THE OAK EGGAR, OR BANDED MONK

Social Life in the Insect World by Jean-Henri Fabre, is part of the HackerNoon Books Series. You can jump to any chapter in this book here. THE OAK EGGAR, OR BANDED MONK

CHAPTER XV. THE OAK EGGAR, OR BANDED MONK

Yes: I was to find it. I even had it already in my possession. An urchin of seven years, with an alert countenance, not washed every day, bare feet, and dilapidated breeches supported by a piece of string, who frequented the house as a dealer in turnips and tomatoes, arrived one day with his basket of vegetables. Having received the few halfpence expected by his mother as the price of the garden-stuff, and having counted them one by one into the hollow of his hand, he took from his pocket an object which he had discovered the day before beneath a hedge when gathering greenstuff for his rabbits.

"And this—will you have this?" he said, handing me the object. "Why, certainly I will have it. Try to find me more, as many as you can, and on Sunday you shall have lots of rides on the wooden horses. In the meantime here is a penny for you. Don't forget it when you make up your accounts; don't mix it with your turnip-money; put it by itself." Beaming with satisfaction at such wealth, little touzle-head promised to search industriously, already foreseeing a fortune.

When he had gone I examined the thing. It was worth examination. It was a fine cocoon, thick and with blunt ends, very like a silkworm's cocoon, firm to the touch and of a tawny colour. A brief reference to the text-books almost convinced me that this was a cocoon of the Bombyx quercus.[4] If so, what a find! I could continue my inquiry and perhaps confirm what my study of the Great Peacock had made me suspect.

The Bombyx of the oak-tree is, in fact, a classic moth; indeed, there is no entomological text-book but speaks of its exploits at mating-time. It is said that a female emerged from the pupa in captivity, in the interior of an apartment, and even in a closed box. It was far from the country, amidst the tumult of a large city. Nevertheless, the event was known to those concerned in the woods and meadows. Guided by some mysterious compass, the males arrived, hastening from the distant fields; they went to the box, fluttered against it, and flew to and fro in the room.

These marvels I had learned by reading; but to see such a thing with one's own eyes, and at the same time to devise experiments, is quite another thing. What had my penny bargain in store for me? Would the famous Bombyx issue from it?

Let us call it by its other name, the Banded Monk. This original name of Monk was suggested by the costume of the male; a monk's robe of a modest rusty red. But in the case of the female the brown fustian gives place to a beautiful velvet, with a pale transversal band and little white eyes on the fore pair of wings.

The Monk is not a common butterfly which can be caught by any one who takes out a net at the proper season. I have never seen it around our village or in the solitude of my grounds during a residence of twenty years. It is true that I am not a fervent butterfly-catcher; the dead insect of the collector's cabinet has little interest for me; I must have it living, in the exercise of its functions. But although I have not the collector's zeal I have an attentive eye to all that flies or crawls in the fields. A butterfly so remarkable for its size and colouring would never have escaped my notice had I encountered it.

The little searcher whom I had enticed by a promise of rides upon wooden horses never made a second find. For three years I requisitioned friends and neighbours, and especially their children, sharp-sighted snappers-up of trifles; I myself hunted often under heaps of withered leaves; I inspected stone-heaps and visited hollow tree-trunks. Useless pains; the precious cocoon was not to be found. It is enough to say that the Banded Monk is extremely rare in my neighbourhood. The importance of this fact will presently appear.

As I suspected, my cocoon was truly that of the celebrated Oak Eggar. On the 20th of August a female emerged from it: corpulent, big-bellied, coloured like the male, but lighter in hue. I placed her under the usual wire cover in the centre of my laboratory table, littered as it was with books, bottles, trays, boxes, test-tubes, and other apparatus. I have explained the situation in speaking of the Great Peacock. Two windows light the room, both opening on the garden. One was closed, the other open day and night. The butterfly was placed in the shade, between the lines of the two windows, at a distance of 12 or 15 feet.

The rest of that day and the next went by without any occurrence worthy of notice. Hanging by the feet to the front of the wire cover, on the side nearest to the light, the prisoner was motionless, inert. There was no oscillation of the wings, no tremor of the antennæ, the female of the Great Peacock behaved in a similar fashion.

The female Bombyx gradually matured, her tender tissues gradually becoming firmer. By some process of which our scientists have not the least idea she elaborated a mysterious lure which would bring her lovers from the four corners of the sky. What was happening in this big-bellied body; what transmutations were accomplished, thus to affect the whole countryside?

On the third day the bride was ready. The festival opened brilliantly. I was in the garden, already despairing of success, for the days were passing and nothing had occurred, when towards three in the afternoon, the weather being very hot and the sun radiant, I perceived a crowd of butterflies gyrating in the embrasure of the open window.

