The Life of the fly Part 3

The Chalicodoma's nests abound, but I cannot see a single Anthrax make a black speck upon their surface. Not one, busy with her laying, settles in front of me. At most, from time to time, I can just see one pa.s.sing far away, with an impetuous rush. I lose her in the distance; and that is all. It is impossible to be present at the laying of the egg. I know the little that I learnt from the cliffs in the Legue and nothing more.

As soon as I recognize the difficulty, I hasten to enlist a.s.sistants.

Shepherds--mere small boys--keep the sheep in these stony meadows, where the flocks graze, to the greater glory of our local mutton, on the camphor saturated badafo, that is to say, spike lavender. I explain as well as I can the object of my search; I talk to them of a big black Fly and the nests on which she ought to settle, the clay nests so well known to those who have learnt how to extract the honey with a straw in springtime and spread it on a crust of bread. They are to watch that fly and take good note of the nests on which they may see her alight; and, on the same evening, when they bring their flocks back to the village, they are to tell me the result of their day's work. On receiving their favorable report, I will go with them, next day, to continue the observations. They shall be paid for their trouble, of course. These latter day Corydons have not the manners of antiquity: they reck little of the seven holed flute cemented with wax, or of the beechen bowl, preferring the coppers that will take them to the village inn on Sunday.

A reward in ready money is promised for each nest that fulfils the desired conditions; and the bargain is enthusiastically accepted.

There are three of them; and I make a fourth. Shall we manage it, among us all? I thought so. By the end of August, however, my last illusions were dispelled. Not one of us had succeeded in seeing the big black Fly perching on the dome of the mason bee.

Our failure, it seems to me, can be explained thus: outside the s.p.a.cious front of the Anthophora's settlement, the Anthrax is in permanent residence. She visits, on the wing, every nook and corner, without moving away from the native cliff, because it would be useless to go farther. There is board and lodging here, indefinitely, for all her family. When some spot is deemed favorable, she hovers round inspecting it, then comes up suddenly and strikes it with the tip of her abdomen.

The thing is done, the egg is laid. So I picture it, at least. Within a radius of a few yards and in a flight broken by short intervals of rest in the sun, she carries on her search of likely places for the laying and dissemination of her eggs. The insect's a.s.siduous attendance upon the same slope is caused by the inexhaustible wealth of the locality exploited.

The Anthrax of the Chalicodoma labors under very different conditions.

Stay-at-home habits would be detrimental to her. With her rushing flight, made easy by the long and powerful spread of her wings, she must travel far and wide if she would found a colony. The bee's nests are not discovered in groups, but occur singly on their pebbles, scattered more or less everywhere over acres of ground. To find a single one is not enough for the fly: on account of the many parasites, not all the cells, by a long way, contain the desired larva; others, too well protected, would not allow of access to the provisions. Very many nests are necessary, perhaps, for the eggs of one alone; and the finding of them calls for long journeys.

I therefore picture the Anthrax coming and going in every direction across the stony plain. Her practiced eye requires no slackened flight to distinguish the earthen dome which she is seeking. Having found it, she inspects it from above, still on the wing; she taps it once and yet once again with the tip of her ovipositor and forthwith makes off, without having set foot on the ground. Should she take a rest, it will be elsewhere, no matter where, on the soil, on a stone, on a tuft of lavender or thyme. Given these habits--and my observations in the Carpentras roads make them seem exceedingly probable--it is small wonder that the perspicacity of my young shepherds and myself should have come to naught. I was expecting the impossible: the Anthrax does not halt on the mason bee's nest to proceed with her laying in a methodical fashion; she merely pays a flying visit.

