Bramble-Bees and Others Part 9

The quarries form part of an extensive plateau which is so arid as to be nearly deserted. In these conditions, the Osmia, at all times faithful to her birth-place, has little or no need to emigrate from her heap of stones and leave the sh.e.l.l for another dwelling which she would have to go and seek at a distance. Since there are heaps of stone there, she probably has no other dwelling than the Snail-sh.e.l.l. Nothing tells us that the present-day generations are not descended in the direct line from the generations contemporary with the quarryman who lost his as or his obol at this spot. All the circ.u.mstances seem to point to it: the Osmia of the quarries is an inveterate user of Snail-sh.e.l.ls; so far as heredity is concerned, she knows nothing whatever of reeds. Well, we must place her in the presence of these new lodgings.

I collect during the winter about two dozen well-stocked Snail-sh.e.l.ls and instal them in a quiet corner of my study, as I did at the time of my enquiries into the distribution of the s.e.xes. The little hive with its front pierced with forty holes has bits of reed fitted to it. At the foot of the five rows of cylinders I place the inhabited sh.e.l.ls and with these I mix a few small stones, the better to imitate the natural conditions. I add an a.s.sortment of empty Snail-sh.e.l.ls, after carefully cleaning the interior so as to make the Osmia's stay more pleasant. When the time comes for nest-building, the stay-at-home insect will have, close beside the house of its birth, a choice of two habitations: the cylinder, a novelty unknown to its race; and the spiral staircase, the ancient ancestral home.

The nests were finished at the end of May and the Osmiae began to answer my list of questions. Some, the great majority, settled exclusively in the reeds; the others remained faithful to the Snail-sh.e.l.l or else entrusted their eggs partly to the spirals and partly to the cylinders.

With the first, who were the pioneers of cylindrical architecture, there was no hesitation that I could perceive: after exploring the stump of reed for a time and recognizing it as serviceable, the insect instals itself there and, an expert from the first touch, without apprentices.h.i.+p, without groping, without any tendencies bequeathed by the long practice of its predecessors, builds its straight row of cells on a very different plan from that demanded by the spiral cavity of the sh.e.l.l which increases in size as it goes on.

The slow school of the ages, the gradual acquisitions of the past, the legacies of heredity count for nothing therefore in the Osmia's education. Without any novitiate on its own part or that of its forebears, the insect is versed straight away in the calling which it has to pursue; it possesses, inseparable from its nature, the qualities demanded by its craft: some which are invariable and belong to the domain of instinct; others, flexible, belonging to the province of discernment. To divide a free lodging into chambers by means of mud part.i.tions; to fill those chambers with a heap of pollen-flour, with a few sups of honey in the central part where the egg is to lie; in short, to prepare board and lodging for the unknown, for a family which the mothers have never seen in the past and will never see in the future: this, in its essential features, is the function of the Osmia's instinct. Here, everything is harmoniously, inflexibly, permanently preordained; the insect has but to follow its blind impulse to attain the goal. But the free lodging offered by chance varies exceedingly in hygienic conditions, in shape and in capacity. Instinct, which does not choose, which does not contrive, would, if it were alone, leave the insect's existence in peril. To help her out of her predicament, in these complex circ.u.mstances, the Osmia possesses her little stock of discernment, which distinguishes between the dry and the wet, the solid and the fragile, the sheltered and the exposed; which recognizes the worth or the worthlessness of a site and knows how to sprinkle it with cells according to the size and shape of the s.p.a.ce at disposal. Here, slight industrial variations are necessary and inevitable; and the insect excels in them without any apprentices.h.i.+p, as the experiment with the native Osmia of the quarries has just proved.

