On the appointed day the week after I returned to the tableland confident of success. My young helpers would no doubt have mentioned this lucrative trade in beetle-balls to their comrades and shown their handsels to convince the incredulous. Accordingly I found a larger party assembled than the first time. On seeing me they ran up, but there was no eagerness, no shout of joy. I saw that things had gone ill. Many times on coming out of [[32]]school had they sought for what I had described, but in vain. Some balls, found underground with the Scarabæus, were brought, but they were mere heaps of food, and there was no grub. Fresh explanations were given and a new appointment was made for the following Thursday. Again the same want of success. The seekers, discouraged, were now few. I made a last appeal, but nothing came of it. Finally, I paid the most zealous, those who had been faithful to the last, and we dissolved partnership. I could count on no one but myself for researches, which seemed simple enough, but really were exceedingly difficult. Even up to the present time, after many years, excavations made in favourable spots and hopeful opportunities have not yet given any clear, consistent result. I am reduced to combining incomplete observations and to filling up gaps by analogy.[1] The little which I have seen, together with observations on other dung beetles—Gymnopleurus, Copris, and Onthophagus—in my enclosure is summed up in the following statement.
The ball destined for the egg is not fashioned in public, in the hurry-scurry of the general workshop. It is a work of art and much patience, demanding minute care impossible amid a crowd. One must retire to meditate one’s plans and set to work, so the mother makes a hollow from four to eight inches deep in the sand. It is a rather spacious hall, communicating with the outside by a much narrower gallery. The insect carries down choice materials, no doubt first rolled into pellets. She must make [[33]]many journeys, for the contents of the hole are out of all proportion with the door, and could not be carried in at once. I recollect a Spanish Copris which, at the moment I came upon it, was finishing a ball as large as an orange at the bottom of a burrow only communicating with the outside world by means of a gallery where I could but just insert my finger. It is true that the Copris do not roll balls or make long journeys to fetch food. They dig a hole immediately under the dung, and crawl backward with successive loads to the bottom of their cavity. The facility for provisioning and the security offered by working under the manure favour a taste for luxury not to be expected in the same degree among beetles belonging to the rude trade of ball-rollers; but should it return two or three times, Scarabæus sacer can amass wealth of which Copris hispanica might well be jealous.
So far the insect has only raw material, put together anyhow. The first thing to do is to select very carefully, taking what is most delicate for the inner layers, upon which the larva will feed, and the coarser for the outer ones which merely serve as a protecting shell. Then around a central hollow which receives the egg the materials must be arranged layer after layer, according to their decreasing fineness and nutritive value; the strata must be made consistent and adhere one to another; and finally, the bits of fibre in the outside crust, which has to protect the whole thing, must be felted together. How can the Scarabæus, clumsy and stiff as it seems, accomplish such a work in complete darkness, at the bottom of a hole so full of provisions that there is [[34]]barely room to move? When I think how delicate is the work done and how rude the tools of the workman,—of the angular feet fitted to hollow the ground, and, if need be, even tufa,—I am reminded of an elephant trying to make lace. Explain who can this miracle of maternal industry; I give it up, especially as it has not been my good fortune to see the artist at work. Let us restrict ourselves to describing this masterpiece.
The ball which contains the egg is generally as large as a middle-sized apple. In the midst is an oval cavity about a centimetre in diameter. At the bottom is the egg, fixed vertically; it is cylindrical, rounded at each end, yellowish-white, about as large as a grain of wheat, but shorter. The wall of the hollow is washed over with a greenish-brown, semi-fluid matter, manure cream, destined as the first food of the larva. Does the mother collect the quintessence of the dung to make this delicate food? The look of it tells me that it is a pap prepared in the maternal stomach. The pigeon softens grain in its crop, and turns it into a kind of milk food which it disgorges for its nestlings. It would seem that the beetle shows the same tender care. It half digests the choice food, and disgorges it in the shape of a delicate film to line the walls of the cavity where the egg is laid. Thus, when first hatched, the larva finds food easy of digestion, which rapidly strengthens its stomach and allows it to attack the under layers which lack the same refinement of preparation. Under the semi-fluid paste is a choice pulp, compact and homogeneous, whence every particle of fibre is banished. Beyond are the coarser strata [[35]]where vegetable fibres abound, and finally the outside of the ball is composed of the coarsest materials felted together into a resistant shell. Manifestly there is a progressive change of diet. On issuing from the egg the feeble grub licks the fine paste on the walls of its dwelling. There is but little of it, still it is strengthening and of high nutritious value. To the bottle of early infancy succeeds the pap of the weanling, intermediate between the dainty fare of the start and the coarse nourishment at the end. This layer is thick enough and abundant enough to make the maggot into a robust grub. Then, strong food for the strong, barley bread with its husks, raw dung full of sharp bits of hay. The larva is superabundantly provisioned with it, and, having attained its growth, comes to the imprisoning outer layer. The capacity of the dwelling has increased with that of its inhabitant. The small original cavity with its excessively thick walls is now a large cell with sides only a few lines thick. The inner layers have turned into larva, nymph, or Scarabæus, as the case may be. In short, the ball is now a shell, hiding within its spacious interior the mysteries of metamorphosis.
