Chapter IV. More Enquiries Into Mason Bees
Jean-Henri Fabre Mason-bees
Leaf-Cutter Bee (Megachile Cenuncularis)
This chapter was to have taken the form of a letter addressed to Charles Darwin, the illustrious naturalist who now lies buried beside Newton in Westminster Abbey. It was my task to report to him the result of some experiments which he had suggested to me in the course of our correspondence: a very pleasant task, for, though facts, as I see them, disincline me to accept his theories, I have none the less the deepest veneration for his noble character and his scientific honesty. I was drafting my letter when the sad news reached me: Darwin was dead; after searching the mighty question of origins, he was now grappling with the last and darkest problem of the hereafter (1). I therefore abandon the epistolary form, which would be unwarranted in view of that grave at Westminster. A free and impersonal statement shall set forth what I intended to relate in a more academic manner.
One thing, above all, had struck the English scientist on reading the first volume of my „Souvenirs entomologiques“, namely, the Mason-bees' faculty of knowing the way back to their nests after being carried to great distances from home. What sort of compass do they employ on their return journeys? What sense guides them? The profound observer thereupon spoke of an experiment which he had always longed to make with Pigeons and which he had always neglected making, absorbed as he was by other interests. This experiment, he thought, I might attempt with my Bees. Substitute the insect for the bird; and the problem remained the same. I quote from his letter the passage referring to the trial which he wished made:
‚Allow me to make a suggestion in relation to your wonderful account of insects finding their way home. I formerly wished to try it with pigeons; namely, to carry the insects in their paper cornets about a hundred paces in the opposite direction to that which you intended ultimately to carry them, but before turning round to return, to put the insects in a circular box with an axle which could be made to revolve very rapidly first in one direction and then in another, so as to destroy for a time all sense of direction in the insects. I have sometimes imagined that animals may feel in which direction they were at the first start carried.‘
This method of experimenting seemed to me very ingeniously conceived. Before going west, I walk eastwards. In the darkness of their paper bags, the mere fact that I am moving them gives my prisoners a sense of the direction in which I am taking them. If nothing happened to disturb this first impression, the insect would be guided by it in returning. This would explain the homing of my Mason-bees carried to a distance of two or three miles amid strange surroundings. But, when the insects have been sufficiently impressed by their conveyance to the east, there comes the rapid twirl, first this way round, then that. Bewildered by all these revolutions first in one direction and then in another, the insect does not know that I have turned round and remains under its original impression. I am now taking it to the west, when it believes itself to be still travelling towards the east. Under the influence of this impression; the insect is bound to lose its bearings. When set free, it will fly in the opposite direction to its home, which it will never find again.
This result seemed to me the more probable inasmuch as the statements of the country-folk around me were all of a nature to confirm my hopes. Favier (2), the very man for this sort of information, was the first to put me on the track. He told me that, when people want to move a Cat from one farm to another at some distance, they place the animal in a bag which they twirl rapidly at the moment of starting, thus preventing the animal from returning to the house which it has quitted. Many others, besides Favier, described the same practice to me. According to them, this twirling round in a bag was an infallible expedient: the bewildered Cat never returned. I communicated what I had learnt to England, I wrote to the sage of Down and told him how the peasant had anticipated the researches of science. Charles Darwin was amazed; so was I; and we both of us almost reckoned on a success.
These preliminaries took place in the winter; I had plenty of time to prepare for the experiment which was to be made in the following May.
‚Favier,‘ I said, one day, to my assistant, ‚I shall want some of those nests. Go and ask our next-door neighbour‘s leave and climb to the roof of his shed, with some new tiles and some mortar, which you can fetch from the builder's. Take a dozen tiles from the roof, those with the biggest nests on them, and put the new ones in their place.'
