Kitabı oku: «The Glow-Worm and Other Beetles», sayfa 18

CHAPTER XVI
THE CRIOCERES

I am a stubborn disciple of St. Thomas the Apostle and, before I agree to anything, I want to see and touch it, not once, but twice, thrice, an indefinite number of times, until my incredulity bows beneath the weight of evidence. Well, the Rhynchites¹¹¹ have told us that the build does not determine the instincts, that the tools do not decide the trade. And now, yes, the Crioceres come and add their testimony. I question three of them, all common, too common, in my paddock. At the proper season, I have them before my eyes, without searching for them, whenever I want to ask them for information.

The first is the Crioceris of the Lily, or Lily-beetle. Since Latin words offend our modesty let us just once mention her scientific name, Crioceris merdigera, LIN., without translating it, or, above all, repeating it. Decency forbids. I have never been able to understand why natural history need inflict upon a lovely flower or an engaging animal an odious name.

As a matter of fact, our Crioceris, so ill-treated by the nomenclators, is a sumptuous creature. She is nicely shaped, neither too large nor too small, and a beautiful coral red, with jet-black head and legs. Everybody knows her who in the spring has ever glanced at the lily, when its stem is beginning to show in the centre of the rosette of leaves. A Beetle, of less than the average size and coloured sealing-wax red, is perched up on the plant. Your hand goes out to seize her. Forthwith, paralysed with fright, she drops to the ground.

Let us wait a few days and return to the lily, which is gradually growing taller and beginning to show its buds, gathered together in a bundle. The red insect is still there. Further, the leaves, which are seriously bitten into, are reduced to tatters and soiled with little heaps of greenish ordure. It looks as if some witchcraft had mashed up the leaves and then splashed the mess all over the place.

Well, this filth moves, travels slowly along. Let us overcome our repugnance and poke the heaps with a straw. We uncover, indeed we unclothe an ugly, pot-bellied, pale-orange larva. It is the grub of the Crioceris.

The origin of the garment of which we have just stripped it would be unmentionable, save in the world of the insect, that manufacturer devoid of shame. This doublet is, in fact, obtained from the creature's excretions. Instead of evacuating downwards, on the superannuated principle, the Crioceris' larva evacuates upwards and receives upon its back the waste products of the intestine, materials which move from back to front as each fresh pat is dabbed upon the others. Réaumur has complacently described how the quilt moves forward from the tail to the head by wriggling along inclined planes, making so many dips in the undulating back. There is no need to return to this stercoral mechanism after the master has done with it.

We now know the reasons that procured the Lily-beetle an ignominious title, confined to the official records: the grub makes itself an overcoat of its excrements.

Once the garment is completed so as to cover the whole of the creature's dorsal surface, the clothing-factory does not cease work on that score. At the back a fresh hem is added from moment to moment; but the overlapping superfluity in front drops off of its own weight at the same time. The coat of dung is under continual repair, being renovated and lengthened at one end as it wears and grows shorter at the other.

Sometimes also the stuff is too thick and the heap capsizes. The denuded grub recks nothing of the lost overcoat; its obliging intestine repairs the disaster without delay.

Whether by reason of the clipping that results from the excessive length of a piece which is always on the loom, or of accidents that cause a part or the whole of the load to fall off, the grub of the Crioceris leaves accumulations of dirt in its track, till the lily, the symbol of purity, becomes a very cess-pool. When the leaves have been browsed, the stem next loses its cuticle, thanks to the nibbling of the grub, and is reduced to a ragged distaff. The flowers even, which have opened by now, are not spared: their beautiful ivory chalices are changed into latrines.

The perpetrator of the misdeed embarks on his career of defilement early. I wanted to see him start, to watch him lay the first course of his excremental masonry. Does he serve an apprenticeship? Does he work badly at first, then a little better and then well? I now know all about it: there is no noviciate, there are no clumsy attempts; the workmanship is perfect from the outset, the product ejected spreads over the hinder part. Let me tell you what I saw.

