February has its sunny days, heralding spring, to which rude winter will reluctantly yield place. In snug corners, among the rocks, the great spurge of our district, the characias of the Greeks, the jusclo of the Provencals, begins to lift its drooping inflorescence and discreetly opens a few sombre flowers. Here the first Midges of the year will come to slake their thirst. By the time that the tip of the stalks reaches the perpendicular, the worst of the cold weather will be over.
Another eager one, the almond-tree, risking the loss of its fruit, hastens to echo these preludes to the festival of the sun, preludes which are too often treacherous. A few days of soft skies and it becomes a glorious dome of white flowers, each twinkling with a roseate eye. The country, which still lacks green, seems dotted everywhere with white-satin pavilions. 'Twould be a callous heart indeed that could resist the magic of this awakening.
The insect nation is represented at these rites by a few of its more zealous members. There is first of all the Honey-bee, the sworn enemy of strikes, who profits by the least lull of winter to find out if some rosemary is not beginning to open somewhere near the hive. The droning of the busy swarm fills the flowery vault, while a snow of petals falls softly to the foot of the tree.
Together with the population of harvesters there mingles another, less numerous, of mere drinkers, whose nesting-time has not yet begun. This is the colony of the Osmiae, with their copper-coloured skin and bright-red fleece. Two species have come hurrying up to take part in the joys of the almond-tree: first, the Horned Osmia, clad in black velvet on the head and breast and in red velvet on the abdomen; and, a little later, the Three-horned Osmia, whose livery must be red and red only. These are the first delegates despatched by the pollen-gleaners to scertain the state of the season and attend the festival of the early blooms. 'Tis but a moment since they burst their cocoon, the winter abode: they have left their retreats in the crevices of the old walls; should the north wind blow and set the almond-tree shivering, they will hasten to return to them. Hail to you, O my dear Osmiae, who yearly, from the far end of the harmas (1), opposite snow-capped Ventoux (2), bring me the first tidings of the awakening of the insect world! I am one of your friends; let us talk about you a little.
Most of the Osmiae of my region have none of the industry of their kinswomen of the brambles, that is to say, they do not themselves prepare the dwelling destined for the laying. They want ready-made lodgings, such as the old cells and old galleries of Anthophorae and Chalicodomae. If these favourite haunts are lacking, then a hiding-place in the wall, a round hole in some bit of wood, the tube of a reed, the spiral of a dead Snail under a heap of stones are adopted, according to the tastes of the several species. The retreat selected is divided into chambers by partition-walls, after which the entrance to the dwelling receives a massive seal. That is the sum-total of the building done.
For this plasterer's rather than mason's work, the Horned and the Three-horned Osmia employ soft earth. This material is different from the Mason-bee's cement, which will withstand wind and weather for many years on an exposed pebble; it is a sort of dried mud, which turns to pap on the addition of a drop of water. The Mason-bee gathers her cementing-dust in the most frequented and driest portions of the road; she wets it with a saliva which, in drying, gives it the consistency of stone. The two Osmiae who are the almond-tree's early visitors are no chemists: they know nothing of the making and mixing of hydraulic mortar; they limit themselves to gathering natural soaked earth, mud in short, which they allow to dry without any special preparation on their part; and so they need deep and well-sheltered retreats, into which the rain cannot penetrate, or the work would fall to pieces.
While exploiting, in friendly rivalry with the Three-horned Osmia, the galleries which the Mason-bee of the Sheds good-naturedly surrenders to both, Latreille's Osmia uses different materials for her partitions and her doors. She chews the leaves of some mucilaginous plant, some mallow perhaps, and then prepares a sort of green putty with which she builds her partitions and finally closes the entrance to the dwelling. When she settles in the spacious cells of the Masked Anthophora (Anthophora personata, ILLIG.), the entrance to the gallery, which is wide enough to admit one's finger, is closed with a voluminous plug of this vegetable paste. On the earthy banks, hardened by the sun, the home is then betrayed by the gaudy colour of the lid. It is as though the authorities had closed the door and affixed to it their great seals of green wax.
So far then as their building-materials are concerned, the Osmiae whom I have been able to observe are divided into two classes: one building compartments with mud, the other with a green-tinted vegetable putty. The first section includes the Horned Osmia and the Three-horned Osmia, both so remarkable for the horny tubercles on their faces.
