This final glazing, so exquisite in its perfection, is preceded by a trimming-process. In the cells that are not yet stocked with provisions, the walls are dotted with tiny dents like those in a thimble. Here we recognize the work of the mandibles, which squeeze the clay with their tips, compress it and purge it of any grains of sand. The result is a milled surface whereon the polished layer will find a solid adhesive base. This layer is obtained with a fine clay, very carefully selected by the insect, purified, softened and then applied atom by atom, after which the trowel of the tongue steps in, diapering and polishing, while saliva, disgorged as needed, gives pliancy to the paste and finally dries into a waterproof varnish.
The humidity of the subsoil, at the time of the spring showers, would reduce the little earthen alcove to a sort of pap. The coating of saliva is an excellent preservative against this danger. It is so delicate that we suspect rather than see it; but its efficacy is none the less evident. I fill a cell with water. The liquid remains in it quite well, without any trace of infiltration.
The tiny pitcher looks as if it were varnished with galenite. The impermeability which the potter obtains by the brutal infusion of his mineral ingredients the Halictus achieves with the soft polisher of her tongue moistened with saliva. Thus protected, the larva will enjoy all the advantages of a dry berth, even in rain-soaked ground.
Should the wish seize us, it is easy to detach the waterproof film, at least in shreds. Take the little shapeless lump in which a cell has been excavated and put it in sufficient water to cover the bottom of it. The whole earthy mass will soon be soaked and reduced to a mud which we are able to sweep with the point of a hair-pencil. Let us have patience and do our sweeping gently; and we shall be able to separate from the main body the fragments of a sort of extremely fine satin. This transparent, colourless material is the upholstery that keeps out the wet. The Spider's web, if it formed a stuff and not a net, is the only thing that could be compared with it.
The Halictus' nurseries are, as we see, structures that take much time in the making. The insect first digs in the clayey earth a recess with an oval curve to it. It has its mandibles for a pick-axe and its tarsi, armed with tiny claws, for rakes. Rough though it be, this early work presents difficulties, for the Bee has to do her excavating in a narrow gully, where there is only just room for her to pass.
The rubbish soon becomes cumbersome. The insect collects it and then, moving backwards, with its fore-legs closed over the load, it hoists it up through the shaft and flings it outside, upon the mole-hill, which rises by so much above the threshold of the burrow. Next come the dainty finishing-touches: the milling of the wall, the application of a glaze of better-quality clay, the assiduous polishing with the long-suffering tongue, the waterproof coating and the jarlike mouth, a masterpiece of pottery in which the stopping-plug will be fixed when the time comes for locking the door of the room. And all this has to be done with mathematical precision.
No, because of this perfection, the grubs' chambers could never be work done casually from day to day, as the ripe eggs descend from the ovaries. They are prepared long beforehand, during the bad weather, at the end of March and in April, when flowers are scarce and the temperature subject to sudden changes. This thankless period, often cold, liable to hail-storms, is spent in making ready the home. Alone at the bottom of her shaft, which she rarely leaves, the mother works at her children's apartments, lavishing upon them those finishing-touches which leisure allows. They are completed, or very nearly, when May comes with the radiant sunshine and wealth of flowers.
We see the evidence of these long preparations in the burrows themselves, if we inspect them before the provisions are brought. All of them show us cells, about a dozen in number, quite finished, but still empty. To begin by getting all the huts built is a sensible precaution: the mother will not have to turn aside from the delicate task of harvesting and egg-laying in order to perform rough navvy's work.
Everything is ready by May. The air is balmy; the smiling lawns are gay with a thousand little flowers, dandelions, rock-roses, tansies and daisies, among which the harvesting Bee rolls gleefully, covering herself with pollen. With her crop full of honey and the brushes of her legs befloured, the Halictus returns to her village. Flying very low, almost level with the ground, she hesitates, with sudden turns and bewildered movements. It seems that the weak-sighted insect finds its way with difficulty among the cottages of its little township.
Which is its mole-hill among the many others near, all similar in appearance? It cannot tell exactly save by the sign-board of certain details known to itself alone. Therefore, still on the wing, tacking from side to side, it examines the locality. The home is found at last: the Halictus alights on the threshold of her abode and dives into it quickly.
What happens at the bottom of the pit must be the same thing that happens in the case of the other Wild Bees. The harvester enters a cell backwards; she first brushes herself and drops her load of pollen; then, turning round, she disgorges the honey in her crop upon the floury mass. This done, the unwearied one leaves the burrow and flies away, back to the flowers. After many journeys, the stack of provisions in the cell is sufficient. This is the moment to bake the cake.