Things were done accordingly. My neighbour assented with a good grace to the exchange of tiles, for he himself is obliged, from time to time, to demolish the work of the Mason-bee, unless he would risk seeing his roof fall in sooner or later. I was merely forestalling a repair which became more urgent every year. That same evening, I was in possession of twelve magnificent rectangular blocks of nest, each lying on the convex surface of a tile, that is to say, on the surface looking towards the inside of the shed. I had the curiosity to weigh the largest: it turned the scale at thirty-five pounds. Now the roof whence it came was covered with similar masses, adjoining one another, over a stretch of some seventy tiles. Reckoning only half the weight, so as to strike an average between the largest and the smallest lumps, we find the total weight of the Bee's masonry to amount to three-quarters of a ton. And, even so, people tell me that they have seen this beaten elsewhere. Leave the Mason-bee to her own devices, in the spot that suits her; allow the work of many generations to accumulate; and, one fine day, the roof will break down under the extra burden. Let the nests grow old; let them fall to pieces when the damp gets into them; and you will have chunks tumbling on your head big enough to crack your skull. There you see the work of a very little-known insect. (a)
These treasures were insufficient, not in regard to quantity, but in regard to quality, for the main object which I had in view. They came from the nearest house, separated from mine by a little field planted with corn and olive-trees. I had reason to fear that the insects issuing from those nests might be hereditarily influenced by their ancestors, who had lived in the shed for many a long year. The Bee, when carried to a distance, would perhaps come back, guided by the inveterate family habit; she would find the shed of her lineal predecessors and thence, without difficulty, reach her nest. As it is the fashion nowadays to assign a prominent part to these hereditary influences, I must eliminate them from my experiments. I want strange Bees, brought from afar, whose return to the place of their birth can in no way assist their return to the nest transplanted to another site.
Favier took the business in hand. He had discovered on the banks of the Aygues, at some miles from the village, a deserted hut where the Mason-bees had established themselves in a numerous colony. He proposed to take the wheelbarrow, in which to move the blocks of cells; but I objected: the jolting of the vehicle over the rough paths might jeopardise the contents of the cells. A basket carried on the shoulder was deemed safer. Favier took a man to help him and set out. The expedition provided me with four well-stocked tiles. It was all that the two men were able to carry between them; and even then I had to stand treat on their arrival: they were utterly exhausted. Le Vaillant tells us of a nest of Republicans (3) with which he loaded a wagon drawn by two oxen. My Mason-bee vies with the South-African bird: a yoke of Oxen would not have been too many to move the whole of that nest from the banks of the Aygues.
The next thing is to place my tiles. I want to have them under my eyes, in a position where I can watch them easily and save myself the worries of earlier days: going up and down ladders, standing for hours at a stretch on a narrow rung that hurt the soles of my feet and risking sunstroke up against a scorching wall. Moreover, it is necessary that my guests should feel almost as much at home with me as where they come from. I must make life pleasant for them, if I should have them grow attached to the new dwelling. And I happen to have the very thing for them.
Under the leads of my house is a wide arch, the sides of which get the sun, while the back remains in the shade. There is something for everybody: the shade for me, the sunlight for my boarders. We fasten a stout hook to each tile and hang it on the wall, on a level with our eyes. Half my nests are on the right, half on the left. The general effect is rather original. Any one walking in and seeing my show for the first time begins by taking it for a display of smoked provisions, gammons of some outlandish bacon curing in the sun. On perceiving his mistake, he falls into raptures at these new hives of mine. The news spreads through the village and more than one pokes fun at it. They look upon me as a keeper of hybrid Bees:
‚I wonder what he‘s going to make out of that!' say they.
My hives are in full swing before the end of April. When the work is at its height, the swarm becomes a little eddying, buzzing cloud. The arch is a much-frequented passage: it leads to a store-room for various household provisions. The members of my family bully me at first for establishing this dangerous commonwealth within the precincts of our home. They dare not go to fetch things: they would have to pass through a swarm of Bees; and then…look out for stings! There is nothing for it but to prove, once and for all, that the danger does not exist, that mine is a most peaceable Bee, incapable of stinging so long as she is not startled. I bring my face close to one of the clay nests, so as almost to touch it, while it is black with Masons at work; I let my fingers wander through the ranks, I put a few Bees on my hand, I stand in the thick of the whirling crowd and never a prick do I receive. I have long known their peaceful character. Time was when I used to share the common fears, when I hesitated before venturing into a swarm of Anthophorae or Chalicodomae; nowadays, I have quite got over those terrors. If you do not tease the insect, the thought of hurting you will never occur to it. At the worst, a single specimen, prompted by curiosity rather than anger, will come and hover in front of your face, examining you with some persistency, but employing a buzz as her only threat. Let her be: her scrutiny is quite friendly.