And so I develop my theory of a primary larval form, differing in every way from the one which I know. The organization of the Anthrax must be such, at the beginning, as to permit of its moving on the surface of the dome where the egg has been dropped so carelessly; the nascent grub must be supplied with tools to pierce the concrete wall and enter the Bee's cell through some cranny. The fly grub, perhaps dragging the remnants of the egg behind it, must set out in quest of board and lodging almost as soon as it is born. It will succeed under the guidance of instinct, that faculty which waits not to number the days and which is as far seeing at the moment of hatching as after the trials of a busy life. This primary grub does not seem to me outside the limits of possibility; I see it, if not in the body, at least in its actions, as plainly as though it were really under the lens. It exists, if reason be not a vain and empty guide; I must find it; I shall find it. Never in the history of my investigations has the logic of things been more insistent; never has it directed me with greater certainty towards a magnificent biological theory.

While vainly trying to witness the laying of the eggs, I inquire, at the same time, into the contents of the Mason bee's nests, in quest of the grub just issued from the egg. My own harvest and that of my young shepherds, whose zeal I employ in a task less difficult than the first, procure me heaps of nests, enough to fill baskets and baskets. These are all inspected at leisure, on my work table, with the excitement which the certainty of an approaching fine discovery never fails to give. The Mason's coc.o.o.ns are taken from the cells, inspected without, opened and inspected within. My lens explores their innermost recesses; speck by speck, it explores the Chalicodoma's slumbering larva; it explores the inner walls of the cells. Nothing, nothing, nothing! For a fortnight and more, nests were rejected and heaped up in a corner; my study was crammed with them. What hecatombs of unfortunate sleepers removed from their silken bags and doomed, for the most part, to a wretched end, despite the care which I took to put them in a place of safety, where the work of the transformation might be pursued! Curiosity makes us cruel. I continue to rip up coc.o.o.ns. And nothing, nothing! It needed the st.u.r.diest faith to make me persevere. That faith I possessed; and well for me that I did.

On the 25th of July--the date deserves to be recorded--I saw, or rather seemed to see, something move on the Chalicodoma's larva. Was it an illusion born of my hopes? Was it a bit of diaphanous down stirred by my breath? It was not an illusion, it was not a bit of down, it was really and truly a grub. What a moment, followed by what perplexities! The thing has nothing in common with the larva of the Anthrax, it suggests rather some microscopic Thread worm that, by accident, has made its way through the skin of its host and come to enjoy itself outside. I do not reckon my discovery as of much value, because I am so greatly puzzled by the creature's appearance. No matter: we will take a small gla.s.s tube and place inside it the Chalicodoma grub and the mysterious thing wriggling on the surface. Suppose it should be what I am looking for?

Who knows?

Once warned of the probable difficulty of seeing the animalcule for which I am hunting, I redouble my attention, so much so that, in a couple of days, I am the owner of half a score of tiny worms similar to the one which caused me such excitement. Each of them is lodged in a gla.s.s tube with its Chalicodoma grub. The infinitesimal thing is so small, so diaphanous, blends to such good purpose with its host that the least fold of skin conceals it from my view. After watching it one day through the lens, I sometimes fail to find it again on the morrow. I think that I have lost it, that it has perished under the weight of the overturned larva and returned to that nothing to which it was so closely akin. Then it moves and I see it again. For a whole fortnight, there was no limit to my perplexity. Was it really the original larva of the Anthrax? Yes, for I at last saw my bantlings transform themselves into the larva previously described and make their first start at draining their victims with kisses. A few moments of satisfaction like those which I then enjoyed make up for many a weary hour.

Let us resume the story of the wee animal, now recognized as the genuine origin of the Anthrax. It is a tiny worm about a millimeter long and almost as slender as a hair. It is very difficult to see because of its transparency. When tucked away in a fold of the skin of its fostering larva, an excessively fine skin, it remains undiscoverable to the lens.

But the feeble creature is very active: it tramps over the sides of the rich morsel, walks all round it. It covers the ground pretty quickly, buckling and unbuckling by turns, very much after the manner of the looper caterpillar. Its two extremities are its chief points of support.

When at a standstill, it moves its front half in every direction, as though to explore the s.p.a.ce around it; when walking, it swells out, magnifies its segments and then looks like a bit of knotted string.