The eggs are laid in May, on the under surface of the leaves, in short trails averaging from three to six. They are cylindrical, rounded at both ends, of a bright orange-red, glossy and varnished with a glutinous wash which makes them stick to the leaves throughout their length. The hatching takes ten days. The shell of the egg, now a little wrinkled, but still of a bright orange colour, retains its position, so that the group of eggs, apart from its slightly withered appearance, remains just as it was.

The young larva measures a millimetre and a half¹¹² in length. The head and legs are black, the rest of the body a dull amber-red. On the first segment of the thorax is a brown sash, interrupted in the middle; lastly, there is a small black speck on each side, behind the third segment. This is the initial costume. Presently orange-red will take the place of the pale amber. The tiny creature, which is exceedingly fat, sticks to the leaf with its short legs and also with its hind-quarters, which act as a lever and push the round belly forwards. The motion reminds you of a cripple sitting in a bowl.

The grubs emerging from any one group of eggs at once begin to browse, each beside the empty skin of its egg. Here, singly, they nibble and dig themselves a little pit in the thickness of the leaf, while sparing the cuticle of the opposite surface. This leaves a translucent floor, a support which enables them to consume the walls of the excavation without risking a fall.

Seeking for better pasture, they move lazily on. I see them scattered at random; a few of them are grouped in the same trench; but I never see them browsing economically abreast as Réaumur relates. There is no order, no understanding between messmates, contemporaries though they be and all sprung from the same row of eggs. Nor is any heed paid to economy: the lily is so generous!

Meanwhile, the paunch swells and the intestine labours. Here we are! I see the first bit of the overcoat evacuated. As is natural in extreme infancy, it is liquid and there is not much of it. The scanty flow is used all the same and is laid methodically, right at the far end of the back. Let the little grub be. In less than a day, piece by piece, it will have made itself a suit.

The artist is a master from the first attempt. If its baby-flannel is so good to start with, what will the future ulster be, when the stuff, brought to perfection, is of much better quality? Let us proceed; we know what we want to know concerning the talents of this manufacturer of excremental broadcloth.

What is the purpose of this nasty great-coat? Does the grub employ it to keep itself cool, to protect itself against the attacks of the sun? It is possible: a tender skin need not be afraid of blistering under such a soothing poultice. Is it the grub's object to disgust its enemies? This again is possible: who would venture to set tooth to such a heap of filth? Or can it be simply a caprice of fashion, an outlandish fancy? I will not say no. We have had the crinoline, that senseless bulwark of steel hoops; we still have the extravagant stove-pipe hat, which tries to mould our heads in its stiff sheath. Let us be indulgent to the evacuator nor disparage his eccentric wardrobe. We have eccentricities of our own.

To feel our way a little in this delicate question, we will question the near kinsmen of the Lily-beetle. In my acre or two of pebbles I have planted a bed of asparagus. The crop, from the culinary point of view, will never repay me for my trouble: I am rewarded in another fashion. On the scanty shoots which I allow to display themselves freely in plumes of delicate green, two Crioceres abound in the spring: the field species (C. campestris, LIN.) and the twelve-spotted species (C. duodecimpunctata, LIN.). A splendid windfall, far better than any bundle of asparagus.

The first has a tricolor costume which is not without merit. Blue wing-cases, braided with white on the outer edge and each adorned with three white dots; a red corselet, with a blue disk in the centre. Its eggs are olive-green and cylindrical and, instead of lying flat, grouped in short lines, after the manner of the lily-dweller's, occur singly and stand on end on the leaves of the asparagus-plant, on the twigs, on the flower-buds, more or less everywhere, without any fixed order.

Though living in the open air on the leaves of its plant and thus exposed to all the various perils that may threaten the Lily-grub, the larva of the Field Crioceris knows nothing whatever of the art of sheltering itself beneath a layer of ordure. It goes through life naked and always perfectly clean.

It is of a bright greenish yellow, fairly fat behind and thinner in front. Its principal organ of locomotion is the end of the intestine, which protrudes, curves like a flexible finger, clasps the twig and supports the creature while pushing it forward. The true legs, which are short and placed too far in front with regard to the length of the body, would find it very difficult by themselves to drag the heavy mass that comes after. Their assistant, the anal finger, is remarkably strong. With no support, the larva turns over, head downwards, and remains suspended when shifting from one sprig to another. This Jack-in-the-bowl is a rope-dancer, a consummate acrobat, performing its evolutions amid the slender sprigs without fear of a fall.