The lovers had at last come to visit their lady. Some were emerging from the room, others were entering it; others, clinging to the wall of the house, were resting as though exhausted by a long journey. I could see others approaching in the distance, flying over the walls, over the screens of cypress. They came from all directions, but at last with decreasing frequency. I had missed the opening of the convocation, and now the gathering was almost complete.

I went indoors and upstairs. This time, in full daylight and without losing a detail, I witnessed once more the astonishing spectacle to which the great nocturnal butterfly had first introduced me. The study contained a cloud of males, which I estimated, at a glance, as being about sixty in number, so far as the movement and confusion allowed me to count them at all. After circling a few times over the cage many of them went to the open window, but returned immediately to recommence their evolutions. The most eager alighted on the cover, trampling on one another, jostling one another, trying to get the best places. On the other side of the barrier the captive, her great body hanging against the wire, waited immovable. She betrayed not a sign of emotion in the face of this turbulent swarm.

Going and entering, perched on the cover or fluttering round the room, for more than three hours they continued their frenzied saraband. But the sun was sinking, and the temperature was slowly falling. The ardour of the butterflies also cooled. Many went out not to return. Others took up their positions to wait for the gaieties of the following day; they clung to the cross-bars of the closed window as the males of the Great Peacock had done. The rejoicings were over for the day. They would certainly be renewed on the morrow, since the courtship was without result on account of the barrier of the wire-gauze cover.

But, alas I to my great disappointment, they were not resumed, and the fault was mine. Late in the day a Praying Mantis was brought to me, which merited attention on account of its exceptionally small size. Preoccupied with the events of the afternoon, and absent-minded, I hastily placed the predatory insect under the same cover as the moth. It did not occur to me for a moment that this cohabitation could lead to any harm. The Mantis was so slender, and the other so corpulent!

Alas! I little knew the fury of carnage animating the creature that wielded those tiny grappling-irons! Next morning I met with a disagreeable surprise: I found the little Mantis devouring the great moth. The head and the fore part of the thorax had already disappeared. Horrible creature! at what an evil hour you came to me! Goodbye to my researches, the plans which I had caressed all night in my imagination! For three years for lack of a subject, I was unable to resume them.

Bad luck, however, was not to make me forget the little I had learned. On one single occasion about sixty males had arrived. Considering the rarity of the Oak Eggar, and remembering the years of fruitless search on the part of my helpers and myself, this number was no less than stupefying. The undiscoverable had suddenly become multitudinous at the call of the female.

Whence did they come? From all sides, and undoubtedly from considerable distances. During my prolonged searches every bush and thicket and heap of stones in my neighbourhood had become familiar to me, and I can assert that the Oak Eggar was not to be found there. For such a swarm to collect as I found in my laboratory the moths must have come from all directions, from the whole district, and within a radius that I dare not guess at.

Three years went by and by chance two more cocoons of the Monk or Oak Eggar again fell into my hands. Both produced females, at an interval of a few days towards the middle of August; so that I was able to vary and repeat my experiments.

I rapidly repeated the experiments which had given me such positive results in the instance of the Great Peacock moth. The pilgrims of the day were no less skilful at finding their mates than the pilgrims of the night. They laughed at all my tricks. Infallibly they found the prisoners in their wire-gauze prisons, no matter in what part of the house they were placed; they discovered them in the depths of a wall-cupboard; they divined the secret of all manner of boxes, provided these were not rigorously air-tight. They came no longer when the box was hermetically sealed. So far this was only a repetition of the feats of the Great Peacock.

A box perfectly closed, so that the air contained therein had no communication with the external atmosphere, left the male in complete ignorance of the recluse. Not a single one arrived, even when the box was exposed and plain to see on the window-sill. Thus the idea of strongly scented effluvia, which are cut off by screens of wood, metal, card, glass, or what not, returns with double force.

I have shown that the great nocturnal moth was not thrown off the scent by the powerful odour of naphthaline, which I thought would mask the extra-subtle emanations of the female, which were imperceptible to human olfactory organs. I repeated the experiment with the Oak Eggar. This time I used all the resources of scent and stench that my knowledge of drugs would permit.

A dozen saucers were arranged, some in the interior of the wire-gauze cover, the prison of the female, and some around it, in an unbroken circle. Some contained naphthaline; others the essential oil of spike-lavender; others petroleum, and others a solution of alkaline sulphur giving off a stench of rotten eggs. Short of asphyxiating the prisoner I could do no more. These arrangements were made in the morning, so that the room should be saturated when the congregation of lovers should arrive.