After a few demonstrations, my household were reassured: all, old and young, moved in and out of the arch as though there were nothing unusual about it. My Bees, far from remaining an object of dread, became an object of diversion; every one took pleasure in watching the progress of their ingenious work. I was careful not to divulge the secret to strangers. If any one, coming on business, passed outside the arch while I was standing before the hanging nests, some such brief dialogue as the following would take place:
‚So they know you; that‘s why they don't sting you?'
‚They certainly know me.‘
‚Oh, you; that‘s another matter!'
Whereupon the intruder would keep at a respectful distance, which was what I wanted.
It is time that we thought of experimenting. The Mason-bees intended for the journey must be marked with a sign whereby I may know them. A solution of gum arabic, thickened with a colouring-powder, red, blue or some other shade, is the material which I use to mark my travellers. The variety in hue will save me from confusing the subjects of my different experiments.
When making my former investigations, I used to mark the Bees at the place where I set them free. For this operation, the insects had to be held in the fingers one after the other; and I was thus exposed to frequent stings, which smarted all the more for being constantly repeated. The consequence was that I was not always quite able to control my fingers and thumbs, to the great detriment of my travellers; for I could easily warp their wing-joints and thus weaken their flight. It was worth while improving the method of operation, both in my own interest and in that of the insect. I must mark the Bee, carry her to a distance and release her, without taking her in my fingers, without once touching her. The experiment was bound to gain by these nice precautions. I will describe the method which I adopted.
The Bee is so much engrossed in her work when she buries her abdomen in the cell and rids herself of her load of pollen, or when she is building, that it is easy, at such times, without alarming her, to mark the upper side of the thorax with a straw dipped in the coloured glue. The insect is not disturbed by that slight touch. It flies off; it returns laden with mortar or pollen. You allow these trips to be repeated until the mark on the thorax is quite dry, which soon happens in the hot sun necessary to the Bee's labours. The next thing is to catch her and imprison her in a paper bag, still without touching her. Nothing could be easier. You place a small test-tube over the Bee engrossed in her work; the insect, on leaving, rushes into it and is thence transferred to the paper bag, which is forthwith closed and placed in the tin box that will serve as a conveyance for the whole party. When releasing the Bees, all you have to do is open the bags. The whole performance is thus effected without once giving that distressing squeeze of the fingers.
Another question remains to be solved before we go further. What time-limit shall I allow for this census of the Bees that return to the nest? Let me explain what I mean. The dot which I have made in the middle of the thorax with a touch of my sticky straw is not very permanent: it merely adheres to the hairs. At the same time, it would have been no more lasting if I had held the insect in my fingers. Now the Bee often brushes her back: she dusts it each time she leaves the galleries; besides, she is always rubbing her coat against the walls of the cell, which she has to enter and to leave each time that she brings honey. A Mason-bee, so smartly dressed at the start, at the end of her work is in rags; her fur is all worn bare and as tattered as a mechanic's overall.
Furthermore, in bad weather, the Mason-bee of the Walls spends the days and nights in one of the cells of her dome, suspended head downwards. The Mason-bee of the Sheds, as long as there are vacant galleries, does very nearly the same: she takes shelter in the galleries, but with her head at the entrance. Once those old habitations are in use, however, and the building of new cells begun, she selects another retreat. In the harmas(4), as I have said elsewhere, are stone heaps, intended for building the surrounding wall. This is where my Chalicodomae pass the night. Piled up promiscuously, both sexes together, they sleep in numerous companies, in crevices between two stones laid closely one on top of the other. Some of these companies number as many as a couple of hundred. The most common dormitory is a narrow groove. Here they all huddle, as far forward as possible, with their backs in the groove. I see some lying flat on their backs, like people asleep. Should bad weather come on, should the sky cloud over, should the north-wind whistle, they do not stir out.
