Be this as it may, the gem-collector is so pleased with her pretty pebbles that she puts them everywhere. The partitions that subdivide the shell into chambers are reproductions of the lid: each has a carefully-finished mosaic of translucent flints on the front surface. In this manner three or four cells are contrived in the shell of the Edible Snail; in that of the Bulimulus, two at most. The cells are small but correctly shaped and strongly protected.
The protection, for that matter, is not restricted to these multiple paved hangings: [[181]]if you hold the Snail-shell to your ear and shake it, you hear a rattle of stones. The Odynerus, in fact, is as familiar as the Anthidia with the art of fortification by means of barricades. I make a breach in the side of the Snail-shell and pour out the heap of loose gravel that blocks the vestibule between the last partition and the lid. One detail should be noted: the materials which I collect are not homogeneous. Small polished pebbles predominate, but they are mixed with fragments of coarse limestone, bits of shell and particles of earth. The Odynerus, so fastidious in choosing the flint for her mosaics, employs for her filling the first rubbish that comes to hand. Even so do the two resin-gatherers act when barricading their Snail-shells. As a conscientious historian, I will add that the incoherent heap of rubbish is not always there: another point of resemblance with the practice of the Anthidia.
To my great regret, I can carry the biography of the Alpine Odynerus no farther. The insect appears to me to be very rare. I come upon its nest at long intervals in winter, the only season propitious to laborious searches in the stone-heaps. With the dwelling and its inhabitant, hatched in my [[182]]specimen-jars, I am familiar; but the egg, the larva and the provisions I do not know.
In compensation, I possess all the details that could be desired about the third species, O. nidulator, Sauss. This insect, like the just mentioned, is ignorant of the art of laying the foundations of its abode and demands a ready-made lodging. Like the Osmiæ, the Megachiles and the cotton-spinning Anthidia, it wants a cylindrical gallery, either natural or excavated by miners. Its art consists in partitioning a tunnel and subdividing it into chambers: plasterer’s art, in short.
Here then, in three species, the only ones whose habits I have had the opportunity of learning, we see three very different trades: the miner’s, the resin-worker’s and the plasterer’s. In these three guilds I find exactly the same equipment of tools; and I defy the most meticulous magnifying-glass to tell us what organic modification suggests to the one insect the pavement of pebbles upon a bed of resin, to the second the mine-shaft with its guilloched chimney, to the third the alien cylinder, partitioned with mud. No and again no: the organ does not constitute the function, the tool does not make the workman. With similar implements, [[183]]the Odynerus group executes the most dissimilar tasks, because each species has its predetermined skill, its art that governs the tool and is not governed by it. How plainly this conclusion would appear had I been privileged to review the entire Odynerus genus! How many industries remain for us to see, with the tool undergoing no modification! I suggest investigations on these lines to whomsoever it may concern, were it only in order to shed a little light upon this numerous and difficult group, of which the future will, I trust, give us a lucid classification based upon its industrial guilds.
Let us leave these generalities and pass to the detailed story of the Nest-building Odynerus. There are few Wasps with whose private life I am better acquainted; and I owe this abundant information to circumstances which, for me, impart a double value to the facts, because of the pleasant memories evoked. I had often extracted the Nest-building Odynerus’ series of cells from the old galleries of the Anthophoræ; I knew that the insect occupies dwellings not dug with its own mandibles and that its labours are confined to the partitions; I knew its yellow larva and its slender, amber-hued [[184]]cocoon. I knew nothing of all the rest, when I received from my daughter Claire a bundle of reed-cuttings which filled me with exultation.
Brought up in a zoological house, the dear child has retained a vivid memory of our evening talks, in which the insect so often cropped up; and her discerning eye is able quickly to distinguish, amid her casual discoveries, anything that may assist me in my studies of instinct. Her country home, in the neighbourhood of Orange, boasts a rustic poultry-house constructed partly of reeds laid in horizontal stages. In the middle of June last year (1889), she noticed, when visiting her Hens, certain Wasps making their way in large and busy numbers into the cut reeds, coming out again and soon returning laden with a load of earth or some malodorous little grub. Her attention once aroused, the rest did not take long: she had discovered a magnificent subject for me to study. That very evening I received a bundle of reeds, with a letter giving me circumstantial details.
The Wasp, as Claire called it and as Réaumur named it of old, when speaking of a species of the same genus but of very different habits, the Wasp, so the letter told [[185]]me, hoards in her nests a dumpy head of game, covered with black spots and smelling strongly of bitter almonds. I informed my daughter that this game was the larva of the Poplar Leaf-beetle (Chrysomela populi), a Beetle with red wing-cases reminding one, on a larger scale, of the Coccinella, or Common Ladybird. Insect and larva should be found together on the poplars of the neighbourhood, browsing promiscuously on the leaves. I added that a glorious opportunity had presented itself and that we must profit by it without delay. She therefore received instructions to keep a watch on this, that and the other and to furnish my insect laboratory with reed-stumps as and when they became colonized and with poplar-branches covered with Chrysomela-grubs. A collaboration was thus set up between Orange and Sérignan, the facts observed on both sides mutually completing and corroborating each other.
Let us come quickly to the bundle of reeds, the first examination of which gratifies my fondest hopes. It contains things that reawaken all the enthusiasm of my youth: cells converted into game-baskets, eggs on the point of hatching beside the victuals, new-born grubs biting into their first victim, [[186]]larvæ of fuller growth, weavers at work on their cocoons, in fact everything that one could wish for. Never, except with the Scoliæ in my heap of garden-mould,[3] has fortune served me better. Let us make an orderly inventory of these rich documents.
Already various Bees that favour borrowed houses have shown us the insect discriminating between one dwelling and another and selecting the best to make their homes in. We now have a predatory Wasp who, following the example of the Osmiæ, the Leaf-cutters and the Cotton-bees, leaves the ancestral cabin for the cylinder of the reed, to which man’s pruning-knife has prepared the access. The natural shelter, of indifferent quality, is succeeded by the artificial and more convenient refuge. The Odynerus’ primitive lodging is the abandoned corridor of the Anthophora, or any other burrow dug in the earth by no matter what miner. The wooden tube, free from damp and bathed in sunshine, is recognized as preferable; and the insect hastens to adopt it when the opportunity occurs. The tunnel of the reed must be recognized as an excellent habitation, [[187]]superior to all others, for never outside any abode of Anthophoræ have I seen a colony of Odyneri so populous as that of the Orange poultry-house.