Chapter II. Experiments
Jean-Henri Fabre Mason-bees
Mason Bee (Osmia Rufa)
As the nests of the Mason-bee of the Walls are erected on small-sized pebbles, which can be easily carried wherever you like and moved about from one place to another, without disturbing either the work of the builder or the repose of the occupants of the cells, they lend themselves readily to practical experiment, the only method that can throw a little light on the nature of instinct. To study the insect's mental faculties to any purpose, it is not enough for the observer to be able to profit by some happy combination of circumstances: he must know how to produce other combinations, vary them as much as possible and test them by substitution and interchange. Lastly, to provide science with a solid basis of facts, he must experiment. In this way, the evidence of formal records will one day dispel the fantastic legends with which our books are crowded: the Sacred Beetle (1) calling on his comrades to lend a helping hand in dragging his pellet out of a rut; the Sphex (2) cutting up her Fly so as to be able to carry him despite the obstacle of the wind; and all the other fallacies which are the stock-in-trade of those who wish to see in the animal world what is not really there. In this way, again, materials will be prepared which will one day be worked up by the hand of a master and consign hasty and unfounded theories to oblivion.
Reaumur, as a rule, confines himself to stating facts as he sees them in the normal course of events and does not try to probe deeper into the insect's ingenuity by means of artificially produced conditions. In his time, everything had yet to be done; and the harvest was so great that the illustrious harvester went straight to what was most urgent, the gathering of the crop, and left his successors to examine the grain and the ear in detail. Nevertheless, in connection with the Chalicodoma of the Walls, he mentions an experiment made by his friend, Duhamel (3). He tells us how a Mason-bee's nest was enclosed in a glass funnel, the mouth of which was covered merely with a bit of gauze. From it there issued three males, who, after vanquishing mortar as hard as stone, either never thought of piercing the flimsy gauze or else deemed the work beyond their strength. The three Bees died under the funnel. R?aumur adds that insects generally know only how to do what they have to do in the ordinary course of nature.
The experiment does not satisfy me, for two reasons: first, to ask workers equipped with tools for cutting clay as hard as granite to cut a piece of gauze does not strike me as a happy inspiration; you cannot expect a navvy's pick-axe to do the same work as a dressmaker's scissors. Secondly, the transparent glass prison seems to me ill-chosen. As soon as the insect has made a passage through the thickness of its earthen dome, it finds itself in broad daylight; and to it daylight means the final deliverance, means liberty. It strikes against an invisible obstacle, the glass; and to it glass is nothing at all and yet an obstruction. On the far side, it sees free space, bathed in sunshine. It wears itself out in efforts to fly there, unable to understand the futile nature of its attempts against that strange barrier which it cannot see. It perishes, at last, of exhaustion, without, in its obstinacy, giving a glance at the gauze closing the conical chimney. The experiment must be renewed under better conditions.
The obstacle which I select is ordinary brown paper, stout enough to keep the insect in the dark and thin enough not to offer serious resistance to the prisoner's efforts. As there is a great difference, in so far as the actual nature of the barrier is concerned, between a paper partition and a clay ceiling, let us begin by enquiring if the Mason-bee of the Walls knows how or rather is able to make her way through one of these partitions. The mandibles are pickaxes suitable for breaking through hard mortar: are they also scissors capable of cutting a thin membrane? This is the point to look into first of all.
In February, by which time the insect is in its perfect state, I take a certain number of cocoons, without damaging them, from their cells and insert them each in a separate stump of reed, closed at one end by the natural wall of the node and open at the other. These pieces of reed represent the cells of the nest. The cocoons are introduced with the insect's head turned towards the opening. Lastly, my artificial cells are closed in different ways. Some receive a stopper of kneaded clay, which, when dry, will correspond in thickness and consistency with the mortar ceiling of the natural nest. Others are plugged with a cylinder of sorghum, at least a centimetre (4) thick; and the remainder with a disk of brown paper solidly fastened by the edge. All these bits of reed are placed side by side in a box, standing upright, with the roof of my making at the top. The insects, therefore, are in the exact position which they occupied in the nest. To open a passage, they must do what they would have done without my interference, they must break through the wall situated above their heads. I shelter the whole under a wide bell-glass and wait for the month of May, the period of the deliverance.
