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. Of 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 prcBScutum 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 is the postdorso- 

 lum of Kirby, f 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. J 



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 prasscutum of the 

 metathorax from the scutellum of the same. Internally however it is more 



* Fig. 9, T. 



t And demi-ceinture of M. Cliabrier. See Int. to Ent. pi. ix. fig. 11. <', 

 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 Formicidie this piece, as well as the scutum, is evanes- 

 cent, owing to the great developement of the scutellum of the mesothorax. 



J 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 Poliste.i, fig. 6, 1, where it is seen from the interior. 

 It is not, however, always of this form in Hymenopteia, nor always concealed ; 

 for in some genera, as for instance, in Pepsin, Fab., it is externally as conspi- 

 cuous as the praescutum of the metathorax. 



