The Glow-Worm and Other Beetles

When the time comes for the grub to bury itself in the ground, there to undergo the transformation, it lays aside its mantle, with the object perhaps of easing itself when it descends from the top of the plant, or else with the object of taking a bath in that kindly sunlight whereof it has hitherto tasted so little under its moist coverlet. This naked journey over the leaves, the last joy of its larval life, is fatal to the traveller. Up comes the Tachina, who, finding a clean skin, all sleek with fat, loses no time in dabbing her eggs upon it.

A census of the intact and of the injured larvæ provides us with particulars which agree with what we foresaw from the nature of their respective lives. The most exposed to parasites is the Field Crioceris, whose larva lives in the open air, without any sort of protection. Next comes the Twelve-spotted Crioceris, who is established in the asparagus-berry from her early infancy. The most favoured is the Lily-beetle, who, while a grub, makes an ulster of her excretions.

For the second time, we are here confronted by three insects which look as if they had all come out of one mould, so much are they alike in shape. If the costumes were not different and the sizes dissimilar, we should not know how to tell one from another. And this pronounced resemblance in figure is accompanied by a no less pronounced lack of resemblance in instinct.

The evacuator that soils its back cannot have inspired the hermit living in cleanly retirement inside its globe; the occupant of the asparagus-berry did not advise the third to live in the open and wander like an acrobat through the leafage. None of the three has initiated the customs of the other two. All this seems to me as clear as daylight. If they have issued from the same stock, how have they acquired such dissimilar talents?

Furthermore, have these talents developed by degrees? The Lily-beetle is prepared to tell us. Her grub, let us suppose, once conceived the notion, when tormented by the Tachina, of making the stercoral slit open above. By accident, with no definite purpose in view, it emptied the contents of its intestine over its back. The natty Fly hesitated in the presence of this filth. The grub, in its cunning, recognized, as time went on, the benefit to be derived from its poultice; and what at first was an unpremeditated pollution became a prudent custom.

As success followed upon success, with the aid of the centuries, of course, for these inventions always take centuries, the dung overcoat was extended from the hinder end to the fore-part, right down to the forehead. Finding itself the gainer by this invention, setting the parasite at defiance under its coverlet, the grub made a strict law of what was an accident; and the Crioceris faithfully handed down the repulsive great-coat to her offspring.

So far this is not so bad. But things now begin to become complicated. If the insect was really the inventor of its defensive methods, if it discovered for itself the advantage of hiding under its ordure, I look to its ingenuity to keep up the tricks until the precise moment has come for burying itself. But, on the contrary, it undresses itself some time beforehand; it wanders about naked, taking the air on the leaves, at a time when its fair round belly is more than ever likely to tempt the Fly. It completely forgets, on its last day, the prudence which it acquired by the long apprenticeship of the centuries.

This sudden change of purpose, this heedlessness in the face of danger tells me that the insect forgets nothing, because it has learnt nothing, because it has invented nothing. When the instincts were being distributed, it received as its share the overcoat, of whose methods it is ignorant, though it benefits by its advantages. It has not acquired it by successive stages, followed by a sudden halt at the most dangerous moment, the moment most calculated to inspire it with distrust; it is no more and no less gifted than it was in the beginning and is unable in any way to alter its tactics against the Tachina and its other enemies.

Nevertheless, we must not be in a hurry to attribute to the garment of filth the exclusive function of protecting the grub against the parasite. It is difficult to see in what respect the Lily-grub is more deserving than the Asparagus-grub, which possesses no defensive arts. Perhaps it is less fruitful and, to make up for the poverty of the ovaries, boasts an ingenuity which safeguards the race. Nor is there anything to tell us that the soft coverlet is not at the same time a shelter which screens a too sensitive skin from the sun. And, if it were a mere fal-lal, a furbelow of larval coquetry, even that would not surprise me. The insect has tastes which we cannot judge by our own. Let us end with a doubt and proceed.

May is not over when the grub, now fully-grown, leaves the lily and buries itself at the foot of the plant, at no great depth. Working with its head and rump, it forces back the earth and makes itself a round recess, the size of a pea. To turn the cell into a hollow pill which will not be liable to collapse, all that remains for it to do is to drench the wall with a glue which soon sets and grips the sand.

To observe this work of consolidation, I unearth some unfinished cells and make an opening which enables me to watch the grub at work. The hermit is at the window in a moment. A stream of froth pours from his mouth like beaten-up white of egg. He slavers, spits profusely; he makes his product effervescence and lays it on the edge of the breach. With a few spurts of froth the opening is plugged.

I collect other grubs at the moment of their interment and install them in glass tubes with a few tiny bits of paper which will serve them as a prop. There is no sand, no building-material other than the creature's spittle and my very few shreds of paper. Under these conditions can the pill-shaped cell be constructed?

