THE PEA-WEEVIL: THE EGGS

The Life of the Weevil by Jean-Henri Fabre and Alexander Teixeira de Mattos, is part of the HackerNoon Books Series. You can jump to any chapter in this book here. THE PEA-WEEVIL: THE EGGS

Chapter XI. THE PEA-WEEVIL: THE EGGS

Man holds the pea in high esteem. Ever since the days of antiquity, he has tried, by devoting greater and greater attention to its cultivation, to make it produce larger, tenderer, and sweeter varieties. The adaptable plant, gently entreated, has complied with his desires and has ended by giving us what the gardener’s ambition aimed at obtaining. How far we moderns have progressed beyond the crop of the Varros1 and Columellas,2 how far, above all, beyond the original peas, beyond the wild seeds confided to the soil by the first man who thought of scraping the earth, maybe with a jaw-bone of the Cave-bear,3 whose mighty canine did duty as a ploughshare!

Where is this plant, the first source of the pea, [185]in the world of spontaneous vegetation? Our regions possess nothing like it. Is it to be found elsewhere? On this point botany is silent, or replies only with vague probabilities.

For that matter, the same ignorance prevails on the subject of most of our edible plants. Whence comes wheat, the blessed grain that gives us bread? No one knows. Except in the fields tilled by man, you need not look for it in this country. You need not look for it abroad either. In the East, where agriculture had its birth, no botanist ever came across the sacred ear increasing of its own accord on ground not broken by the plough.

Barley, oats and rye, the turnip and the radish, the beet, the carrot, the pumpkin leave us in a like uncertainty: their origin is unknown, or at most suspected behind the impenetrable mist of the ages. Nature delivered them to us in the full vigour of things untamed, when they were of little value as food, as she nowadays offers us the wild blackberry and the sloe; she gave them to us in a rudimentary and incomplete state; and it was for our husbandry and ingenuity patiently to hoard the nutritive pulp, that earliest form of capital, with dividends always increasing in the most excellent bank of the tiller of the soil.

As storehouses of provisions, the cereal and the garden vegetable are, for the most part, the work of man. The founders of the species, a poor resource in their original condition, we borrowed [186]as we found them from nature’s green treasury; the improved race, rich in nourishing matter, is the result of our art.

But, if wheat, peas and the rest are indispensable to us, our care, in fair exchange, is absolutely necessary to their maintenance. Such as our needs have made them, incapable of resistance in the savage conflict of living things, these plants, if left to themselves, without cultivation, would rapidly disappear, despite the numerical immensity of their seeds, even as the silly Sheep would shortly disappear were there no sheepfolds.

They are our work, but not always our exclusive property. Wherever food is amassed, consumers flock from the four corners of the sky; they invite themselves to the copious feast; and, the richer the victuals, the greater their numbers. Man, who alone is capable of provoking agrarian luxuriance, becomes by this very fact the giver of an immense banquet whereat legions of guests take their places. By creating more palatable and more generous victuals, he willy-nilly summons to his granaries thousands and thousands of famished creatures against whose teeth his prohibitions battle in vain. The more he produces, the larger tribute he has to pay. Big crops and sumptuous hoards favour the insects, our rivals as consumers.

It is the prevailing law. Nature offers her mighty breast with equal zeal to all her children, [187]to those who live by others’ goods no less than to the producers. For us who plough and sow and reap, wearing ourselves out with toil, she ripens the wheat; she ripens it also for the little Corn-weevil, who, though exempted from the labour of the fields, will nevertheless settle in our granaries and with her pointed beak nibble the heap of corn, grain by grain, to the husk. For us who dig and weed and water, bent with fatigue and burnt by the heat of the day, nature swells the pea-pods; she swells them also for the Pea-weevil, who, doing no gardener’s work, will all the same take her share of the crop at her own time, when the earth is joyful with the new life of spring.

Let us watch the actions of this zealous tax-collector, who levies her tithes in green peas. I, a well-meaning rate-payer, will let her have her way: it is precisely for her benefit that I have sown a few rows of the beloved plant in my enclosure. With no other invitation from me than this modest seed-plot, she arrives punctually in the course of May. She has learnt that in this stony soil, unfitted for market-gardening, peas are flourishing for the first time. And she has hastened thither to exercise her privileges as an entomological revenue-officer.

