EXTERNAL ANATOMY OF INSECTS. 707 
them*. In some insects the piece we are considering 
appears to consist of fwo segments; in the male of Lo- 
custa morbillosa the whole podex is rhomboidal, but it 
is formed by two triangular pieces which articulate with 
each other; this structure permits the more easy eleva- 
tion of the terminal one for the extrusion of the feces. 
Ventral Segments», We are now to turn our atten- 
tion to the ventral segments of the abdomen. The first 
of them is what is called the epigastrium* in the table. 
This part, according to M. Chabrier, is of considerable 
importance to the animal in flight, as, by its pressure 
against the trunk, not only regulating the movements of 
the abdomen, but as, in his opinion, contributing to push 
forward the trunk in the descent of the animal. It is 
remarkable only in the Coleoptera and Heteropterous 
Hemiptera, to which my observations upon it will be 
confined. It may be stated as usually consisting of two 
articulations, that nearest the trunk being narrow, and 
in the Predaceous beetles‘, as also in Scutellera, Penta- 
toma, &c., interrupted in the middle‘. In many La- 
mellicorns this joint is concealed under the posterior 
core, and with the anterior part of the second forms a 
hollow cavity for their reception; this last joint is what 
is properly the Zpigastrium, the former, especially when 
* Daldorf(Asiat. Trans. vii.) has divided Geotrupes into two fami- 
lies, one with the podex covered (G. vernalis, &c.) which he calls 
modesti, the other with it wncovered (G. stercorarius, &c.) which he 
calls obsceeni. > Prate VIII. £’. 
£ Ibid. 2); ‘ Sur le Vol des Ins. c. i. Addend. 299. 
¢ In Dytiseus marginalis the upper side of the margin of the Hy- 
pochondria is curiously cut into transverse corrugations. 
f Prate VIII. Fic. 6. C'. 
FATED, 
