Bramble-Bees and Others Part 3

The work begins with a thorough spring-cleaning of the home. Remnants of coc.o.o.ns, dirt consisting of spoilt honey, bits of plaster from broken part.i.tions, remains of dried Mollusc at the bottom of a sh.e.l.l: 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 gla.s.s 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 part.i.tion-walls. Here the order of the work changes according to the diameter of the cylinder. My gla.s.s tubes vary greatly in dimensions. The largest have an inner width of a dozen millimetres (Nearly half an inch.--Translator's Note.); the narrowest measure six or seven. (About a quarter of an inch.--Translator's Note.) 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 pa.s.sage.

I imagine that, in a straitened gallery, the rubbing of her whole body against the sides gives the harvester a support for her brus.h.i.+ng-work.

In a s.p.a.cious 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 part.i.tioning.

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 s.p.a.ce 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 part.i.tion 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 part.i.tion 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 part.i.tion is built, again with a side-pa.s.sage, 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 part.i.tion 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 fas.h.i.+ons a delicate sheet in which she cuts a graceful arch. The Chinaman part.i.tions 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 gla.s.s 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-p.r.o.nged 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 s.p.a.ce 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 gla.s.s tubes.

The Osmia is working at her big part.i.tion, 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 part.i.tion 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 a.n.a.l extremity is a builder's tool; I see it facing the mandibles on the other side of the part.i.tion, 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 part.i.tion 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 gla.s.s tube, we are forthwith struck by one detail, namely, the uneven distances between the part.i.tions, 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 part.i.tions, 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 n.i.g.g.ardly and reduced to one-half or even one-third in the cells of lesser height.

Here are a few examples of these inequalities. A gla.s.s tube with a diameter of 12 millimetres (.468 inch.--Translator's Note.), inside measurement, contains ten cells. The five lower ones, beginning with the bottom-most, have as the respective distances between their part.i.tions, in millimetres:

11, 12, 16, 13, 11. (.429,.468,.624,.507,.429 inch.--Translator's Note.)

The five upper ones measure between their part.i.tions:

7, 7, 5, 6, 7. (.273,.273,.195,.234,.273 inch.--Translator's Note.)

A reed-stump 11 millimetres (.429 inch.--Translator's Note.) across the inside contains fifteen cells; and the respective distances between the part.i.tions of those cells, starting from the bottom, are:

13, 12, 12, 9, 9, 11, 8, 8, 7, 7, 7, 6, 6, 6, 7. (.507,.468,.468, .351,.351,.429,.312,.312,.273,.273,.273,.234,.234,.234, .273 inch.--Translator's Note.)

When the diameter of the tunnel is less, the part.i.tions 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 (.195 inch.--Translator's Note.) in diameter, gives me the following distances, always starting from the bottom:

22, 22, 20, 20, 12, 14. (.858,.858,.78,.78,.468,.546 inch.--Translator's Note.)

Another, of 9 millimetres (.351 inch.--Translator's Note.), gives me:

15, 14, 11, 10, 10, 9, 10. (.585,.546,.429,.39,.39,.351,.39 inch.--Translator's Note.)

A gla.s.s tube of 8 millimetres (.312 inch.--Translator's Note.) yields:

15, 14, 20, 10, 10, 10. (.585,.546,.78,.39,.39,.39 inch.--Translator's Note.).

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 s.e.x? 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 compa.s.ses 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 part.i.tion 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 quant.i.ty of the victuals fulfil the regular requirements of one or the other s.e.x.

Then what does the Osmia do when she repeatedly stops to touch the front part.i.tion with her forehead and the back part.i.tion, 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 part.i.tion 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 ma.s.sy work of fortification, whereon the Osmia spends enough mortar to part.i.tion off any number of cells. A whole day is not too long for making this barricade, especially in view of the minute finis.h.i.+ng-touches, when the Osmia fills up with putty every c.h.i.n.k 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 (Cf. "The Life of the Fly": chapters 2 and 4.--Translator's Note.), 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 coc.o.o.n. 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 ama.s.sed 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 (The cells of the Hunting Wasps.--Translator's Note.), 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 ma.s.s. 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 ma.s.s, 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 sh.e.l.l 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 ma.s.s. 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 coc.o.o.n: you are now safe from the Tachina! Shall you be safe from the Anthrax'

sucker later on? Alack!

CHAPTER 3. THE DISTRIBUTION OF THE s.e.xES.