The microscope shows us thirteen rings, including the head. This head is small, slightly h.o.r.n.y, as is proved by its amber color, and bristles in front with a small number of short, stiff hairs. On each of the three segments of the thorax there are two long hairs, fixed to the lower surface; and there are two similar and still longer hairs at the end of the terminal ring. These four pairs of bristles, three in front and one behind, are the locomotory organs, to which we must add the hairy edge of the head and also the a.n.a.l b.u.t.ton, a sustaining base which might very well work with the aid of a certain stickiness, as happens with the primary larva of the Sitaris [a Parasitic Beetle noted for the multiplicity of transformations undergone by the grub]. We see, through the transparent skin, two long air tubes running parallel to each other from the first thoracic segment to the last abdominal segment but one.

They ought to end in two pairs of breathing holes which I have not succeeded in distinguishing quite plainly. Those two big respiratory vessels are characteristic of the grubs of flies. Their mouths correspond exactly with the points at which the two sets of stigmata open in the Anthrax larva in its second form.

For a fortnight, the feeble grub remains in the condition which I have described, without growing and very probably also without nourishment.

a.s.siduous though my visits be, I never perceive it taking any refreshment. Besides, what would it eat? In the coc.o.o.n invaded there is nothing but the larva of the mason bee; and the worm cannot make use of this before acquiring the sucker that comes with the second form.

Nevertheless, this life of abstinence is not a life of idleness. The animalcule explores its dish, now here, now elsewhere; it runs all over it with looper strides; it pries into the neighborhood by lifting and shaking its head.

I see a need for this long wait under a transitory form that requires no feeding. The egg is laid by the mother on the surface of the nest, somewhere near a suitable cell, I dare say, but still at a distance from the fostering larva, which is protected by a thick rampart. It is for the new born grub to make its own way to the provisions, not by violence and house breaking, of which it is incapable, but by patiently slipping through a maze of cracks, first tried, then abandoned, then tried again.

It is a very difficult task, even for this most slender worm, for the bee's masonry is exceedingly compact. There are no c.h.i.n.ks due to bad building; no fissures due to the weather; nothing but an apparently impenetrable h.o.m.ogeneity. I see but one weak part and that only in a few nests: it is the line where the dome joins the surface of the stone. An imperfect soldering between two materials of different nature, cement and flint, may leave a breach wide enough to admit besiegers as thin as a hair. Nevertheless, the lens is far from always finding an inlet of this kind on the nests occupied by Anthrax flies.

And so I am ready to allow that the animalcule wandering in search of its cell has the whole area of the dome at its disposal when selecting an entrance. Where the line auger of the Leucospis can enter, is there not room enough for the even slimmer Anthrax grub? True, the Leucospis possesses muscular force and a hard boring tool. The Anthrax is extremely weak and has nothing but invincible patience. It does at great length of time what the other, furnished with superior implements, accomplishes in three hours. This explains the fortnight spent by the Anthrax under the initial form, the object of which is to overcome the obstacle of the mason's wall, to pierce through the texture of the coc.o.o.n and to reach the victuals.

I even believe that it takes longer. The work is so laborious and the worker so feeble! I cannot tell how long it is since my bantlings attained their object. Perhaps, aided by easy roads, they had reached their fostering larvae long before the completion of their first babyhood, the end of which they were spending before my eyes, with no apparent purpose, in exploring their provisions. The time had not yet come for them to change their skins and take their seats at the table.

Their fellows must still, for the most part, be wandering through the pores of the masonry; and this was what made my search so vain at the start.

A few facts seem to suggest that the entrance into the cell may be delayed for several months by the difficulty of the pa.s.sages. There are a few Anthrax grubs beside the remains of pupae not far removed from the final metamorphosis; there are others, but very rarely, on Mason bees already in the perfect state. These grubs are sickly and appear to be ailing; the provisions are too solid and do not lend themselves to the delicate suckling of the worms. Who can these laggards be but animalcules that have roamed too long in the walls of the nest? Failing to make their entrance at the proper time, they no longer find viands to suit them. The primary larva of the Sitaris continues from the autumn to the following spring. Even so the initial form of the Anthrax might well continue, not in inactivity, but in stubborn attempts to overcome the thick bulwark.

