THE BROAD-NECKED SCARAB; THE GYMNOPLEURI

What we have learnt from the Sacred Beetle must not lead us into rash generalizations and make us attribute it in every slightest detail to the other Dung-beetles of the same family. Similarity of structure does not entail parity of instincts. A common basis no doubt exists, resulting from identity of equipment; but many variations of the essential theme are possible and are dictated by inherent aptitudes of which the insect’s organization gives us no inkling. In fact, the study of these variations, of these peculiarities, with their hidden reasons, forms the most attractive part of the observer’s researches as he explores his corner of the entomological domain. Unsparing of time and patience, sometimes of ingenuity, you have at last learnt what this one does. See now what that one does, his near neighbour structurally. To what extent does number two repeat the habits of number one? Has he ways of his own, tricks of the trade, industrial specialities unknown to the other? It is a highly interesting problem, for the impassable line of demarcation between the two species is much more conspicuous in these psychological differences than in the differences of the wing-case or antenna.

The Scarab clan is represented in my district by the Sacred Beetle (Scarabæus sacer, Lin.), the Half-spotted Scarab (S. semipunctatus, Fab.) and the Broad-necked Scarab (S. laticollis, Lin.). The two former are chilly creatures and hardly stir from the Mediterranean; the third goes pretty far north. The Half-spotted Scarab does not leave the coast; he abounds on the sandy beaches of the Golfe Juan, Cette and Palavas. I have, in my time, admired his prowess at pill-rolling, of which he is as fervent a devotee as his colleague the Sacred Beetle. To-day, though we are old friends, I cannot, to my great regret, give my attention to him: we are too far away from each other. I recommend him to any one wishing to add a chapter to Scarab biography: he also must have—I feel nearly sure of it—peculiarities worth noting.

And so, to complete this study, there remains in my immediate proximity only the Broad-necked Scarab, the smallest of the three. He is very rare around Sérignan, though widely distributed in other parts of the Vaucluse. This scarcity deprives me of opportunities for observing the insect in the open fields; and my only resource is to bring up a few chance specimens in captivity.

Behind the wire-gauze of his prison, the Broad-necked Scarab does not display the Sacred Beetle’s athletic prowess nor his bold and hasty temper. In his case we see no scuffles between robber and robbed, no pills manufactured purely for art’s sake, rolled for a little while with wild enthusiasm and then consigned to the rubbish-heap without being employed at all. The same blood does not flow in the veins of the two pill-rollers.

Of a quieter disposition and less wasteful of his gleanings, the Beetle with the broad corselet attacks discreetly the heap of manna provided by the Sheep; he picks from the best part some armfuls of material which he makes into a ball; he attends to his business without troubling the others or being troubled by them. For the rest, his methods are the same as those of the Sacred Beetle. The sphere, which is always an easier object to convey, is fashioned on the spot before being set in motion. With his wide fore-legs the Beetle pats and kneads and moulds it, making it smooth and level by adding an armful here and there. The perfect roundness of the ball is achieved before it leaves the place.

When the requisite size has been obtained, the pill-roller makes his way with his booty to the spot where the burrow is to be dug. The journey is effected exactly as it would be by the Sacred Beetle. Head downwards, hind-legs lifted against the rolling mechanism, the insect pushes backwards. So far there is nothing new, save for a certain slowness in the performance. But wait a little while: soon a striking difference in habits will separate the two insects.

As each pill is carted away, I seize it, together with its owner, and place both on the surface of a layer of fresh, close-packed sand in a flower-pot. A sheet of glass serves as a lid, keeps the sand nice and cool, prevents escape and admits the light. By interning each Beetle separately, I am saved from the mistakes which might arise if I put them in the common cage, where a number of my boarders are at work; and I shall not risk ascribing to several what may be the performance of one alone. By this solitary confinement, each individual Beetle’s work can be studied more easily.

The interned mother makes hardly any protest against her servitude. Soon she is digging the sand and disappears in it with her pill. Let us give her time to establish her quarters and to get on with her domestic labours.

Three or four weeks go by. The Beetle has not reappeared upon the surface, a proof of her patient absorption [115]in her maternal duties. At last I remove the contents of the pot, very carefully, layer by layer, until I uncover a spacious burrow. The rubbish from this cavity was heaped up on the surface, forming a little mound. This is the secret chamber, the gynæceum in which the mother now and for a long time to come keeps watch over her budding family.

