672 EXTERNAL ANATOMY OF INSECTS. 
that in all those insects in which the fore-legs are calcu- 
lated for digging or seizing their prey, as in the Petalo- 
cerous beetles, the Gryllotalpa, Mantis, &c., this joint 
of the leg is usually much enlarged and more conspicu- 
ous than the others. 
As to its figure and shape—most commonly the #zbza 
grows thicker from the base to the apex, as in the ma- 
jority of Coleoptera, Hymenoptera, &c.; in the Ortho- 
ptera, Neuroptera, &c., it is generally equally thick every 
where. Another peculiarity relating to this head ob- 
servable in it, is its tendency to a trigonal figure: this, 
however, though very general, is not universal ;—thus, 
in some Orthoptera, as Pterophylla, its horizontal section 
is quadrangular; in others, as Locusta Leach and many 
other insects, it is nearly a circle; in some scorpions it 
is almost a hexagon. The superficial shape also of this 
joint in numerous instances is more or less triangular, 
but it sometimes recedes from this form :—thus, in Ce- 
rambyx phyllopus it is a segment of a circle; in some 
Empides it is clavate; in Onztis Sphinz, dolabriform ; in 
the Orthoptera, Neuroptera, &c., it is usually linear; in 
some Lyga@i it is angular*: but the most remarkable 
tibi@ in this respect are those of such species of this last 
genus as have the posterior ones winged or foliaceous, 
so that they resemble the leaf of some plant—the tzbza 
being the rachis, and the wing (which in some species 
is veined) representing the leaf itself. This structure is 
exemplified in Rhinuchus compresstpes, Petalopus phyllo- 
pus, foliaceus, &c.” Under this head I must say a few 
* Stoll Punaises, t. x. f. 67. t. xvi. f. 114. 
b Ibid. t. ii. f. 14. t. viii. f. 54. t. xxviil. f. 201. Prate XY. 
Fic. 2. See above, Vor. iI. p. 348. 