In the afternoon the laboratory was filled with the most abominable stench, in which the penetrating aroma of spike-lavender and the stink of sulphuretted hydrogen were predominant. I must add that tobacco was habitually smoked in this room, and in abundance. The concerted odours of a gas-works, a smoking-room, a perfumery, a petroleum well, and a chemical factory—would they succeed in confusing the male moths?

By no means. About three o'clock the moths arrived in as great numbers as usual. They went straight to the cage, which I had covered with a thick cloth in order to add to their difficulties. Seeing nothing when once they had entered, and immersed in an extraordinary atmosphere in which any subtle fragrance should have been annihilated, they nevertheless made straight for the prisoner, and attempted to reach her by burrowing under the linen cloth. My artifice had no result.

After this set-back, so obvious in its consequences, which only repeated the lesson of the experiments made with naphthaline when my subject was the Great Peacock, I ought logically to have abandoned the theory that the moths are guided to their wedding festivities by means of strongly scented effluvia. That I did not do so was due to a fortuitous observation. Chance often has a surprise in store which sets us on the right road when we have been seeking it in vain.

One afternoon, while trying to determine whether sight plays any part in the search for the female once the males had entered the room, I placed the female in a bell-glass and gave her a slender twig of oak with withered leaves as a support. The glass was set upon a table facing the open window. Upon entering the room the moths could not fail to see the prisoner, as she stood directly in the way. The tray, containing a layer of sand, on which the female had passed the preceding day and night, covered with a wire-gauze dish-cover, was in my way. Without premeditation I placed it at the other end of the room on the floor, in a corner where there was but little light. It was a dozen yards away from the window.

The result of these preparations entirely upset my preconceived ideas. None of the arrivals stopped at the bell-glass, where the female was plainly to be seen, the light falling full upon her prison. Not a glance, not an inquiry. They all flew to the further end of the room, into the dark corner where I had placed the tray and the empty dish-cover.

They alighted on the wire dome, explored it persistently, beating their wings and jostling one another. All the afternoon, until sunset, the moths danced about the empty cage the same saraband that the actual presence of the female had previously evoked. Finally they departed: not all, for there were some that would not go, held by some magical attractive force.

Truly a strange result! The moths collected where there was apparently nothing to attract them, and remained there, unpersuaded by the sense of sight; they passed the bell-glass actually containing the female without halting for a moment, although she must have been seen by many of the moths both going and coming. Maddened by a lure, they paid no attention to the reality.

What was the lure that so deceived them? All the preceding night and all the morning the female had remained under the wire-gauze cover; sometimes clinging to the wire-work, sometimes resting on the sand in the tray. Whatever she touched—above all, apparently, with her distended abdomen—was impregnated, as a result of long contact, with a certain emanation. This was her lure, her love-philtre; this it was that revolutionised the Oak Eggar world. The sand retained it for some time and diffused the effluvium in turn.

They passed by the glass prison in which the female was then confined and hastened to the meshes of wire and the sand on which the magic philtre had been poured; they crowded round the deserted chamber where nothing of the magician remained but the odorous testimony of her sojourn.

The irresistible philtre requires time for its elaboration. I conceive of it as an exhalation which is given off during courtship and gradually saturates whatever is in contact with the motionless body of the female. If the bell-glass was placed directly on the table, or, still better, on a square of glass, the communication between the inside and the outside was insufficient, and the males, perceiving no odour, did not arrive so long as that condition of things obtained. It was plain that this failure of transmission was not due to the action of the glass as a screen simply, for if I established a free communication between the interior of the bell-glass and the open air by supporting it on three small blocks, the moths did not collect round it at once, although there were plenty in the room; but in the course of half an hour or so the feminine alembic began to operate, and the visitors crowded round the bell-glass as usual.

In possession of these data and this unexpected enlightenment I varied the experiments, but all pointed to the same conclusion. In the morning I established the female under the usual wire-gauze cover. For support I gave her a little twig of oak as before. There, motionless as if dead, she crouched for hours, half buried in the dry leaves, which would thus become impregnated with her emanations.

When the hour of the daily visits drew near I removed the twig, which was by then thoroughly saturated with the emanations, and laid it on a chair not far from the open window. On the other hand I left the female under the cover, plainly exposed on the table in the middle of the room.

The moths arrived as usual: first one, then two, then three, and presently five and six. They entered, flew out again, re-entered, mounted, descended, came and went, always in the neighbourhood of the window, not far from which was the chair on which the twig lay. None made for the large table, on which, a few steps further from the window, the female awaited them in the wire-gauze cover. They hesitated, that was plain; they were still seeking.

