Thorax in winged Insects. 175 
which have not been distinguished by Mr. Kirby. Between the episterna 
and the squamulz is a small piece called by M. Chabrier the clavicle. It 
is not, however, the clavicula of Mr. Kirby. As however it, like the 
squamula, does not properly belong to the thorax, being a rudimentary 
bone of the wing, I shall not say more of it until I come to treat of the 
Comparative Anatomy of the Wings of Insects in a future paper.* 
4. The epimera of the mesothorax are two sub-quadrangular pieces. 
Three of thesides of an epimeron are bounded by the episternum of the 
mesothorax in front, by the mesosternum below, and by the pectus of the 
metathorax behind; the upper side being bounded by the rudimentary 
bones of the wing and by part of that lateral process of the postscutellum 
of the mesothorax which joins the scutellum of the same. In my draw- 
ing of the medipectus I have carefully avoided representing any part of 
the postscutellum, because it belongs to the tergum. The point of junc- 
tion, however, with the epimeron is marked.t Mr. Kirby has noticed 
the epimera when he very correctly states that ‘in Vespa asmall sub- 
* triangular piece just below the base of the upper wing is probably 
“ analogous to the scapularia in Coleoptera ;” scapularia being appa- 
rently his name for the epimera of the mesothorax. 
3. OF THE PECTUS OF THE METATHORAX. 
This consists of the usual parts, but I cannot here pretend to make 
Mr. Kirby’s nomenclature harmonize with M. Audouin’s. I shall there- 
fore describe the parts in the usual way. 
1. The metasternum is subquadrate, carinated above, and having a 
small slit below in the middle. The anterior angles are elevated. It is 
a very conspicuous piece, yet Mr. Kirby denies its existence.} 
2. The postfurca is composed of two branches, which run off from 
a strong base to meet the junction of the metasternum with its episterna.§ 
3. The episterna are two sub-triangular pieces, each situated close 
* The first pair of stigmata are situated between the collar and the clavicles 
of M. Chabrier. See fig. 1, y. 
+ Fig. 9, R. 
t Fig. 5and10, P. Also see Int, to Ent,, Vol. IIL, p. 383. 
§ Fig. 10, W. 
