The nymph of the Onthophagi provides us with another surprise. My observations are confined to two species only: the Bull Onthophagus and the Forked Onthophagus; but the difference between the two, in size and shape, is great enough to allow me to generalize and apply the following singular fact to the whole genus.
About the middle of the fore-edge of the corselet the nymph is armed with a very distinct horn, projecting for about one-twelfth of an inch. The horn is transparent, colourless and limp, as are all the budding organs at this period, particularly the legs, the cornicles of the forehead and the mouth-parts. This crystalline protuberance proclaims a future horn as clearly as the mandible is proclaimed by its initial nipple or the wing-case by its sheath. Any insect-collector will understand my amazement. A horn there, on the prothorax! But no Onthophagus wears such a weapon as that! The register of my insect-house duly records the genus of the insect, but I dare not believe it.
The nymph moults. Together with the cast skin, the unfamiliar horn dries up and falls off, leaving not the least trace behind it. My two Onthophagi, recently disguised in strange armour, now have their corselets bare.
This fleeting organ, which disappears without leaving even an excrescence, this temporary horn at a spot destined in the end to be unmailed, gives rise to a few reflections. The Dung-beetles, those placid creatures, generally favour a warlike harness: they love outlandish weapons, halberds, spears, grappling-irons, scimitars. [[183]]Let us hurriedly recall the horn of the Spanish Copris. No Rhinoceros in the Indian jungles boasts one to compare with it upon his nose. Broad at the base, pointed at the tip, curved like a bow, when the head is lifted the horn bends back till it touches the keel of the obliquely truncated corselet. It might be a harpoon intended for ripping up some monster. Remember also the Minotaur,[4] who looks as though he were going to spit his foe with his sheaf of three couched lances, and the Lunary Copris, horned on the forehead, armed with a pike on each shoulder and wearing a corselet notched with little crescents that remind us of the short curved knife of the pork-butcher.
The Onthophagi have a most varied arsenal. One, O. taurus, wears the Bull’s crescent-shaped horns; a second, O. vacca, prefers a wide, short blade, with its point sheathed in a notch in the corselet; a third, O. furcatus, wields a trident; yet another, O. nuchicornis, owns a dagger with a winged handle; and again O. cænobita sports a cavalryman’s sword. The worst-equipped crown their foreheads with a transversal crest, with a pair of cornicles.
What is the good of this panoply? Are we to look upon it as a set of tools, pickaxes, mattocks, pitchforks, spades, levers, which the insect might ply in digging? By no means. The only industrial implements are the forehead and the legs, especially the fore-legs. I have never discovered a Dung-beetle of any sort making use of her weapons either to excavate her burrow or to mix her provisions. Besides, as a rule, the direction of the things alone would prevent their employment as utensils. For a digging-job performed forwards, what would you have a Spanish Copris do with her pickaxe, which points backwards? [[184]]The powerful horn does not face the obstacle attacked; it turns its back upon it.
The Minotaur’s trident, though arranged in a suitable direction, likewise remains unemployed. When deprived of this armour with a clip of my scissors, the Beetle loses none of his mining-talents; he goes underground quite as easily as his unmutilated fellow. And here is an even more conclusive argument: the mothers, to whose lot the labour of nest-building falls; the mothers, those conspicuous workers, are deprived of these horny growths or possess them only on a greatly reduced scale. They simplify the armour, or reject it entirely, because it is more of an impediment than an assistance to their work.
Are we to look upon them as means of defence? Not that either. The ruminants, the main feeders of the dung-eaters, are also given to wearing frontal armour. The analogy of taste is obvious, though it is impossible for us to suspect its remote reasons. The Ram, the Bull, the Goat, the Chamois, the Stag, the Reindeer and the rest of them are armed with horns and antlers which they use in amorous jousts or for the protection of the threatened herd. The Onthophagi know nothing of these contests. There is no strife among them; and, should danger arise, they content themselves with shamming death by gathering their legs under their abdomen.
Their armour then is a mere ornament, the fine feathers of masculine coquetry. According to life’s law of competition, the best-dressed carry off the palm. Though we may regard those rapiers on the nose as queer, their wearers are of another opinion; and the most eccentric enjoy the highest favour. The smallest extra pimple, springing up by accident, is an added beauty which may [[185]]decide the choice among the suitors. The best-adorned captivate the mothers, perpetuate the breed and hand down to their offspring the cornicle or the knob that caused their triumph. Thus by degrees was the ornamentation at which the entomologist wonders to-day formed and transmitted from generation to generation, improving as it went.
To this dictum of the evolutionists the nymph of the Onthophagus replies as follows: