In a few insects one of the claws of each foot is atrophied, as in the feet of the Pediculidæ, of many Mallophaga, all of the Coccidæ, in Bittacus, Hybusa (Orthoptera), several beetles of the family Pselaphidæ, and a weevil (Brachybamus). Hoplia, etc., bear but a single claw on the hind feet, while the allied Gymnoloma has only a single claw on all the feet. Cybister has in general a single immovable claw on the hind feet, but _Cybister scutellaris_ has, according to Sharp, on the same feet an outer small and movable claw. In the water bugs, Belostoma, etc., the fore feet end in a single claw, while in others (Corisa) both claws are wanting on the fore feet. Corisa also has no claws on the hind feet; Notonecta has two claws on the anterior four feet, but none on the hind pair. In Diplonychus, however, there are two small claws present. (Kolbe.) [Illustration: FIG. 110.—Last tarsal joint of _Melolontha vulgaris_, drawn as if transparent to show the inner mechanism: _un_, claws; _str_, extensor plate; _s_, tendon of the flexor muscle; _vb_, elastic membrane between the extensor plate and the sliding surface _u_; _krh_, process of the ungual joint; _emp_, extensor spine, and _th_, its two tactile hairs.—After Ockler, from Kolbe. ] Among the Scarabæidæ, the individuals of both sexes of the fossorial genus Ateuchus (_A. sacer_) and eight other genera, among them _Deltochilum gibbosum_ of the United States, have no tarsi on the anterior feet in either sex. The American genera Phanæus (Fig. 111), Gromphas, and Streblopus have no tarsal joints in the male, but they are present in the female, though much reduced in size, and also wanting, Kolbe states, in many species of Phanæus. The peculiar genus Stenosternus not only lacks the anterior feet, but also those of the second and third pair of legs are each reduced to a vestige in the shape of a simple, spur-like, clawless joint. The ungual joint is wanting in the weevil Anoplus, and becomes small and not easily seen in four other genera.