Animal resources have a certain elasticity, within narrow limits. What we learn from the animals' industry at a given moment is not always the full measure of their skill. They possess latent powers held in reserve for certain emergencies. Long generations can succeed one another without employing them; but, should some circ.u.mstance require it, suddenly those powers burst forth, free of any previous attempts, even as the spark potentially contained in the flint flashes forth independently of all preceding gleams. Could one who knew nothing of the Sparrow but her nest under the eaves suspect the ball-shaped nest at the top of a tree? Would one who knew nothing of the Osmia save her home in the Snail-sh.e.l.l expect to see her accept as her dwelling a stump of reed, a paper funnel, a gla.s.s tube? My neighbour the Sparrow, impulsively taking it into her head to leave the roof for the plane-tree, the Osmia of the quarries, rejecting her natal cabin, the spiral of the sh.e.l.l, for my cylinder, alike show us how sudden and spontaneous are the industrial variations of animals.

CHAPTER 7. ECONOMY OF ENERGY.

What stimulus does the insect obey when it employs the reserve powers that slumber in its race? Of what use are its industrial variations? The Osmia will yield us her secret with no great difficulty. Let us examine her work in a cylindrical habitation. I have described in full detail, in the foregoing pages, the structure of her nests when the dwelling adopted is a reed-stump or any other cylinder; and I will content myself here with recapitulating the essential features of that nest-building.

We must first distinguish three cla.s.ses of reeds according to their diameter: the small, the medium-sized and the large. I call small those whose narrow width just allows the Osmia to go about her household duties without discomfort. She must be able to turn where she stands in order to brush her abdomen and rub off its load of pollen, after disgorging the honey in the centre of the heap of flour already collected. If the width of the tube does not admit of this operation, if the insect is obliged to go out and then come in again backwards in order to place itself in a favourable posture for the discharge of the pollen, then the reed is too narrow and the Osmia is rather reluctant to accept it. The middle-sized reeds and a fortiori the large ones leave the victualler entire liberty of action; but the former do not exceed the width of a cell, a width agreeing with the bulk of the future coc.o.o.n, whereas the latter, with their excessive diameter, require more than one chamber on the same floor.

When free to choose, the Osmia settles by preference in the small reeds.

Here, the work of building is reduced to its simplest expression and consists in dividing the tube by means of earthen part.i.tions into a straight row of cells. Against the part.i.tion forming the back wall of the preceding cell the mother places first a heap of honey and pollen; next, when the portion is seen to be enough, she lays an egg in the centre of it. Then and then only she resumes her plasterer's work and marks out the length of the new cell with a mud part.i.tion. This part.i.tion in its turn serves as the rear-wall of another chamber, which is first victualled and then closed; and so on until the cylinder is sufficiently colonized and receives a thick terminal stopper at its orifice. In a word, the chief characteristic of this method of nest-building, the roughest of all, is that the part.i.tion in front is not undertaken so long as the victualling is still incomplete, or, in other words, that the provisions and the egg are deposited before the Bee sets to work on the part.i.tion.

At first sight, this latter detail hardly deserves attention: is it not right to fill the pot before we put a lid on? The Osmia who owns a medium-sized reed is not at all of this opinion; and other plasterers share her views, as we shall see when we watch the Odynerus building her nest. (A genus of Mason-wasps, the essays on which have not yet been translated into English.--Translator's Note.) Here we have an excellent ill.u.s.tration of one of those latent powers held in reserve for exceptional occasions and suddenly brought into play, although often very far removed from the insect's regular methods. If the reed, without being of inordinate width from the point of view of the coc.o.o.n, is nevertheless too s.p.a.cious to afford the Bee a suitable purchase against the wall at the moment when she is disgorging honey and brus.h.i.+ng off her load of pollen; the Osmia altogether changes the order of her work; she sets up the part.i.tion first and then does the victualling.

All round the inside of the tube she places a ring of mud, which, as the result of her constant visits to the mortar, ends by becoming a complete diaphragm minus an orifice at the side, a sort of round dog-hole, just large enough for the insect to pa.s.s through. When the cell is thus marked out and almost wholly closed, the Osmia attends to the storing of her provisions and the laying of her eggs. Steadying herself against the margin of the hole at one time with her fore-legs and at another with her hind-legs, she is able to empty her crop and to brush her abdomen; by pressing against it, she obtains a foothold for her little efforts in these various operations. When the tube was narrow, the outer wall supplied this foothold and the earthen part.i.tion was postponed until the heap of provisions was completed and surmounted by the egg; but in the present case the pa.s.sage is too wide and would leave the insect floundering helplessly in s.p.a.ce, so the part.i.tion with its serving-hatch takes precedence of the victuals. This method is a little more expensive than the other, first in materials, because of the diameter of the reed, and secondly in time, if only because of the dog-hole, a delicate piece of mortar-work which is too soft at first and cannot be used until it has dried and become harder. Therefore the Osmia, who is sparing of her time and strength, accepts medium-sized reeds only when there are no small ones available.