Whence does she come? It is impossible to say exactly. She has come from some refuge or other where she has spent the winter in a state of torpor. The plane-tree, which strips itself of its own [188]initiative during the heat of summer, furnishes excellent shelters for homeless paupers under its patches of loose-hanging bark. I have often found our Pea-thief in one of these winter sanctuaries. Sheltered under the dead covering of the plane, or otherwise protected while the winter raged, she woke from her slumbers at the first kisses of a kindly sun. The almanac of the instincts has taught her; she knows as well as the gardener when the peas are in flower, and she comes to her plant more or less from every direction, ambling at a slow pace, but swift in flight.

A small head, a slender snout, a dress of ashen grey sprinkled with brown, flat wing-cases, a squat thick-set figure, with two large black dots on the flat of the tail: there you have a rough sketch of my visitor. The vanguard arrives by the end of the first fortnight in May.

The Weevils settle on the flowers, which are like so many white Butterflies’ wings: I see some installed at the foot of the upper petal, I see some hidden in the casket of the keel. Others, more numerous these, explore the blossoms and take possession of them. The laying-time has not yet come. It is a mild morning; the sun is hot without being oppressive. This is the moment for nuptial exploits and for raptures amid the splendour of the light. Life therefore is enjoyed for a little while. Couples form, soon part and soon come together again. When the heat grows too [189]great, towards the middle of the day, each Jack and Jill retire into the shade, in a fold of the flower whose secret recesses they know so well. To-morrow they will resume the festival and the next day too, until the pod, splitting the sheath of its keel, appears outside, more and more swollen from day to day.

A few pregnant mothers, harder-pressed than the rest, confide their eggs to the growing pod, as it issues flat and tiny from its floral scabbard. These eggs laid prematurely, pushed out perhaps through the exigencies of an ovary which can wait no longer, seem to me in serious danger. The seed in which the grub is to make its home is as yet but a feeble granule, without substance and without floury contents. No Weevil-larva would ever find an adequate meal there, unless by biding its time until the seed ripened.

But is the grub, once hatched, capable of long fasting? It is doubtful. The little that I have seen tells me that the new-born larva begins eating with all speed and, if it cannot do so, dies. I therefore regard as lost the eggs laid upon immature pods. The prosperity of the race will hardly suffer, thanks to the Weevil’s fertility. Moreover, we shall see presently with what reckless prodigality she scatters her germs, most of which are doomed to perish.

The bulk of the mother’s work is finished by the end of May, when the pods begin to bulge [190]with protuberances revealing the pressure of the peas, which have now attained their final size, or very nearly. I was anxious to see the Bruchus at work, in her quality of a Curculio, which is how she is classified.4 The other Weevils are Rhynchophoræ, beak-wearers, armed with a rod that prepares the hollow in which the egg is laid. Our friend possesses only a short snout, which does capitally for sipping a few sweet mouthfuls, but which is of no value as a boring-tool.

Therefore the method of installing the family is quite different. Here we see no ingenious preparations, such as the Balanini, the Larini and the Rhynchites showed us. Having no probe among her tools, the mother scatters her eggs in the open, with no protection against the heat of the sun or the inclemencies of the weather. Nothing could be simpler and nothing more dangerous to the germs, in the absence of a special constitution made to withstand the alternate trials of heat and cold, drought and wet.

In the mild sunshine of ten o’clock in the morning, the mother, with a jerky, capricious, unmethodical step, runs up and down the chosen pod, first on one and then on the other surface. She protrudes at every instant a short oviscapt, which swings [191]right and left as though to scrape the skin. An egg follows and is abandoned as soon as laid.

A hasty touch of the oviscapt, first here, then there, on the green skin of the pea-pod; and that is all. The germ is left there, unprotected, right in the sun. Nor is any choice of site made, to assist the coming grub and shorten its quest when it has to make its way unaided into the larder. There are eggs placed on the swellings created by the peas; there are just as many in the barren dividing valleys. It is for the grub to take its bearings accordingly. In short, the Bruchus’ eggs are laid anyhow, as though sown on the wing.

