The Glow-Worm and Other Beetles Part 24

A garment should be neither too short nor too tight. It is not enough to add a piece which lengthens it as the body grows longer; we must also see that it has sufficient fulness not to hamper the wearer and to give him liberty of movement.

The Snail and all the molluscs with turbinate sh.e.l.ls increase the diameter of their corkscrew staircase by degrees, so that the last whorl is always an exact measure of their actual condition. The lower whorls, those of childhood, when they become too narrow, are not abandoned, it is true; they become lumber-rooms in which the organs of least importance to active life find shelter, drawn out into a slender appendage. The essential portion of the animal is lodged in the upper story, which increases in capacity.

The big Broken Bulimus, that lover of crumbling walls and limestone rocks leaning in the sun, sacrifices the graces of symmetry to utility. When the lower spirals are no longer wide enough, he abandons them altogether and moves higher up, into the s.p.a.cious staircase of recent formation. He closes the occupied part with a stout part.i.tion-wall at the back; then, das.h.i.+ng against the sharp stones, he chips off the superfluous portion, the hovel not fit to live in. The broken sh.e.l.l loses its accurate form in the process, but gains in lightness.

The Clythra does not employ the Bulimus' method. It also disdains that of our dressmakers, who split the overtight garment and let in a piece of suitable width between the edges of the opening. To break the jar when it becomes too small would be a wilful waste of material; to split it lengthwise and increase its capacity by inserting a strip would be an imprudent expedient, which would expose the occupant to danger during the slow work of repair. The hermit of the jar can do better than that. It knows how to enlarge its gown while leaving it, except for its fulness, as it was before.

Its paradoxical method is this: of the lining it makes cloth, bringing to the outside what was inside. Little by little, as the need makes itself felt, the grub sc.r.a.pes and strips the interior of its cell.

Reduced to a soft paste by means of a little putty furnished by the intestine, the sc.r.a.pings are applied over the whole of the outer surface, down to the far end, which the grub, thanks to its perfect flexibility, is able to reach without taking too much trouble or leaving its house.

This turning of the coat is accomplished with a delicate precision which preserves the symmetrical arrangement of the ornamental ridges; lastly, it increases the capacity by a gradual transfer of the material from the inside to the outside. This method of renewing the old coat is so accurate that nothing is thrown aside, nothing treated as useless, not even the baby-wear, which remains encrusted in the keystone at the original top of the structure.

If fresh materials were not added, obviously the jar would gain in size at the cost of thickness. The sh.e.l.l would become too thin, by dint of being turned in order to make s.p.a.ce, and would sooner or later lack the requisite solidity. The grub guards against that. It has in front of it as much earth as it can wish for; it keeps putty in a back-shop; and the factory which produces it never slacks work. There is nothing to prevent it from thickening the structure at will and adding as much material as it thinks proper to the inner sc.r.a.pings from the sh.e.l.l.

Invariably clad in a garment that is an exact fit, neither too loose nor too tight, the grub, when the cold weather comes, closes the mouth of its earthenware jar with a lid of the same mixed compound, a paste of earth and stercoral cement. It then turns round and makes its preparations for the metamorphosis, with its head at the back of the pot and its stern near the entrance, which will not be opened again.

It reaches the adult stage in April and May, when the ilex becomes covered with tender shoots, and emerges from its sh.e.l.l by breaking open the hinder end. Now come the days of revelry on the leaf.a.ge, in the mild morning sun.

The Clythra's jar is a piece of work entailing no little delicacy of execution. I can quite well see how the grub lengthens and enlarges it; but I cannot imagine how it begins it. If it has nothing to serve as a mould and a base, how does it set to work to a.s.semble the first layers of paste into a neatly-shaped cup?

Our potters have their lathe, the tray which keeps the work rotating and implements to determine its outline. Could the Clythra, an exceptional ceramic artist, work without a base and without a guide?