With all these things to take into consideration, I cannot expect my dot on the Bee's thorax to last any length of time. By day, the constant brushing and the rubbing against the partitions of the galleries soon wipe it off; at night, things are worse still, in the narrow sleeping-room where the Mason-bees take refuge by the hundred. After a night spent in the crevice between two stones, it is not advisable to trust to the mark made yesterday. Therefore, the counting of the number of Bees that return to the nest must be taken in hand at once; tomorrow would be too late. And so, as it would be impossible for me to recognize those of my subjects whose dots had disappeared during the night, I will take into account only the Bees that return on the same day.
The question of the rotary machine remains. Darwin advised me to use a circular box with an axle and a handle. I have nothing of the kind in the house. It will be simpler and quite as effective to employ the method of the countryman who tries to lose his Cat by swinging him in a bag. My insects, each one placed by itself in a paper cornet (5) or screw, shall be placed in a tin box; the screws of paper shall be wedged in so as to avoid collisions during the rotation; lastly, the box shall be tied to a cord and I will whirl the whole thing round like a sling. With this contrivance, it will be quite easy to obtain any rate of speed that I wish, any variety of inverse movements that I consider likely to make my captives lose their bearings. I can whirl my sling first in one direction and then in another, turn and turn about; I can slacken or increase the pace; if I like, I can make it describe figures of eight, combined with circles; if I spin on my heels at the same time, I am able to make the process still more complicated by compelling my sling to trace every known curve. That is what I shall do.
On the 2nd of May 1880, I make a white mark on the thorax of ten Mason-bees busied with various tasks: some are exploring the slabs of clay in order to select a site; others are brick-laying; others are garnering stores. When the mark is dry, I catch them and pack them as I have described. I first carry them a quarter of a mile in the opposite direction to the one which I intend to take. A path skirting my house favours this preliminary manoeuvre; I have every hope of being alone when the time comes to make play with my sling. There is a way-side cross at the end; I stop at the foot of the cross. Here I swing my Bees in every direction. Now, while I am making the box describe inverse circles and loops, while I am pirouetting on my heels to achieve the various curves, up comes a woman from the village and stares at me. Oh, how she stares at me, what a look she gives me! At the foot of the cross! Acting in such a silly way! People talked about it. It was sheer witchcraft. Had I not dug up a dead body, only a few days before? Yes, I had been to a prehistoric burial-place, I had taken from it a pair of venerable, well-developed tibias, a set of funerary vessels and a few shoulders of horse, placed there as a viaticum for the great journey. I had done this thing; and people knew it. And now, to crown all, the man of evil reputation is found at the foot of a cross indulging in unhallowed antics.
No matter — and it shows no small courage on my part — the gyrations are duly accomplished in the presence of this unexpected witness. Then I retrace my steps and walk westward of Serignan. I take the least-frequented paths, I cut across country so as, if possible, to avoid a second meeting. It would be the last straw if I were seen opening my paper bags and letting loose my insects! When half-way, to make my experiment more decisive still, I repeat the rotation, in as complicated a fashion as before. I repeat it for the third time at the spot chosen for the release.
I am at the end of a flint-strewn plain, with here and there a scanty curtain of almond-trees and holm-oaks. Walking at a good pace, I have taken thirty minutes to cover the ground in a straight line. The distance therefore is, roughly, two miles. It is a fine day, under a clear sky, with a very light breeze blowing from the north. I sit down on the ground, facing the south, so that the insects may be free to take either the direction of their nest or the opposite one. I let them loose at a quarter past two. When the bags are opened, the Bees, for the most part, circle several times around me and then dart off impetuously in the direction of Serignan, as far as I can judge. It is not easy to watch them, because they fly off suddenly, after going two or three times round my body, a suspicious-looking object which they wish, apparently, to reconnoitre before starting. A quarter of an hour later, my eldest daughter, Antonia, who is on the look-out beside the nests, sees the first traveller arrive. On my return, in the course of the evening, two others come back. Total: three home on the same day, out of ten scattered abroad.