A more serious flaw: the number of eggs confided to one pod is not in proportion to that of the peas contained in it. Let us first realize that each grub needs a ration of one pea, an obligatory ration, amply sufficient for the welfare of one larva, but not big enough for several consumers, nor even for two. A pea for each grub, no more and no less, is the invariable rule.

Procreative economy would therefore demand that the mother, familiar with the pod which she has just explored, should, when emitting her germs, more or less limit their number to that of the peas which it contains. Now there is no limit. To a single ration the impetuous ovaries always offer a multiplicity of consumers.

My notes are unanimous on this point. The number of eggs laid on a pod always exceeds, and [192]often in a scandalous fashion, the number of peas available. However scanty the food-wallet may be, the guests are superabundant. Dividing the number of eggs perceived on a given pod by that of the peas inside it, I find from five to eight claimants for each pea; I find as many as ten; and there is nothing to tell me that the prodigality does not go farther still. Many are called, but few are chosen! Why all these supernumeraries, who are necessarily excluded from the banquet for want of space?

The eggs are a fairly bright amber-yellow, cylindrical in form, smooth and rounded at both ends. They are a millimetre long at most.5 Each of them is fixed to the pod by a thin network of threads of coagulated albumen. Neither the rain nor the wind can loosen their hold.

The mother often emits them two at a time, one above the other; often also the uppermost of the pair succeeds in hatching, whereas the lower fades and perishes. What did this latter lack, to produce a grub? A sun-bath, perhaps, the gentle incubation of which the upper egg robs it. Whether through the effect of the untimely screen that overshadows it, or for some other reason, the elder of the eggs in a group of two rarely follows the normal course. It withers on the pod, dead before it has come to life.

There are exceptions to this premature end. [193]Sometimes the twin eggs develop equally well; but these instances are so rare that the family of the Bruchus would be reduced by nearly one-half if the binary system were a fixed rule. To the detriment of the peas and to the Weevil’s advantage there is one thing that lessens this destructive factor: the eggs are laid one by one and in separate places.

A recent hatching is marked by a whitish, winding little ribbon, which raises and fades the skin of the pod near the sloughed egg-shell. It is the work of the new-born larva and is a subcutaneous tunnel along which the tiny creature wends its way in search of a point through which to penetrate. When it has found this spot, the grub, measuring hardly a millimetre and pale-bodied, with a black cap, pierces the outer wrapper and dives into the capacious sheath of the pod.

It reaches the peas and perches on the nearest. I watch it through the magnifying-glass, exploring its globe, its world. It sinks a well at right angles to the sphere. I see some which, half-way down, wriggle their tails to stimulate their efforts. After a short spell of work, the miner disappears and is at home.

The entrance-hole is minute, but is easily recognized at any time by its brown colouring against the pale-green or yellow-green background of the pea. It has no fixed site; we see it more or less anywhere on the surface of the pea, excepting [194]generally on the lower half, that is to say, the hemisphere whose pole is formed by the base of the funicular cord.

It is precisely in this part that the germ is found which will not be consumed and will remain capable of developing into an embryo plant, in spite of the large hole made by the adult insect in leaving. Why is this portion left unscathed? What are the reasons that safeguard the germ of the exploited seed?

It goes without saying that the Bruchus does not consider the gardener. The pea is meant for it and none other. In refusing to take the few bites which would entail the death of the seed, it has no intention of reducing the damage. It abstains from other motives.

Remark that the peas touch at the sides, where they are pressed one against the other. The grub seeking the point of attack cannot move about at its ease. Remark also that the lower pole rests upon the umbilical excrescence and opposes to any attempt at boring difficulties which do not exist in the parts protected by the skin alone. It is even possible that this umbilicus, which is differently organized, contains special juices distasteful to the little larva.

This, beyond a doubt, is the secret of the peas exploited by the Bruchus and yet remaining fit to sprout. They are injured but not dead, because they are invaded in the free hemisphere, [195]the part which is at the same time easier to enter and less easy to wound. Moreover, as the whole pea is too much for a single grub, the loss of substance is reduced to the piece preferred by the consumer; and this piece is not the essential part of the pea.