The original pill has disappeared. In its stead are two little pears, elegantly shaped and wonderfully finished: two, not one, as I naturally expected from the information already in my possession. They strike me as being even more delicately and gracefully rounded than the Sacred Beetle’s. Perhaps their tiny dimensions cause my preference: maxime miranda in minimis. They measure 33 millimetres in length and 24 millimetres across their greatest width.1 Let us drop figures and admit that the dumpy modeller, with her slow and awkward ways, is the artistic rival or even the superior of her famous kinswoman. I expected to see some clumsy apprentice; I find a consummate artificer. We must not judge people by appearances; it is a wise maxim, even when applied to insects.

If we examine the pot somewhat earlier, it will tell us how the pear is made. I find sometimes a perfectly round ball and a pear without any traces of the original pill; sometimes a ball only, with a nearly hemispherical remnant of the pill, a lump from which the materials subjected to modelling have been detached in one piece. The method of work can be deduced from these facts.

The pill which the Scarab fashions on the surface of the soil by taking armfuls from the heap encountered is but a temporary piece of work, which is given a round form with [116]the sole object of facilitating its transport. He gives his attention to it, no doubt, but is not unduly anxious about it; all that he wants is that the journey should be effected without any crumbling of his treasure or impediment in the rolling. The surface of the sphere, therefore, is not thoroughly treated; it is not compressed into a rind or made scrupulously even.

Underground, when it is a question of getting the egg’s casket ready, the casket that is to be both larder and cradle, it becomes another matter. An incision is made all round the pill, dividing it into two almost equal portions, and one half is subjected to manipulation, while the other lies just against it, destined to receive the same treatment later. The hemisphere worked upon is rounded into a ball, which will be the belly of the prospective pear. This time, the modelling is performed with the nicest care: the future of the larva, which also is exposed to the dangers of overdry bread, is at stake. The surface of the ball is therefore patted at one spot after the other, conscientiously hardened by compression and levelled along a regular curve. The spherule thus obtained possesses geometrical precision, or very nearly so. Let us not forget that this difficult work is accomplished without rolling, as the clean condition of the surface shows.

The rest of the business may be guessed from the proceedings of the Sacred Beetle. The sphere is hollowed into a crater and becomes a sort of bulging, shallow pot. The lips are drawn out into a pocket which receives the egg. The pocket is closed, polished outside and joined neatly to the sphere. The pear is finished. The other half of the pill is now similarly treated.

The notable feature of this work is the elegant regularity of the forms obtained without any rolling. Chance enables [117]me to add another and a most striking proof to the many that I have given of this modelling done on the spot. Once and once only I managed to get from the Broad-necked Scarab two pears closely soldered together by their bellies and lying in opposite directions. The first one constructed can teach us nothing new, but the second tells us this: when, for a reason that is not apparent, for lack of room perhaps, the insect left this second pear touching the other and soldered it to its neighbour while working at it, obviously, with this appendage, any rolling or any moving became impracticable. Nevertheless, the pretty shape was secured to perfection.

From the point of view of instinct, the distinguishing features which make of the two pear-modellers two entirely different species are absolutely clear from these details and much more conclusive than the peculiarities in the corselet and wing-case. The Sacred Beetle’s burrow never contains more than one pear. The Broad-necked Scarab’s contains two. I even suspect that there are sometimes three, when the haul is a large one: we shall learn more on this subject from the Copres. The first, when she gets her pill underground, uses it just as she obtained it in the workyard and does not subdivide it at all. The second breaks up hers, though it is a little smaller, into two equal parts and fashions each half into a pear. The single ball gives place to two and sometimes even perhaps to three. If the two Dung-beetles have a common origin, I should like to know how this radical difference in their domestic economy declared itself.

The story of the Gymnopleuri is the same as that of the Scarabs, on a more modest scale. To pass it over in silence, for fear of too much sameness, would be to deprive ourselves of evidence calculated to confirm certain theories [118]whose truth is established by the recurrence of similar facts. Let us set it forth, in an abridged form.