Does the insect know beforehand the s.e.x of the egg which it is about to lay? When examining the stock of food in the cells just now, we began to suspect that it does, for each little heap of provisions is carefully proportioned to the needs at one time of a male and at another of a female. What we have to do is to turn this suspicion into a certainty demonstrated by experiment. And first let us find out how the s.e.xes are arranged.

It is not possible to ascertain the chronological order of a laying, except by going to suitably-chosen species. Digging up the burrows of Cerceris-, Bembex- or Philanthus-wasps will never tell us that this grub has taken precedence of that in point of time nor enable us to decide whether one coc.o.o.n in a colony belongs to the same family as another. To compile a register of births is absolutely impossible here. Fortunately there are a few species in which we do not find this difficulty: these are the Bees who keep to one gallery and build their cells in storeys.

Among the number are the different inhabitants of the bramble-stumps, notably the Three-p.r.o.nged Osmiae, who form an excellent subject for observation, partly because they are of imposing-size--bigger than any other bramble-dwellers in my neighbourhood--partly because they are so plentiful.

Let us briefly recall the Osmia's habits. Amid the tangle of a hedge, a bramble-stalk is selected, still standing, but a mere withered stump. In this the insect digs a more or less deep tunnel, an easy piece of work owing to the abundance of soft pith. Provisions are heaped up right at the bottom of the tunnel and an egg is laid on the surface of the food: that is the first-born of the family. At a height of some twelve millimetres (About half an inch.--Translator's Note.), a part.i.tion is fixed, formed of bramble saw-dust and of a green paste obtained by masticating particles of the leaves of some plant that has not yet been identified. This gives a second storey, which in its turn receives provisions and an egg, the second in order of primogeniture. And so it goes on, storey by storey, until the cylinder is full. Then a thick plug of the same green material of which the part.i.tions are formed closes the home and keeps out marauders.

In this common cradle, the chronological order of births is perfectly clear. The first-born of the family is at the bottom of the series; the last-born is at the top, near the closed door. The others follow from bottom to top in the same order in which they followed in point of time. The laying is numbered automatically; each coc.o.o.n tells us its respective age by the place which it occupies.

To know the s.e.xes, we must wait for the month of June. But it would be unwise to postpone our investigations until that period. Osmia-nests are not so common that we can hope to pick one up each time that we go out with that object; besides, if we wait for the hatching-period before examining the brambles, it may happen that the order has been disturbed through some insects' having tried to make their escape as soon as possible after bursting their coc.o.o.ns; it may happen that the male Osmiae, who are more forward than the females, are already gone. I therefore set to work a long time beforehand and devote my leisure in winter to these investigations.

The bramble-sticks are split and the coc.o.o.ns taken out one by one and methodically transferred to gla.s.s tubes, of approximately the same diameter as the native cylinder. These coc.o.o.ns are arranged one on top of the other in exactly the same order that they occupied in the bramble; they are separated from one another by a cotton plug, an insuperable obstacle to the future insect. There is thus no fear that the contents of the cells may become mixed or transposed; and I am saved the trouble of keeping a laborious watch. Each insect can hatch at its own time, in my presence or not: I am sure of always finding it in its place, in its proper order, held fast fore and aft by the cotton barrier. A cork or sorghum-pith part.i.tion would not fulfil the same purpose: the insect would perforate it and the register of births would be muddled by changes of position. Any reader wis.h.i.+ng to undertake similar investigations will excuse these practical details, which may facilitate his work.

We do not often come upon complete series, comprising the whole laying, from the first-born to the youngest. As a rule, we find part of a laying, in which the number of coc.o.o.ns varies greatly, sometimes falling as low as two, or even one. The mother has not deemed it advisable to confide her whole family to a single bramble-stump; in order to make the exit less toilsome, or else for reasons which escape me, she has left the first home and elected to make a second home, perhaps a third or more.

We also find series with breaks in them. Sometimes, in cells distributed at random, the egg has not developed and the provisions have remained untouched, but mildewed; sometimes, the larva has died before spinning its coc.o.o.n, or after spinning it. Lastly, there are parasites, such as the Unarmed Zonitis (Zonitis mutica, one of the Oil-beetles.--Translator's Note.) and the Spotted Sapyga (A Digger-wasp.--Translator's Note.), who interrupt the series by subst.i.tuting themselves for the original occupant. All these disturbing factors make it necessary to examine a large number of nests of the Three-p.r.o.nged Osmia, if we would obtain a definite result.