Social Life in the Insect World

One night, the female being in the dining-room, on the table, facing the open window, a petroleum lamp, furnished with a large reflector in opaline glass, was hanging from the ceiling. The arrivals alighted on the dome of the wire-gauze cover, crowding eagerly about the prisoner; others, saluting her in passing, flew to the lamp, circled round it a few times, and then, fascinated by the luminous splendour radiating from the opal cone of light, clung there motionless under the reflector. Already the children were raising their hands to seize them. "Leave them," I said, "leave them. Let us be hospitable: do not disturb the pilgrims who have come to the tabernacle of the light."

During the whole evening not one of them moved. Next day they were still there. The intoxication of the light had made them forget the intoxication of love.

With creatures so madly in love with the light precise and prolonged experimentation is impracticable the moment the observer requires artificial light. I renounced the Great Peacock and its nocturnal habits. I required a butterfly with different habits; equally notable as a lover, but seeking out the beloved by day.

Before going on to speak of my experiments with a subject fulfilling these conditions, let me break the chronological order of my record in order to say a few words concerning another insect, which appeared after I had completed these inquiries. I refer to the Lesser Peacock (Attacus pavonia minor, Lin.).

Some one brought me, from what locality I do not know, a superb cocoon enveloped in an ample wrapping of white silk. From this covering, which lay in large irregular folds, the chrysalis was easily detached; in shape like that of the Great Peacock, but considerably less in size. The anterior extremity, which is defended by an arrangement of fine twigs, converging, and free at the converging ends, forming a device not unlike an eel-pot, which presents access to the chrysalis while allowing the butterfly to emerge without breaking the defence, indicated a relative of the great nocturnal butterfly; the silk-work denoted a spinning caterpillar.

Towards the end of March this curious cocoon yielded up a female of the Lesser Peacock, which was immediately sequestered under a wire-gauze cover in my study. I opened the window to allow news of the event to reach the surrounding country, and left it open so that such visitors as presented themselves should find free access to the cage. The captive clung to the wire gauze and did not move for a week.

She was a superb creature, this prisoner of mine, with her suit of brown velvet, crossed by undulating lines. The neck was surrounded by white fur; there was a carmine spot at the extremity of the upper wings, and four great eyes in which were grouped, in concentric crescents, black, white, red, and yellow ochre: almost the colouring of the Great Peacock, but more vivid. Three or four times in my life I had encountered this butterfly, so remarkable for its size and its costume. The cocoon I had recently seen for the first time; the male I had never seen. I only knew that, according to the books, it was half the size of the female, and less vividly coloured, with orange-yellow on the lower wings.

Would he appear, the elegant unknown, with waving plumes; the butterfly I had never yet seen, so rare does the Lesser Peacock seem to be in our country? Would he, in some distant hedge, receive warning of the bride who waited on my study table? I dared to hope it, and I was right. He arrived even sooner than I had hoped.

Noon struck as we were sitting down to table, when little Paul, delayed by his absorption in the expected event, suddenly ran to rejoin us, his cheeks glowing. Between his fingers we saw the fluttering wings of a handsome butterfly, caught but a moment before, while it was hovering in front of my study. He showed it me, questioning me with his eyes.

"Aha!" I cried, "this is precisely the pilgrim we are waiting for. Fold your napkin and come and see what happens. We will dine later."

Dinner was forgotten before the marvels that came to pass. With inconceivable punctuality the butterflies hastened to meet the magical call of the captive. With tortuous flight they arrived one by one. All came from the north. This detail is significant. A week earlier there had been a savage return of the winter. The bise blew tempestuously, killing the early almond blossom. It was one of those ferocious storms which in the South commonly serve as a prelude to the spring. But the temperature had now suddenly softened, although the wind still blew from the north.