The large tubes she will use only in grave emergencies and I am unable to state exactly what these exceptional circ.u.mstances are. Perhaps she decides to make use of those roomy dwellings when the eggs have to be laid at once and there is no other shelter in the neighbourhood. While my cylinder-hives gave me plenty of well-filled reeds of the first and second cla.s.s, they provided me with but half-a-dozen at most of the third, notwithstanding my precaution to furnish the apparatus with a varied a.s.sortment.

The Osmia's repugnance to big cylinders is quite justified. The work in fact is longer and more costly when the tubes are wide. An inspection of a nest constructed under these conditions is enough to convince us. It now consists not of a string of chambers obtained by simple transverse part.i.tions, but of a confused heap of clumsy, many-sided compartments, standing back to back, with a tendency to group themselves in storeys without succeeding in doing so, because any regular arrangement would mean that the ceilings possessed a span which it is not in the builder's power to achieve. The edifice is not a geometrical masterpiece and it is even less satisfactory from the point of view of economy. In the previous constructions, the sides of the reed supplied the greater part of the walls and the work was limited to one part.i.tion for each cell.

Here, except at the actual periphery, where the tube itself supplies a foundation, everything has to be obtained by sheer building: the floor, the ceiling, the walls of the many-sided compartment are one and all made of mortar. The structure is almost as costly in materials as that of the Chalicodoma or the Pelopaeus.

It must be pretty difficult, too, when one thinks of its irregularity.

Fitting as best she can the projecting angles of the new cell into the recessed corners of the cell already built, the Osmia runs up walls more or less curved, upright or slanting, which intersect one another at various points, so that each compartment requires a new and complicated plan of construction, which is very different from the circular-part.i.tion style of architecture, with its row of parallel dividing-disks. Moreover, in this composite arrangement, the size of the recesses left available by the earlier work to some extent decides the a.s.sessment of the s.e.xes, for, according to the dimensions of those recesses, the walls erected take in now a larger s.p.a.ce, the home of a female, and now a smaller s.p.a.ce, the home of a male. Roomy quarters therefore have a double drawback for the Osmia: they greatly increase the outlay in materials; and also they establish in the lower layers, among the females, males who, because of their earlier hatching, would be much better placed near the mouth of the nest. I am convinced of it: if the Osmia refuses big reeds and accepts them only in the last resort, when there are no others, it is because she objects to additional labour and to the mixture of the s.e.xes.

The Snail-sh.e.l.l, then, is but an indifferent home for her, which she is quite ready to abandon should a better offer. Its expanding cavity represents an average between the favourite small cylinder and the unpopular large cylinder, which is accepted only when there is no other obtainable. The first whorls of the spiral are too narrow to be of use to the Osmia, but the middle ones have the right diameter for coc.o.o.ns arranged in single file. Here things happen as in a first-cla.s.s reed, for the helical curve in no way affects the method of structure employed for a rectilinear series of cells. Circular part.i.tions are erected at the required distances, with or without a serving-hatch, according to the diameter. These mark out the first cells, one after the other, which are reserved solely for the females. Then comes the last whorl, which is much too wide for a single row of cells; and here we once more find, exactly as in a wide reed, a costly profusion of masonry, an irregular arrangement of the cells and a mixture of the s.e.xes.

Having said so much, let us go back to the Osmia of the quarries. Why, when I offer them simultaneously Snail-sh.e.l.ls and reeds of a suitable size, do the old frequenters of the sh.e.l.ls prefer the reeds, which in all probability have never before been utilized by their race? Most of them scorn the ancestral dwelling and enthusiastically accept my reeds.