Its attitude in repose is curious. The heavy stern rests on the two hind-legs and especially on the crooked finger, the end of the intestine. The fore-part is lifted in a graceful curve, the little black head is raised and the creature looks rather like the crouching Sphinx of antiquity. This pose is common at times of slumber and blissful digestion in the sun.

An easy prey is this naked, plump, defenceless grub, snoozing in the heat of a blazing day. Various Gnats, of humble size, but very likely terribly treacherous, haunt the foliage of the asparagus. The larva of the Crioceris, motionless in its sphinx-like attitude, does not appear to be on its guard against them, even when they come buzzing above its rump. Can they be as harmless as their peaceful frolics seem to proclaim? It is extremely doubtful: the Fly rabble are not there merely to imbibe the scanty exudations of the plant. Experts in mischief, they have no doubt hastened hither with another object.

And, in truth, on the greater number of the Crioceris-larvæ we find, adhering firmly to the skin, certain white specks, very small and of a china-white. Can these be the sowing of a bandit, the spawn of a Midge?

I collect the grubs marked with these white specks and rear them in captivity. A month later, about the middle of June, they shrivel, wrinkle and turn brown. All that is left of them is a dry skin which tears from end to end, half uncovering a Fly-pupa. A few days later, the parasite emerges.

It is a small, greyish Fly, fiercely bristling with sparse hairs, half the size of the House-fly, whom it resembles slightly. It belongs to the Tachina group, who, in their larval form, so often inhabit the bodies of caterpillars.

The white spots sprinkled over the larva of the Crioceris were the eggs of the hateful Fly. The vermin born of those eggs have perforated the victim's paunch. By subtle wounds, which cause little pain and are almost immediately healed, they have penetrated the body, reaching the humours in which the entrails are bathed. At first the larva invaded is not aware of its danger; it continues to perform its rope-dancer's gymnastics, to fill its belly and to take its siestas in the sun, as though nothing serious had occurred.

Reared in a glass tube and often examined under the lens, my parasite-ridden larvæ betray no uneasiness. The fact is that the Tachina's children display an infernal judgment in their first actions. Until the moment when they are ready for the transformation, their portion of game has to hold out, must be kept fresh and alive. They therefore gorge themselves with the reserves intended for future use, the fats, the savings which the Crioceris hoards in view of the remodelling whence the perfect insect will emerge; they consume what is not essential to the life of the moment and are very careful not to touch the organs which are indispensable at the present time. If these received a bite, the host would die and so would they. Towards the end of their growth, prudence and discretion being no longer essential, they make a complete clearance of the victim, leaving only the skin, which will serve them for a shelter.

One satisfaction is vouchsafed me in these horrible orgies: I see that the Tachina in her turn is subjected to severe reductions. How many were there on the larva's back? Perhaps eight, ten or more. One Midge, never more than one, comes out of the victim's skin, for the morsel is too small to provide food for many. What has become of the others? Has there been an internecine battle inside the poor wretch's body? Have they eaten one another up, leaving only the strongest to survive, or the one most favoured by the chances of the fight? Or has one of them, earlier developed than the rest, found himself master of the stronghold and have the others preferred to die outside rather than enter a grub already occupied, where famine would be rife if the messmates numbered even two? I am all for mutual extermination. Kinsman's flesh or stranger's flesh must be all one to the fangs of the vermin swarming in the Crioceris' belly.

Fierce though the competition is among these bandits, the Beetle's race does not threaten to die out. I review the innumerable troop on my asparagus-bed. A good half of them have Tachina-eggs plainly visible as tiny white specks on their green skins. The blemished larvæ tell me of a paunch already or on the point of being invaded. On the other hand, it is doubtful whether those which are unscathed will all remain in that condition. The malefactor is incessantly prowling around the green plumes, watching for a favourable opportunity. Many larvæ free from white spots to-day will show them to-morrow or some other day, so long as the Fly's season lasts.

I estimate that the vast majority of the troop will end by being infested. My rearing-experiments tell me much on this point. If I do not make a careful selection when I am stocking my wire-gauze-covers, if I go to work at random in picking the branches colonized with larvæ, I obtain very few adult Crioceres; nearly all of them are resolved into a cloud of Midges.

