The other cavities, which are wider and form irregular polygons, penetrate to the stone. The opening measures nearly four millimetres;[3] and the walls, instead of slanting like those of the food-pits, rise vertically from the exposed stone. Let us note yet another detail whose importance we shall see presently: it is rare to find any gum in them, though the other cavities usually contain it. These pits, which are free from obstruction, are family establishments. I count two, three, four on the same sloe; sometimes only one. Very often they are accompanied, where the Weevil has fed, by funnel-shaped surface erosions.
The larger pits descending to the stone form a sort of irregular crater, in the centre of which there is always a little cone of brown pulp. Not infrequently the magnifying-glass reveals a fine perforation at the top of this central cone; at other times the orifice is closed, but in a careless fashion, which makes one suspect a connection with the depths below.
Cut this cone down the axis. At its base is a tiny hemispherical cup hollowed in the thickness of the stone. Here, on a bed of fine dust due to the work of erosion, lies a yellow egg, oval and about a millimetre[4] long. Above the egg, like a [[169]]protecting roof, rises the cone of brown pulp, pierced throughout its length by a fine channel, which is sometimes free and sometimes half obstructed.
The structure of the work tells us how the operation is conducted. In the fleshy layer of the sloe the mother, eating the substance, or discarding it if there be more than her appetite calls for, first makes a pit with perpendicular walls and lays a suitable surface of the stone absolutely bare. Then, in the centre of this area, she chases with her graver a little cup sinking half-way through the thickness of the shell. Here, on a soft bed of raspings, the egg is laid. Lastly, as a defensive device, the mother erects above the cup and its contents a pointed roof, a cone of pulp obtained from the walls of the pit.
The insect works very well in captivity, if given plenty of space, sunlight and a twig covered with sloes. It is easy to watch the proceedings of the egg-laying mother; but the result of diligent observation amounts to very little.
Almost the whole day, the mother remains clinging to one spot on the fruit, motionless, with her rostrum driven into the pulp. As a rule, there is no movement on her part, nothing to betray any effort.
From time to time a male visits her, climbs on her back, throws his legs around her and, himself swaying from side to side, rocks her very [[170]]gently to and fro. Without permitting herself to be diverted from her serious labours, the female thus embraced passively yields to the rolling motion. Perhaps it is a means of whiling away the long hours needed for establishing an egg.
To see more than this is very difficult. The rostrum does its work in the hidden seclusion of the pulp and, as the pit opens and widens, the digger covers it with the fore-part of her body. The hollow is ready. The mother withdraws and turns round. For a moment I catch a glimpse of the bare stone at the bottom of the crater, with a tiny cup in the centre of the denuded area. As soon as the egg is laid in this cup, the insect turns round again and nothing more is visible until the work is completed.
How does the pregnant mother contrive to raise above the egg a protective heap, a cone, an obelisk somewhat irregular in shape, but very curious with its narrow ventilating-shaft? Above all, how does she manage to make this communicating passage in the soft mass? These are details which we can scarcely hope to detect, so discreetly does the insect work. We must be content to know that the rostrum alone, without the aid of the legs, digs the crater and erects the central cone.
In the heat of June, less than a week is enough for the hatching. By good fortune, solicited, so far as that goes, by attempts that come near to exhausting my small stock of patience, I witness [[171]]an interesting sight. I have a new-born grub before my eyes. It has just cast the skin of the egg; it is very busily wriggling in its powdery cup. Why so much excitement? For this reason: to reach the kernel, its ration, the tiny creature has to finish the pit and turn it into an entrance-window.