Some, it is true, take up their quarters in the Snail-sh.e.l.l; but even among these a goodly number refuse my new sh.e.l.ls and return to their birth-place, the old Snail-sh.e.l.l, in order to utilize the family property, without much labour, at the cost of a few repairs. Whence, I ask, comes this general preference for the cylinder, never used hitherto? The answer can be only this: of two lodgings at her disposal the Osmia selects the one that provides a comfortable home at a minimum outlay. She economizes her strength when restoring an old nest; she economizes it when replacing the Snail-sh.e.l.l by the reed.

Can animal industry, like our own, obey the law of economy, the sovran law that governs our industrial machine even as it governs, at least to all appearances, the sublime machine of the universe? Let us go deeper into the question and bring other workers into evidence, those especially who, better equipped perhaps and at any rate better fitted for hard work, attack the difficulties of their trade boldly and look down upon alien establishments with scorn. Of this number are the Chalicodomae, the Mason-bees proper.

The Mason-bee of the Pebbles does not make up her mind to build a brand-new dome unless there be a dearth of old and not quite dilapidated nests. The mothers, sisters apparently and heirs-at-law to the domain, dispute fiercely for the ancestral abode. The first who, by sheer brute force, takes possession of the dome, perches upon it and, for long hours, watches events while polis.h.i.+ng her wings. If some claimant puts in an appearance, forthwith the other turns her out with a volley of blows. In this way the old nests are employed so long as they have not become uninhabitable hovels.

Without being equally jealous of the maternal inheritance, the Mason-bee of the Sheds eagerly uses the cells whence her generation issued. The work in the huge city under the eaves begins thus: the old cells, of which, by the way, the good-natured owner yields a portion to Latreille's Osmia and to the Three-horned Osmia alike, are first made clean and wholesome and cleared of broken plaster and then provisioned and shut. When all the accessible chambers are occupied, the actual building begins with a new stratum of cells upon the former edifice, which becomes more and more ma.s.sive from year to year.

The Mason-bee of the Shrubs, with her spherical nests hardly larger than walnuts, puzzled me at first. Does she use the old buildings or does she abandon them for good? To-day perplexity makes way for certainty: she uses them very readily. I have several times surprised her lodging her family in the empty rooms of a nest where she was doubtless born herself. Like her kinswoman of the Pebbles, she returns to the native dwelling and fights for its possession. Also, like the dome-builder, she is an anchorite and prefers to cultivate the lean inheritance alone.

Sometimes, however, the nest is of exceptional size and harbours a crowd of occupants, who live in peace, each attending to her business, as in the colossal hives in the sheds. Should the colony be at all numerous and the estate descend to two or three generations in succession, with a fresh layer of masonry each year, the normal walnut-sized nest becomes a ball as large as a man's two fists. I have gathered on a pine-tree a nest of the Mason-bee of the Shrubs that weighed a kilogram (2.205 pounds avoirdupois.--Translator's Note.) and was the size of a child's head. A twig hardly thicker than a straw served as its support. The casual sight of that lump swinging over the spot on which I had sat down made me think of the mishap that befell Garo. (The hero of La Fontaine's fable, "Le Gland et la Citrouille," who wondered why acorns grew on such tall trees and pumpkins on such low vines, until he fell asleep under one of the latter and a pumpkin dropped upon his nose.--Translator's Note.) If such nests were plentiful in the trees, any one seeking the shade would run a serious risk of having his head smashed.

After the Masons, the Carpenters. Among the guild of wood-workers, the most powerful is the Carpenter-bee (Xylocopa violacea (Cf. "The Life of the Spider": chapter 1.--Translator's Note.)), a very large Bee of formidable appearance, clad in black velvet with violet-coloured wings.

The mother gives her larvae as a dwelling a cylindrical gallery which she digs in rotten wood. Useless timber lying exposed to the air, vine-poles, large logs of fire-wood seasoning out of doors, heaped up in front of the farmhouse porch, stumps of trees, vine-stocks and big branches of all kinds are her favourite building-yards. A solitary and industrious worker, she bores, bit by bit, circular pa.s.sages the width of one's thumb, as clear-cut as though they were made with an auger.