The great reed of the south, the Arundo donax, is often used, in the country, for rough garden-shelters against the mistral or just for fences. These reeds, the ends of which are chopped off to make them all the same length, are planted perpendicularly in the earth. I have often explored them in the hope of finding Osmia-nests. My search has very seldom succeeded. The failure is easily explained. The partitions and the closing-plug of the Horned and of the Three-horned Osmia are made, as we have seen, of a sort of mud which water instantly reduces to pap. With the upright position of the reeds, the stopper of the opening would receive the rain and would become diluted; the ceilings of the storeys would fall in and the family would perish by drowning. Therefore the Osmia, who knew of these drawbacks before I did, refuses the reeds when they are placed perpendicularly.
The same reed is used for a second purpose. We make canisses of it, that is to say, hurdles, which, in spring, serve for the rearing of silk-worms and, in autumn, for the drying of figs. At the end of April and during May, which is the time when the Osmiae work, the canisses are indoors, in the silk-worm nurseries, where the Bee cannot take possession of them; in autumn, they are outside, exposing their layers of figs and peeled peaches to the sun; but by that time the Osmiae have long disappeared. If, however, during the spring, an old, disused hurdle is left out of doors, in a horizontal position, the Three-horned Osmia often takes possession of it and makes use of the two ends, where the reeds lie truncated and open.
There are other quarters that suit the Three-horned Osmia, who is not particular, it seems to me, and will make shift with any hiding-place, so long as it has the requisite conditions of diameter, solidity, sanitation and kindly darkness. The most original dwellings that I know her to occupy are disused Snail-shells, especially the house of the Common Snail (Helix aspersa). Let us go to the slope of the hills thick with olive-trees and inspect the little supporting-walls which are uilt of dry stones and face the south. In the crevices of this insecure masonry, we shall reap a harvest of old Snail-shells, plugged with earth right up to the orifice. The family of the Three-horned Osmia is settled in the spiral of those shells, which is subdivided into chambers by mud partitions.
Let us inspect the stone-heaps, especially those which come from the quarry-works. Here we often find the Field-mouse sitting on a grass mattress, nibbling acorns, almonds, olive-stones and apricot-stones. The Rodent varies his diet: to oily and farinaceous foods he adds the Snail. When he is gone, he has left behind him, under the overhanging stones, mixed up with the remains of other victuals, an assortment of empty shells, sometimes plentiful enough to remind me of the heap of Snails which, cooked with spinach and eaten country-fashion on Christmas Eve, are flung away next day by the housewife. This gives the Three-horned Osmia a handsome collection of tenements; and she does not fail to profit by them. Then again, even if the Field-mouse's conchological museum be lacking, the same broken stones serve as a refuge for Garden-snails who come to live there and end by dying there. When we see Three-horned Osmiae enter the crevices of old walls and of stone-heaps, there is no doubt about their occupation: they are getting free lodgings out of the old Snail-shells of those labyrinths.
The Horned Osmia, who is less common, might easily also be less ingenious, that is to say, less rich in varieties of houses. She seems to scorn empty shells. The only homes that I know her to inhabit are the reeds of the hurdles and the deserted cells of the Masked Anthophora.
All the other Osmiae whose method of nest-building I know work with green putty, a paste made of some crushed leaf or other; and none of them, except Latreille's Osmia, is provided with the horned or tubercled armour of the mud-kneaders. I should like to know what plants are used in making the putty; probably each species has its own preferences and its little professional secrets; but hitherto observation has taught me nothing concerning these details. Whatever worker prepare it, the putty is very much the same in appearance. When fresh, it is always a clear dark green. Later, especially in the parts exposed to the air, it changes, no doubt through fermentation, to the colour of dead leaves, to brown, to dull-yellow; and the leafy character of its origin is no longer apparent. But uniformity in the materials employed must not lead us to believe in uniformity in the lodging; on the contrary, this lodging varies greatly with the different species, though there is a marked predilection in favour of empty shells. Thus Latreille's Osmia, together with the Three-horned Osmia, uses the spacious structures of the Mason-bee of the Sheds; she likes the magnificent cells of the Masked Anthophora; and she is always ready to establish herself in the cylinder of any reed lying flat on the ground.