Now on this first occasion all the butterflies hastening to the prisoner entered the garden from the north. They followed the direction of the wind; not one flew against it. If their guide was a sense of smell like ours, if they were guided by fragrant atoms suspended in the air, they should have arrived in the opposite direction. Coming from the south, we might believe them to be warned by effluvia carried on the wind; coming from the north in time of mistral, that resistless sweeper of earth and air, how can we suppose that they had perceived, at a remote distance, what we will call an odour? The idea of a flow of odoriferous atoms in a direction contrary to that of the aerial torrent seems to me inadmissible.

For two hours, under a radiant sun, the visitors came and went before the outer wall of the study. Most of them sought for a long time, exploring the wall, flying on a level with the ground. To see them thus hesitating you would say that they were puzzled to find the exact position of the lure which called them. Although they had come from such a distance without a mistake, they seemed imperfectly informed once they were on the spot. Nevertheless, sooner or later they entered the room and saluted the captive, without showing any great ardour. At two o'clock all was over. Ten butterflies had arrived.

During the whole week, and always about noon, at the hour of the brightest sunlight, the butterflies arrived, but in decreasing numbers. The total approached forty. I thought it useless to repeat experiments which would add nothing to what I had already learned. I will confine myself to stating two facts. In the first place, the Lesser Peacock is diurnal; that is to say, it celebrates its mating under the dazzling brilliance of noon. It needs the full force of the sunlight. The Great Peacock, on the contrary, which it so closely resembles both in its adult form and the work of its caterpillar, requires the darkness of the first hours of the night. Who can explain this strange contrast in habits?

In the second place, a powerful current of air, sweeping away in a contrary direction all particles that might inform the sense of smell, does not prevent the butterflies from arriving from a direction opposite to that taken by the effluvial stream, as we understand such matters.

To continue: I needed a diurnal moth or butterfly: not the Lesser Peacock, which came too late, when I had nothing to ask of it, but another, no matter what, provided it was a prompt guest at the wedding feast. Was I to find such an insect?

CHAPTER XV

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.

CHAPTER XVI

A miserable caterpillar, the Processional caterpillar, found on the pine-tree, has its back covered with meteorological spiracles which sense the coming weather and foretell the storm; the bird of prey, that incomparable watchman, sees the fallen mule from the heights of the clouds; the blind bats guided their flight without collision through the inextricable labyrinth of threads devised by Spallanzani; the carrier pigeon, at a hundred leagues from home, infallibly regains its loft across immensities which it has never known; and within the limits of its more modest powers a bee, the Chalicodoma, also adventures into the unknown, accomplishing its long journey and returning to its group of cells.

Those who have never seen a dog seeking truffles have missed one of the finest achievements of the olfactory sense. Absorbed in his duties, the animal goes forward, scenting the wind, at a moderate pace. He stops, questions the soil with his nostrils, and, without excitement, scratches the earth a few times with one paw. "There it is, master!" his eyes seem to say: "there it is! On the faith of a dog, there are truffles here!"

He says truly. The master digs at the point indicated. If the spade goes astray the dog corrects the digger, sniffing at the bottom of the hole. Have no fear that stones and roots will confuse him; in spite of depth and obstacles, the truffle will be found. A dog's nose cannot lie.

I have referred to the dog's speciality as a subtle sense of smell. That is certainly what I mean, if you will understand by that that the nasal passages of the animal are the seat of the perceptive organ; but is the thing perceived always a simple smell in the vulgar acceptation of the term—an effluvium such as our own senses perceive? I have certain reasons for doubting this, which I will proceed to relate.

On various occasions I have had the good fortune to accompany a truffle-dog of first-class capacities on his rounds. Certainly there was not much outside show about him, this artist that I so desired to see at work; a dog of doubtful breed, placid and meditative; uncouth, ungroomed, and quite inadmissible to the intimacies of the hearthrug. Talent and poverty are often mated.

His master, a celebrated rabassier[5] of the village, being convinced that my object was not to steal his professional secrets, and so sooner or later to set up in business as a competitor, admitted me of his company, a favour of which he was not prodigal. From the moment of his regarding me not as an apprentice, but merely as a curious spectator, who drew and wrote about subterranean vegetable affairs, but had no wish to carry to market my bagful of these glories of the Christmas goose, the excellent man lent himself generously to my designs.