My young worms, when transferred with their provisions into tubes, remained stationary, on the average, for a couple of weeks. At last, I saw them shrink and then rid themselves of their epidermis and become the grub which I was so anxiously expecting as the final reply to all my doubts. It was indeed, from the first, the grub of the Anthrax, the cream-colored cylinder with the little b.u.t.ton of a head, followed by a hump. Applying its cupping gla.s.s to the mason bee, the worm, without delay, began its meal, which lasts another fortnight. The reader knows the rest.

Before taking leave of the animalcule, let us devote a few lines to its instinct. It has just awakened to life under the fierce kisses of the sun. The bare stone is its cradle, the rough clay its welcomer, as it makes its entrance into the world, a poor thread of scarce cohering alb.u.men. But safety lies within; and behold the atom of animated glair embarking on its struggle with the flint. Obstinately, it sounds each pore; it slips in, crawls on, retreats, begins again. The radical of the germinating seed is no more persevering in its efforts to descend into the cool earth than is the Anthrax grub in creeping into the lump of mortar. What inspiration urges it towards its food at the bottom of the clod, what compa.s.s guides it? What does it know of those depths, of what lies therein or where? Nothing. What does the root know of the earth's fruitfulness? Again nothing. Yet both make for the nourishing spot.

Theories are put forward, most learned theories, introducing capillary action, osmosis and cellular imbibition, to explain why the caulicle ascends and the radical descends. Shall physical or chemical forces explain why the animalcule digs into the hard clay? I bow profoundly, without understanding or even trying to understand. The question is far above, our inane means.

The biography of the Anthrax is now complete, save for the details relating to the egg, as yet unknown. In the vast majority of insects subject to metamorphoses, the hatching yields the larval form which will remain unchanged until the nymphosis. By virtue of a remarkable variation, revealing a new vein of observation to the entomologist, the Anthrax flies, in the larval state, a.s.sume two successive shapes, differing greatly one from the other, both in structure and in the part which they are called upon to play. I will describe this double stage of the organism by the phrase 'larval dimorphism.' The initial form, that issuing from the egg, I will call 'the primary larva;' the second form shall be 'the secondary larva.' Among the Anthrax flies, the function of the primary larva is to reach the provisions, on which the mother is unable to lay her egg. It is capable of moving and endowed with ambulatory bristles, which allow the slim creature to glide through the smallest interstices in the wall of a Bee's nest, to slip through the woof of the coc.o.o.n and to make its way to the larva intended for its successor's food. When this object is attained, its part is played.

Then appears the secondary larva, deprived of any means of progression.

Relegated to the inside of the invaded cell, as incapable of leaving it by its own efforts as it was of entering, this one has no mission in life but that of eating. It is a stomach that loads itself, digests and goes on adding to its reserves. Next comes the pupa, armed for the exit even as the primary larva was equipped for entering. When the deliverance is accomplished, the perfect insect appears, busy with its laying. The Anthrax cycle is thus divided into four periods, each of which corresponds with special forms and functions. The primary larva enters the casket containing provisions; the secondary larva consumes these provisions; the pupa brings the insect to light by boring through the enclosing wall; the perfect insect strews its eggs; and the cycle starts afresh.

CHAPTER V. HEREDITY

Facts which I have set forth elsewhere prove that certain dung beetles'

make an exception to the rule of paternal indifference--a general rule in the insect world--and know something of domestic cooperation. The father works with almost the same zeal as the mother in providing for the settlement of the family. Whence do these favored ones derive a gift that borders on morality?