Finally they found. And what did they find? Simply the twig, which that morning had served the ample matron as bed. Their wings rapidly fluttering, they alighted on the foliage; they explored it over and under, probed it, raised it, and displaced it so that the twig finally fell to the floor. None the less they continued to probe between the leaves. Under the buffets and the draught of their wings and the clutches of their eager feet the little bundle of leaves ran along the floor like a scrap of paper patted by the paws of a cat.

While the twig was sliding away with its band of investigators two new arrivals appeared. The chair lay in their path. They stopped at it and searched eagerly at the very spot on which the twig had been lying. But with these, as with the others, the real object of their desires was there, close by, under a wire cover which was not even veiled. None took any note of it. On the floor, a handful of butterflies were still hustling the bunch of leaves on which the female had reposed that morning; others, on the chair, were still examining the spot where the twig had lain. The sun sank, and the hour of departure struck. Moreover, the emanations were growing feebler, were evaporating. Without more ado the visitors left. We bade them goodbye till the morrow.

The following tests showed me that the leaf-covered twig which accidentally enlightened me might be replaced by any other substance. Some time before the visitors were expected I placed the female on a bed of cloth or flannel, card or paper. I even subjected her to the rigours of a camp-bed of wood, glass, marble, and metal. All these objects, after a contact of sufficient duration, had the same attraction for the males as the female moth herself. They retained this property for a longer or shorter time, according to their nature. Cardboard, flannel, dust, sand, and porous objects retained it longest. Metals, marble, and glass, on the contrary, quickly lost their efficacy. Finally, anything on which the female had rested communicated its virtues by contact; witness the butterflies crowding on the straw-bottomed chair after the twig fell to the ground.

Using one of the most favourable materials—flannel, for example—I witnessed a curious sight. I placed a morsel of flannel on which the mother moth had been lying all the morning at the bottom of a long test-tube or narrow-necked bottle, just permitting of the passage of a male moth. The visitors entered the vessels, struggled, and did not know how to extricate themselves. I had devised a trap by means of which I could exterminate the tribe. Delivering the prisoners, and removing the flannel, which I placed in a perfectly closed box, I found that they re-entered the trap; attracted by the effluvia that the flannel had communicated to the glass.

I was now convinced. To call the moths of the countryside to the wedding-feast, to warn them at a distance and to guide them the nubile female emits an odour of extreme subtlety, imperceptible to our own olfactory sense-organs. Even with their noses touching the moth, none of my household has been able to perceive the faintest odour; not even the youngest, whose sensibility is as yet unvitiated.

This scent readily impregnates any object on which the female rests for any length of time, when this object becomes a centre of attraction as active as the moth herself until the effluvium is evaporated.

Nothing visible betrays the lure. On a sheet of paper, a recent resting-place, around which the visitors had crowded, there was no visible trace, no moisture; the surface was as clean as before the impregnation.

The product is elaborated slowly, and must accumulate a little before it reveals its full power. Taken from her couch and placed elsewhere the female loses her attractiveness for the moment and is an object of indifference; it is to the resting-place, saturated by long contact, that the arrivals fly. But the female soon regains her power.

The emission of the warning effluvium is more or less delayed according to the species. The recently metamorphosed female must mature a little and her organs must settle to their work. Born in the morning, the female of the Great Peacock moth sometimes has visitors the night of the same day; but more often on the second day, after a preparation of forty hours or so. The Oak Eggar does not publish her banns of marriage before the third or fourth day.

Let us return for a moment to the problematical function of the antennæ. The male Oak Eggar has a sumptuous pair, as has the Great Peacock or Emperor Moth. Are we to regard these silky "feelers" as a kind of directing compass?—I resumed, but without attaching much importance to the matter, my previous experiment of amputation. None of those operated on returned. Do not let us draw conclusions from that fact alone. We saw in the case of the Great Peacock that more serious reasons than the truncation of the antennæ made return as a rule impossible.

Moreover, a second Bombyx or Eggar, the Clover Moth, very like the Oak Eggar, and like it superbly plumed, poses us a very difficult problem. It is fairly abundant around my home; even in the orchard I find its cocoon, which is easily confounded with that of the Oak Eggar. I was at first deceived by the resemblance. From six cocoons, which I expected to yield Oak Eggars, I obtained, about the end of August, six females of the other species. Well: about these six females, born in my house, never a male appeared, although they were undoubtedly present in the neighbourhood.

If the ample and feathery antennæ are truly sense-organs, which receive information of distant objects, why were not my richly plumed neighbours aware of what was passing in my study? Why did their feathery "feelers" leave them in ignorance of events which would have brought flocks of the other Eggar? Once more, the organ does not determine the aptitude. One individual or species is gifted, but another is not, despite an organic equality.

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