It was agreed between us that the dog should act according to his own instincts, receiving the customary reward, after each discovery, no matter what its size, of a crust of bread the size of a finger-nail. Every spot scratched by his paw should be excavated, and the object indicated was to be extracted without reference to its marketable value. In no case was the experience of the master to intervene in order to divert the dog from a spot where the general aspect of things indicated that no commercial results need be expected, for I was more concerned with the miserable specimens unfit for the market than with the choice specimens, though of course the latter were welcomed.

Thus conducted, this subterranean botanising was extremely fruitful. With that perspicacious nose of his the dog obtained for me both large and small, fresh and putrid, odorous and inodorous, fragrant and offensive. I was amazed at my collection, which comprised the greater number of the hypogenous fungi of the neighbourhood.

What a variety of structure, and above all of odour, the primordial quality in this question of scent! There were some that had no appreciable scent beyond a vague fungoid flavour, more or less common to all. Others smelt of turnips, of sour cabbage; some were fetid, sufficiently so to make the house of the collector noisome. Only the true truffle possessed the aroma dear to epicures. If odour, as we understand it, is the dog's only guide, how does he manage to follow that guide amidst all these totally different odours? Is he warned of the contents of the subsoil by a general emanation, by that fungoid effluvium common to all the species? Thus a somewhat embarrassing question arises.

I paid special attention to the ordinary toadstools and mushrooms, which announced their near advent by cracking the surface of the soil. Now these points, where my eyes divined the cryptogam pushing back the soil with its button-like heads, these points, where the ordinary fungoid odour was certainly very pronounced, were never selected by the dog. He passed them disdainfully, without a sniff, without a stroke of the paw. Yet the fungi were underground, and their odour was similar to that I have already referred to.

I came back from my outings with the conviction that the truffle-finding nose has some better guide than odour such as we with our sense-organs conceive it. It must perceive effluvia of another order as well; entirely mysterious to us, and therefore not utilised. Light has its dark rays—rays without effect upon our retinas, but not apparently on all. Why should not the domain of smell have its secret emanations, unknown to our senses and perceptible to a different sense-organ?

If the scent of the dog leaves us perplexed in the sense that we cannot possibly say precisely, cannot even suspect what it is that the dog perceives, at least it is clear that it would be erroneous to refer everything to human standards. The world of sensations is far larger than the limits of our own sensibility. What numbers of facts relating to the interplay of natural forces must escape us for want of sufficiently sensitive organs!

The unknown—that inexhaustible field in which the men of the future will try their strength—has harvests in store for us beside which our present knowledge would show as no more than a wretched gleaning. Under the sickle of science will one day fall the sheaves whose grain would appear to-day as senseless paradoxes. Scientific dreams? No, if you please, but undeniable positive realities, affirmed by the brute creation, which in certain respects has so great an advantage over us.

Despite his long practice of his calling, despite the scent of the object he was seeking, the rabassier could not divine the presence of the truffle, which ripens in winter under the soil, at a depth of a foot or two; he must have the help of a dog or a pig, whose scent is able to discover the secrets of the soil. These secrets are known to various insects even better than to our two auxiliaries. They have in exceptional perfection the power of discovering the tubers on which their larvæ are nourished.