The results far exceed my anticipations. The clay stopper, the work of my fingers, is perforated with a round hole, differing in no wise from that which the Mason-bee contrives through her native mortar dome. The vegetable barrier, new to my prisoners, namely, the sorghum cylinder, also opens with a neat orifice, which might have been the work of a punch. Lastly, the brown-paper cover allows the Bee to make her exit not by bursting through, by making a violent rent, but once more by a clearly defined round hole. My Bees therefore are capable of a task for which they were not born; to come out of their reed cells they do what probably none of their race did before them; they perforate the wall of sorghum-pith, they make a hole in the paper barrier, just as they would have pierced their natural clay ceiling. When the moment comes to free themselves, the nature of the impediment does not stop them, provided that it be not beyond their strength; and henceforth the argument of incapacity cannot be raised when a mere paper barrier is in question.
In addition to the cells made out of bits of reed, I put under the bell-glass, at the same time, two nests which are intact and still resting on their pebbles. To one of them I have attached a sheet of brown paper pressed close against the mortar dome. In order to come out, the insect will have to pierce first the dome and then the paper, which follows without any intervening space. Over the other, I have placed a little brown paper cone, gummed to the pebble. There is here, therefore, as in the first case, a double wall — a clay partition and a paper partition — with this difference, that the two walls do not come immediately after each other, but are separated by an empty space of about a centimetre at the bottom, increasing as the cone rises.
The results of these two experiments are quite different. The Bees in the nest to which a sheet of paper was tightly stuck come out by piercing the two enclosures, of which the outer wall, the paper wrapper, is perforated with a very clean round hole, as we have already seen in the reed cells closed with a lid of the same material. We thus become aware, for the second time, that, when the Mason-bee is stopped by a paper barrier, the reason is not her incapacity to overcome the obstacle. On the other hand, the occupants of the nest covered with the cone, after making their way through the earthen dome, finding the sheet of paper at some distance, do not even try to perforate this obstacle, which they would have conquered so easily had it been fastened to the nest. They die under the cover without making any attempt to escape. Even so did R?aumur's Bees perish in the glass funnel, where their liberty depended only upon their cutting through a bit of gauze.
This fact strikes me as rich in inferences. What! Here are sturdy insects, to whom boring through granite is mere play, to whom a stopper of soft wood and a paper partition are walls quite easy to perforate despite the novelty of the material; and yet these vigorous housebreakers allow themselves to perish stupidly in the prison of a paper bag, which they could have torn open with one stroke of their mandibles! They are capable of tearing it, but they do not dream of doing so! There can be only one explanation of this suicidal inaction. The insect is well-endowed with tools and instinctive faculties for accomplishing the final act of its metamorphosis, namely, the act of emerging from the cocoon and from the cell. Its mandibles provide it with scissors, file, pick-axe and lever wherewith to cut, gnaw through and demolish either its cocoon and its mortar enclosure or any other not too obstinate barrier substituted for the natural covering of the nest. Moreover — and this is an important proviso, except for which the outfit would be useless — it has, I will not say the will to use those tools, but a secret stimulus inviting it to employ them. When the hour for the emergence arrives, this stimulus is aroused and the insect sets to work to bore a passage. It little cares in this case whether the material to be pierced be the natural mortar, sorghum-pith, or paper: the lid that holds it imprisoned does not resist for long. Nor even does it care if the obstacle be increased in thickness and a paper wall be added outside the wall of clay: the two barriers, with no interval between them, form but one to the Bee, who passes through them because the act of getting out is still one act and one only. With the paper cone, whose wall is a little way off, the conditions are changed, though the total thickness of wall is really the same. Once outside its earthen abode, the insect has done all that it was destined to do in order to release itself; to move freely on the mortar dome represents to it the end of the release, the end of the act of boring. Around the nest a new barrier appears, the wall made by the paper bag; but, in order to pierce this, the insect would have to repeat the act which it has just accomplished, the act which it is not intended to perform more than once in its life; it would, in short, have to make into a double act that which by nature is a single one; and the insect cannot do this, for the sole reason that it has not the wish to. The Mason-bee perishes for lack of the smallest gleam of intelligence. And this is the singular intellect in which it is the fashion nowadays to see a germ of human reason! The fashion will pass and the facts remain, bringing us back to the good old notions of the soul and its immortal destinies.
