The Mason-Bees Part 11

As there is nothing, except the mark of my pencil, a mark devoid of meaning to the insect, to indicate that the auger has already been at work there, it may easily happen that the same operator, finding under her feet a spot already exploited by herself but effaced from her memory, repeats the thrust of her tool in a compartment which she believes herself to be discovering for the first time. However retentive its memory for places may be, we cannot admit that the insect remembers for weeks on end, as well as point by point, the topography of a nest covering a surface of some square yards. Its recollections, if it have any, serve it badly; the outward appearance gives it no information; and its drill enters wherever it may happen to discover a cell, at points that have already perhaps been pierced several times over.

It may also happen--and this appears to me the most frequent case--that one exploiter of a cell is succeeded by a second, a third, a fourth and others still, all fired with the newcomer's zeal because their predecessors have left no trace of their pa.s.sage. In one way or another, the same cell is exposed to manifold layings, though its contents, the Chalicodoma-grub, be only the bare ration of a single Leucopsis-grub.

These reiterated borings are not at all rare: I noted a score of them on my tiles; and, in the case of some cells, the operation was repeated before my eyes as often as four times. Nothing tells us that this number was not exceeded in my absence. The little that I observed prevents me from fixing any limit. And now a momentous question arises: is the egg really laid each time that the probe enters a cell? I can see not the slightest excuse for supposing the contrary. The ovipositor, because of its h.o.r.n.y nature, can have but a very dull sense of touch. The insect is apprised of the contents of the cell only by the end of that long horse-hair, a not very trustworthy witness, I should imagine. The absence of resistance tells it that it has reached an empty s.p.a.ce; and this is probably the only information that the insensible implement can supply. The drill boring through the rock cannot tell the miner anything about the contents of the cavern which it has entered; and the case must be the same with the rigid filament of the Leucopses.

Now that the thread has reached its goal, what does the cell contain?

Mildewed honey, dust and rubbish, a shrivelled larva, or a larva in good condition? Above all, does it already contain an egg? This last question calls for a definite answer, but as a matter of fact it is impossible for the insect to learn anything from a horse-hair on that most delicate matter, the presence or absence of an egg, a mere atom of a thing, in that vast apartment. Even admitting some sense of touch at the end of the drill, one insuperable difficulty would always remain: that of finding the exact spot where the tiny speck lies in those s.p.a.cious and mysterious regions. I go so far as to believe that the ovipositor tells the insect nothing, or at any rate very little, of the inside of the cell, whether propitious or not to the development of the germ. Perhaps each thrust of the instrument, provided that it meets with no resistance from solid matter, lays the egg, to whose lot there falls at one time good, wholesome food, at another mere refuse.

These anomalies call for more conclusive proofs than the rough deductions drawn from the nature of the h.o.r.n.y ovipositor. We must ascertain in a direct fas.h.i.+on whether the cell into which the auger has been driven several times over actually contains several occupants in addition to the larva of the Mason-bee. When the Leucopses had finished their borings, I waited a few days longer so as to give the young grubs time to develop a little, which would make my examination easier. I then moved the tiles to the table in my study, in order to investigate their secrets with the most scrupulous care. And here such a disappointment as I have rarely known awaited me. The cells which I had seen, actually seen, with my own eyes, pierced by the probe two or three or even four times, contained but one Leucopsis-grub, one alone, eating away at its Chalicodoma. Others, which had also been repeatedly probed, contained spoilt remnants, but never a Leucopsis. O holy patience, give me the courage to begin again! Dispel the darkness and deliver me from doubt!

I begin again. The Leucopsis-grub is familiar to me; I can recognize it, without the possibility of a mistake, in the nests of both the Chalicodoma of the Pebbles and the Chalicodoma of the Sheds. All through the winter, I rush about, getting my nests from the roofs of old sheds and the pebbles of the waste-lands; I stuff my pockets with them, fill my box, load Favier's knapsack; I collect enough to litter all the tables in my study; and, when it is too cold out of doors, when the biting mistral blows, I tear open the fine silk of the coc.o.o.ns to discover the inhabitant. Most of them contain the Mason in the perfect state; others give me the larva of the Anthrax; others--very numerous, these--give me the larva of the Leucopsis. And this last is alone, always alone, invariably alone. The whole thing is utterly incomprehensible when one knows, as I know, how many times the probe entered those cells.

My perplexity only increases when, on the return of summer, I witness for the second time the Leucopsis' repeated operations on the same cells and for the second time find a single larva in the compartments which have been bored several times over. Shall I then be forced to accept that the auger is able to recognize the cells already containing an egg and that it thenceforth refrains from laying there? Must I admit an extraordinary sense of touch in that bit of horse-hair, or even better, a sort of divination which declares where the egg lies without having to touch it? But I am raving! There is certainly something that escapes me; and the obscurity of the problem is simply due to my incomplete information. O patience, supreme virtue of the observer, come to my aid once more! I must begin all over again for the third time.