From truffles dug up in a spoiled condition, peopled with vermin, and placed in that condition, with a bed of fresh sand, in a glass jar, I have in the past obtained a small red beetle, known as the truffle-beetle (Anisotoma cinnamomea, Panz.), and various Diptera, among which is a Sapromyzon which, by its sluggish flight and its fragile form, recalls the Scatophaga scybalaria, the yellow velvety fly which is found in human excrement in the autumn. The latter finds its refuge on the surface of the soil, at the foot of a wall or hedge or under a bush; but how does the former know just where the truffle lies under the soil, or at what depth? To penetrate to that depth, or to seek in the subsoil, is impossible. Its fragile limbs, barely able to move a grain of sand, its extended wings, which would bar all progress in a narrow passage, and its costume of bristling silken pile, which would prevent it from slipping through crevices, all make such a task impossible. The Sapromyzon is forced to lay its eggs on the surface of the soil, but it does so on the precise spot which overlies the truffle, for the grubs would perish if they had to wander at random in search of their provender, the truffle being always thinly sown.

The truffle fly is informed by the sense of smell of the points favourable to its maternal plans; it has the talents of the truffle-dog, and doubtless in a higher degree, for it knows naturally, without having been taught, what its rival only acquires through an artificial education.

It would be not uninteresting to follow the Sapromyzon in its search in the open woods. Such a feat did not strike me as particularly possible; the insect is rare, flies off quickly when alarmed, and is lost to view. To observe it closely under such conditions would mean a loss of time and an assiduity of which I do not feel capable. Another truffle-hunter will show us what we could hardly learn from the fly.

This is a pretty little black beetle, with a pale, velvety abdomen; a spherical insect, as large as a biggish cherry-stone. Its official title is Bolboceras gallicus, Muls. By rubbing the end of the abdomen against the edge of the wing-cases it produces a gentle chirping sound like the cheeping of nestlings when the mother-bird returns to the nest with food. The male wears a graceful horn on his head; a duplicate, in little, of that of the Copris hispanus.

Deceived by this horn, I at first took the insect for a member of the corporation of dung-beetles, and as such I reared it in captivity. I offered it the kind of diet most appreciated by its supposed relatives, but never, never would it touch such food. For whom did I take it? Fie upon me! To offer ordure to an epicure! It required, if not precisely the truffle known to our chefs and gourmets, at least its equivalent.

This characteristic I grasped only after patient investigation. At the southern foot of the hills of Sérignan, not far from the village, is a wood of maritime pines alternating with rows of cypress. There, towards Toussaint, after the autumnal rains, you may find an abundance of the mushrooms or "toadstools" that affect the conifers; especially the delicious Lactaris, which turns green if the points are rubbed and drips blood if broken. In the warm days of autumn this is the favourite promenade of the members of my household, being distant enough to exercise their young legs, but near enough not to fatigue them.

There one finds and sees all manner of things: old magpies' nests, great bundles of twigs; jays, wrangling after filling their crops with the acorns of the neighbouring oaks; rabbits, whose little white upturned scuts go bobbing away through the rosemary bushes; dung-beetles, which are storing food for the winter and throwing up their rubbish on the threshold of their burrows. And then the fine sand, soft to the touch, easily tunnelled, easily excavated or built into tiny huts which we thatch with moss and surmount with the end of a reed for a chimney; and the delicious meal of apples, and the sound of the æolian harps which softly whisper among the boughs of the pines!

For the children it is a real paradise, where they can receive the reward of well-learned lessons. The grown-ups also can share in the enjoyment. As for myself, for long years I have watched two insects which are found there without getting to the bottom of their domestic secrets. One is the Minotaurus typhæus, whose male carries on his corselet three spines which point forward. The old writers called him the Phalangist, on account of his armour, which is comparable to the three ranks of lances of the Macedonian phalanx.

This is a robust creature, heedless of the winter. All during the cold season, whenever the weather relents a little, it issues discreetly from its lodging, at nightfall, and gathers, in the immediate neighbourhood of its dwelling, a few fragments of sheep-dung and ancient olives which the summer suns have dried. It stacks them in a row at the end of its burrow, closes the door, and consumes them. When the food is broken up and exhausted of its meagre juices it returns to the surface and renews its store. Thus the winter passes, famine being unknown unless the weather is exceptionally hard.