I have already spoken of an Osmia (O. cyanoxantha, PEREZ) who elects to make her home in the old nests of the Mason-bee of the Pebbles (3). Her closing-plug is made of a stout concrete, consisting of fair-sized bits of gravel sunk in the green paste; but for the inner partitions she employs only unalloyed putty. As the outer door, situated on the curve of an unprotected dome, is exposed to the inclemencies of the weather, the mother has to think of fortifying it. Danger, no doubt, is the originator of that gritty concrete.
The Golden Osmia (O. aurulenta, LATR.) absolutely insists on an empty Snail-shell as her residence. The Brown or Girdled Snail, the Garden Snail and especially the Common Snail, who has a more spacious spiral, all scattered at random in the grass, at the foot of the walls and of the sun-swept rocks, furnish her with her usual dwelling-house. Her dried putty is a kind of felt full of short white hairs. It must come from some hairy-leaved plant, one of the Boragineae perhaps, rich both in mucilage and the necessary bristles.
The Red Osmia (O. rufo-hirta, LATR.) has a weakness for the Brown Snail and the Garden Snail, in whose shells I find her taking refuge in April when the north-wind blows. I am not yet much acquainted with her work, which should resemble that of the Golden Osmia.
The Green Osmia (O. viridana, MORAWITZ) takes up her quarters, tiny creature that she is, in the spiral staircase of Bulimulus radiatus. It is a very elegant, but very small lodging, to say nothing of the fact that a considerable portion is taken up with the green-putty plug. There is just room for two.
The Andrenoid Osmia (O. andrenoides, LATR.), who looks so curious, with her naked red abdomen, appears to build her nest in the shell of the Common Snail, where I discover her refuged.
The Variegated Osmia (O. versicolor, LATR.) settles in the Garden Snail's shell, almost right at the bottom of the spiral.
The Blue Osmia (O. cyanea, KIRB.) seems to me to accept many different quarters. I have extracted her from old nests of the Mason-bee of the ebbles, from the galleries dug in a roadside bank by the Colletes (4) and lastly from the cavities made by some digger or other in the decayed trunk of a willow-tree.
Morawitz' Osmia (O. Morawitzi, PEREZ) is not uncommon in the old nests of the Mason-bee of the Pebbles, but I suspect her of favouring other lodgings besides.
The Three-pronged Osmia (O. tridentata, DUF. and PER.) creates a home of her own, digging herself a channel with her mandibles in dry bramble and sometimes in danewort. It mixes a few scrapings of perforated pith with the green paste. Its habits are shared by the Ragged Osmia (O. detrita, PEREZ) and by the Tiny Osmia (O. parvula, DUF.)
The Chalicodoma works in broad daylight, on a tile, on a pebble, on a branch in the hedge; none of her trade-practises is kept a secret from the observer's curiosity. The Osmia loves mystery. She wants a dark retreat, hidden from the eye. I would like, nevertheless, to watch her in the privacy of her home and to witness her work with the same facility as if she were nest-building in the open air. Perhaps there are some interesting characteristics to be picked up in the depths of her retreats. It remains to be seen whether my wish can be realized.
When studying the insect's mental capacity, especially its very retentive memory for places, I was led to ask myself whether it would not be possible to make a suitably-chosen Bee build in any place that I wished, even in my study. And I wanted, for an experiment of this sort, not an individual but a numerous colony. My preference leant towards the Three-horned Osmia, who is very plentiful in my neighbourhood, where, together with Latreille's Osmia, she frequents in particular the monstrous nests of the Chalicodoma of the Sheds. I therefore thought out a scheme for making the Three-horned Osmia accept my study as her settlement and build her nests in glass tubes, through which I could easily watch the progress. To these crystal galleries, which might well inspire a certain distrust, were to be added more natural retreats: reeds of every length and thickness and disused Chalicodoma-cells taken from among the biggest and the smallest. A scheme like this sounds mad. I admit it, while mentioning that perhaps none ever succeeded so well with me. We shall see as much presently.
My method is extremely simple. All I ask is that the birth of my insects, that is to say, their first seeing the light, their emerging from the cocoon, should take place on the spot where I propose to make them settle. Here there must be retreats of no matter what nature, but of a shape similar to that in which the Osmia delights. The first impressions of sight, which are the most long-lived of any, shall bring back my insects to the place of their birth. And not only will the Osmiae return, through the always open windows, but they will always nidify on the natal spot if they find something like the necessary conditions.