Reaumur tells us how his friend Duhamel, having seized a Mason-bee with a forceps when she had half entered the cell, head foremost, to fill it with pollen-paste, carried her to a closet at some distance from the spot where he captured her. The Bee got away from him in this closet and flew out through the window. Duhamel made straight for the nest. The Mason arrived almost as soon as he did and renewed her work. She only seemed a little wilder, says the narrator, in conclusion.
Why were you not here with me, revered master, on the banks of the Aygues, which is a vast expanse of pebbles for three-fourths of the year and a mighty torrent when it rains? I should have shown you something infinitely better than the fugitive escaping from the forceps. You would have witnessed — and in so doing, would have shared my surprise — not the brief flight of the Mason who, carried to the nearest room, releases herself and forthwith returns to her nest in that familiar neighbourhood, but long journeys through unknown country. You would have seen the Bee whom I carried to a great distance from her home, to quite unfamiliar ground, find her way back with a geographical sense of which the Swallow, the Martin and the Carrier-pigeon would not have been ashamed; and you would have asked yourself, as I did, what incomprehensible knowledge of the local map guides that mother seeking her nest.
To come to facts: it is a matter of repeating with the Mason-bee of the Walls my former experiments with the Cerceris-wasps(5), of carrying the insect, in the dark, a long way from its nest, marking it and then leaving it to its own resources. In case any one should wish to try the experiment for himself, I make him a present of my manner of operation, which may save him time at the outset. The insect intended for a long journey must obviously be handled with certain precautions. There must be no forceps employed, no pincers, which might maim a wing, strain it and weaken the power of flight. While the Bee is in her cell, absorbed in her work, I place a small glass test-tube over it. The Mason, when she flies away, rushes into the tube, which enables me, without touching her, to transfer her at once into a screw of paper. This I quickly close. A tin box, an ordinary botanizing-case, serves to convey the prisoners, each in her separate paper bag.
The most delicate business, that of marking each captive before setting her free, is left to be done on the spot selected for the starting-point. I use finely-powdered chalk, steeped in a strong solution of gum arabic. The mixture, applied to some part of the insect with a straw, leaves a white patch, which soon dries and adheres to the fleece. When a particular Mason-bee has to be marked so as to distinguish her from another in short experiments, such as I shall describe presently, I confine myself to touching the tip of the abdomen with my straw while the insect is half in the cell, head downwards. The slight touch is not noticed by the Bee, who continues her work quite undisturbed; but the mark is not very deep and moreover it is in a rather bad place for any prolonged experiment, for the Bee is constantly brushing her belly to detach the pollen and is sure to rub it off sooner or later. I therefore make another one, dropping the sticky chalk right in the middle of the thorax, between the wings.
It is hardly possible to wear gloves at this work: the fingers need all their deftness to take up the restless Bee delicately and to overpower her without rough pressure. It is easily seen that, though the job may yield no other profit, you are at least sure of being stung. The sting can be avoided with a little dexterity, but not always. You have to put up with it. In any case, the Mason-bee's sting is far less painful than that of the Hive-bee. The white spot is dropped on the thorax; the Mason flies off; and the mark dries on the journey.