Given other conditions, with seeds either very small or exceedingly large, we should see the results changing entirely. In the first case, the germ would be gnawed like the remainder and would perish by the tooth of the too niggardly served grub; in the second case, the abundant food would allow of several guests. The common vetch and the broad bean, exploited in the absence of the pea, tell us something in this connection; the smaller seed, devoured all but the skin, is a ruin whose germination we may expect in vain; the larger, on the contrary, despite the Weevil’s numerous cells, is still capable of sprouting.

Admitting that the number of eggs on the pod is always much greater than that of the peas contained, and that, on the other hand, each pea is the exclusive property of one grub, we wonder what becomes of the surplus. Do these larvæ perish outside, when the more precocious have taken their places one by one in the leguminous larder? Do they succumb to the intolerant teeth of the early occupants? They do neither. Let us set forth the facts.

On all old peas, now dry, from which the adult [196]Weevil has issued, leaving a gaping hole, the magnifying-glass reveals a varying number of fine, reddish-brown dots, perforated at the centre. What are these spots, of which I count five or six or even more on a single pea? There is no mistake possible: they are the entrance-points of so many grubs. Several workers have therefore penetrated into the seed; and of the whole gang only one has survived, waxed big and fat and attained the adult age. And the others? We shall see.

At the end of May and in June, during the laying-season, inspect the still green and tender peas. Nearly all the seeds invaded show us the multiple dots which we already observed on the dry peas abandoned by the Weevils. Does this actually mean an assembly of guests? Yes. Skin the aforesaid seeds, separate the seed-lobes, subdivide them if necessary. We discover several larvæ, very young, bent into a bow, fat and wriggling, each in a little round hollow in the heart of the victuals.

Peace and comfort seem to reign in the community. There is no quarrelling, no jealous competition among neighbours. The eating has begun, provisions are plentiful and the banqueters are separated from one another by partitions formed by the as yet untouched portions of the seed-lobes. With this isolation in separate cells, there is no fear of squabbles; the guests will not bite one another, by accident or intention. All the occupants [197]enjoy the same rights of property, the same appetite and the same strength. What will be the end of the communal working?

I split some peas which I have found to be well-stocked and place them in a glass tube. I add others daily. This method keeps me informed of the boarders’ progress. At first there is nothing special. Isolated in its narrow recess, each grub nibbles around itself and eats frugally and peacefully. It is still quite small; a speck of food surfeits it. Nevertheless, a dish consisting of one pea cannot satisfy so large a number until the end. Famine threatens; all save one must die.

Soon indeed the aspect of things changes. One of the grubs, the one occupying the central position in the pea, grows faster than the others. He has hardly begun to be larger than his competitors when these cease to eat and refrain from digging any farther. They lie motionless and resigned; they die the gentle death which reaps unconscious lives. They disappear, wasted away to nothing. They were so tiny, the poor victims! Henceforth the whole pea belongs to the sole survivor. But what has happened, to produce this desolation around the privileged one? For lack of a relevant answer, I will propound a suggestion.

In the centre of the pea, more gently stewed than the rest by the sun’s chemistry, may there not be an infant-pap, a pulp of a quality better-suited to the delicate organs of a grub? Here [198]perhaps, stimulated by tender, highly flavoured and sweeter food, the stomach becomes more vigorous and fit to cope with food less easily digested. A baby is fed on milk before it receives the basin of broth and the bread of the able-bodied. Might not the central portion of the pea be the Weevil-grub’s feeding-bottle?

Fired by one ambition and endowed with equal rights, all the occupants of the seed set out towards the delicious morsel. It is a laborious journey; and frequent halts are made in temporary recesses. The grubs rest; pending better things to come, they frugally crunch the ripe substance around them; they gnaw even more to open a way than to fill their stomachs.

At last one of the excavators, favoured by the direction taken, reaches the central dairy. It settles there and the thing is done: there is nothing for the rest but to die. How do they come to know that the place is taken? Do they hear their kinsman’s mandibles striking against the wall of his cell? Can they feel the vibration of the nibbling at a distance? Something of the sort must happen, for from that moment they cease their attempts to burrow any farther. Without struggling with the lucky winner, without seeking to dislodge him, those beaten in the race allow themselves to die. I like this frank resignation on the part of the late arrivals.

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