The Gymnopleurus family owes its name to a lateral notch in the wing-cases, which leaves a part of the sides bare. It is represented in France by two species. One, with smooth wing-cases (G. pilularius, Fab.), is fairly common everywhere; the other (G. flagellatus, Fab.), stippled on the top with little holes, as though the insect had been pitted with small-pox, is rarer and prefers the south. Both species abound in the pebbly plains of my neighbourhood, where the Sheep pass amid the lavender and thyme. Their shape is not unlike that of the Sacred Beetle; but they are much smaller. For the rest, they have the same habits, the same fields of operation, the same nesting-period: May and June, down to July.

Applying themselves to similar labours, Gymnopleuri and Scarabs are brought into each other’s society rather by the force of things than by the love of company. I not infrequently see them settling next door to each other; I even oftener find them seated at the same heap. In bright sunshine the banqueters are sometimes very numerous. The Gymnopleuri predominate largely.

One would be inclined to think that these insects, endowed with powers of nimble and sustained flight, explore the country in swarms and that, when they find rich plunder, they all swoop down upon it at once. Though the sight of so large a crowd might seem to mean something of the kind, I am very sceptical about these expeditions in large squadrons. I am more ready to believe that the Gymnopleuri have come, from everywhere in the neighbourhood, one by one, guided by keenness of scent. What I see is a gathering of individuals who have hastened from [119]every point of the compass, and not the halt of a swarm engaged on a common search. No matter: the teeming colony is at times so numerous that it would be possible to pick up the Gymnopleuri by handfuls.

But they hardly give one time. When the peril is realized, which soon happens, most of them fly off with all speed; the others crouch low and hide themselves under the heap. In a moment the tumult of activity is succeeded by absolute stillness. The Sacred Beetle is not subject to these sudden attacks of panic, which empty the busiest yard in the twinkling of an eye. When surprised at his task and examined at close quarters, however importunately, he impassively continues his work. He knows no fear. Here we see a thorough difference in temperament between insects which are identical in structure and which follow the same trade.

The difference is equally marked in another respect: the Sacred Beetle is a fervent pill-roller. When the ball is made, his supreme felicity, his summa voluptas, is to cart it backwards for hours at a time, to juggle with it, so to speak, under a blazing sun. His epithet pilularius notwithstanding, the Gymnopleurus does not show so much enthusiasm over a round pellet. Unless he means to feed upon it quietly in a burrow or to use it as a ration for his larva, he never kneads a ball only to roll it about ecstatically and then abandon it when this violent exercise has given him his fill of pleasure.

Both in his wild state and in captivity, the Gymnopleurus makes his meal on the spot where he finds his food; it is hardly his habit to make a round loaf in order to consume it afterwards in some underground retreat. The pill to which the insect owes its name is rolled, so far as I have seen, only in the interests of its family.[120]

The mother takes from the heap the amount of material required for rearing a larva and kneads it into a ball at the spot where it is gathered. Then, going backwards, with her head down, like the Scarabs, she rolls it and finally stores it in a burrow, in order to give it the necessary treatment for the egg to thrive.

Of course the rolling ball never contains the egg. The laying takes place not on the public highway but in the privacy of the subsoil. A burrow is dug, two or three inches deep at most. It is spacious in proportion to its contents, proving that the Sacred Beetle’s studio-work is repeated by the Gymnopleurus. I am speaking of that modelling in which the artist must have full liberty of movement. When the egg is laid, the cell remains empty; only the passage is filled up, as witness the little mound outside, the surplus of the unreplaced refuse.

A minute’s digging with my pocket-trowel and the humble cabin is laid bare. The mother is often present, occupied in some trifling household duties before quitting the cell for good. In the middle of the room lies her work, the cradle of the germ and the ration of the coming larva. Its shape and size are those of a Sparrow’s egg; and I am here speaking of both Gymnopleuri, whose habits and labours are so much alike that I need not distinguish between them. Unless we found the mother beside it, we should be unable to tell whether the ovoid which we have dug up is the work of the smooth or of the pock-marked insect. At most, a slight advantage in size might point to the former; and even so this characteristic is far from trustworthy.

