Thorax in winged Insects. 169 



Mr. Kirby's " most powerful argument" for the collare not belonging to 

 the prothorax is the fact that in Vespa and certain other insects, where the 

 mesothorax is excessively developed, there is both a prothorax (meaning 

 thereby a scutum) and a collare.* And so there would be in the pro- 

 thorax of every winged insect, if perfectly developed, as may be learned 

 from the prothorax of a Gryllus, or the study of M. Audouin's observations. 

 Therefore this " powerful argument" cuts the wrong way. 



In Polistes the scutellum of the prothorax is emarginate, offering a large 

 sinus in the middle, which embraces two sides of the sub-pentagonal 

 scutum of the mesothorax. 



2. Of the Tergum of the Mesothorax. 



1. The preBscutum of the mesothorax is the first piece that comes 

 under our notice.f Under the name of prophragma it is mentioned by 

 Kirby as existing in Hymcnoptera, and so separating, as it ought to do, 

 the collare from the scutum of the mesothorax. It is an internal and 

 vertical piece.J 



2. The scutum, whether the collar be apparent or not, is therefore the 

 second piece of the mesothorax.§ It appears externally joined to the 

 collare, the sides of which embrace it. It is, as Mr. Kirby observes, ex- 

 cessively developed in Hymenoptera, and forms indeed the most con- 

 spicuous piece of the thorax. || 



3. The scutellum of the mesothorax, the third piece,5[ and also 

 externally conspicuous in our Polistes, follows the scutum.** It is the 

 postdorsum of M. Chabrier. 



• From this remark it would appear that Mr. Kirby is not aware that the 

 prothorax is a compound piece as well as the mesothorax and metathorax. 



t Fig. 4 and fig. 5, E. J See Int. to Ent, Vol, III, p. 549, 



§ Fig. 4 and fig. 5, F. 



II By looking at some Hymenoptera, where this piece is most developed, it 

 would almost seem to be composed of three confluent pieces, the two lateral 

 yet requiring a name. I suspect, however, not having yet dissected a Chalets 

 carefully, that these last pieces are a third pair of paraptera, possibly those be- 

 longing to the prothorax, pushed out of their proper place. 



f Fig. 4 and fig. 5, G. 



*♦ On the subject of this piece, Mr. Kirby gives his only citation of M. 