One might suggest the cost of installing the youngsters. Once they have to be furnished with a lodging and to be left the wherewithal to live, is it not an advantage, in the interests of the race, that the father should come to the mother's a.s.sistance? Work divided between the two will ensure the comfort which solitary work, its strength overtaxed, would deny. This seems excellent reasoning; but it is much more often contradicted than confirmed by the facts. Why is the Sisyphus a hard working paterfamilias and the sacred beetle an idle vagabond? And yet the two pill rollers practice the same industry and the same method of rearing their young. Why does the Lunary Copris know what his near kinsman, the Spanish Copris, does not? The first a.s.sists his mate, never forsakes her. The second seeks a divorce at an early stage and leaves the nuptial roof before the children's rations are ma.s.sed and kneaded into shape. Nevertheless, on both sides, there is the same big outlay on a cellarful of egg-shaped pills, whose neat rows call for long and watchful supervision. The similarity of the produce leads one to believe in similarity of manners; and this is a mistake.

Let us turn elsewhere, to the wasps and bees, who unquestionably come first in the laying up of a heritage for their offspring. Whether the treasure h.o.a.rded for the benefit of the sons be a pot of honey or a bag of game, the father never takes the smallest part in the work. He does not so much as give a sweep of the broom when it comes to tidying the outside of the dwelling. To do nothing is his invariable rule. The bringing up of the family, therefore, however expensive it may be in certain cases, has not given rise to the instinct of paternity. Then where are we to look for a reply?

Let us make the question a wider one. Let us leave the animal, for a moment, and occupy ourselves with man. We have our own instincts, some of which take the name of genius when they attain a degree of might that towers over the plain of mediocrity. We are amazed by the unusual, springing out of flat commonplaces; we are spellbound by the luminous speck shining in the wonted darkness. We admire; and, failing to understand whence came those glorious harvests in this one or in that, we say of them: "They have the gift."

A goatherd amuses himself by making combinations with heaps of little pebbles. He becomes an astoundingly quick and accurate reckoner without other aid than a moment's reflection. He terrifies us with the conflict of enormous numbers which blend in an orderly fashion in his mind, but whose mere statement overwhelms us by its inextricable confusion. This marvelous arithmetical juggler has an instinct, a genius, a gift for figures.

A second, at the age when most of us delight in tops and marbles, leaves the company of his boisterous playmates and listens to the echo of celestial harps singing within him. His head is a cathedral filled with the strains of an imaginary organ. Rich cadences, a secret concert heard by him and him alone, steep him in ecstasy. All hail to that predestined one who, some day, will rouse our n.o.blest emotions with his musical chords. He has an instinct, a genius, a gift for sounds.

A third, a brat who cannot yet eat his bread and jam without smearing his face all over, takes a delight in fashioning clay into little figures that are astonishingly lifelike for all their artless awkwardness. He takes a knife and makes the briar root grin into all sorts of entertaining masks; he carves boxwood in the semblance of a horse or sheep; he engraves the effigy of his dog on sandstone. Leave him alone; and, if Heaven second his efforts, he may become a famous sculptor. He has an instinct, a gift, a genius for form.

And so with others in every branch of human activity: art and science, industry and commerce, literature and philosophy. We have within us, from the start, that which will distinguish us from the vulgar herd.

Now to what do we owe this distinctive character? To some throwback of atavism, men tell us. Heredity, direct in one case, remote in another, hands it down to us, increased or modified by time. Search the records of the family and you will discover the source of the genius, a mere trickle at first, then a stream, then a mighty river.

The darkness that lies behind that word heredity! Metaphysical science has tried to throw a little light upon it and has succeeded only in making unto itself a barbarous jargon, leaving obscurity more obscure than before. As for us, who hunger after lucidity, let us relinquish abstruse theories to whoever delights in them and confine our ambition to observable facts, without pretending to explain the quackery of the plasma. Our method certainly will not reveal to us the origin of instinct; but it will at least show us where it would be waste of time to look for it.

In this sort of research, a subject known through and through, down to its most intimate peculiarities, is indispensable. Where shall we find that subject? There would be a host of them and magnificent ones, if it were possible to read the sealed pages of others' lives; but no one can sound an existence outside his own and even then he can think himself lucky if a retentive memory and the habit of reflection give his soundings the proper accuracy. As none of us is able to project himself into another's skin, we must needs, in considering this problem, remain inside our own.