The second insect which I have observed for so long among the pines is the Bolboceras. Its burrows, scattered here and there, higgledy-piggledy with those of the Minotaur, are easy to recognise. The burrow of the Phalangist is surmounted by a voluminous rubbish-dump, the materials of which are piled in the form of a cylinder as long as the finger. Each of these dumps is a load of refuse and rubbish pushed outward by the little sapper, which shoulders it up from below. The orifice is closed whenever the insect is at home, enlarging its tunnel or peacefully enjoying the contents of its larder.

The lodging of the Bolboceras is open and surrounded simply by a mound of sand. Its depth is not great; a foot or hardly more. It descends vertically in an easily shifted soil. It is therefore easy to inspect it, if we take care first of all to dig a trench so that the wall of the burrow may be afterwards cut away, slice by slice, with the blade of a knife. The burrow is thus laid bare along its whole extent, from the surface to the bottom, until nothing remains of it but a demi-cylindrical groove.

Often the violated dwelling is empty. The insect has departed in the night, having finished its business there. It is a nomad, a night-walker, which leaves its dwelling without regret and easily acquires another. Often, on the other hand, the insect will be found at the bottom of the burrow; sometimes a male, sometimes a female, but always alone. The two sexes, equally zealous in excavating their burrows, work apart without collaboration. This is no family mansion for the rearing of offspring; it is a temporary dwelling, made by each insect for its own benefit.

Sometimes the burrow contains nothing but the well-sinker surprised at its work: sometimes—and not rarely—the hermit will be found embracing a small subterranean fungus, entire or partly consumed. It presses it convulsively to its bosom and will not be parted from it. This is the insect's booty: its worldly wealth. Scattered crumbs inform us that we have surprised the beetle at a feast.

Let us deprive the insect of its booty. We find a sort of irregular, rugged, purse-like object, varying in size from the largeness of a pea to that of a cherry. The exterior is reddish, covered with fine warts, having an appearance not unlike shagreen; the interior, which has no communication with the exterior, is smooth and white. The pores, ovoidal and diaphanous, are contained, in groups of eight, in long capsules. From these characteristics we recognise an underground cryptogam, known to the botanists as Hydnocystis arenaria, and a relation of the truffle.

This discovery begins to throw a light on the habits of the Bolboceras and the cause of its burrows, so frequently renewed. In the calm of the twilight the little truffle-hunter goes abroad, chirping softly to encourage itself. It explores the soil, and interrogates it as to its contents, exactly as does the truffle-gatherer's dog. The sense of smell warns it that the desired object is beneath it, covered by a few inches of sand. Certain of the precise point where the treasure lies, it sinks a well vertically downwards, and infallibly reaches it. So long as there is food left it does not again leave the burrow. It feasts happily at the bottom of its well, heedless of the open or imperfectly closed burrow.

When no more food is left it removes in search of further booty, which becomes the occasion of another burrow, this too in its turn to be abandoned. So many truffles eaten necessitate so many burrows, which are mere dining-rooms or pilgrim's larders. Thus pass the autumn and the spring, the seasons of the Hydnocystis, in the pleasures of the table and removal from one house to another.

To study the insect rabassier in my own house I had to obtain a small store of its favourite food. To seek it myself, by digging at random, would have resulted merely in waste of time; the little cryptogam is not so common that I could hope to find it without a guide. The truffle-hunter must have his dog; my guide should be the Bolboceras itself. Behold me, then, a rabassier of a kind hitherto unknown. I have told my secret, although I fear my original teacher will laugh at me if he ever hears of my singular form of competition.

The subterranean fungi grow only at certain points, but they are often found in groups. Now, the beetle has passed this way; with its subtle sense of smell it has recognised the ground as favourable; for its burrows are numerous. Let us dig, then, in the neighbourhood of these holes. The sign is reliable; in a few hours, thanks to the signs of the Bolboceras, I obtain a handful of specimens of the Hydnocystis. It is the first time I have ever found this fungus in the ground. Let us now capture the insect—an easy matter, for we have only to excavate the burrows.

