660 EXTERNAL ANATOMY OF INSECTS. 
noticed when I treated of the sexes of insects ?, J shall not 
here repeat my observations, but confine myself to cases 
not then adverted to. Some insects have all their legs 
very hairy, as many spiders, the diamond-beetle (Entimus 
imperialis), or at least a species very near it and com- 
mon in Brazil, &c.: in others they are nearly naked, 
as in the stag-beetle. In the Crepuscular Lepidoptera 
(Sphinx L.) and some of the Nocturnal ones (Bombyx L.) 
the thighs are much more hairy than the rest of the legs : 
and in Lucanus, Geotrupes, and many other Lamellicorns, 
&c., the anterior ones have a yellow or golden spot at 
their base, composed of decumbent hairs, which prevent 
them from suffering by the violent friction to which they 
are exposed in burrowing. In most Petalocerous beetles 
the tibize are set with scattered bristles, and sometimes 
the thighs. The Tiger-beetles (Czczndela) are similarly 
circumstanced : but the bristles, which are white, are ge- 
nerally arranged in rows. In Dytiscus, Hydrophilus, &c., 
the four posterior tarsi; and in Notonecta the posterior 
pair, and also the tibize—are fringed on each side with a 
dense series of hairs, which structure assists them in 
swimming °. The tarsi, especially the anterior pair, in a 
certain family of Lamia (Ll. papulosa, &c.*), are simi- 
larly fringed, only the hairs curl inwards; and the hand 
in Sphex and Ammophila, but not in Pelopeus and Chlo- 
rion, is fringed externally with long bristles. 
7. Composition. With regard to their composition, 
both arms and legs generally consist of five pieces, which 
* See above, p. 305—. > This variety appears to differ 
very little from the Curculio imperialis of Fabricius and Olivier, ex- 
cept in the remarkable hairiness of its legs. ° Vor. II. p. 359. 
@ Oliv. Ins. n. 67. t. xx. f. 156. 
Ae eT 