It strikes me as an insurmountable difficulty. I know the insect to be capable of many remarkable industrial feats; but, before admitting that the jar can be based on nothing, we should have to see the new-born artist at work. Perhaps it has resources bequeathed to it by its mother; perhaps the egg presents peculiarities which will solve the riddle. Let us rear the insect, collect its eggs; then the pottery will tell us the secret of its beginnings.

I install three species of Clythrae under wire-gauze covers, each with a bed of sand and a bottle of water containing a few young ilex-shoots, which I renew as and when they fade. All three species are common on the holm-oak: they are the Long-legged Clythra (_C.

longipes_, FAB.), the Four-spotted Clythra (_C. quadripunctata_, LIN.), and the Taxicorn Clythra (_C. taxicornis_, FAB.).

I set up a second menagerie with some Cryptocephali, who are closely related to the Clythrae. The inmates are the Ilex Cryptocephalus (_C.

ilicis_, OLIV.), the Two-spotted Cryptocephalus (_C. bipunctatus_, LIN.) and the Golden Cryptocephalus (_C. hypoch.o.e.ridis_, LIN.), who wears a resplendent costume. For the first two I provide sprigs of ilex; for the third, the heads of a centaury (_Centaurea aspera_), which is the favourite plant of this living gem.

There is nothing striking in the habits of my captives, who spend the morning very quietly, the first five browsing on their oak-leaves and the sixth on her centaury-blooms. When the sun grows hot, they fly from the bunch of leaves in the centre to the wire trellis and back from the trellis to the leaves, or wander about the top of the cage in a state of great excitement.

Every moment couples are formed. They pester each other, pair without preliminaries, part without regrets and begin elsewhere all over again. Life is sweet; and there are enough for all to choose from.

Several are persistent. Mounted on the back of the patient female, who lowers her head and seems untouched by the pa.s.sionate storm, they shake her violently. Thus do the amorous insects declare their flame and win the consent of the hesitating fair.

The att.i.tude of the couple now tells us the use of a certain organic detail peculiar to the Clythra. In several species, though not in all, the males' fore-legs are of inordinate length. What is the object of these extravagant arms, these curious grappling-irons out of all proportion to the insect's size? The Gra.s.shoppers and Locusts prolong their hind-legs into levers to a.s.sist them in leaping. There is nothing of the sort here: it is the fore-legs which are exaggerated; and their excessive length has nothing to do with locomotion. The insect, whether resting or walking, seems even to be embarra.s.sed by these outrageous stilts, which it bends awkwardly and tucks away as best it can, not knowing exactly what to do with them.

But wait for the pairing; and the extravagant becomes reasonable. The couple take up their pose in the form of a T. The male, standing perpendicularly, or nearly, represents the cross-piece and the female the shaft of the letter, lying on its side. To steady his att.i.tude, which is so contrary to the usual position in pairing, the male flings out his long grappling-hooks, two sheet-anchors which grip the female's shoulders, the fore-edge of her corselet, or even her head.

At this moment, the only moment that counts in the adult insect's life, it is a good thing indeed to possess long arms, long hands, like _Clythra longimana_ and _C. longipes_, as the scientific nomenclature calls them. Although their names are silent on the subject, the Taxicorn Clythra and the Six-spotted Clythra (_C. s.e.xmaculata_, FAB.) and many others also have recourse to the same means of equilibrium: their fore-legs are utterly exaggerated.

Is the difficulty of pairing in a transversal position the explanation of the long grappling-irons thrown out to a distance? We will not be too certain, for here is the Four-spotted Clythra, who would flatly contradict us. The male has fore-legs of modest dimensions, in conformity with the usual rules; he places himself crosswise like the others and nevertheless achieves his ends without hindrance. He finds it enough to modify slightly the gymnastics of his embrace. The same may be said of the different Cryptocephali, who all have stumpy limbs.

Wherever we look, we find special resources, known to some and unknown to others.