A heap of saw-dust acc.u.mulates on the ground and bears witness to the severity of the task. Usually, the same aperture is the entrance to two or three parallel corridors. With several galleries there is accommodation for the entire laying, though each gallery is quite short; and the Bee thus avoids those long series which always create difficulties when the moment of hatching arrives. The laggards and the insects eager to emerge are less likely to get in each other's way.

After obtaining the dwelling, the Carpenter-bee behaves like the Osmia who is in possession of a reed. Provisions are collected, the egg is laid and the chamber is walled in front with a saw-dust part.i.tion. The work is pursued in this way until the two or three pa.s.sages composing the house are completely stocked. Heaping up provisions and erecting part.i.tions are an invariable feature of the Xylocopa's programme; no circ.u.mstance can release the mother from the duty of providing for the future of her family, in the matter both of ready-prepared food and of separate compartments for the rearing of each larva. It is only in the boring of the galleries, the most laborious part of the work, that economy can occasionally be exercised by a piece of luck. Well, is the powerful Carpenter, all unheeding of fatigue, able to take advantage of such fortunate occasions? Does she know how to make use of houses which she has not tunnelled herself? Why, yes: a free lodging suits her just as much as it does the various Mason-bees. She knows as well as they the economic advantages of an old nest that is still in good condition: she settles down, as far as possible, in her predecessors' galleries, after freshening up the sides with a superficial sc.r.a.ping. And she does better still. She readily accepts lodgings which have never known a drill, no matter whose. The stout reeds used in the trellis-work that supports the vines are valuable discoveries, providing as they do sumptuous galleries free of cost. No preliminary work or next to none is required with these. Indeed, the insect does not even trouble to make a side-opening, which would enable it to occupy the cavity contained within two nodes; it prefers the opening at the end cut by man's pruning-knife. If the next part.i.tion be too near to give a chamber of sufficient length, the Xylocopa destroys it, which is easy work, not to be compared with the labour of cutting an entrance through the side. In this way, a s.p.a.cious gallery, following on the short vestibule made by the pruning-knife, is obtained with the least possible expenditure of energy.

Guided by what was happening on the trellises, I offered the black Bee the hospitality of my reed-hives. From the very beginning, the insect gladly welcomed my advances; each spring, I see it inspect my rows of cylinders, pick out the best ones and instal itself there. Its work, reduced to a minimum by my intervention, is limited to the part.i.tions, the materials for which are obtained by sc.r.a.ping the inner sides of the reed.

As first-rate joiners, next to the Carpenter-bees come the Lithurgi, of whom my district possesses two species: L. cornutus, FAB., and L.

chrysurus, BOY. By what aberration of nomenclature was the name of Lithurgus, a worker in stone, given to insects which work solely in wood? I have caught the first, the stronger of the two, digging galleries in a large block of oak that served as an arch for a stable-door; I have always found the second, who is more widely distributed, settling in dead wood--mulberry, cherry, almond, poplar--that was still standing. Her work is exactly the same as the Xylocopa's, on a smaller scale. A single entrance-hole gives access to three or four parallel galleries, a.s.sembled in a serried group; and these galleries are subdivided into cells by means of saw-dust part.i.tions. Following the example of the big Carpenter-bee, Lithurgus chrysurus knows how to avoid the laborious work of boring, when occasion offers: I find her coc.o.o.ns lodged almost as often in old dormitories as in new ones. She too has the tendency to economize her strength by turning the work of her predecessors to account. I do not despair of seeing her adopt the reed if, one day, when I possess a large enough colony, I decide to try this experiment on her. I will say nothing about L. cornutus, whom I only once surprised at her carpentering.

The Anthophorae, those children of the precipitous earthy banks, show the same thrifty spirit as the other members of the mining corporation.