The egg-shape, with its two unequal ends, one large and round, the other more pointed, shaped like an elliptical nipple, or even drawn out into the neck of a pear, confirms [121]the conclusions with which we are already acquainted. An outline of this kind is not obtained by rolling, which is only reconcilable with a sphere. To get it, the mother must knead her lump of stuff. This may be already more or less round, as the result of the work done in the yard whence it came and of the subsequent carting, or it may still be shapeless, if the heap was near enough to allow of immediate storing. In short, once at home, she acts like the Sacred Beetle, and does modelling-work.

The material lends itself well to this. Taken from the most plastic stuff supplied by the Sheep, it is shaped as easily as clay. In this way the graceful, firm, polished ovoid is obtained, a work of art like the pear and as exquisite in its soft curve as a bird’s egg.

Where, inside it, is the insect’s germ? If we argued rightly when discussing the Sacred Beetle, if really the questions of ventilation and warmth demand that the egg be as near as possible to the surrounding atmosphere, while remaining protected by a rampart, it is evident that the egg must be installed at the small end of the ovoid, behind a thin defensive wall.

And this in fact is where it lies, lodged in a tiny hatching-chamber and wrapped on every side in a blanket of air, which is easily renewed through a slender partition and a matted plug. This position did not surprise me; from what the Sacred Beetle had already taught me I expected it. The point of my knife, this time no novice, went straight to the ovoid’s pointed teat and scratched. The egg appeared, magnificently confirming the argument which had at first been merely suspected, then dimly seen and finally changed into certainty by the recurrence of the fundamental facts under varying conditions.[122]

Scarabs and Gymnopleuri are modellers who were not educated in the same school; they differ in the outline of their masterpiece. With the same materials, the first manufacture pears, the second for the most part ovoids; and yet, despite this divergence, they both conform to the essential conditions demanded by the egg and by the grub. The grub wants provisions that are not liable to become prematurely dry. This condition is fulfilled, so far as may be, by giving the mass a round shape, which evaporates less quickly because of its smaller surface. The egg requires unrestricted air and the heat of the sun’s rays, conditions which are fulfilled in the one case by the pear with its neck and in the other by the ovoid with its pointed end.

Laid in June, the egg of either species of Gymnopleuri hatches in less than a week. The average is five or six days. Any one who has seen the larva of the Sacred Beetle knows, so far as essentials go, the larva of the two small pill-rollers. In each case it is a big-bellied grub, curved into a hook and carrying a hump or knapsack which contains a portion of the mighty digestive apparatus. The body is cut off slantwise at the back and forms a stercoral trowel, denoting habits similar to those of the Sacred Beetle’s larva.

We see repeated, in fact, the peculiarities described in the story of the big pill-roller. In the larval state, the Gymnopleuri also are great excreters, ever ready with mortar to make good the imperilled dwelling. They instantly repair the breaches which I make, either to observe them in the privacy of their home or to provoke their plastering-industry. They fill up the chinks with putty, solder the parts that become disjointed, mend the broken cell. When the nymphosis approaches, the mortar that [123]remains is expended in a layer of stucco, which reinforces and polishes the inner walls.

The same dangers give rise to the same defensive methods. Like the Sacred Beetles’, the shell of the Gymnopleuri is liable to crack. The free admission of air to the interior would have disastrous consequences, by drying the food, which must keep soft until the grub has attained its full growth. An intestine which is never empty and which displays unparalleled docility gets the threatened grub out of its trouble. There is no need to enlarge upon this point; the Sacred Beetle has told us all about it.

The insects reared in captivity tell me that, in the Gymnopleuri, the larva lasts seventeen to twenty-five days and the nymph fifteen to twenty. These figures are bound to vary, but within narrow limits. I shall therefore fix each period at approximately three weeks.

Nothing remarkable happens during the nymphal stage. The only thing to be noted is the curious costume worn by the perfect insect on its first appearance. It is the costume which the Sacred Beetle showed us: head, corselet, legs and chest a rusty red; wing-cases and abdomen white. We may add that, being powerless to burst his shell, which has been turned into a strong-box by the heat of August, the prisoner, in order to release himself, waits until the first September rains come to his help and soften the wall.