Until now, my investigations have been made some time after the laying, at a period when the larva is at least fairly developed. Who knows?

Something perhaps happens, at the very commencement of infancy, that may mislead me afterwards. I must apply to the egg itself if I would learn the secret which the grub will not reveal. I therefore resume my observations in the first fortnight of July, when the Leucopses are beginning to visit busily both Mason-bee's nests. The pebbles in the waste-lands supply me with plenty of buildings of the Chalicodoma of the Walls; the byres scattered here and there in the fields give me, under their dilapidated roofs, in fragments broken off with the chisel, the edifices of the Chalicodoma of the Sheds. I am anxious not to complete the destruction of my home hives, already so sorely tried by my experiments; they have taught me much and can teach me more. Alien colonies, picked up more or less everywhere, provide me with my booty.

With my lens in one hand and my forceps in the other, I go through my collection on the same day, with the prudence and care which only the laboratory-table permits. The results at first fall far short of my expectations. I see nothing that I have not seen before. I make fresh expeditions, after a few days' interval; I bring back fresh loads of lumps of mortar, until at last fortune smiles upon me.

Reason was not at fault. Each thrust means the laying of an egg when the probe reaches the cell. Here is a coc.o.o.n of the Mason-bee of the Pebbles with an egg side by side with the Chalicodoma-grub. But what a curious egg! Never have my eyes beheld the like; and then is it really the egg of the Leucopsis? Great was my apprehension. But I breathed again when I found, a couple of weeks later, that the egg had become the larva with which I was familiar. Those coc.o.o.ns with a single egg are as numerous as I can wish; they exceed my wishes: my little gla.s.s receptacles are too few to hold them.

And here are others, more precious ones still, with manifold layings.

I find plenty with two eggs; I find some with three or four; the best-colonised offer me as many as five. And, to crown my delight, the joy of the seeker to whom success comes at the last moment, when he is on the verge of despair, here again, duly furnished with an egg, is a sterile coc.o.o.n, that is to say, one containing only a shrivelled and decaying larva. All my suspicions are confirmed, down to the most inconsequent: the egg housed with a ma.s.s of putrefaction.

The nests of the Mason-bee of the Walls are the more regular in structure and are easier to examine, because their base is wide open once it is separated from the supporting pebble; and it was these which supplied me with by far the greater part of my information. Those of the Mason-bee of the Sheds have to be chipped away with a hammer before one can inspect their cells, which are heaped up anyhow; and they do not lend themselves anything like so well to delicate investigations, as they suffer both from the shock and the ill-treatment.

And now the thing is done: it remains certain that the Leucopsis' laying is exposed to very exceptional dangers. She can entrust the egg to sterile cells, without provisions fit to use; she can establish several in the same cell, though this cell contains nourishment for one only.

Whether they proceed from a single individual returning several times, by inadvertence, to the same place, or are the work of different individuals unaware of the previous borings, those multiple layings are very frequent, almost as much so as the normal layings. The largest which I have noticed consisted of five eggs, but we have no authority for looking upon this number as an outside limit. Who could say, when the perforators are numerous, to what lengths this acc.u.mulation can go? I will set forth on some future occasion how the ration of one egg remains in reality the ration of one egg, despite the multiplicity of banqueters.

I will end by describing the egg, which is a white, opaque object, shaped like a much-elongated oval. One of the ends is lengthened out into a neck or pedicle, which is as long as the egg proper. This neck is somewhat wrinkled, sinuous and as a rule considerably curved. The whole thing is not at all unlike certain gourds with an elongated paunch and a snake-like neck. The total length, pedicle and all, is about 3 millimetres. (About one-eighth of an inch.--Translator's Note.) It is needless to say, after recognizing the grub's manner of feeding, that this egg is not laid inside the fostering larva. Yet, before I knew the habits of the Leucopsis, I would readily have believed that every Hymenopteron armed with a long probe inserts her eggs into the victim's sides, as the Ichneumon-flies do to the Caterpillars. I mention this for the benefit of any who may be under the same erroneous impression.

The Leucopsis' egg is not even laid upon the Mason-bee's larva; it is hung by its bent pedicle to the fibrous wall of the coc.o.o.n. When I go to work very delicately, so as not to disturb the arrangement in knocking the nest off its support, and then extract and open the coc.o.o.n, I see the egg swinging from the silken vault. But it takes very little to make it fall. And so, most often, even though it be merely the effect of the shock sustained when the nest is removed from its pebble, I find the egg detached from its suspension-point and lying beside the larva, to which it never adheres in any circ.u.mstances. The Leucopsis' probe does not penetrate beyond the coc.o.o.n traversed; and the egg remains fastened to the ceiling, in the crook of some silky thread, by means of its hooked pedicle.