And so, all through the winter, I collect Osmia-cocoons, picked up in the nests of the Mason-bee of the Sheds; I go to Carpentras to glean a more plentiful supply in the nests of the Hairy-footed Anthophora, that old acquaintance whose wonderful cities I used to undermine when I was studying the history of the Oil-beetles (5). Later, at my request, a pupil and intimate friend of mine, M. Henri Devillario, president of the civil court at Carpentras, sends me a case of fragments broken off the banks frequented by the Hairy-footed Anthophora and the Anthophora of the Walls, useful clods which furnish a handsome adjunct to my collection. Indeed, at the end, I find myself with handfuls of cocoons of the Three-horned Osmia. To count them would weary my patience without serving any particular purpose.
I spread out my stock in a large open box on a table which receives a bright diffused light but not the direct rays of the sun. The table stands between two windows facing south and overlooking the garden. When the moment of hatching comes, those two windows will always remain open to give the swarm entire liberty to go in and out as it pleases. The glass tubes and the reed-stumps are laid here and there, in fine disorder, close to the heap of cocoons and all in a horizontal position, for the Osmia will have nothing to do with upright reeds. The hatching of some of the Osmiae will therefore take place under cover of the galleries destined to be the building-yard later; and the site will be all the more deeply impressed on their memory. When I have made these comprehensive arrangements, there is nothing more to be done; and I wait patiently for the building-season to open.
My Osmiae leave their cocoons in the second half of April. Under the immediate rays of the sun, in well-sheltered nooks, the hatching would occur a month earlier, as we can see from the mixed population of the snowy almond-tree. The constant shade in my study has delayed the awakening, without, however, making any change in the nesting-period, which synchronizes with the flowering of the thyme. We now have, around my working-table, my books, my jars and my various appliances, a buzzing crowd that goes in and out of the windows at every moment. I enjoin the household henceforth not to touch a thing in the insects' laboratory, to do no more sweeping, no more dusting. They might disturb the swarm and make it think that my hospitality was not to be trusted. I suspect that the maid, wounded in her self-esteem at seeing so much dust accumulating in the master's study, did not always respect my prohibitions and came in stealthily, now and again, to give a little sweep of the broom. At any rate, I came across a number of Osmiae who seemed to have been crushed under foot while taking a sunbath on the floor in front of the window. Perhaps it was I myself who committed the misdeed in a heedless moment. There is no great harm done, for the population is a numerous one; and, notwithstanding those crushed by inadvertence, notwithstanding the parasites wherewith many of the cocoons are infested, notwithstanding those who may have come to grief outside or been unable to find their way back, notwithstanding the deduction of one-half which we must make for the males: notwithstanding all this, during four or five weeks I witness the work of a number of Osmiae which is much too large to allow of my watching their individual operations. I content myself with a few, whom I mark with different-coloured spots to distinguish them; and I take no notice of the others, whose finished work will have my attention later.
The first to appear are the males. If the sun is bright, they flutter around the heap of tubes as if to take careful note of the locality; blows are exchanged and the rival swains indulge in mild skirmishing on the floor, then shake the dust off their wings and fly away. I find them, opposite my window, in the refreshment-bar of the lilac-bush, whose branches bend with the weight of their scented panicles. Here the Bees get drunk with sunshine and draughts of honey. Those who have had their fill come home and fly assiduously from tube to tube, placing their heads in the orifices to see if some female will at last make up her mind to emerge.
One does, in point of fact. She is covered with dust and has the disordered toilet that is inseparable from the hard work of the deliverance. A lover has seen her, so has a second, likewise a third. All crowd round her. The lady responds to their advances by clashing her mandibles, which open and shut rapidly, several times in succession. The suitors forthwith fall back; and they also, no doubt to keep up their dignity, execute savage mandibular grimaces. Then the beauty retires into the arbour and her wooers resume their places on the threshold. A fresh appearance of the female, who repeats the play with her jaws; a fresh retreat of the males, who do the best they can to flourish their own pincers. The Osmiae have a strange wayof declaring their passion: with that fearsome gnashing of their mandibles, the lovers look as though they meant to devour each other. It suggests the thumps affected by our yokels in their moments of gallantry.