I resume the experiment next morning. I mark ten Mason-bees with red, which will enable me to distinguish them from those who returned on the day before and from those who may still return with the white spot uneffaced. The same precautions, the same rotations, the same localities as on the first occasion; only, I make no rotation on the way, confining myself to swinging my box round on leaving and on arriving. The insects are released at a quarter past eleven. I preferred the forenoon, as this was the busiest time at the works. One Bee was seen by Antonia to be back at the nest by twenty minutes past eleven. Supposing her to be the first let loose, it took her just five minutes to cover the distance. But there is nothing to tell me that it is not another, in which case she needed less. It is the fastest speed that I have succeeded in noting. I myself am back at twelve and, within a short time, catch three others. I see no more during the rest of the evening. Total: four home, out of ten.
The 4th of May is a very bright, calm, warm day, weather highly propitious for my experiments. I take fifty Chalicodomae marked with blue. The distance to be travelled remains the same. I make the first rotation after carrying my insects a few hundred steps in the direction opposite to that which I finally take; in addition, three rotations on the road; a fifth rotation at the place where they are set free. If they do not lose their bearings this time, it will not be for lack of twisting and turning. I begin to open my screws of paper at twenty minutes past nine. It is rather early, for which reason my Bees, on recovering their liberty, remain for a moment undecided and lazy; but, after a short sunbath on a stone where I place them, they take wing. I am sitting on the ground, facing the south, with Serignan on my left and Piolenc on my right. When the flight is not too swift to allow me to perceive the direction taken, I see my released captives disappear to my left. A few, but only a few, go south; two or three go west, or to right of me. I do not speak of the north, against which I act as a screen. All told, the great majority take the left, that is to say, the direction of the nest. The last is released at twenty minutes to ten. One of the fifty travellers has lost her mark in the paper bag. I deduct her from the total, leaving forty-nine.
According to Antonia, who watches the home-coming, the earliest arrivals appeared at twenty-five minutes to ten, say fifteen minutes after the first was set free. By twelve o'clock mid-day, there are eleven back; and, by four o'clock in the evening, seventeen. That ends the census. Total: seventeen, out of forty-nine.
I resolved upon a fourth experiment, on the 14th of May. The weather is glorious, with a light northerly breeze. I take twenty Mason-bees, marked in pink, at eight o'clock in the morning. Rotations at the start, after a preliminary backing in a direction opposite to that which I intend to take; two rotations on the road; a fourth on arriving. All those whose flight I am able to follow with my eyes turn to my left, that is to say, towards Serignan. Yet I had taken care to leave the choice free between the two opposite directions: in particular, I had sent away my Dog, who was on my right. To-day, the Bees do not circle round me: some fly away at once; the others, the greater number, feeling giddy perhaps after the pitching of the journey and the rolling of the sling, alight on the ground a few yards away, seem to wait until they are somewhat recovered and then fly off to the left. I perceived this to be the general flight, whenever I was able to observe at all. I was back at a quarter to ten. Two Bees with pink marks were there before me, of whom one was engaged in building, with her pellet of mortar in her mandibles. By one o'clock in the afternoon there were seven arrivals; I saw no more during the rest of the day. Total: seven out of twenty.
Let us be satisfied with this: the experiment has been repeated often enough, but it does not conclude as Darwin hoped, as I myself hoped, especially after what I had been told about the Cat. In vain, adopting the advice given, do I carry my insects first in the opposite direction to the place at which I intend to release them; in vain, when about to retrace my steps, do I twirl my sling with every complication in the way of whirls and twists that I am able to imagine; in vain, thinking to increase the difficulties, do I repeat the rotation as often as five times over: at the start, on the road, on arriving; it makes no difference: the Mason-bees return; and the proportion of returns on the same day fluctuates between thirty and forty per cent. It goes to my heart to abandon an idea suggested by so famous a man of science and cherished all the more readily inasmuch as I thought it likely to provide a final solution. The facts are there, more eloquent than any number of ingenious views; and the problem remains as mysterious as ever.