If it were possible for us to wage war effectually upon an insect, I should advise asparagus-growers to have recourse to the Tachina, though I should cherish no illusions touching the results of the expedient. The exclusive tastes of the insect auxiliary draw us into a vicious circle: the remedy allays the evil, but the evil is inseparable from the remedy. To rid ourselves of the ravages of the asparagus-beds, we should need a great many Tachinæ; and to obtain a great many Tachinæ we should first of all need a great many ravagers. Nature's equilibrium balances things as a whole. Whenever Crioceres abound, the Midges that reduce them arrive in numbers; when Crioceres become rare, the Midges decrease, but are always ready to return in masses and repress a surplus of the others during a return of prosperity.

Under its thick mantle of ordure the grub of the Lily-beetle escapes the troubles so fatal to its cousin of the asparagus. Strip it of its overcoat: you will never find the terrible white specks upon its skin. The method of preservation is most effective.

Would it not be possible to find a defensive system of equal value without resorting to detestable filth? Yes, of course: the insect need only house itself under a covering where there would be nothing to fear from the Fly's eggs. This is what the Twelve-spotted Crioceris does, occupying the same quarters as the Field Crioceris, from whom she differs in size, being rather larger, and still more in her costume, which is rusty red all over, with twelve black spots distributed symmetrically on the wing-cases.

Her eggs, which are a deep olive-green and cylindrical, pointed at one pole and squared off at the other, closely resemble those of the Field Crioceris and, like these, usually stand up on the supporting surface, to which they are fastened by the square end. It would be easy to confuse the two if we had not the position which they occupy to guide us. The Field Crioceris fastens her eggs to the leaves and the thin sprays; the other plants them exclusively on the still green fruit of the asparagus, globules the size of a pea.

The grubs have to open a tiny passage for themselves and to make their own way into the fruit, of which they eat the pulp. Each globule harbours one larva, no more, or the ration would be insufficient. Often, however, I see two, three or four eggs on the same fruit. The first grub hatched is the one favoured by luck. He becomes the owner of the pill, an intolerant owner capable of wringing the neck of any who should come and sit down at table beside him. Always and everywhere this pitiless competition!

The grub of the Twelve-spotted Crioceris is a dull white, with an interrupted black scarf on the first segment of the thorax. This sedentary creature has none of the talents of the acrobat grazing on the swaying foliage of the asparagus; it cannot take a grip with its posterior, turned into a prehensile finger. What use would it have for such a prerogative, loving repose as it does and destined to put on fat in its cell, without roaming in quest of food? In the same group each species has its own gifts, according to the kind of life that awaits it.

It is not long before the occupied fruit falls to the ground. Day by day, it loses its green colour as the pulp is consumed. It becomes, at last, a pretty, diaphanous opal sphere, while the berries which have not been injured ripen on the plant and acquire a rich scarlet hue.

When there is nothing left to eat inside the skin of its pill, the grub makes a hole in it and goes underground. The Tachinæ have spared it. Its opal box, the hard rind of the berry, has ensured its safety just as well as a filthy overcoat would have done and perhaps even better.

CHAPTER XVII
THE CRIOCERES (continued)

The Crioceris has found safety inside its opal globe. Safety? Ah, but what an unfortunate expression I have used! Is there any one in the world who can flatter himself that he has escaped the spoiler?

In the middle of July, at the time when the Twelve-spotted Crioceris comes up from under the ground in the adult form, my rearing-jars yield me swarms of a very small Gall-fly, a slender, graceful, blue-black Chalcid, without any visible boring-tool. Has the puny creature a name? Have the nomenclators catalogued it? I do not know, nor do I much care; the main thing is to learn that the covering of the asparagus-berry, which becomes an opal globe when the grub has emptied it, has failed to save the recluse. The Tachina-midge drains her victim by herself; this other, tinier creature feasts in company. Twenty or more of them batten on the grub together.

When everything seems to foretell a quiet life, a pigmy among pigmies appears, charged with the express duty of exterminating an insect which is protected first by the casket of the berry and next by the shell, the underground work of the grub. To eat the Twelve-spotted Crioceris is its mission in life, its special function. When and how does it deliver its attack? I do not know.