I start with two Mason-bees of the Walls working at their nests on the pebbles in the alluvia of the Aygues, not far from Serignan. I carry them home with me to Orange, where I release them after marking them. According to the ordnance-survey map, the distance is about two and a half miles as the crow flies. The captives are set at liberty in the evening, at a time when the Bees begin to leave off work for the day. It is therefore probable that my two Bees will spend their night in the neighbourhood.
Next morning, I go to the nests. The weather is still too cool and the works are suspended. When the dew has gone, the Masons begin work. I see one, but without a white spot, bringing pollen to one of the nests which had been occupied by the travellers whom I am expecting. She is a stranger who, finding the cell whose owner I myself had exiled untenanted, has installed herself there and made it her property, not knowing that it is already the property of another. She has perhaps been victualling it since yesterday evening. Close upon ten o'clock, when the heat is at its full, the mistress of the house suddenly arrives: her title-deeds as the original occupant are inscribed for me in undeniable characters on her thorax white with chalk. Here is one of my travellers back.
Over waving corn, over fields all pink with sainfoin, she has covered the two miles and a half; and here she is, back at the nest, after foraging on the way, for the doughty creature arrives with her abdomen yellow with pollen. To come home again from the verge of the horizon is wonderful in itself; to come home with a well-filled pollen-brush is superlative economy. A journey, even a forced journey, always becomes a foraging-expedition.
She finds the stranger in the nest:
‚What‘s this? I'll teach you!'
And the owner falls furiously upon the intruder, who possibly was meaning no harm. A hot chase in mid-air now takes place between the two Masons. From time to time, they hover almost without movement, face to face, with only a couple of inches separating them, and here, doubtless measuring forces with their eyes, they buzz insults at each other. Then they go back and alight on the nest in dispute, first one, then the other. I expect to see them come to blows, to make them draw their stings. But my hopes are disappointed: the duties of maternity speak in too imperious a voice for them to risk their lives and wipe out the insult in a mortal duel. The whole thing is confined to hostile demonstrations and a few insignificant cuffs.
Nevertheless, the real proprietress seems to derive double courage and double strength from the feeling that she is in her rights. She takes up a permanent position on the nest and receives the other, each time that she ventures to approach, with an angry quiver of her wings, an unmistakable sign of her righteous indignation. The stranger, at last discouraged, retires from the field. Forthwith the Mason resumes her work, as actively as though she had not just undergone the hardships of a long journey.
One more word on these quarrels about property. It is not unusual, when one Mason-bee is away on an expedition, for another, some homeless vagabond, to call at the nest, take a fancy to it and set to work on it, sometimes at the same cell, sometimes at the next, if there are several vacant, which is generally the case in the old nests. The first occupier, on her return, never fails to drive away the intruder, who always ends by being turned out, so keen and invincible is the mistress' sense of ownership. Reversing the savage Prussian maxim, ‚Might is right,‘ among the Mason-bees right is might, for there is no other explanation of the invariable retreat of the usurper, whose strength is not a whit inferior to that of the real owner. If she is less bold, this is because she has not the tremendous moral support of knowing herself in the right, which makes itself respected, among equals, even in the brute creation.
The second of my travellers does not reappear, either on the day when the first arrived or on the following days. I decide upon another experiment, on this occasion with five subjects. The starting-place is the same; and the place of arrival, the distance, the time of day, all remain unchanged. Of the five with whom I experiment, I find three at their nests next day; the two others are missing.
It is therefore fully established that the Mason-bee of the Walls, carried to a distance of two and a half miles and released at a place which she has certainly never seen before, is able to return to the nest. But why do first one out of two and then two out of five fail to join their fellows? What one can do cannot another do? Is there a difference in the faculty that guides them over unknown ground? Or is it not rather a difference in flying-power? I remember that my Bees did not all start off with the same vigour. Some were hardly out of my fingers before they darted furiously into the air, where I at once lost sight of them, whereas the others came dropping down a few yards away from me, after a short flight. The latter, it seems certain, must have suffered on the journey, perhaps from the heat concentrated in the furnace of my box. Or I may have hurt the articulation of the wings in marking them, an operation difficult to perform when you are guarding against stings. These are maimed, feeble creatures, who will linger in the sainfoin-fields close by, and not the powerful aviators required by the journey.