My observations go no further; my certificates of the birth and condition of the Scarabæus do not go beyond the egg; I have not actually seen the larva which, however, is known and described by various authors. Neither have I seen the perfect insect while yet enclosed in the cell, previous to exercising its functions as ball-roller and excavator, and that is exactly what I should most have desired to see. I should have liked to find the [[36]]creature in its birthplace, recently transformed, new to all labour, so that I might have examined the worker’s hand before it set to its tasks, and for the following reason.
Insects have each foot terminated by a kind of finger or tarsus, composed of a series of delicate portions which may be compared to the joints of our fingers. They end in a crooked nail. One claw to each foot is the rule, and this claw, at least in the case of the superior Coleoptera, especially the scavenger beetles, contains five joints. Now by a strange exception, the Scarabæus has no tarsi on its forefeet, while possessing well-shaped ones with five joints on the two other pairs. They are imperfect, maimed, wanting in their front limbs in that which represents, roughly indeed, our hand in an insect. A like anomaly is found in the Onitis and Bubas, also of the scavenger family. Entomology has long noted this curious fact without being able to give a satisfactory explanation. Is it a birth imperfection? Does the beetle come into the world without fingers on its front limbs, or does it lose them as soon as it enters on its toilsome labours?
One might easily suppose such mutilation a consequence of the insect’s hard work. To grope, to excavate, to rake, to divide now among the gravel in the soil, now in the fibrous mass of manure, is not a work in which organs so delicate as the tarsi can be used without danger. Yet graver is it that when the insect is rolling its ball backward, head downward, it is with the end of the forefeet that it grips the ground. What becomes of the weak feet, no thicker than a thread, in this perpetual contact [[37]]with all the inequalities of the soil? They are useless—merely in the way, and sooner or later they are bound to disappear, crushed, torn off, worn out. Our workmen, alas! are too often maimed by handling heavy tools, and lifting great weights, and the same may be the case with the Scarabæus which rolls a ball that to it is a huge load. In that case the maimed arms would be a noble certificate of a life of toil.
But serious doubts at once suggest themselves. If these mutilations be accidental, and the result of laborious work, they should be the exception, not the rule. Because a workman or several workmen have had a hand crushed in machinery, it does not follow that all others should be maimed. If the Scarabæus often, or even very often, loses the fore-claws in its trade of ball-roller, there must be some which, cleverer or more fortunate, have preserved their tarsi. Let us then consult facts. I have observed a very large number of the species of Scarabæus which inhabit France, the S. sacer, common in Provence; S. semipunctatus, which is seldom found far from the sea, and frequents the sandy shores of Cette, Palavas, and of the Gulf of Juan; also S. longicollis, which is much more widely spread than the two others, and found at least as far up the Rhône Valley as Lyons. Finally, I have observed an African kind, S. cicatricosus, found in the environs of Constantine, and the want of tarsi on the forefeet has proved invariable in all four species, at all events as far as my observations go. Therefore the Scarabæus is maimed from birth, and it must be no accident but a natural peculiarity. [[38]]
Moreover, we have further proof in another reason. Were the absence of fore-claws accidental, and the consequence of rough labour, there are other insects, especially among the scavenger beetles, which undertake excavations yet more difficult than those of the Scarabæus, and which ought therefore to be still more liable to lose their front claws, as these are useless and in the way when the foot has to serve as a strong tool for excavation. For instance, the Geotrupes, who deserve their name of Earth-piercer so well, make hollows in the hard and beaten soil of paths among pebbles cemented by clay—vertical pits so deep that to reach the lowest cell one has to use powerful digging tools, and even then one does not always succeed. Now these miners par excellence, who easily open long galleries in surroundings whose surface the Scarabæus sacer could hardly disturb, have their front tarsi intact, as if to perforate tufa were a work calling for delicacy rather than strength. Everything then points to the belief that, if observed in its natal cell, the baby Scarabæus would be found mutilated like the veteran who has travelled the world and grown worn with labour.
On this absence of fingers might be based an argument in favour of the theories now in fashion—the struggle for life and the evolution of the species. One might say that the Scarabæus had originally tarsi on all its feet in conformity with the general laws of insect organisation. One way or another, some have lost these embarrassing appendages on their forefeet, they being hurtful rather than useful. Finding themselves the better for this mutilation, [[39]]which proved favourable to their work, little by little they gained a superiority over the less favoured ones, founded a race by transmitting their fingerless stumps to their descendants, and finally, the primitively fingered insect became the fingerless Scarabæus of our time. I am willing to agree to this reasoning if it could first be demonstrated why, with like labours,—labours even far harder,—the Geotrupes has preserved his tarsi. Meantime let us continue to believe that the first Scarabæus who rolled a ball, perhaps on the shores of some lake where bathed the Palæotherium, was as much without tarsi as him of our own day. [[40]]