EXTERNAL ANATOMY OF INSECTS. 397 



white, like Oniscidce ; while those of the Scolopendridce 

 retain it. 



ii. 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 Tetyra F. (Scutellera Latr.), a kind 

 of bug, are as broad as they are long 3 ; in the genus 

 Gonyleptes K. b amongst the Aptera, and Epeira cancri- 

 Jbrmis, a crab-shaped spider, the breadth exceeds the 

 length ; in Cy?iips, and several other Hymenoptera, in 

 Acrida K. c (Locust a F.), and other Orthopterous in- 

 sects, the depth exceeds the breadth ; and in that singu- 

 lar beetle, JEurychora ; the cockroach (Blattci), &c. the 

 upper surface is flat. 



iii. The scidpture 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, 

 many important purposes, that at first sight do not strike 

 the observer, may be served : such as giving firmness 

 to the crust in those places where it is most wanted ; di- 



a Coquebert Ittustr. Icon. ii. t. xviii./. 14, 15. 



b Linn. Trans, xii. t. xxii./. 1 6. 



c This name I would give to Locusta F., reserving, with Dr. Leach, 

 the latter name to the true locust (Gryllus F.). The name Conoce- 

 phalus,by which Locusta¥. has been distinguished, is better restricted 

 to those with a conical head. 