The experiment must be tried again, taking count only of the Bees who start off straight from between my fingers with a clean, vigorous flight. The waverers, the laggards who stop almost at once on some bush shall be left out of the reckoning. Moreover, I will do my best to estimate the time taken in returning to the nest. For an experiment of this kind, I need plenty of subjects, as the weak and the maimed, of whom there may be many, are to be disregarded. The Mason-bee of the Walls is unable to supply me with the requisite number: there are not enough of her; and I am anxious not to interfere too much with the little Aygues-side colony, for whom I have other experiments in view. Fortunately, I have at my own place, under the eaves of a shed, a magnificent nest of Chalicodoma sicula in full activity. I can draw to whatever extent I please on the populous city. The insect is small, less than half the size of C. muraria, but no matter: it will deserve all the more credit if it can traverse the two miles and a half in store for it and find its way back to the nest. I take forty Bees, isolating them, as usual, in screws of paper.
In order to reach the nest, I place a ladder against the wall: it will be used by my daughter Aglae and will enable her to mark the exact moment of the return of the first Bee. I set the clock on the mantelpiece and my watch at the same time, so that we may compare the instant of departure and of arrival. Things being thus arranged, I carry off my forty captives and go to the identical spot where C. muraria works, in the pebbly bed of the Aygues. The trip will have a double object: to observe Reaumur's Mason and to set the Sicilian Mason at liberty. The latter, therefore, will also have two and a half miles to travel home.
At last my prisoners are released, all of them being first marked with a big white dot in the middle of the thorax.
You do not come off scot-free when handling one after the other forty wrathful Bees, who promptly unsheathe and brandish their poisoned stings. The stab is but too often given before the mark is made. My smarting fingers make movements of self-defence which my will is not always able to control. I take hold with greater precaution for myself than for the insect; I sometimes squeeze harder than I ought to if I am to spare my travellers. To experiment so as to lift, if possible, a tiny corner of the veil of truth is a fine and noble thing, a mighty stimulant in the face of danger; but still one may be excused for displaying some impatience when it is a matter of receiving forty stings in one's fingers at one short sitting. If any man should reproach me for being too careless with my thumbs, I would suggest that he should have a try: he can then judge for himself the pleasures of the situation.
To cut a long story short, either through the fatigue of the journey, or through my fingers pressing too hard and perhaps injuring some articulations, only twenty out of my forty Bees start with a bold, vigorous flight. The others, unable to keep their balance, wander about on the nearest bit of grass or remain on the osier-shoots on which I have placed them, refusing to fly even when I tickle them with a straw. These weaklings, these cripples, these incapables injured by my fingers must be struck off my list. Those who started with an unhesitating flight number about twenty. That is ample.
At the actual moment of departure, there is nothing definite about the direction taken, none of that straight flight to the nest which the Cerceris-wasps once showed me in similar circumstances. As soon as they are liberated, the Mason-bees flee as though scared, some in one direction, some in exactly the opposite direction. Nevertheless, as far as their impetuous flight allows, I seem to perceive a quick return on the part of those Bees who have started flying towards a point opposite to their home; and the majority appear to me to be making for those blue distances where their nest lies. I leave this question with certain doubts which are inevitable in the case of insects which I cannot follow with my eyes for more than twenty yards.