The ingenious idyll is soon over. By turns greeting and greeted with a clash of jaws, the female leaves her gallery and begins impassively to polish her wings. The rivals rush forward, hoist themselves on top of one another and form a pyramid of which each struggles to occupy the base by toppling over the favoured lover. He, however, is careful not to let go; he waits for the strife overhead to calm down; and, when the supernumeraries realize that they are wasting their time and throw up the game, the couple fly away far from the turbulent rivals. This is all that I have been able to gather about the Osmia's nuptials.
The females, who grow more numerous from day to day, inspect the premises; they buzz outside the glass galleries and the reed dwellings; they go in, stay for a while, come out, go in again and then fly away briskly into the garden. They return, first one, then another. They halt outside, in the sun, on the shutters fastened back against the wall; they hover in the window-recess, come inside, go to the reeds and give a glance at them, only to set off again and to return soon after. Thus do they learn to know their home, thus do they fix their birthplace in their memory. The village of our childhood is always a cherished spot, never to be effaced from our recollection. The Osmia's life endures for a month; and she acquires a lasting remembrance of her hamlet in a couple of days. 'Twas there that she was born; 'twas there that she loved; 'tis there that she will return. Dulces reminiscitur Argos.
('Now falling by another's wound, his eyes
He casts to heaven, on Argos thinks and dies.'
"Aeneid," Book 10 Dryden's translation.)
At last each has made her choice. The work of construction begins; and my expectations are fulfilled far beyond my wishes. The Osmiae build nests in all the retreats which I have placed at their disposal. The glass tubes, which I cover with a sheet of paper to produce the shade and mystery favourable to concentrated toil, do wonderfully well. All, from first to last, are occupied. The Osmiae quarrel for the possession of these crystal palaces, hitherto unknown to their race. The reeds and the paper tubes likewise do wonderfully. The number provided is too small; and I hasten to increase it. Snail-shells are recognized as excellent abodes, though deprived of the shelter of the stone-heap; old Chalicodoma-nests, down to those of the Chalicodoma of the Shrubs (6), whose cells are so small, are eagerly occupied. The late-comers, finding nothing else free, go and settle in the locks of my table-drawers. There are daring ones who make their way into half-open boxes containing ends of glass tubes in which I have stored my most recent acquisitions: grubs, pupae and cocoons of all kinds, whose evolution I wished to study. Whenever these receptacles have an atom of free space, they claim the right to build there, whereas I formally oppose the claim. I hardly reckoned on such a success, which obliges me to put some order into the invasion with which I am threatened. I seal up the locks, I shut my boxes, I close my various receptacles for old nests, in short I remove from the building-yard any retreat of which I do not approve. And now, O my Osmiae, I leave you a free field!
The work begins with a thorough spring-cleaning of the home. Remnants of cocoons, dirt consisting of spoilt honey, bits of plaster from broken partitions, remains of dried Mollusc at the bottom of a shell: these and much other insanitary refuse must first of all disappear. Violently the Osmia tugs at the offending object and tears it out; and then off she goes, in a desperate hurry, to dispose of it far away from the study. They are all alike, these ardent sweepers: in their excessive zeal, they fear lest they should block up the place with a speck of dust which they might drop in front of the new house. The glass tubes, which I myself have rinsed under the tap, are not exempt from a scrupulous cleaning. The Osmia dusts them, brushes them thoroughly with her tarsi and then sweeps them out backwards. What does she pick up? Not a thing. It makes no difference: as a conscientious housewife, she gives the place a touch of the broom nevertheless.
Now for the provisions and the partition-walls. Here the order of the work changes according to the diameter of the cylinder. My glass tubes vary greatly in dimensions. The largest have an inner width of a dozen millimetres (Nearly half an inch. (7); the narrowest measure six or seven. (8) In the latter, if the bottom suit her, the Osmia sets to work bringing pollen and honey. If the bottom do not suit her, if the sorghum-pith plug with which I have closed the rear-end of the tube be too irregular and badly-joined, the Bee coats it with a little mortar. When this small repair is made, the harvesting begins.
In the wider tubes, the work proceeds quite differently. At the moment when the Osmia disgorges her honey and especially at the moment when, with her hind-tarsi, she rubs the pollen-dust from her ventral brush, she needs a narrow aperture, just big enough to allow of her passage. I imagine that, in a straitened gallery, the rubbing of her whole body against the sides gives the harvester a support for her brushing-work. In a spacious cylinder, this support fails her; and the Osmia starts with creating one for herself, which she does by narrowing the channel. Whether it be to facilitate the storing of the victuals or for any other reason, the fact remains that the Osmia housed in a wide tube begins with the partitioning.
