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In many butterflies the fore legs are small and shortened, and of little use, and held pressed against the breast. In the Lycænidæ the fore tarsi are without claws; in Erycinidæ and Libytheidæ the fore legs of the males are shortened, but completely developed in the females, while in the Nymphalidæ the fore legs in both sexes are shortened, consisting in the males of one or two joints, the claws being absent in the females. Among moths loss of the fore tarsi is less frequent. J. B. Smith^[21] notices the lack of the fore tarsi in the male of a deltoid, Litognatha nubilifasciata (Fig. 113), while the hind feet of Hepialus hectus are shortened. In an aphid (Mastopoda pteridis, Esl.) all the tarsi are reduced to a single vestigial joint (Fig. 114).

Fig. 113.—Leg of Litognatha: cx, coxa; f, femur; t, tibia; ep, its epiphysis, and sh, its shield-like process. The tarsus entirely wanting.—After Smith.

Entirely legless adult insects are rare, and the loss is clearly seen to be an adaptation due to disuse; such are the females of the Psychidæ, the females of several genera of Coccidæ (Mytilaspis, etc.), and the females of the Stylopidæ.