396 EXTERNAL ANATOMY OF INSECTS. 
white, like Oniscide ; while those of the Scolopendride 
retain it. 
il. The form of insects is so variable, that it can be 
reduced to no other general rules—than that, for the 
most part, the length exceeds the breadth, and the 
breadth the depth, and that the upper surface is usually 
convex. But to these rules there are numerous excep- 
tions. Thus many Scutellere, a kind of bug, are as 
broad as they are long?; in the genus Gonyleptes” 
amongst the Aptera, and Carkinodes cancriformis, one 
of the crab-shaped spiders*, the breadth exceeds the 
length; in Cynips, and several other Hymenoptera, in 
Acrida*, and other Orthopterous insects, the depth ex- 
ceeds the breadth; and in that singular beetle, Eury- 
chora ; the cockroach (Blatta), &c. the upper surface is 
flat. 
ili. The sculpture of the integument of insects is often 
very remarkable ; but as this will call for attention here- 
after, I shall only here observe in general, that ornament 
and variety seem not to be the sole object of those eleva- 
tions and depressions which form so prominent a feature 
of many of the animals in question ; for by means of these, 
@ Coquebert Ilustr. Icon. ii. t. xvill. f. 14, 15. 
> Linn. Trans. xii. t. xxii. f. 16. 
° These spiders form a distinct genus: I therefore separate them » 
from Epeira under the above name, from xaexivos Cancer. 
¢ This name I would give to Locusta F., reserving, with Dr. Leach, 
the latter name to the true locust (Gryllus F.). ‘The name Conoce- 
phala, by which Locusta F. has been distinguished, is better restricted 
to these with a conical head, 
