Thorax in winged Insects. 171 
5. The paraptera of the mesothorax are two small suborbicular pieces 
situated immediately above the rudimentary bones of the wing, and being 
at this point free, are bounded by the base of the wing below and by 
the scutum of the mesothorax above.* 
3. Or THE TERGUM OF THE METATHORAX. 
An Hymenopterous Insect, provided as it is with under wings and 
posterior feet, ought to have the tergum of the metathorax well deve- 
loped, and accordingly we find its four pieces all distinct. 
1. The prescutum of the metathorax is in Polistes transverse, and in 
immediate connexion with the scutellum of the mesothorax except at the 
angles: having, as we have shewn, displaced the postscutellum of the 
mesothorax, which is only connected with the said scutellum at the an- 
gles. The manner in which this curious process takes place can only be 
completely understood on a dissection of the parts. It isthe postdorso- 
lum of Kirby, t only that this naturalist makes the posterior point of it 
correspond with that part in Coleoptera which is the centre of the scutel- 
lum of the metathorax.t 
2. The scutum of the metathorax is in Polistes internal and con- 
cealed, taking a vertical direction so as to form a septum.§ It still, how- 
ever, preserves the essential character of the part, that of articulating with 
the wings. Externally indeed there is nothing apparent of it but the 
margin or edge, which is the line that separates the prescutum of the 
metathord from the scutellum of the same. Internally however it is more 
* Fig. 9, T. 
+ And demi-ceinture of M. Chabrier. See Int.to Ent. pl. rm. fig. 11. 2’, 
where, in fact, if Mr. Kirby had been inclined to generalize, it ought to have 
been called by him the mesophragma. In my drawings of Polistes it is fig. 5, 
H. «In some species of Formicidz this piece, as well as the scutum, is evanes- 
cent, owing to the great developement of the scutellum of the mesothorax. 
{ It is this mistake which has caused the whole description of the metatho- 
rax in Mr. Kirby’s work to be so inaccurate. 
§ M. Chabrier does not seem to have clearly detected this piece, I have re- 
presented it as it occurs in Polistes, fig. 6,1, where it is seen from the interior, 
It is not, however, always of this form in Hymenoptera, nor always concealed ; 
for in some genera, as for instance, in Pepsis, Fab,, it is externally as consp i- 
cuous as the prascutum of the metathorax. 
