How and why do these “beans,” or, rather, fruit-segments (for they are not beans), move in this determined purposeful manner? The whole proceeding has a mysterious and uncanny aspect. They have no legs, no spring; they are simple little smooth capsules, and yet they jump and seemingly “walk” about. The explanation is that there is a grub inside each so-called “bean.” Cut one of the beans or capsules open, and you find that it is a very thin-walled and hollow case, but coiled on itself in the cavity you open, and about half filling it, is a yellowish white grub (Figs. 52 and 53). It is not a “maggot,” but a “caterpillar,” that is to say, it is not legless, but has eight pairs of legs—namely, three pairs of short walking legs in front, four pairs of sucker-like legs, and a hinder pair of larger size called “claspers.” It has a hard brown plate on its head, and possesses hard jaws. It refuses to leave the opened capsule, and crawls back again if forcibly removed, and in the course of a few hours spins a silken cover to replace the piece of “shell” you have cut away. Mr. Rollo has lately succeeded in getting the caterpillar to patch up its injured residence with a thin piece of glass, such as is used by microscopists, which he put in place of a side of the capsule removed by a knife. He was thus able subsequently to watch through the glass the movements of the little creature when it causes the mended capsule or “bean” to jump. It rears itself from the lower surface of the capsule, and gives a series of sharp blows to the roof, projecting its body with each blow, and thus overbalances the capsule, or, if the flat side is lying downwards, jerks it along much as one may sit with one’s feet on the rail of a chair and cause it to jerk along the floor by the swinging movements of the body. The caterpillar does not die at once when removed from the capsule; it has been kept alive in a glass tube for a month. [Illustration: FIG. 53.—The caterpillar of the moth, _Carpocapsa saltitans_, removed from the jumping bean: magnified three diameters. Observe the jaws (with which the circular plate is cut in the bean before the grub becomes a chrysalis), eyes, three pairs of pointed legs, four sucker legs placed in the middle region, and followed by three segments without legs, and a terminal segment with a pair of suckers. (Drawn from nature for this work.)]