perish atrophied. It succeeds no better than the Bull Onthophagus in its attempt to grow a pointed stake upon its back; it loses a glorious opportunity of making itself fine for the wedding and terrible in battle. [[289]]

The others are no more successful. I bring up six different species. All, in the nymphal state, possess the thoracic horn and the eight-pointed ventral coronet; not one benefits by these advantages, which disappear altogether when the adult bursts its wrapping. My near neighbourhood numbers a dozen species of Onthophagi; the world contains some hundreds. All, natives and foreigners, have the same general structure; all most probably possess the dorsal appendage at an early age; and none of them, in spite of the variety of climate, torrid in one place, temperate in another, has succeeded in hardening it into a permanent horn.

Could not the future complete a work whose design is so very clearly traced? We are the more inclined to ask this, because appearances are all in favour of the question. Examine under the magnifying-glass the frontal horns of the Bull Onthophagus in the nymphal state; then with the same scrupulous care look at the spear upon the corselet. At first, there is no difference between them, except for the general configuration. In both cases we find the same glassy aspect, the same sheath swollen with colourless fluid, the same incipient organ plainly marked. A leg in process of formation is not more clearly announced than the horn on the corselet or those on the forehead.

Can time be lacking for the thoracic growth to become organized into a stiff and permanent appendage? The evolution of the nymph is swift; the insect is perfect in a few weeks. Could it not be that, though this brief space suffices to promote the maturity of the horns on the forehead, the thoracic horn requires a longer time to ripen? Let us prolong the nymphal period artificially [[290]]and give the germ time to develop. It seems to me that a decrease of temperature, moderated and maintained for some weeks, for months if necessary, should be capable of bringing about this result, by delaying the progress of the evolution. Then, with a gentle slowness, favourable to delicate formations, the promised organ will crystallize, so to speak, and become the spear promised by appearances.

The experiment attracted me. I was unable to undertake it for lack of the means whereby to produce a cold, even temperature over a long time. What should I have obtained if my penury had not made me abandon the enterprise? A retarding of the progress of the metamorphosis, but nothing more, apparently. The horn on the corselet would have persisted in its sterility and, sooner or later, would have disappeared.

I have reasons for my conviction. The abode of the Onthophagus engaged on his metamorphosis is not deep down; variations of temperature are easily felt. On the other hand, the seasons are capricious, especially the spring. Under the skies of Provence, the months of May and June, if the mistral lend a hand, have periods when the thermometer drops in such a way as to suggest a return of winter.