In the following year, 1881, I began experimenting again, but in a different way. Hitherto, I had worked on the level. To return to the nest, my lost Bees had only to cross slight obstacles, the hedges and spinneys of the tilled fields. To-day, I propose to add to the difficulties of distance those of the ground to be traversed. Discontinuing all my backing- and whirling-tactics, things which I recognize as useless, I think of releasing my Chalicodomae in the thick of the Serignan Woods. How will they escape from that labyrinth, where, in the early days, I needed a compass to find my way? Moreover, I shall have an assistant with me, a pair of eyes younger than mine and better-fitted to follow my insects' first flight. That immediate start in the direction of the nest has already been repeated very often and is beginning to interest me more than the return itself. A pharmaceutical student, spending a few days with my parents, shall be my eyewitness. With him, I shall feel at ease; science and he are no strangers.
The trip to the woods takes place on the 16th of May. The weather is hot and hints at a coming storm. There is a perceptible breeze from the south, but not enough to upset my travellers. Forty Mason-bees are caught. To shorten the preparations, because of the distance, I do not mark them while they are on the nests; I shall mark them at the starting-point, as I release them. It is the old method, prolific of stings; but I prefer it to-day, in order to save time. It takes me an hour to reach the place. The distance, therefore, allowing for windings, is about three miles.
The site selected must permit me to recognize the direction of the insects' first flight. I choose a clearing in the middle of the copses. All around is a great expanse of dense woods, shutting out the horizon on every side; on the south, in the direction of the nests, a curtain of hills rises to a height of some three hundred feet above the spot at which I stand. The wind is not strong, but it is blowing in the opposite direction to that which my insects will have to take in order to reach their home. I turn my back on Serignan, so that, when leaving my fingers, the Bees, to return to the nest, will be obliged to fly sideways, to right and left of me; I mark the insects and release them one by one. I begin operations at twenty minutes past ten.
One half of the Bees seem rather indolent, flutter about for a while, drop to the ground, appear to recover their spirits and then start off. The other half show greater decision. Although the insects have to fight against the soft wind that is blowing from the south, they make straight for the nest. All go south, after describing a few circles, a few loops, around us. There is no exception in the case of any of those whose departure we are able to follow. The fact is noted by myself and my colleague beyond dispute or doubt. My Mason-bees head for the south as though some compass told them which way the wind was blowing.
I am back at twelve o'clock. None of the strays is at the nest; but, a few minutes later, I catch two. At two o'clock, the number has increased to nine. But now the sky clouds over, the wind freshens and the storm is approaching. We can no longer rely on any further arrivals. Total: nine out of forty, or twenty-two per cent.
The proportion is smaller than in the former cases, when it varied between thirty and forty per cent. Must we attribute this result to the difficulties to be overcome? Can the Mason-bees have lost their way in the maze of the forest? It is safer not to give an opinion: other causes intervened which may have decreased the number of those who returned. I marked the insects at the starting-place; I handled them; and I am not prepared to say that they were all in the best of condition on leaving my stung and smarting fingers. Besides, the sky has become overcast, a storm is imminent. In the month of May, so variable, so fickle, in my part of the world, we can hardly ever count on a whole day of fine weather. A splendid morning is swiftly followed by a fitful afternoon; and my experiments with Mason-bees have often suffered by these variations. All things considered, I am inclined to think that the homeward journey across the forest and the mountain is effected just as readily as across the corn-fields and the plain.
I have one last resource left whereby to try and put my Bees out of their latitude. I will first take them to a great distance; then, describing a wide curve, I will return by another road and release my captives when I am near enough to the village, say, about two miles. A conveyance is necessary, this time. My collaborator of the day in the woods offers me the use of his gig. The two of us set off, with fifteen Mason-bees, along the road to Orange, until we come to the viaduct. Here, on the right, is the straight ribbon of the old Roman road, the Via Domitia. We take it, driving north towards the Uchaux Mountains, the classic home of superb Turonian fossils. We next turn back towards Serignan, by the Piolenc Road. A halt is made by the stretch of country known as Font-Claire, the distance from which to the village is about one mile and five furlongs. The reader can easily follow my route on the ordnance-survey map; and he will see that the loop described measures not far short of five miles and a half.
