382 EXTERNAL ANATOMY OF INSECTS. 
C. Metasternum (the Metasternum). The central and 
often elevated part of the Mesostethium. Its anterior 
mucro, in Coleoptera, often meets the posterior one 
of the Mesosternum, and sometimes appears to form 
one piece with it, as in Hydrophilus, and many 
Lamellicorn beetles. Sometimes, as in Gnathocera 
witticollis, it even passes between the arms, and covers 
the Prosternum, or supplies its place. Behind, it 
often terminates in a bifid mucro. It is not present 
in many Orders: as in the Hymenoptera, Diptera, 
&e.? It includes the Pectines. 
a. Prctines (the Pectines). Two moveable processes, 
fixed one on each side by its base below the posterior 
legs to the Metasternum in Scorpio: on the lower side 
is fixed a series of parallel biarticulate processes, re- 
sembling the teeth of a comb °. 
D. Postrurca (the Postfurca). A process of the En- 
dosternum, terminating in three subhorizontal acute 
branches, resembling the letter Y, and forming an 
acute angle with the Endosternum, to which the 
muscles that move the hind-legs, &c. are affixed °. 
E. Oprercuta (the Opercula). Plates that cover the 
vocal spiracles in humming insects; and likewise 
two large cartilaginous plates fixed to the posterior 
part of the Postpectus, which cover the Tympana 
in male Cicade‘. Perhaps these may be re- 
garded as a kind of Metapnystega in a new situ- 
ation. 
F. Pepes Postici (the Hind-legs). The pair of legs 
2 Prares VIII. IX. et. > Prate XXVII. Fie. 50. 
© Prate XXII. Fic. 5. 6 +. 
4 Prats VIII. Fie. 18.; and XXII. Fre. 13. ct. 