Her division is made by a dab of clay placed at right angles to the axis of the cylinder, at a distance from the bottom determined by the ordinary length of a cell. This wad is not a complete round; it is more crescent-shaped, leaving a circular space between it and one side of the tube. Fresh layers are swiftly added to the dab of clay; and soon the tube is divided by a partition which has a circular opening at the side of it, a sort of dog-hole through which the Osmia will proceed to knead the Bee-bread. When the victualling is finished and the egg laid upon the heap, the hole is closed and the filled-up partition becomes the bottom of the next cell. Then the same method is repeated, that is to say, in front of the just completed ceiling a second partition is built, again with a side-passage, which is stouter, owing to its distance from the centre, and better able to withstand the numerous comings and goings of the housewife than a central orifice, deprived of the direct support of the wall, could hope to be. When this partition is ready, the provisioning of the second cell is effected; and so on until the wide cylinder is completely stocked.
The building of this preliminary party-wall, with a narrow, round dog-hole, for a chamber to which the victuals will not be brought until later is not restricted to the Three-horned Osmia; it is also frequently found in the case of the Horned Osmia and of Latreille's Osmia. Nothing could be prettier than the work of the last-named, who goes to the plants for her material and fashions a delicate sheet in which she cuts a graceful arch. The Chinaman partitions his house with paper screens; Latreille's Osmia divides hers with disks of thin green cardboard perforated with a serving-hatch which remains until the room is completely furnished. When we have no glass houses at our disposal, we can see these little architectural refinements in the reeds of the hurdles, if we open them at the right season.
By splitting the bramble-stumps in the course of July, we perceive also that the Three-pronged Osmia, notwithstanding her narrow gallery, follows the same practice as Latreille's Osmia, with a difference. She does not build a party-wall, which the diameter of the cylinder would not permit; she confines herself to putting up a frail circular pad of green putty, as though to limit, before any attempt at harvesting, the space to be occupied by the Bee-bread, whose depth could not be calculated afterwards if the insect did not first mark out its confines. Can there really be an act of measuring? That would be superlatively clever. Let us consult the Three-horned Osmia in her glass tubes.
The Osmia is working at her big partition, with her body outside the cell which she is preparing. From time to time, with a pellet of mortar in her mandibles, she goes in and touches the previous ceiling with her forehead, while the tip of her abdomen quivers and feels the pad in course of construction. One might well say that she is using the length of her body as a measure, in order to fix the next ceiling at the proper distance. Then she resumes her work. Perhaps the measure was not correctly taken; perhaps her memory, a few seconds old, has already become muddled. The Bee once more ceases laying her plaster and again goes and touches the front wall with her forehead and the back wall with the tip of her abdomen. Looking at that body trembling with eagerness, extended to its full length to touch the two ends of the room, how can we fail to grasp the architect's grave problem? The Osmia is measuring; and her measure is her body. Has she quite done, this time? Oh dear no! Ten times, twenty times, at every moment, for the least particle of mortar which she lays, she repeats her mensuration, never being quite certain that her trowel is going just where it should.
Meanwhile, amid these frequent interruptions, the work progresses and the partition gains in width. The worker is bent into a hook, with her mandibles on the inner surface of the wall and the tip of her abdomen on the outer surface. The soft masonry stands between the two points of purchase. The insect thus forms a sort of rolling-press, in which the mud wall is flattened and shaped. The mandibles tap and furnish mortar; the end of the abdomen also pats and gives brisk trowel-touches. This anal extremity is a builder's tool; I see it facing the mandibles on the other side of the partition, kneading and smoothing it all over, flattening the little lump of clay. It is a singular implement, which I should never have expected to see used for this purpose. It takes an insect to conceive such an original idea, to do mason's work with its behind! During this curious performance, the only function of the legs is to keep the worker steady by spreading out and clinging to the walls of the tunnel.
The partition with the hole in it is finished. Let us go back to the measuring of which the Osmia was so lavish. What a magnificent argument in favour of the reasoning-power of animals! To find geometry, the surveyor's art, in an Osmia's tiny brain! An insect that begins by taking the measurements of the room to be constructed, just as any master-builder might do! Why, it's splendid, it's enough to cover with confusion those horrible sceptics who persist in refusing to admit the animal's 'continuous little flashes of atoms of reason!'