The same evening I begin my experiments. A wide earthen pan is filled with fresh sand which has been passed through a sieve. With the aid of a stick the thickness of a finger I make six vertical holes in the sand: they are conveniently far apart, and are eight inches in depth. A Hydnocystis is placed at the bottom of each; a fine straw is then inserted, to show me the precise position later. Finally the six holes are filled with sand which is beaten down so that all is firm. When the surface is perfectly level, and everywhere the same, except for the six straws, which mean nothing to the insect, I release my beetles, covering them with a wire-gauze cover. They are eight in number.

At first I see nothing but the inevitable fatigue due to the incidents of exhumation, transport, and confinement in a strange place. My exiles try to escape: they climb the wire walls, and finally all take to earth at the edge of their enclosure. Night comes, and all is quiet. Two hours later I pay my prisoners a last visit. Three are still buried under a thin layer of sand. The other five have sunk each a vertical well at the very foot of the straws which indicate the position of the buried fungi. Next morning the sixth straw has its burrow like the rest.

It is time to see what is happening underground. The sand is methodically removed in vertical slices. At the bottom of each burrow is a Bolboceras engaged in eating its truffle.

Let us repeat the experiment with the partly eaten fungi. The result is the same. In one short night the food is divined under its covering of sand and attained by means of a burrow which descends as straight as a plumb-line to the point where the fungus lies. There has been no hesitation, no trial excavations which have nearly discovered the object of search. This is proved by the surface of the soil, which is everywhere just as I left it when smoothing it down. The insect could not make more directly for the objective if guided by the sense of sight; it digs always at the foot of the straw, my private sign. The truffle-dog, sniffing the ground in search of truffles, hardly attains this degree of precision.

Does the Hydnocystis possess a very keen odour, such as we should expect to give an unmistakable warning to the senses of the consumer? By no means. To our own sense of smell it is a neutral sort of object, with no appreciable scent whatever. A little pebble taken from the soil would affect our senses quite as strongly with its vague savour of fresh earth. As a finder of underground fungi the Bolboceras is the rival of the dog. It would be the superior of the dog if it could generalise; it is, however, a rigid specialist, recognising nothing but the Hydnocystis. No other fungus, to my knowledge, either attracts it or induces it to dig.[6]

Both dog and beetle are very near the subsoil which they scrutinise; the object they seek is at no great depth. At a greater depth neither dog nor insect could perceive such subtle effluvia, nor even the odour of the truffle. To attract insect or animal at a great distance powerful odours are necessary, such as our grosser senses can perceive. Then the exploiters of the odorous substance hasten from afar off and from all directions.

If for purposes of study I require specimens of such insects as dissect dead bodies I expose a dead mole to the sunlight in a distant corner of my orchard. As soon as the creature is swollen with the gases of putrefaction, and the fur commences to fall from the greenish skin, a host of insects arrive—Silphidæ, Dermestes, Horn-beetles, and Necrophori—of which not a single specimen could ever be obtained in my garden or even in the neighbourhood without the use of such a bait.

They have been warned by the sense of smell, although far away in all directions, while I myself can escape from the stench by recoiling a few paces. In comparison with their sense of smell mine is miserable; but in this case, both for me and for them, there is really what our language calls an odour.

I can do still better with the flower of the Serpent Arum (Arum dracunculus), so noteworthy both for its form and its incomparable stench. Imagine a wide lanceolated blade of a vinous purple, some twenty inches in length, which is twisted at the base into an ovoid purse about the size of a hen's egg. Through the opening of this capsule rises the central column, a long club of a livid green, surrounded at the base by two rings, one of ovaries and the other of stamens. Such, briefly, is the flower or rather the inflorescence of the Serpent Arum.

For two days it exhales a horrible stench of putrid flesh; a dead dog could not produce such a terrible odour. Set free by the sun and the wind, it is odious, intolerable. Let us brave the infected atmosphere and approach; we shall witness a curious spectacle.