Instinct, which under normal conditions amazes us with its unerring prescience, astonishes us no less with its dense ignorance when unaccustomed conditions supervene. Each insect has its trade, in which it excels, its series of actions logically arranged. Here it is really a master. Its foresight, though unwitting, here surpasses our deliberate science; its unconscious inspiration is here [124]the superior of our conscious reason. But divert it from its natural course; and forthwith darkness succeeds the splendours of light. Nothing will rekindle the extinguished rays, not even the greatest stimulus that exists, the stimulus of maternity.

I have given many instances of this strange antithesis,2 which is the death-blow to certain theories; I find another and an exceedingly striking one in the Dung-beetles whose story I have now nearly finished telling. We are surprised at this clear vision of the future possessed by our manufacturers of spheres, pears and ovoids; but we are no less surprised by something totally different, namely, the mother’s profound indifference to the nursery which but now was the object of her tenderest cares.

My remarks apply equally to the Sacred Beetle and the two Gymnopleuri, all of whom display the same admirable zeal when the grub’s comfort has to be assured, and later, with no less unanimity, the same indifference. I surprise the mother in her burrow before she has laid her eggs, or, if the laying be over, before she has added those meticulous after-touches dictated by her exaggerated conscientiousness. I install her in a pot packed full of earth, placing her on the surface of the artificial soil, together with her work, in its more or less advanced state. In this place of banishment, provided that it be quiet, there is not much hesitation. The mother, who until now has held her precious materials tight-clutched, decides to dig a burrow. As the work of excavation progresses, she drags her pellet down with her, for it is a sacred thing with which she must not part at any time, even amid the difficulties [125]of her digging. Soon the cell in which the pear or the ovoid is to be made is in existence at the bottom of the pot.

I now intervene and turn the pot upside down. Everything is topsy-turvy; the entrance-gallery and the terminal hall disappear. I extract the mother and the pellet from the ruins. Once more the pot is filled with earth; and the same test begins all over again. A few hours are enough to restore the courage shaken by all this upheaval. For the second time, the mother buries herself with the heap of provisions destined for the grub. For the second time also, when the establishment is finished, the overturning of the pot unsettles everything. The experiment is renewed. Persisting in its maternal solicitude, if necessary until its strength gives way, the insect again buries itself, together with its sphere.

Four times over, in two days, I have thus seen the mother Beetle bear up under the devastation which I have wrought and start afresh, with touching patience, on the ruined dwelling. I did not think fit to pursue the test. You feel some scruples in submitting maternal affection to such tribulations as these. However, it seems probable that, sooner or later, the exhausted and bewildered insect would have refused to go on digging.

My experiments of this kind are numerous; and they all prove that, when taken from her burrow with her work unfinished, the mother shows indefatigable perseverance in burying and depositing in a place of safety the cradle which has begun to take shape though as yet untenanted. For the sake of a pellet of stuff which the presence of the egg has not yet turned into a sacred thing, she displays exaggerated prudence and caution, as well as amazing foresight. No tricks of the experimenter, no all-upsetting [126]accidents, nothing, unless her strength be worn out, can divert her from her object. She is filled with a sort of indomitable obsession. The future of her race requires that the lump of stuff should descend into the earth; and descend it will, whatever happens.

Now for the other side of the medal. The egg is laid; everything is in order underground. The mother comes out. I take hold of her as she does so; I dig up the pear or ovoid; I place the work and the worker side by side on the surface of the soil, in the conditions that prevailed just now. This assuredly is the right moment for burying the pill. It contains the egg, a delicate thing which a touch of the sun will wither in its thin wrapper. Expose it for fifteen minutes to the heat of the sun’s rays; and all will be lost. What will the mother do in this grave emergency?

She does nothing at all. She does not even seem to perceive the presence of the object which was so precious to her yesterday, when the egg was not yet laid. Zealous to excess before the laying is over, she is indifferent afterwards. The finished work no longer concerns her. Imagine a pebble in the place of the ovoid or pear: the mother would treat it no better and no worse. One sole preoccupation urges her: to get away. I can see that by the manner in which she paces the enclosure that keeps her prisoner.

That is instinct’s way: it buries perseveringly the lifeless lump and leaves the quickened lump to perish on the surface. The work to be done is everything; the work done no longer counts. Instinct sees the future and knows nothing of the past.