O common-sense, veil your face! It is with this gibberish about continuous flashes of atoms of reason that men pretend to build up science to-day! Very well, my masters; the magnificent argument with which I am supplying you lacks but one little detail, the merest trifle: truth! Not that I have not seen and plainly seen all that I am relating; but measuring has nothing to do with the case. And I can prove it by facts.
If, in order to see the Osmia's nest as a whole, we split a reed lengthwise, taking care not to disturb its contents; or, better still, if we select for examination the string of cells built in a glass tube, we are forthwith struck by one detail, namely, the uneven distances between the partitions, which are placed almost at right angles to the axis of the cylinder. It is these distances which fix the size of the chambers, which, with a similar base, have different heights and consequently unequal holding-capacities. The bottom partitions, the oldest, are farther apart; those of the front part, near the orifice, are closer together. Moreover, the provisions are plentiful in the loftier cells, whereas they are niggardly and reduced to one-half or even one-third in the cells of lesser height.
Here are a few examples of these inequalities. A glass tube with a diameter of 12 millimetres (9), inside measurement, contains ten cells. The five lower ones, beginning with the bottom-most, have as the respective distances between their partitions, in millimetres:
11, 12, 16, 13, 11. (10)
The five upper ones measure between their partitions:
7, 7, 5, 6, 7. (11)
A reed-stump 11 millimetres (12) across the inside contains fifteen cells; and the respective distances between the partitions of those cells, starting from the bottom, are:
13, 12, 12, 9, 9, 11, 8, 8, 7, 7, 7, 6, 6, 6, 7. (13)
When the diameter of the tunnel is less, the partitions can be still further apart, though they retain the general characteristic of being closer to one another the nearer they are to the orifice. A reed of five millimetres (14) in diameter, gives me the following distances, always starting from the bottom:
22, 22, 20, 20, 12, 14. (15)
Another, of 9 millimetres (16), gives me:
15, 14, 11, 10, 10, 9, 10. (17)
A glass tube of 8 millimetres (18) yields:
15, 14, 20, 10, 10, 10. (19).
I could fill pages and pages with such figures, if I cared to print all my notes. Do they prove that the Osmia is a geometrician, employing a strict measure based on the length of her body? Certainly not, because many of those figures exceed the length of the insect; because sometimes a higher number follows suddenly upon a lower; because the same string contains a figure of one value and another figure of but half that value. They prove only one thing: the marked tendency of the insect to shorten the distance between the party-walls as the work proceeds. We shall see later that the large cells are destined for the females and the small ones for the males.
Is there not at least a measuring adapted to each sex? Again, not so; for in the first series, where the females are housed, instead of the interval of 11 millimetres, which occurs at the beginning and the end, we find, in the middle of the series, an interval of 16 millimetres, while in the second series, reserved for the males, instead of the interval of 7 millimetres at the beginning and the end, we have an interval of 5 millimetres in the middle. It is the same with the other series, each of which shows a striking discrepancy in its figures. If the Osmia really studied the dimensions of her chambers and measured them with the compasses of her body, how could she, with her delicate mechanism, fail to notice mistakes of 5 millimetres, almost half her own length?
Besides, all idea of geometry vanishes if we consider the work in a tube of moderate width. Here, the Osmia does not fix the front partition in advance; she does not even lay its foundation. Without any boundary-pad, with no guiding mark for the capacity of the cell, she busies herself straightway with the provisioning. When the heap of Bee-bread is judged sufficient, that is, I imagine, when her tired body tells her that she has done enough harvesting, she closes up the chamber. In this case, there is no measuring; and yet the capacity of the cell and the quantity of the victuals fulfil the regular requirements of one or the other sex.
Then what does the Osmia do when she repeatedly stops to touch the front partition with her forehead and the back partition, the one in the course of building, with the tip of her abdomen? I have no idea what she does or what she has in view. I leave the interpretation of this performance to others, more venturesome than I. Plenty of theories are based on equally shaky foundations. Blow on them and they sink into the quagmire of oblivion.