Yes, it can; and without much difficulty. Supporting itself partly on the glass, partly on the paper, the larva begins to slaver all around it, to froth copiously. After a spell of some hours, it has disappeared within a solid shell. This is white as snow and highly porous; it might almost be a globule of whipped albumen. Thus, to stick together the sand in its pill-shaped nest, the larva employs a frothy albuminous substance.

Let us now dissect the builder. Around the oesophagus, which is fairly long and soft, are no salivary glands, no silk-tubes. The frothy cement is therefore neither silk nor saliva. One organ forces itself upon our attention: it is the crop, which is very capacious, and dilated with irregular protuberances that put it out of shape. It is filled with a colourless, viscous fluid. This is certainly the raw material of the frothy spittle, the glue that binds the grains of sand together and consolidates them into a spherical whole.

When the preparations for the metamorphosis are at hand, the stomachic pouch, having no longer to do duty as a digestive laboratory, serves the insect as a factory, or a warehouse for different purposes. Here the Sitares store up their uric waste products; here the Capricorns collect the chalky paste which becomes the stone lid for the entrance to the cell; here caterpillars keep in reserve the gums and powders with which they strengthen the cocoon; hence the Hymenoptera draw the lacquer which they employ to upholster their silken edifice. And now we find the Lily-beetle using it as a store for frothy cement.[113 - This subject is continued in the essay on the Foamy Cicadella. Cf. The Life of the Grasshopper: chap. xx. —Translator's Note.] What an obliging organ is this digestive pouch!

The two Asparagus-beetles are likewise proficient dribblers, worthy rivals of their kinswoman of the lily in the matter of building. In all three cases the underground shell has the same shape and the same structure.

When, after a subterranean visit of two months' duration, the Lily-beetle returns to the surface in her adult form, a botanical problem remains to be solved before the history of the insect is completed. We are now at the height of summer. The lilies have had their day. A dry, leafless stick, surmounted by a few tattered capsules, is all that is left of the magnificent plant of the spring. Only the onion-like bulb remains a little way down. There, postponing the process of vegetation, it waits for the steady rains of the autumn, which will renew its strength and make it burgeon into a sheaf of leaves.

How does the Lily-beetle live during the summer, before the return of the green foliage dear to its race? Does it fast during the extreme heat? If abstinence is its rule of life in this season of vegetable dearth, why does it emerge from underground, why does it abandon its shell, where it could sleep so peacefully, without the necessity of eating? Can it be need of food that drives it from the substratum and sends it to the sunlight so soon as the wing-cases have assumed their vermilion hue? It is very likely. For the rest, let us look into the matter.

On the ruined stems of my white lilies I find a portion covered with a scrap of green skin. I set it before the prisoners in my jars, who emerged from their sandy bed a day or two ago. They attack it with an appetite which is extremely conclusive; the green morsel is stripped bare to the wood. Soon I have nothing left, in the way of their regulation diet, to offer my famished captives. I know that all the lilies, native or exotic, the Turk's cap lily, or Martagon, the lily of Chalcedon, the tiger lily and many others, are to their taste; I do not forget that the crown imperial fritillary and the Persian fritillary are equally welcome; but most of these delicate plants have refused the hospitality of my two acres of pebbles and those which it is more or less possible for me to grow are now as tattered as the common lily. There is not a patch of green left on them.

In botany the lily gives its name to the family of the Liliaceæ, of which it is the leading representative. Those who feed upon the lily ought also, in the absence of anything better, to accept the other plants of the same group. This is my opinion at first; it is not that of the Crioceris, who knows more than I do about the virtues of plants.

The family of the Liliaceæ is subdivided into three tribes: the lilies, the daffodils and the asparaguses. Not any of the daffodil tribe suit my famishing prisoners, who allow themselves to die of inanition on the leaves of the following genera, the only varieties with which the modest resources of my garden have allowed me to experiment: asphodel, funkia, or niobe, agapanthus, or African lily, tritelia, hemerocallis, or day lily, tritoma, garlic, ornithogalum, or star of Bethlehem, squill, hyacinth, muscari, or grape-hyacinth. I record, for whom it may concern, this profound contempt of the Crioceris for the daffodils. An insect's opinion is not to be despised: it tells us that we should obtain a more natural arrangement by separating the daffodils farther from the lilies.

In the first of the three tribes, the classic white lily, the plant preferred by the insect, takes the chief place; next come the other lilies and the fritillaries, a diet almost as much sought after; and lastly the tulips, which the season is too far advanced to allow me to submit for the approval of the Crioceris.

The third tribe had a great surprise in store for me. The red Crioceris fed, though with a very scornful tooth, on the foliage of the asparagus, the favourite dish of the Field Crioceris and the Twelve-spotted Crioceris. On the other hand, she feasted rapturously on the lily of the valley (Convallaria maialis) and on Solomon's seal (Polygonatum vulgare), both of which are so different from the lily to any eye untrained in the niceties of botanical analysis.