Warned by the stench, which travels far and wide, a host of insects are flying hither; such insects as dissect the corpses of frogs, adders, lizards, hedgehogs, moles and field-mice—creatures that the peasant finds beneath his spade and throws disembowelled on the path. They fall upon the great leaf, whose livid purple gives it the appearance of a strip of putrid flesh; they dance with impatience, intoxicated by the corpse-like odour which to them is so delicious; they roll down its steep face and are engulfed in the capsule. After a few hours of hot sunlight the receptacle is full.

Let us look into the capsule through the narrow opening. Nowhere else could you see such a mob of insects. It is a delirious mixture of backs and bellies, wing-covers and legs, which swarms and rolls upon itself, rising and falling, seething and boiling, shaken by continual convulsions, clicking and squeaking with a sound of entangled articulations. It is a bacchanal, a general access of delirium tremens.

A few, but only a few, emerge from the mass. By the central mast or the walls of the purse they climb to the opening. Do they wish to take flight and escape? By no means. On the threshold of the cavity, while already almost at liberty, they allow themselves to fall into the whirlpool, retaken by their madness. The lure is irresistible. None will break free from the swarm until the evening, or perhaps the next day, when the heady fumes will have evaporated. Then the units of the swarm disengage themselves from their mutual embraces, and slowly, as though regretfully, take flight and depart. At the bottom of this devil's purse remains a heap of the dead and dying, of severed limbs and wing-covers torn off; the inevitable sequels of the frantic orgy. Soon the woodlice, earwigs, and ants will appear to prey upon the injured.

What are these insects doing? Were they the prisoners of the flower, converted into a trap which allowed them to enter but prevented their escape by means of a palisade of converging hairs? No, they were not prisoners; they had full liberty to escape, as is proved by the final exodus, which is in no way impeded. Deceived by a fallacious odour, were they endeavouring to lay and establish their eggs as they would have done under the shelter of a corpse? No; there is no trace of eggs in the purse of the Arum. They came convoked by the odour of a decaying body, their supreme delight; an intoxication seized them, and they rushed into the eddying swarm to take part in a festival of carrion-eaters.

I was anxious to count the number of those attracted. At the height of the bacchanal I emptied the purse into a bottle. Intoxicated as they were, many would escape my census, and I wished to ensure its accuracy. A few drops of carbon bisulphide quieted the swarm. The census proved that there were more than four hundred insects in the purse of the Arum. The collection consisted entirely of two species—Dermestes and Saprinidæ—both eager prospectors of carrion and animal detritus during the spring.

My friend Bull, an honest dog all his lifetime if ever there was one, amongst other eccentricities had the following: finding in the dust of the road the shrivelled body of a mole, flattened by the feet of pedestrians, mummified by the heat of the sun, he would slide himself over it, from the tip of his nose to the root of his tail, he would rub himself against it deliciously over and over again, shaken with nervous spasms, and roll upon it first in one direction, then in the other.

It was his sachet of musk, his flask of eau-de-Cologne. Perfumed to his liking, he would rise, shake himself, and proceed on his way, delighted with his toilet. Do not let us scold him, and above all do not let us discuss the matter. There are all kinds of tastes in a world.

Why should there not be insects with similar habits among the amateurs of corpse-like savours? We see Dermestes and Saprinidæ hastening to the arum-flower. All day long they writhe and wriggle in a swarm, although perfectly free to escape; numbers perish in the tumultuous orgy. They are not retained by the desire of food, for the arum provides them with nothing eatable; they do not come to breed, for they take care not to establish their grubs in that place of famine. What are these frenzied creatures doing? Apparently they are intoxicated with fetidity, as was Bull when he rolled on the putrid body of a mole.

This intoxication draws them from all parts of the neighbourhood, perhaps over considerable distances; how far we do not know. The Necrophori, in quest of a place where to establish their family, travel great distances to find the corpses of small animals, informed by such odours as offend our own senses at a considerable distance.