Three species, A. parietina, A. personata and A. pilipes, dig long corridors leading to the cells, which are scattered here and there and one by one. These pa.s.sages remain open at all seasons of the year. When spring comes, the new colony uses them just as they are, provided that they are well preserved in the clayey ma.s.s baked by the sun; it increases their length if necessary, runs out a few more branches, but does not decide to start boring in new ground until the old city, which, with its many labyrinths, resembles some monstrous sponge, is too much undermined for safety. The oval niches, the cells that open on those corridors, are also profitably employed. The Anthophora restores their entrance, which has been destroyed by the insect's recent emergence; she smooths their walls with a fresh coat of whitewash, after which the lodging is fit to receive the heap of honey and the egg. When the old cells, insufficient in number and moreover partly inhabited by diverse intruders, are all occupied, the boring of new cells begins, in the extended sections of the galleries, and the rest of the eggs are housed.

In this way, the swarm is settled at a minimum of expense.

To conclude this brief account, let us change the zoological setting and, as we have already spoken of the Sparrow, see what he can do as a builder. The simplest form of his nest is the great round ball of straw, dead leaves and feathers, in the fork of a few branches. It is costly in material, but can be set up anywhere, when the hole in the wall or the shelter of a tile are lacking. What reasons induced him to give up the spherical edifice? To all seeming, the same reasons that led the Osmia to abandon the Snail-sh.e.l.l's spiral, which requires a fatiguing expenditure of clay, in favour of the economical cylinder of the reed.

By making his home in a hole in the wall, the Sparrow escapes the greater part of his work. Here, the dome that serves as a protection from the rain and the thick walls that offer resistance to the wind both become superfluous. A mere mattress is sufficient; the cavity in the wall provides the rest. The saving is great; and the Sparrow appreciates it quite as much as the Osmia.

This does not mean that the primitive art has disappeared, lost through neglect; it remains an ineffaceable characteristic of the species, ever ready to declare itself should circ.u.mstances demand it. The generations of to-day are as much endowed with it as the generations of yore; without apprentices.h.i.+p, without the example of others, they have within themselves, in the potential state, the industrial apt.i.tude of their ancestors. If aroused by the stimulus of necessity, this apt.i.tude will pa.s.s suddenly from inaction to action. When, therefore, the Sparrow still from time to time indulges in spherical building, this is not progress on his part, as is sometimes contended; it is, on the contrary, a retrogression, a return to the ancient customs, so prodigal of labour.

He is behaving like the Osmia who, in default of a reed, makes s.h.i.+ft with a Snail-sh.e.l.l, which is more difficult to utilize but easier to find. The cylinder and the hole in the wall stand for progress; the spiral of the Snail-sh.e.l.l and the ball-shaped nest represent the starting-point.

I have, I think, sufficiently ill.u.s.trated the inference which is borne out by the whole ma.s.s of a.n.a.logous facts. Animal industry manifests a tendency to achieve the essential with a minimum of expenditure; after its own fas.h.i.+on, the insect bears witness to the economy of energy. On the one hand, instinct imposes upon it a craft that is unchangeable in its fundamental features; on the other hand, it is left a certain lat.i.tude in the details, so as to take advantage of favourable circ.u.mstances and attain the object aimed at with the least possible expenditure of time, materials and work, the three elements of mechanical labour. The problem in higher geometry solved by the Hive-bee is only a particular case--true, a magnificent case,--of this general law of economy which seems to govern the whole animal world. The wax cells, with their maximum capacity as against a minimum wall-s.p.a.ce, are the equivalent, with the superaddition of a marvellous scientific skill, of the Osmia's compartments in which the stonework is reduced to a minimum through the selection of a reed. The artificer in mud and the artificer in wax obey the same tendency: they economize. Do they know what they are doing? Who would venture to suggest it in the case of the Bee grappling with her transcendental problem? The others, pursuing their rustic art, are no wiser. With all of them, there is no calculation, no premeditation, but simply blind obedience to the law of general harmony.

CHAPTER 8. THE LEAF-CUTTERS.

