78 PARTIAL ORISMOLOGY. 



that some insects (Fespa, Cimbex) possess both a collar and a prono- 

 tum ; and that in others (Xylocopa), the collar forms a complete ring. 

 Their first observation is perfectly correct, but not convincing; it 

 frequently happens that the first segment of the thorax is more 

 strongly affixed to the thorax than to the abdomen, and remains attached 

 to the former when we wish to separate the latter (Hister, Gryllus, 

 Gryllolalpa, &c. &c.); the same remark may be made with respect 

 to the COXCB, and with still greater latitude, but which are, notwith- 

 standing, joints of the legs : why should not, therefore, the pronotum 

 occasionally be affixed more firmly to the second segment of the thorax 

 than to the prosternurn ? The second observation is absolutely erro- 

 neous ; for what Kirby and Spence consider as their prolhorax, (our 

 pronotum), is sometimes the extended membrane of the neck (Fespa, 

 Cimbex), sometimes a plate, as in the Libellulina, representing the 

 anterior part of the mesonotum ; and which, in the Coleoptera, is 

 covered by the pronotum. The third observation is also imaginary, 

 for proportions of that kind are always the peculiarities of entire 

 families ; and this conformation of the prothoracic segment is found 

 as little among the rest of the bees as in Xylocopa. Whereas, on 

 the contrary, the following reasons clearly prove this part to be the 

 pronotum : 



1st. In all those orders which possess a collar, the pronotnm would 

 necessarily be deficient, as they possess no part excepting this which 

 responds to it. On the other side these orders would have a cor- 

 neous part more upon the mesothoracic segment than any of those 

 provided with a distinct and free prothorax, in which we in vain seek 

 upon the mesothoracic segment for a part analogous to the collar. 



2ndly. That Kirby and Spence's collare is our pronotum, is proved 

 incontestibly by the circumstance, that, upon its separation from the 

 second segment, there is a spiracle. We observe this spiracle very 

 distinctly in the Diptera (PI. XIV. No. 1, f. 2, a), which shows us 

 very evidently the limits of the prothorax, for which, without this 

 indication, we might look in vain, as the entire order is deficient in a 

 clear separation of the plates of the thorax. (See also PI. XIV. 

 No. 2, f. 2, .) In the Hymenoptera and Lepidoptera, this spiracle 

 lies beneath the patagitim, and, in the former (Fespa, Scolia, &c.), 

 appears as a distinct opening beneath the superior wing. This process, 

 which forms a sort of flap, may be called TILE (tegula), for the organ 

 which Kirby and Spence have so called is the same with their patagium 