Hitherto, the operation has been favoured by calm weather; but now things become complicated. The heat is stifling and the sky becomes stormy. A stiff breeze springs up, blowing from the south, the very direction which my Bees must take to return to the nest. Can they overcome this opposing current and cleave the aerial torrent with their wings? If they try, they will have to fly close to the ground, as I now see the Bees do who continue their foraging; but soaring to lofty regions, whence they can obtain a clear view of the country, is, so it seems to me, prohibited. I am therefore very apprehensive as to the success of my experiment when I return to Orange, after first trying to steal some fresh secret from the Aygues Mason-bee of the Pebbles.
I have scarcely reached the house before Aglae greets me, her cheeks flushed with excitement:
‚Two!‘ she cries. ‚Two came back at twenty minutes to three, with a load of pollen under their bellies!‘
A friend of mine had appeared upon the scene, a grave man of the law, who on hearing what was happening, had neglected code and stamped paper and insisted upon also being present at the arrival of my Carrier-pigeons. The result interested him more than his case about a party-wall. Under a tropical sun, in a furnace heat reflected from the wall of the shed, every five minutes he climbed the ladder bare-headed, with no other protection against sunstroke than his thatch of thick, grey locks. Instead of the one observer whom I had posted, I found two good pairs of eyes watching the Bees' return.
I had released my insects at about two o'clock; and the first arrivals returned to the nest at twenty minutes to three. They had therefore taken less than three-quarters of an hour to cover the two miles and a half, a very striking result, especially when we remember that the Bees did some foraging on the road, as was proved by the yellow pollen on their bellies, and that, on the other hand, the travellers' flight must have been hindered by the wind blowing against them. Three more came home before my eyes, each with her load of pollen, an outward and visible sign of the work done on the journey. As it was growing late, our observations had to cease. When the sun goes down, the Mason-bees leave the nest and take refuge somewhere or other, perhaps under the tiles of the roofs, or in little corners of the walls. I could not reckon on the arrival of the others before work was resumed, in the full sunshine.
Next day, when the sun recalled the scattered workers to the nest, I took a fresh census of Bees with a white spot on the thorax. My success exceeded all my hopes: I counted fifteen, fifteen of the transported prisoners of the day before, storing their cells or building as though nothing out of the way had happened. The weather had become more and more threatening; and now the storm burst and was followed by a succession of rainy days which prevented me from continuing.
The experiment suffices as it stands. Of some twenty Bees who had seemed fit to make the long journey when I released them, fifteen at least had returned: two within the first hour, three in the course of the evening and the rest next morning. They had returned in spite of having the wind against them and — a graver difficulty still — in spite of being unacquainted with the locality to which I had transported them. There is, in fact, no doubt that they were setting eyes for the first time on those osier-beds of the Aygues which I had selected as the starting-point. Never would they have travelled so far afield of their own accord, for everything that they want for building and victualling under the roof of my shed is within easy reach. The path at the foot of the wall supplies the mortar; the flowery meadows surrounding my house furnish nectar and pollen. Economical of their time as they are, they do not go flying two miles and a half in search of what abounds at a few yards from the nest. Besides, I see them daily taking their building-materials from the path and gathering their harvest on the wild-flowers, especially on the meadow sage. To all appearance, their expeditions do not cover more than a radius of a hundred yards or so. Then how did my exiles return? What guided them? It was certainly not memory, but some special faculty which we must content ourselves with recognizing by its astonishing effects without pretending to explain it, so greatly does it transcend our own psychology.
1. A Dung-beetle who rolls the manure of cattle into balls for his own consumption and that of his young. Cf. „Insect Life“, by J.H. Fabre, translated by the author of „Mademoiselle Mori“: chapters 1 and 2; and „The Life and Love of the Insect“, by J. Henri Fabre, translated by Alexander Teixeira de Mattos: chapters 1 to 4.
2. A species of Hunting Wasp. Cf. „Insect Life“: chapters 6 to 12.
3. Henri Louis Duhamel du Monceau (1700–1781), a distinguished writer on botany and agriculture.
4. .39 inch.
5. Cf. „Insect Life“: chapter 19.