CHAPTER XIX THE CLYTHRae: THE EGG

Let us leave the long-armed and short-armed to pursue their amorous contests as they please and come to the egg, the main object of my insect-rearing. The Taxicorn Clythra is the first in the field; I see her at working during the last days of May. A most singular and disconcerting batch of eggs is hers! Is it really a group of eggs? I hesitate until I surprise the mother using her hind-legs to finish extracting the strange germ which issues slowly and perhaps laboriously from her oviduct.

It is indeed the Taxicorn Clythra's batch. a.s.sembled in bundles of one to three dozen and each fastened by a slender transparent thread slightly longer than itself, the eggs form a sort of inverted umbel, which dangles sometimes from the trelliswork of the cover, sometimes from the leaves of the twigs that provide the grub with food. The bunch of grains quivers at the least breath.

We know the egg-cl.u.s.ter of the Hemerobius, the object of so many mistakes to the untrained observer. The little Lace-winged Fly with the gold eggs sets up on a leaf a group of long, tiny columns as fine as a spider's thread, each bearing an egg as a capital. The whole resembles pretty closely a tuft of some long-stemmed mildew. Remember also the Eumenes' hanging egg,[1] which swings at the end of a thread, thus protecting the grub when it takes its first mouthfuls of the heap of dangerous game. The Taxicorn Clythra provides us with a third example of eggs fitted with suspension-threads, but so far nothing has given me an inkling of the function or the use of this string. Though the mother's intentions escape me, I can at least describe her work in some detail.

[Footnote 1: Cf. _The Mason-wasps_: chap. i.--_Translator's Note_.]

The eggs are smooth, coffee-coloured and shaped like a thimble. If you hold them to the light, you see in the thickness of their skin five circular zones, darker than the rest and producing almost the same effect as the hoops of a barrel. The end attached to the suspension-thread is slightly conical; the other is lopped off abruptly and the section is hollowed into a circular mouth. A good lens shows us inside this, a little below the rim, a fine white membrane, as smooth as the skin of a drum.

In addition, from the edge of the orifice there rises a wide membranous tab, whitish and delicate, which might be taken for a raised lid. Nevertheless there is no raising of a lid after the eggs are laid. I have seen the egg leave the oviduct; it is then what it will be later, but lighter in colour. No matter: I cannot believe that so complicated a machine can make its way, with all sail set, through the maternal straits. I imagine that the lid-like appendage remains lowered, closing the mouth, until the moment when the egg sees the light. Then and not till then does it rise.

Guided by the rather less complex structure of the eggs of the other Clythrae and of the Cryptocephali, I think of trying to take the strange germ to pieces; and I succeed after a fas.h.i.+on. Under the coffee-coloured sheath, which forms a little five-hooped barrel, is a white membrane. This is what we see through the mouth and what I compared with the skin of a drum. I recognize it as the regulation tunic, the usual envelope of any insect's egg. The rest, the little brown barrel, broached at one end and bearing a raised lid, must therefore be an accessory integument, a sort of exceptional sh.e.l.l, of which I do not as yet know any other example.

The Long-legged Clythra and the Four-spotted Clythra know nothing of packing their eggs in long-stemmed bundles. In June, from the height of the branches in which they are grazing, both of them carelessly allow their eggs to drop to the ground, one by one, here and there, at random and at long intervals, without giving the least thought to their installation. They might be little grains of excrement, unworthy of interest and ejected at hazard. The egg-factory and the dung-factory scatter their products with the same indifference.

Nevertheless, let us bring the lens to bear upon the minute particle so contumeliously treated. It is a miracle of elegance. In both species of Clythrae the eggs have the form of truncated ellipsoids, measuring about a millimetre in length.[2] The Long-legged Clythra's are a very dark brown and remind one of a thimble, a comparison which is the more exact inasmuch as they are dented with quadrangular pits, arranged in spiral series which cross one another with exquisite precision.

[Footnote 2: .039 inch.--_Translator's Note_.]

