EXTERNAL ANATOMY OF INSECTS. 543 
the external appearance of a quite different tribe*; in 
others again it is dehind them, as in most of the Lamel- 
licorn beetles. In the common dung-chafer (Geotrupes 
stercorarius), it is a hairy process, which, when the head 
is bent downwards, is received by a deep cavity of the 
mesosternum. ‘The Dynastide may always be known 
by a columnar prosternum rising vertically between the 
arms and the medipectus. . Lastly, in other tribes there 
is a prosternal elevation both Jdefore and behind the 
arms, as in Trachyderes succinctus, dimidiatus, and affini- 
ties. Of the second description, those that have a less 
elevated horizontal prosternum, the point in most is to 
the anus, but in some to the head: thus in the ground 
beetles (Hutrechina) it is generally a subspathulate flat 
piece, the point of which slides over the mesosternum, or 
covers it; but in Acznopus megacephalus», one of this 
tribe, though similarly shaped, its point is to the head. 
These horizontal prosterna vary in their termination. In 
that of the ground beetles the apex is obtuse; in that of 
Elater, above described *, and Dyfiscus it is acute ; in 
Prionus lineatus, Xyloborus Spencit K. MS., &c., it is b7- 
lobed; and in Buprestis variabilis, attenuata, &c., obso- 
letely ¢ralobed. With regard to the other Orders no 
striking features of this part are observable, except in 
some Orthoptera. In Acrida viridissima it is represented 
by two long filiform vertical processes ; and in Locusta by 
a single conical horn‘, mistaken by Lichtenstein for a 
process of the throat *. In one instance, Gryllotalpa, this 
* Kirby in Linn. Trans. xiv. t. iii. f. 4.1. 
> It is doubtful whether M, Latreille’s Harpalus megacephalus is 
synonymous with Carabus megacephalus Fab, Comp. Gen. Crust. et 
Ins. 1. 206. with Syst. Eleuth, i. 187. 95, © Vor. IL. p, 314—. 
d Prave VILE; Pies th. & © Linn. Trans. iv. 53. 