She did more: she browsed, with every appearance of a contented stomach, on a prickly creeper, Smilax aspera, which tangles itself in the hedges with its corkscrew tendrils and produces, in the autumn, graceful clusters of small red berries, which are used for Christmas decorations. The fully-developed leaves are too hard for her, too tough; she wants the tender tips of the nascent foliage. When I take this precaution, I can feed her on the intractable vine as readily as on the lily.

The fact that the smilax is accepted gives me confidence in the prickly butcher's-broom (Ruscus aculeatus), another shrub of sturdy constitution, admitted to the family rejoicings at Christmas because of its handsome green leaves and its red berries, which are like big coral beads. In order not to discourage the consumer with leaves that are too hard, I select some young seedlings, newly sprouted and still bearing the round berry, the nutritive gourd, hanging at their base. My precautions lead to nothing: the insect obstinately refuses the butcher's-broom, on which I thought that I might rely after the smilax had been accepted.

We have our botany; the Crioceris has hers, which is subtler in its appreciation of affinities. Her domain comprises two very natural groups, that of the lily and that of the smilax, which, with the advance of science, has become the family of the Smilaceæ. In these two groups she recognizes certain genera – the more numerous – as her own; she refuses the others, which ought perhaps to be revised before being finally classified.

An exclusive taste for the asparagus, one of the foremost representatives of the Smilaceæ, characterizes the two other Crioceres, those eager exploiters of the cultivated asparagus. I find them also pretty often on the needle-leaved asparagus (A. acutifolius), a forbidding-looking shrub with long, flexible stems bearing many branches, which the Provençal vine-grower uses, under the name of roumiéu, as a filter before the tap of the wine-vat, to prevent the refuse of the grapes from choking up the vent-hole. Apart from these two plants, the two Crioceres refuse absolutely everything, even when in July they come up from the earth with the famishing stomachs which the long fast of the metamorphosis has given them. On the same wild asparagus, disdainful of the rest, lives a fourth Crioceris (C. paracenthesia), the smallest of the group. I do not know enough of her habits to say anything more about her.

These botanical details tell us that the Crioceres, which hatch early, in the middle of summer, have no reason to fear famine. If the Lily-beetle can no longer find her favourite plant, she can browse upon Solomon's seal and smilax, not to mention the lily of the valley and, I dare say, a few others of the same family. The other three are more favoured. Their food-plant remains erect, green and well provided with leaves until the end of autumn. The wild asparagus even, undaunted by the extreme cold, maintains a sturdy existence all the year round. Belated resources, moreover, are superfluous. After a brief period of summer freedom, the various Crioceres seek their winter quarters and go to earth under the dead leaves.

CHAPTER XVIII

THE CLYTHRÆ

The Lily-beetle dresses herself: with her ordure she makes herself a cosy gown, an infamous garment, it is true, but an excellent protection against parasites and sunstroke. The weaver of fæcal cloth has hardly any imitators. The Hermit-crab dresses himself: he selects to fit him, from the discarded wardrobe of the Sea-snail, an empty shell, damaged by the waves; he slips his poor abdomen, which is incapable of hardening, inside it and leaves outside his great fists of unequal size, clad in stone boxing-gloves. This is yet another example rarely followed.

With a few exceptions, all the more remarkable because they are so rare, the animal, in fact, is not burdened by the need of clothing itself. Endowed, without having to manufacture a thing, with all that it wants, it knows nothing of the art of adding defensive extras to its natural covering.

The bird has no need to take thought of its plumage, the furry beast of its coat, the reptile of its scales, the Snail of his shell, the Ground-beetle of his jerkin. They display no ingenuity with the object of securing protection from the inclemencies of the atmosphere. Hair, down, scales, mother-of-pearl and other items of the animal's apparel: these are all produced of their own accord, on an automatic loom.

Man, for his part, is naked; and the severities of the climate oblige him to wear an artificial skin to protect his own. This poverty has given rise to one of our most attractive industries.

He invented clothing who, shivering with cold, first thought of flaying the Bear and covering his shoulders with the brute's hide. In a distant future this primitive cloak was gradually to be replaced by cloth, the product of our industry. But under a mild sky the traditional fig-leaf, the screen of modesty, was for a long while sufficient. Among peoples remote from civilization, it still suffices in our day, together with its ornamental complement, the fish-bone through the cartilage of the nose, the red feather in the hair, the string round the loins. We must not forget the smear of rancid butter, which serves to keep off the Mosquito and reminds us of the unguent employed by the grub that dreads the Tachina.

In the first rank of the animals protected against the bite of the atmosphere without the intervention of a handicraft are those which go clad in hair, dressed free of cost in fleeces, furs or pelts. Some of these natural coats are magnificent, surpassing our downiest velvets in softness.