It is not enough that animal industry should be able, to a certain extent, to adapt itself to casual exigencies when choosing the site of a nest; if the race is to thrive, something else is required, something which hide-bound instinct is unable to provide. The Chaffinch, for instance, introduces a great quant.i.ty of lichen into the outer layer of his nest. This is his method of strengthening the edifice and making a stout framework in which to place first the bottom mattress of moss, fine straw and rootlets and then the soft bed of feathers, wool and down. But, should the time-honoured lichen be lacking, will the bird refrain from building its nest? Will it forgo the delight of hatching its brood because it has not the wherewithal to settle its family in the orthodox fas.h.i.+on?

No, the chaffinch is not perplexed by so small a matter; he is an expert in materials, he understands botanical equivalents. In the absence of the branches of the evernias, he picks the long beards of the usneas, the wartlike rosettes of the parmelias, the membranes of the stictises torn away in shreds; if he can find nothing better, he makes s.h.i.+ft with the bushy tufts of the cladonias. As a practical lichenologist, when one species is rare or lacking in the neighbourhood, he is able to fall back on others, varying greatly in shape, colour and texture. And, if the impossible happened and lichen failed entirely, I credit the Chaffinch with sufficient talent to be able to dispense with it and to build the foundations of his nest with some coa.r.s.e moss or other.

What the worker in lichens tells us the other weavers of textile materials confirm. Each has his favourite flora, which hardly ever varies when the plant is easily accessible and which can be supplemented by plenty of others when it is not. The bird's botany would be worth examining; it would be interesting to draw up the industrial herbal of each species. In this connection, I will quote just one instance, so as not to stray too far from the subject in hand.

The Red-backed Shrike (Lanius collurio), the commonest variety in my district, is noteworthy because of his savage mania for forked gibbets, the thorns in the hedgerows whereon he impales the voluminous contents of his game-bag--little half-fledged birds, small Lizards, Gra.s.shoppers, caterpillars, Beetles--and leaves them to get high. To this pa.s.sion for the gallows, which has pa.s.sed unnoticed by the country-folk, at least in my part, he adds another, an innocent botanical pa.s.sion, which is so much in evidence that everybody, down to the youngest bird's-nester, knows all about it. His nest, a ma.s.sive structure, is made of hardly any other materials than a greyish and very fluffy plant, which is found everywhere among the corn. This is the Filago spathulata of the botanists; and the bird also makes use, though less frequently, of the Filago germanica, or common cotton-rose. Both are known in Provencal by the name herbo dou tarnagas, or Shrike-herb. This popular designation tells us plainly how faithful the bird is to its plant. To have struck the agricultural labourer, a very indifferent observer, the Shrike's choice of materials must be remarkably persistent.

Have we here a taste that is exclusive? Not in the least. Though cotton-roses of all species are plentiful on level ground, they become scarce and impossible to find on the parched hills. The bird, on its side, is not given to journeys of exploration and takes what it finds to suit it in the neighbourhood of its tree or hedge. But on arid ground, the Micropus erectus, or upright micropus, abounds and is a satisfactory subst.i.tute for the Filago so far as its tiny, cottony leaves and its little fluffy b.a.l.l.s of flowers are concerned. True, it is short and does not lend itself well to weaver's work. A few long sprigs of another cottony plant, the Helichrysum staechas, or wild everlasting, inserted here and there, will give body to the structure. Thus does the Shrike manage when hard up for his favourite materials: keeping to the same botanical family, he is able to find and employ subst.i.tutes among the fine cotton-clad stalks.

He is even able to leave the family of the Compositae and to go gleaning more or less everywhere. Here is the result of my botanizings at the expense of his nests. We must distinguish between two genera in the Shrike's rough cla.s.sification: the cottony plants and the smooth plants.