The Hydnocystis, the food of the Bolboceras, emits no such brutal emanations as these, which readily diffuse themselves through space; it is inodorous, at least to our senses. The insect which seeks it does not come from a distance; it inhabits the places wherein the cryptogam is found. Faint as are the effluvia of this subterranean fungus, the prospecting epicure, being specially equipped, perceives them with the greatest ease; but then he operates at close range, from the surface of the soil. The truffle-dog is in the same case; he searches with his nose to the ground. The true truffle, however, the essential object of his search, possesses a fairly vivid odour.

But what are we to say of the Great Peacock moth and the Oak Eggar, both of which find their captive female? They come from the confines of the horizon. What do they perceive at that distance? Is it really an odour such as we perceive and understand? I cannot bring myself to believe it.

The dog finds the truffle by smelling the earth quite close to the tuber; but he finds his master at great distances by following his footsteps, which he recognises by their scent. Yet can he find the truffle at a hundred yards? or his master, in the complete absence of a trail? No. With all his fineness of scent, the dog is incapable of such feats as are realised by the moth, which is embarrassed neither by distance nor the absence of a trail.

It is admitted that odour, such as affects our olfactory sense, consists of molecules emanating from the body whose odour is perceived. The odorous material becomes diffused through the air to which it communicates its agreeable or disagreeable aroma. Odour and taste are to a certain extent the same; in both there is contact between the material particles causing the impression and the sensitive papillæ affected by the impression.

That the Serpent Arum should elaborate a powerful essence which impregnates the atmosphere and makes it noisome is perfectly simple and comprehensible. Thus the Dermestes and Saprinidæ, those lovers of corpse-like odours, are warned by molecular diffusion. In the same way the putrid frog emits and disseminates around it atoms of putrescence which travel to a considerable distance and so attract and delight the Necrophorus, the carrion-beetle.

But in the case of the Great Peacock or the Oak Eggar, what molecules are actually disengaged? None, according to our sense of smell. And yet this lure, to which the males hasten so speedily, must saturate with its molecules an enormous hemisphere of air—a hemisphere some miles in diameter! What the atrocious fetor of the Arum cannot do the absence of odour accomplishes! However divisible matter may be, the mind refuses such conclusions. It would be to redden a lake with a grain of carmine; to fill space with a mere nothing.

Moreover, where my laboratory was previously saturated with powerful odours which should have overcome and annihilated any particularly delicate effluvium, the male moths arrived without the least indication of confusion or delay.

A loud noise stifles a feeble note and prevents it from being heard; a brilliant light eclipses a feeble glimmer. Heavy waves overcome and obliterate ripples. In the two cases cited we have waves of the same nature. But a clap of thunder does not diminish the feeblest jet of light; the dazzling glory of the sun will not muffle the slightest sound. Of different natures, light and sound do not mutually interact.

My experiment with spike-lavender, naphthaline, and other odours seems to prove that odour proceeds from two sources. For emission substitute undulation, and the problem of the Great Peacock moth is explained. Without any material emanation a luminous point shakes the ether with its vibrations and fills with light a sphere of indefinite magnitude. So, or in some such manner, must the warning effluvium of the mother Oak Eggar operate. The moth does not emit molecules; but something about it vibrates, causing waves capable of propagation to distances incompatible with an actual diffusion of matter.

From this point of view, smell would have two domains—that of particles dissolved in the air and that of etheric waves.[7] The former domain alone is known to us. It is also known to the insect. It is this that warns the Saprinidæ of the fetid arum, the Silphidæ and the Necrophori of the putrid mole.

The second category of odour, far superior in its action through space, escapes us completely, because we lack the essential sensory equipment. The Great Peacock moth and the Oak Eggar know it at the time of their nuptial festivities. Many others must share it in differing degrees, according to the exigencies of their way of life.

Like light, odour has its X-rays. Let science, instructed by the insect, one day give us a radiograph sensitive to odours, and this artificial nose will open a new world of marvels.