Those of the Four-spotted Clythra are pale in colour. They are covered with convex scales, overlapping in diagonal rows, ending in a point at the lower extremity, which is free and more or less askew. This collection of scales has rather the appearance of a hop-cone. Surely a very curious egg, ill-adapted to gliding gently through the narrow pa.s.sages of the ovaries. I feel sure that it does not bristle in this fas.h.i.+on when it descends the delicate natal sheath; it is near the end of the oviduct that it receives its coat of scales.

In the case of the three Cryptocephali reared in my cages, the eggs are laid later; their season is the end of June and July. As in the Clythrae, there is the same lack of maternal care, the same hap-hazard dropping of the seeds from the centaury-blossoms and the ilex-twigs.

The general form of the egg is still that of a truncated ellipsoid.

The ornaments vary. In the eggs of the Golden Cryptocephalus and the Ilex Cryptocephalus they consist of eight flattened, wavy ribs, winding corkscrew-wise; in those of the Two-spotted Cryptocephalus they take the form of spiral rows of pits.

What can this envelope be, so remarkable for its elegance, with its spiral mouldings, its thimble-pits and its hop-scales? A few little accidental facts put me on the right track. To begin with, I acquire the certainty that the egg does not descend from the ovaries as I find it on the ground. Its ornamentation, incompatible with a gentle gliding movement, had already told me as much; I now have a clear proof.

Mingled with the normal eggs of both the Golden Cryptocephalus and the Long-legged Clythra, I find others which differ in no respect from the usual run of insects' eggs. The eggs are perfectly smooth, with a soft, pale-yellow sh.e.l.l. As the cage contains no other insects than the Clythra under consideration or the Cryptocephalus, I cannot be mistaken as to the origin of my finds.

Moreover, if any doubts remained, they would be dispelled by the following evidence: in addition to the bare, yellow eggs there are some whose base is set in a tiny brown, pitted cup, obviously the work of either the Two-spotted Cryptocephalus or the Long-legged Clythra, according to the cage, but unfinished work, which half-clothed the egg, as it left the ovaries, and then, when the dress-material ran short, or something went wrong with the machinery, allowed it to cross the outer threshold in the likeness of an acorn fixed in its cup.

Nothing could be prettier than this yellow egg, standing in its artistic egg-cup. Nor could anything tell us more conclusively where the jewel is manufactured. It is in the cloaca, the chamber common to the oviduct and the intestine, that the bird wraps its egg in a calcareous sh.e.l.l, often decorating it with magnificent hues: olive-green for the Nightingale, sky-blue for the Wheatear, soft pink for the Icterine Warbler. It is in the cloaca also that the Clythra and the Cryptocephalus produce the elegant armour of their eggs.

It remains to decide upon the material employed. From its h.o.r.n.y appearance there is reason to believe that the little barrel of the Taxicorn Clythra and the scales of the Four-spotted Clythra are the products of a special secretion; and, now that it is too late, I much regret that I neglected to look for the apparatus yielding this secretion in the neighbourhood of the cloaca. As for the thing so prettily wrought by the Long-legged Clythra and the Cryptocephali, let us admit without false shame that it is made of faecal matter.

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 sh.e.l.l formed of the chalky secretions.

_Materiem superabat opus, nam Mulciber illic aequora 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-sh.e.l.l is a temporary defensive cell which at hatching-time is broken and abandoned and is henceforth useless. Made of h.o.r.n.y matter or stercoral paste, the sh.e.l.l 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 sh.e.l.l, 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-sh.e.l.l intact, save for an opening through which they pa.s.s their head, and which, all their lives long, remain clad in this sh.e.l.l, on condition that they themselves enlarge it as they grow. This absurd dream is realized by our grub: it is dressed in the sh.e.l.l 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 gla.s.s 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 sh.e.l.ls, 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 refres.h.i.+ng herself by soberly notching some tender leaf. The Taxicorn Clythra fits a long stalk to her eggs and fixes them in cl.u.s.ters 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 Clythrae and the Cryptocephali are scattered over the ground beneath the tree or plant on which the adult feeds.