Among the first, my notes mention the following: Convolvulus cantabrica, or flax-leaved bindweed; Lotus symmetricus, or bird's-foot trefoil; Teucrium polium, or poly; and the flowery heads of the Phragmites communis, or common reed. Among the second are these: Medicago lupulina, or nonesuch; Trifolium repens, or white clover; Lathyrus pratensis, or meadow lathyrus; Capsella bursa pastoris, or shepherd's purse; Vicia peregrina, or broad-podded vetch; Convolvulus arvensis, or small bindweed; Pterotheca nemausensis, a sort of hawkweed; and Poa pratensis, or smooth-stalked meadow-gra.s.s. When it is downy, the plant forms almost the whole nest, as is the case with the flax-leaved bindweed; when smooth, it forms only the framework, destined to support a crumbling ma.s.s of micropus, as is the case with the small bindweed. When making this collection, which I am far from giving as the birds' complete herbarium, I was struck by a wholly unexpected detail: of the various plants, I found only the heads still in bud; moreover, all the sprigs, though dry, possessed the green colouring of the growing plant, a sign of swift desiccation in the sun. Save in a few cases, therefore, the Shrike does not collect the dead and withered remains: it is from the growing plants that he reaps his harvest, mowing them down with his beak and leaving the sheaves to dry in the sun before using them. I caught him one day hopping about and pecking at the twigs of a Biscayan bindweed. He was getting in his hay, strewing the ground with it.

The evidence of the Shrike, confirmed by that of all the other workers--weavers, basket-makers or woodcutters--whom we may care to call as witnesses, shows us what a large part must be a.s.signed to discernment in the bird's choice of materials for its nest. Is the insect as highly gifted? When it works with vegetable matter, is it exclusive in its tastes? Does it know only one definite plant, its special province? Or has it, for employment in its manufactures, a varied flora, in which its discernment exercises a free choice? For answers to these questions we may look, above all, to the Leaf-cutting Bees, the Megachiles. Reaumur has told the story of their industry in detail; and I refer the reader who wishes for further particulars to the master's Memoirs.

The man who knows how to use his eyes in his garden will observe, some day or other, a number of curious holes in the leaves of his lilac- and rose-trees, some of them round, some oval, as if idle but skilful hands had been at work with the pinking-iron. In some places, there is scarcely anything but the veins of the leaves left. The author of the mischief is a grey-clad Bee, a Megachile. For scissors, she has her mandibles; for compa.s.ses, producing now an oval and anon a circle, she has her eye and the pivot of her body. The pieces cut out are made into thimble-shaped wallets, destined to contain the honey and the egg: the larger, oval pieces supply the floor and sides; the smaller, round pieces are reserved for the lid. A row of these thimbles, placed one on top of the other, up to a dozen or more, though often there are less: that is, roughly, the structure of the Leaf-cutter's nest.

When taken out of the recess in which the mother has manufactured it, the cylinder of cells seems to be an indivisible whole, a sort of tunnel obtained by lining with leaves some gallery dug underground. The real thing does not correspond with its appearance: under the least pressure of the fingers, the cylinder breaks up into equal sections, which are so many compartments independent of their neighbours as regards both floor and lid. This spontaneous break up shows us how the work is done. The method agrees with those adopted by the other Bees. Instead of a general scabbard of leaves, afterwards subdivided into compartments by transverse part.i.tions, the Megachile constructs a string of separate wallets, each of which is finished before the next is begun.

A structure of this sort needs a sheath to keep the pieces in place while giving them the proper shape. The bag of leaves, in fact, as turned out by the worker, lacks stability; its numerous pieces, not glued together, but simply placed one after the other, come apart and give way as soon as they lose the support of the tunnel that keeps them united. Later, when it spins its coc.o.o.n, the larva infuses a little of its fluid silk into the gaps and solders the pieces to one another, especially the inner ones, so much so that the insecure bag in due course becomes a solid casket whose component parts it is no longer possible to separate entirely.

The protective sheath, which is also a framework, is not the work of the mother. Like the great majority of the Osmiae, the Megachiles do not understand the art of making themselves a home straight away: they want a borrowed lodging, which may vary considerably in character.

The deserted galleries of the Anthophorae, the burrows of the fat Earth-worms, the tunnels bored in the trunks of trees by the larva of the Cerambyx-beetle (The Capricorn, the essay on which has not yet been published in English.--Translator's Note.), the ruined dwellings of the Mason-bee of the Pebbles, the Snail-sh.e.l.l nests of the Three-horned Osmia, reed-stumps, when these are handy, and crevices in the walls are all so many homes for the Leaf-cutters, who choose this or that establishment according to the tastes of their particular genus.