The laying is finished, or perhaps the cylinder is full. A final partition closes the last cell. A rampart is now built, at the orifice of the tube itself, to forbid the ill-disposed all access to the home. This is a thick plug, a massy work of fortification, whereon the Osmia spends enough mortar to partition off any number of cells. A whole day is not too long for making this barricade, especially in view of the minute finishing-touches, when the Osmia fills up with putty every chink through which the least atom could slip. The mason completing a wall smooths his plaster and brings it to a fine surface while it is still wet; the Osmia does the same, or almost. With little taps of the mandibles and a continual shaking of her head, a sign of her zest for the work, she smooths and polishes the surface of the lid for hours at a time. After such pains, what foe could visit the dwelling?
And yet there is one, an Anthrax, A. sinuata (20), who will come later on, in the height of summer, and succeed, invisible bit of thread that she is, in making her way to the grub through the thickness of the door and the web of the cocoon. In many cells, mischief of another kind has already been done. During the progress of the works, an impudent Midge, one of the Tachina-flies, who feeds her family on the victuals amassed by the Bee, hovers in front of the galleries. Does she penetrate to the cells and lay her eggs there in the mother's absence? I could never catch the sneak in the act. Does she, like that other Tachina who ravages cells stocked with game (21), nimbly deposit her eggs on the Osmia's harvest at the moment when the Bee is going indoors? It is possible, though I cannot say for certain. The fact remains that we soon see the Midge's grub-worms swarming around the larva, the daughter of the house. There are ten, fifteen, twenty or more of them gnawing with their pointed mouths at the common dish and turning the food into a heap of fine, orange-coloured vermicelli. The Bee's grub dies of starvation. It is life, life in all its ferocity even in these tiny creatures. What an expenditure of ardent labour, of delicate cares, of wise precautions, to arrive at...what? Her offspring sucked and drained dry by the hateful Anthrax; her family sweated and starved by the infernal Tachina.
The victuals consist mostly of yellow flour. In the centre of the heap, a little honey is disgorged, which turns the pollen-dust into a firm, reddish paste. On this paste the egg is laid, not flat, but upright, with the fore-end free and the hind-end lightly held and fixed in the plastic mass. When hatched, the young grub, kept in its place by its rear-end, need only bend its neck a little to find the honey-soaked paste under its mouth. When it grows stronger, it will release itself from its support and eat up the surrounding flour.
All this is touching, in its maternal logic. For the new-born, dainty bread-and-honey; for the adolescent, dry bread. In cases where the provisions are all of a kind, these delicate precautions are superfluous. The victuals of the Anthophorae and the Chalicodomae consist of flowing honey, the same throughout. The egg is then laid at full length on the surface, without any particular arrangement, thus compelling the new-born grub to take its first mouthfuls at random. This has no drawback, as the food is of the same quality throughout. But, with the Osmia's provisions dry powder on the edges, jam in the centre the grub would be in danger if its first meal were not regulated in advance. To begin with pollen not seasoned with honey would be fatal to its stomach. Having no choice of its mouthfuls because of its immobility and being obliged to feed on the spot where it was hatched, the young grub must needs be born on the central mass, where it has only to bend its head a little way in order to find what its delicate stomach calls for. The place of the egg, therefore, fixed upright by its base in the middle of the red jam, is most judiciously chosen. What a contrast between this exquisite maternal forethought and the horrible destruction by the Anthrax and the Midge!
The egg is rather large for the size of the Osmia. It is cylindrical, slightly curved, rounded at both ends and transparent. It soon becomes cloudy, while remaining diaphanous at each extremity. Fine lines, hardly perceptible to the most penetrating lens, show themselves in transverse circles. These are the first signs of segmentation. A contraction appears in the front hyaline part, marking the head. An extremely thin opaque thread runs down either side. This is the cord of tracheae communicating between one breathing-hole and another. At last, the segments show distinctly, with their lateral pads. The grub is born.
At first, one would think that there was no hatching in the proper sense of the word that is to say, no bursting and casting of a wrapper. The most minute attention is necessary to show that appearances are deceptive and that actually a fine membrane is thrown off from front to back. This infinitesimal shred is the shell of the egg.
The grub is born. Fixed by its base, it curves into an arc and bends its head, until now held erect, down to the red mass. The meal begins. Soon a yellow cord occupying the front two-thirds of the body proclaims that the digestive apparatus is swelling out with food. For a fortnight, consume your provender in peace, my child; then spin your cocoon: you are now safe from the Tachina! Shall you be safe from the Anthrax' sucker later on? Alack!