Despite the progress of weaving, man is still jealous of them. To-day, as in the ages when he sheltered under a rock, he values furs greatly for the winter. At all seasons he holds them in high esteem as ornamental accessories; he glories in sewing on his attire a shred of some wretched flayed beast. The ermine of kings and judges, the white rabbit-tails with which the university graduate adorns his left shoulder on solemn occasions carry us back in thought to the age of the cave-dwellers.

Moreover, the fleecy animals still clothe us in a less primitive fashion. Our woollens are made of hairs interlaced. Ever since the beginning, without hoping to find anything better, man has clothed himself at the expense of the hairy orders of creation.

The bird, a more active producer of heat, whose maintenance is a more delicate matter, covers itself with feathers, which overlap evenly, and puts round its body a thick cushion of air on a bed of down. It has on its tail a pot of cosmetic, a bottle of hair-oil, a fatty gland from which the beak obtains an ointment wherewith it preens the feathers one by one and renders them impermeable to moisture. A great expender of energy by reason of the exigencies of flight, it is essentially, chilly creature that it is, better-adapted than any other to the retention of heat.

For the slow-moving reptile the scales suffice, preserving it from hurtful contacts, but playing hardly any part as a bulwark against changes of temperature.

In its liquid environment, which is far more constant than the air, the fish requires no more. Without effort on its part, without violent expenditure of motor force, the swimmer is borne up by the mere pressure of the water. A bath whose temperature varies but little enables it to live in ignorance of excessive cold or heat.

In the same way, the mollusc, for the most part a denizen of the seas, leads a blissful life in its shell, which is a defensive fortress rather than a garment. Lastly the crustacean confines itself to making a suit of armour out of its mineral skin.

In all these, from the hairy to the crustaceous, the real coat, the coat turned out by a special industry, does not exist. Hair, fur, feather, scale, shell, stony armour require no intervention of the wearer; they are natural products, not the artificial creations of the animal. To find clothiers able to place upon their backs that which their organization refuses them, we must descend from man to certain insects.

Ridiculous attire, of which we are so proud, made from the slaver of a caterpillar or the fleece of a silly sheep: among its inventors the first and foremost is the Crioceris-larva, with its jacket of dung! In the art of clothing itself, it preceded the Eskimo, who scrapes the bowels of the seal to make himself a suit of dittos; it forestalled our ancestor the troglodyte, who borrowed the fur-coat of his contemporary the Cave-bear. We had not got beyond the fig-leaf, when the Crioceris already excelled in the manufacture of homespun, both providing the raw material and piecing it together.

For reasons of economy and easy acquisition, its disgusting method, but with very elegant modifications, suits the clan of the Clythræ and Cryptocephali, those pretty and magnificently coloured Beetles. Their larva, a naked little grub, makes itself a long, narrow pot, in which it lives just like the Snail in his shell. As a coat and as a dwelling the timid creature makes use of a jar, better still, of a graceful vase, the product of its industry.

Once inside, it never comes out. If anything alarms it, with a sudden recoil it withdraws completely into its urn, the opening of which is closed with the disk formed by the flat top of the head. When quiet is restored, it ventures to put out its head and the three segments with legs to them, but is very careful to keep the rest, which is more delicate and fastened to the back, inside.

With tiny steps, weighted by the burden, it makes its way along, lifting its earthenware container behind it in a slanting position. It makes one think of Diogenes, dragging his house, a terra-cotta tub, about with him. The thing is rather unwieldy, because of the weight, and is liable to heel over, owing to the excessive height of the centre of gravity. It makes progress all the same, tilting like a busby rakishly cocked over one ear. One of our Land-snails, the Bulimus, whose shell is continued into a turret, moves almost in the same fashion, tumbling repeatedly as he goes.

The Clythra's is a shapely jar and does credit to the insect's art of pottery. It is firm to the touch, of earthy appearance and smooth as stucco inside, while the outside is relieved by delicate diagonal, symmetrical ribs, which are the traces of successive enlargements. The back part is slightly dilated and is rounded off at the end with two slight bumps. These two terminal projections, with the central furrow which divides them, and the ribs marking additions, which match on either side, are evidence of work done in two parts, in which the artist has followed the rules of symmetry, the first condition of the beautiful.

The front part is of rather smaller diameter and is cut off on a slant, which enables the jar to be lifted and supported on the larva's back as it moves. Lastly, the mouth is circular, with a blunt edge.

Any one finding one of these jars for the first time, among the stones at the foot of an oak, and wondering what its origin could be, would be greatly puzzled. Is it the stone of some unknown fruit, emptied of its kernel by the patient tooth of the Field-mouse? Is it the capsule of a plant, from which the lid has dropped, allowing the seeds to fall? It has all the accuracy, all the elegance of the masterpieces of the vegetable kingdom.