674 EXTERNAL ANATOMY OF INSECTS. 



exemplified in Lygaas compressipes, phyllopus, foliaceus, 

 &c. a Under this head 1 must say a few words upon 

 the Jlexure of this joint, which in some cases merits no- 

 tice. I have before mentioned its bend at the knee b or 

 base : the apex also is sometimes incurved — in the ante- 

 rior one of the male ofMacropus longimanus so as almost 

 to form a hook c : in Lygceus Pharaonis the posterior pair 

 are flexuose d ; in Bruchus Bactris, Leucospis, and several 

 species of Chalcis, these tibia curve so as to adapt them- 

 selves to the bend of the thigh when folded. The notch 

 on the inside of the anterior pair, in a large majority of 

 Carabus L., armed above by a spur e , a structure which 

 probably assists them in seizing and detaining their prey, 

 may also here be introduced : in the generality it is a lit- 

 tle removed from the apex of the joint in question; but 

 in Pamborus it is very near to it, and in Cychrus, Caret* 

 bus, &c, it becomes obsolete. I may mention here also 

 a singular character which distinguishes the cubit of both 

 sexes of Gryllus campestris, domesticus, &c. At the base 

 there is an aperture which passes through the joint — an- 

 teriorly it is oval, and posteriorly elliptical and much 

 larger, and on both sides is closed by a tense membrane. 

 The most striking peculiarities as to the clothing of 

 his joint have been chiefly noticed under the sexual cha- 

 racters of insects f , but some appear not to be of that de- 

 scription. In Sphceridium Leach, while the thighs and 

 tarsi are naked, the posterior tibiae are remarkably beset 



a Stoll Punaises, t. ii. /. 14. t. viii./. 54. t. xxviii. /. 201. Plate 

 XV. Fig. 2. b See above, p. 6/1. 



e Oliv. Iris. n. 66. t. iii. /. 12. Compare Scarabceus longimanus, 

 Ibid. n. 3. t. iv.f. 27- d Stoll Punaises, t. iii./. 20. 



* Plate XXVII. Fig. 31. * See above p. 306 — 