At any rate, proud of her vocation and finding life sweet, the Chalcid curls her antennæ into a crook and waves them to and fro: she rubs her tarsi together, a sign of satisfaction; she dusts her belly. I can hardly see her with the naked eye; and yet she is an agent of the universal extermination, a wheel in the implacable machine which crushes life as in a wine-press.

The tyranny of the belly turns the world into a robber's cave. Eating means killing. Distilled in the alembic of the stomach, the life destroyed by slaughter becomes so much fresh life. Everything is melted down again, everything has a fresh beginning in death's insatiable furnace.

Man, from the alimentary point of view, is the chief brigand, consuming everything that lives or might live. Here is a mouthful of bread, the sacred food. It represents a certain number of grains of wheat which asked only to sprout, to turn green in the sun, to shoot up into tall stalks crowned with ears. They died that we might live. Here are some eggs. Left undisturbed with the Hen, they would have emitted the Chickens' gentle cheep. They died that we might live. Here is beef, mutton, poultry. Horror, it smells of blood, it is eloquent of murder! If we gave it a thought, we should not dare to sit down to table, that altar of cruel sacrifices.

How many lives does the Swallow, to mention only the most peaceable, harvest in the course of a single day! From morning to evening he gulps down Crane-flies, Gnats and Midges joyously dancing in the sunbeams. Quick as lightning he passes; and the dancers are decimated. They perish; then their melancholy remnants fall from the nest containing the young brood, in the form of guano which becomes the turf's inheritance. And so it is with all and everything, with large and small, from end to end of the animal progression. A perpetual massacre perpetuates the flux of life.

Appalled by these butcheries, the thinker begins to dream of a state of affairs which would free us from the horrors of the maw. This ideal of innocence, as our poor nature vaguely sees it, is not an impossibility; it is partly realized for all of us, men and animals.

Breathing is the most imperious of needs. We live by the air before we live by bread; and this happens of itself, without painful struggles, without costly labour, almost without our knowledge. We do not set out, armed for war, to conquer the air by rapine, violence, cunning, barter and desperate labour; the supreme element of life enters our bodies of its own accord; it penetrates us and quickens us. Each of us has his generous share of it without giving the matter a thought.

To crown perfection, it is free. And this will last indefinitely until an ever ingenious Treasury invents distributing-taps and pneumatic receivers from which the air will be doled out to us at so much a piston-stroke. Let us hope that we shall be spared this particular item of scientific progress, for that, woe betide us, would be the end of all things: the tax would kill the tax-payer!

Chemistry, in its lighter moods, promises us, in the future, pills containing the concentrated essence of food. These cunning compounds, the product of our laboratories, would not end our longing to possess a stomach no more burdensome than our lungs and to feed even as we breathe.

The plant partly knows this secret: it draws its carbon quietly from the air, in which each leaf is impregnated with the wherewithal to grow tall and green. But the vegetable is inactive; hence its innocent life. Action calls for strongly flavoured spices, won by fighting. The animal acts; therefore it kills. The highest phase, perhaps, of a self-conscious intelligence, man, deserving nothing better, shares with the brute the tyranny of the belly as the irresistible motive of action.

But I have wandered too far afield. A living speck, swarming in the paunch of a grub, tells us of the brigandage of life. How well it understands its trade as an exterminator! In vain does the Crioceris-larva take refuge in an unassailable casket: its executioner makes herself so small that she is able to reach it.

Adopt such precautions as you please, you pitiable grubs, pose on your sprigs in the attitude of a threatening Sphinx, take refuge in the mysteries of a box, arm yourself with a cuirass of dung: you will none the less pay your tribute in the pitiless conflict; there will always be operators who, varying in cunning, in size, in implements, will inoculate you with their deadly germs.

Not even the lily-dweller, with her dirty ways, is safe. Her grub is as often the prey of another Tachina, larger than that of the Field Crioceris. The parasite, I am convinced, does not sow her eggs upon the victim so long as the latter is wrapped in its repulsive great-coat; but a moment's imprudence gives her a favourable opportunity.

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.