By the time that July is nearly over the Anthrax has finished eating the Bee-grub. From that time until the following May it lies motionless in the Mason-bee’s cocoon, beside the remains of its victim. When the fine [[259]]days of May arrive it shrivels, and casts its skin; and it is then that the pupa appears, fully clad in a stout, reddish, horny hide.
The head is round and large, and is crowned on top and in front with a sort of diadem of six hard, sharp, black spikes, arranged in semi-circle. This sixfold ploughshare is the chief digging-implement. Lower down the instrument is finished off with a separate group of two small black spikes, placed close together.
Four segments in the middle of the body are armed on the back with a belt of little horny arches, set in the skin upside down. They are arranged parallel to one another, and are finished at both ends with a hard, black point. The belt forms a double row of little thorns, with a hollow in between. There are about two hundred spikes on the four segments. The use of this rasp, or grater, is obvious: it helps the pupa to steady itself on the wall of the gallery as the work proceeds. Thus anchored on a host of points the brave pioneer is able to hit the obstacle harder with its crown of awls. Moreover, to make it more difficult for the instrument to recoil, there are long, stiff bristles, pointing backwards, scattered here and there among the rows of spikes. There are some also on other segments, and on the sides they are arranged in clusters. Two more belts of thorns, less powerful than the others, and a sheaf of eight spikes at the tip of the body—two of which are longer than the [[260]]rest—completes the strange boring-machine that prepares an outlet for the feeble Anthrax.
About the end of May the colouring of the pupa alters, and shows that the transformation is close at hand. The head and fore-part of the creature become a handsome, shiny black, prophetic of the black livery worn by the coming insect. I was anxious to see the boring-tools in action, and, since this could not be done in natural conditions, I confined the Anthrax in a glass tube, between two thick stoppers of sorghum-pith. The space between the stoppers was about the same size as the Bee’s cell, and the partitions, though not so strong as the Bee’s masonry, were firm enough to withstand considerable effort. On the other hand the side-walls, being of glass, could not be gripped by the toothed belts, which made matters much harder for the worker.
No matter: in the space of a single day the pupa pierced the front partition, three-quarters of an inch thick. I saw it fixing its double ploughshare against the back partition, arching itself into a bow, and then suddenly releasing itself and striking the stopper in front of it with its barbed forehead. Under the blows of the spikes the pith slowly crumbled to pieces, atom by atom. At long intervals the method of work changed. The animal drove its crown of awls into the pith, and fidgeted and swayed about for a time; then the blows began again. [[261]]Now and then there were intervals of rest. At last the hole was made. The pupa slipped into it, but did not pass through entirely. The head and chest appeared beyond the hole, but the rest of the body remained held in the tunnel.
The glass cell certainly puzzled my Anthrax. The hole through the pith was wide and irregular: it was a clumsy breach and not a gallery. When made through the Mason-bee’s walls it is fairly neat, and exactly of the animal’s diameter. For narrowness and evenness in the exit-tunnel are necessary. The pupa always remains half-caught in it, and even pretty securely fixed by the graters on its back. Only the head and chest emerge into the outer air. A fixed support is indispensable, for without it the Anthrax could not issue from her horny sheath, unfurling her great wings and drawing out her slender legs.
She therefore remains steadily fixed by the graters on her back, in the narrow exit-gallery. All is now ready. The transformation begins. Two slits appear on the head: one along the forehead, and a second, crossing it, dividing the skull in two and extending down the chest. Through this cross-shaped opening the Anthrax Fly suddenly appears. She steadies herself upon her trembling legs, dries her wings and takes to flight, leaving her cast skin at the doorway of the gallery. The sad-coloured [[262]]Fly has five or six weeks before her wherein to explore the clay nests amid the thyme and to take her small share of the joys of life.