EXTERNAL ANATOMY OF INSECTS. 567 
cumstance be divided into several families. ‘Thus in 
C. Molossus and affinities its termination represents the 
letter 4 reversed, or a triangle surmounted by a mucro ; 
in C. orientalis, &c., it ends in an acute-angled triangle ; 
in C. lunaris, &e., in an obtuse-angled one; and in C. 
Lacchus, &c., in the segment of a circle. 
The part we are considering is not so important in 
the other Orders. In the Orthoptera, however, it is 
occasionally remarkable. In Acrida viridissima attached 
to the anterior margin of the peristethium are two long 
triangular pieces which appear to represent this part; 
in the kindred subgenus, Conocephalus*, it is a single 
piece bifid at the apex; in Gryllotalpa it is a very ele- 
vated hairy ridge; and in Locusta, it is a flat anterior 
process of the mesostethium. In the Heteropterous He- 
miptera this part is often merely a portion of the chan- 
nel in which the promuscis reposes; but sometimes, as 
in Edessa, it is an elevated piece varying in its termina- 
tion. Inthe remaining Orders, as far as I have had an 
opportunity to examine them, it can scarcely be said to 
exist separately from the medipectus, except that in Z7- 
pula a bipartite subtriangular membranous piece seems 
to be its analogue. 
We are now to consider the last segment of the ali- 
trunk, which, as a whole, may be denominated the po- 
druncus ; it bears the second pair of the organs of flight, 
and the last pair of legs. The upper side of this is the 
metathorax, and its lower side the postpectus. 
9. Postdorsolum’. The first external piece of the 
2 | would restrict this name to the conical-headed Locuste F. 
> Prare VII IX. ¢. Linn. Trans. xi. t. ix. f. 16. c. 