To talk about one's self is hateful, I know. The reader must have the kindness to excuse me for the sake of the study in hand. I shall take the silent beetle's place in the witness box, cross-examining myself in all simplicity of soul, as I do the animal, and asking myself whence that one of my instincts which stands out above the others is derived.

Since Darwin bestowed upon me the t.i.tle of 'incomparable observer,' the epithet has often come back to me, from this side and from that, without my yet understanding what particular merit I have shown. It seems to me so natural, so much within everybody's scope, so absorbing to interest one's self in everything that swarms around us! However, let us pa.s.s on and admit that the compliment is not unfounded.

My hesitation ceases if it is a question of admitting my curiosity in matters that concern the insect. Yes, I possess the gift, the instinct that impels me to frequent that singular world; yes, I know that I am capable of spending on those studies an amount of precious time which would be better employed in making provision, if possible, for the poverty of old age; yes, I confess that I am an enthusiastic observer of the animal. How was this characteristic propensity, at once the torment and delight of my life, developed? And, to begin with, how much does it owe to heredity?

The common people have no history: persecuted by the present, they cannot think of preserving the memory of the past. And yet what surpa.s.singly instructive records, comforting too and pious, would be the family papers that should tell us who our forebears were and speak to us of their patient struggles with harsh fate, their stubborn efforts to build up, atom by atom, what we are today. No story would come up with that for individual interest. But by the very force of things the home is abandoned; and, when the brood has flown, the nest is no longer recognized.

I, a humble journeyman in the toilers' hive, am therefore very poor in family recollections. In the second degree of ancestry, my facts become suddenly obscured. I will linger over them a moment for two reasons: first, to inquire into the influence of heredity; and, secondly, to leave my children yet one more page concerning them.

I did not know my maternal grandfather. This venerable ancestor was, I have been told, a process server in one of the poorest parishes of the Rouergue. He used to engross on stamped paper in a primitive spelling.

With his well-filled pen case and ink horn, he went drawing out deeds up hill and down dale, from one insolvent wretch to another more insolvent still. Amid his atmosphere of pettifoggery, this rudimentary scholar, waging battle on life's acerbities, certainly paid no attention to the insect; at most, if he met it, he would crush it under foot. The unknown animal, suspected of evil doing, deserved no further enquiry.

Grandmother, on her side, apart from her housekeeping and her beads, knew still less about anything. She looked on the alphabet as a set of hieroglyphics only fit to spoil your sight for nothing, unless you were scribbling on paper bearing the government stamp. Who in the world, in her day, among the small folk, dreamt of knowing how to read and write?

That luxury was reserved for the attorney, who himself made but a sparing use of it. The insect, I need hardly say, was the least of her cares. If sometimes, when rinsing her salad at the tap, she found a caterpillar on the lettuce leaves, with a start of fright she would fling the loathsome thing away, thus cutting short relations reputed dangerous. In short, to both my maternal grandparents, the insect was a creature of no interest whatever and almost always a repulsive object, which one dared not touch with the tip of one's finger. Beyond a doubt, my taste for animals was not derived from them.

I have more precise information regarding my grandparents on the father's side, for their green old age allowed me to know them both.

They were people of the soil, whose quarrel with the alphabet was so great that they had never opened a book in their lives; and they kept a lean farm on the cold granite ridge of the Rouergue tableland. The house, standing alone among the heath and broom, with no neighbor for many a mile around and visited at intervals by the wolves, was to them the hub of the universe. But for a few surrounding villages, whither the calves were driven on fair days, the rest was only very vaguely known by hearsay. In this wild solitude, the mossy fens, with their quagmires oozing with iridescent pools, supplied the cows, the princ.i.p.al source of wealth, with rich, wet gra.s.s. In summer, on the short swards of the slopes, the sheep were penned day and night, protected from beasts of prey by a fence of hurdles propped up with pitchforks. When the gra.s.s was cropped close at one spot, the fold was shifted elsewhere. In the center was the shepherd's rolling hut, a straw cabin. Two watchdogs, equipped with spiked collars, were answerable for tranquillity if the thieving wolf appeared in the night from out the neighboring woods.