At the same time, Favier came and joined me at Font-Claire, by the direct road, the one that runs through Piolenc. He brought with him fifteen Mason-bees, intended for purposes of comparison with mine. I am therefore in possession of two sets of insects. Fifteen, marked in pink, have taken the five-mile bend; fifteen, marked in blue, have come by the straight road, the shortest road for returning to the nest. The weather is warm, exceedingly bright and very calm; I could not hope for a better day for my experiment. The insects are given their freedom at mid-day.
At five o'clock, the arrivals number seven of the pink Mason-bees, whom I thought that I had bewildered by a long and circuitous drive, and six of the blue Mason-bees, who came to Font-Claire by the direct route. The two proportions, forty-six and forty per cent., are almost equal; and the slight excess in favour of the insects that went the roundabout way is evidently an accidental result which we need not take into consideration. The bend described cannot have helped them to find their way home; but it has also certainly not hampered them.
There is no need of further proof. The intricate movements of a rotation such as I have described; the obstacle of hills and woods; the pitfalls of a road which moves on, moves back and returns after making a wide circuit: none of these is able to disconcert the Chalicodomae or prevent them from going back to the nest.
I had written to Charles Darwin telling him of my first, negative results, those obtained by swinging the Bees in a box. He expected a success and was much surprised at the failure. Had he had time to experiment with his Pigeons, they would have behaved just like my Bees; the preliminary twirling would not have affected them. The problem called for another method; and what he proposed was this:
‚To place the insect within an induction coil, so as to disturb any magnetic or diamagnetic sensibility which it seems just possible that they may possess.‘
To treat an insect as you would a magnetic needle and to subject it to the current from an induction coil in order to disturb its magnetism or diamagnetism appeared to me, I must confess, a curious notion, worthy of an imagination in the last ditch. I have but little confidence in our physics, when they pretend to explain life; nevertheless, my respect for the great man would have made me resort to the induction-coils, if I had possessed the necessary apparatus. But my village boasts no scientific resources: if I want an electric spark, I am reduced to rubbing a sheet of paper on my knees. My physics cupboard contains a magnet; and that is about all. When this penury was realised, another method was suggested, simpler than the first and more certain in its results, as Darwin himself considered:
‚To make a very thin needle into a magnet; then breaking it into very short pieces, which would still be magnetic, and fastening one of these pieces with some cement on the thorax of the insects to be experimented on. I believe that such a little magnet, from its close proximity to the nervous system of the insect, would affect it more than would the terrestrial currents.‘
There is still the same idea of turning the insect into a sort of bar magnet. The terrestrial currents guide it when returning to the nest. It becomes a living compass which, withdrawn from the action of the earth by the proximity of a loadstone, loses its sense of direction. With a tiny magnet fastened on its thorax, parallel with the nervous system and more powerful than the terrestrial magnetism by reason of its comparative nearness, the insect will lose its bearings. Naturally, in setting down these lines, I take shelter behind the mighty reputation of the learned begetter of the idea. It would not be accepted as serious coming from a humble person like myself. Obscurity cannot afford these audacious theories.
The experiment seems easy; it is not beyond the means at my disposal. Let us attempt it. I magnetise a very fine needle by rubbing it with my bar magnet; I retain only the slenderest part, the point, some five or six millim?tres long. (6) This broken piece is a perfect magnet: it attracts and repels another magnetised needle hanging from a thread. I am a little puzzled as to the best way to fasten it on the insect's thorax. My assistant of the moment, the pharmaceutical student, requisitions all the adhesives in his laboratory. The best is a sort of cerecloth which he prepares specially with a very fine material. It possesses the advantage that it can be softened at the bowl of one's pipe when the time comes to operate out of doors.
I cut out of this cerecloth a small square the size of the Bee's thorax; and I insert the magnetised point through a few threads of the material. All that we now have to do is to soften the gum a little and then dab the thing at once on the Mason-bee's back, so that the broken needle runs parallel with the spine. Other engines of the same kind are prepared and due note taken of their poles, so as to enable me to point the south pole at the insect's head in some cases and at the opposite end in others.
