550 EXTERNAL ANATOMY OF INSECTS. 



the table the prophragm, which enters the chest and se- 

 parates the cavity of the mesothorax from that of the pro- 

 thorax ; now in Hymenoptera this septum is a process 

 of the piece behind the collar, and excludes it from 

 having any share in that cavity. These arguments at 

 first sight seem to prove satisfactorily the identity of the 

 collar and prothorax. But audi alteram partem, and I 

 think you will allow that the scale containing the claims 

 of the collar to be considered as a piece sui generis, dips 

 much the lowest. And, first, I must observe, that 

 though in Hymenoptera the collar seems to replace the 

 prothorax by its situation, yet it is in fact a part of the 

 alitrunk ; for, if the manitrunk be separated from the lat- 

 ter, the collar remains, in most cases, attached to it a , 

 while the aidepectus and arm, with the ligament that covers 

 its cavity above, the real representative of the prothorax, 

 are easily removed, and this in recent individuals: as a 

 further proof of this, I must request you will examine a 

 neuter Mid Ma ; you will see that in this the collar is 

 not separated from the alitrunk in any respect, but forms 

 one piece with it, while the antepectus is distinct and 

 capable of separate motion : further, the action of the 

 collar is upon the alitrunk, it being of essential import- 

 ance in Might, whereas the prothorax is of no other im- 

 portance than as a counterpoise to that part 5 . A further 

 argument to prove the distinction of these parts may be 

 drawn from the case of Xylocopa, a kind of bee. In this 

 genus the collar forms a complete annidus or segment of 



a In CMorion, Ammophtia, &c, this part separates more readily 

 from the alitrunk. 



b Chabrier Sur le Vol des Ins. c. i. 413-. c. iv. 54. This author 

 seems to regard the collar as something peculiar to Hymenoptera. 