My assistant and I begin by rehearsing the performance; we must have a little practice before trying the experiment away from home. Besides, I want to see how the insect will behave in its magnetic harness. I take a Mason-bee at work in her cell, which I mark. I carry her to my study, at the other end of the house. The magnetised outfit is fastened on the thorax; and the insect is let go. The moment she is free, the Bee drops to the ground and rolls about, like a mad thing, on the floor of the room. She resumes her flight, flops down again, turns over on her side, on her back, knocks against the things in her way, buzzes noisily, flings herself about desperately and ends by darting through the open window in headlong flight.
What does it all mean? The magnet appears to have a curious effect on my patient's system! What a fuss she makes! How terrified she is! The Bee seemed utterly distraught at losing her bearings under the influence of my knavish tricks. Let us go to the nests and see what happens. We have not long to wait: my insect returns, but rid of its magnetic tackle. I recognize it by the traces of gum that still cling to the hair of the thorax. It goes back to its cell and resumes its labours.
Always on my guard when searching the unknown, unwilling to draw conclusions before weighing the arguments for and against, I feel doubt creeping in upon me with regard to what I have seen. Was it really the magnetic influence that disturbed my Bee so strangely? When she struggled and kicked on the floor, fighting wildly with both legs and wings, when she fled in terror, was she under the sway of the magnet fastened on her back? Can my appliance have thwarted the guiding influence of the terrestrial currents on her nervous system? Or was her distress merely the result of an unwonted harness? This is what remains to be seen and that without delay.
Chalicodoma Sculpturalis Smith (Megachilidae)
I construct a new apparatus, but provide it with a short straw in place of the magnet. The insect carrying it on its back rolls on the ground, kicks and flings herself about like the first, until the irksome contrivance is removed, taking with it a part of the fur on the thorax. The straw produces the same effects as the magnet, in other words, magnetism had nothing to do with what happened. My invention, in both cases alike, is a cumbrous tackle of which the Bee tries to rid herself at once by every possible means. To look to her for normal actions so long as she carries an apparatus, magnetized or not, upon her back is the same as expecting to study the natural habits of a Dog after tying a kettle to his tail.
The experiment with the magnet is impracticable. What would it tell us if the insect consented to it? In my opinion, it would tell us nothing. In the matter of the homing instinct, a magnet would have no more influence than a bit of straw.
1. The insect is so little known that I made a serious mistake when treating of it in the first volume of these „Souvenirs.“ Under my erroneous denomination of Chalicodoma sicula are really comprised two species, one building its nests in our dwellings and particularly under the tiles of outhouses, the other building its nests on the branches of shrubs. The first species has received various names, which are, in order of priority: Chalicodoma pyrenaica, LEP. (Megachile); Chalicodoma pyrrhopeza, GERSTACKER; Chalicodoma rufitarsis, GIRAUD. It is a pity that the name occupying the first place should lend itself to misconception. I hesitate to apply the epithet of Pyrenean to an insect which is much less common in the Pyrenees than in my own district. I shall call it the Chalicodoma, or Mason-bee, of the Sheds. There is no objection to the use of this name in a book where the reader prefers lucidity to the tyranny of systematic entomology. The second species, that which builds its nests on the branches, is Chalicodoma rufescens, J. PEREZ. For a like reason, I shall call it the Chalicodoma of the Shrubs. I owe these corrections to the kindness of Professor Jean Perez, of Bordeaux, who is so well-versed in the lore of Wasps and Bees.
1. Darwin died at Down, in Kent, on the 19th of April 1882.
2. The author's gardener and factotum. Cf. „The Life of the Fly“: chapter 4.
3. Social Weaver-birds.
4. The piece of enclosed waste ground on which the author studies his insects in their natural state. Cf. „The Life of the Fly“: chapter 1.
5. A cornet is simply the old ‚sugar-bag,‘ the funnel-shaped paper bag so common on the continent and still used occasionally by small grocers and tobacconists in England.
6. .2 to .23 inch.