12 MR. A. HAMMOND ON THE 



that the part here referred to as overreaching the spiracle, and 

 described as part of the mesothoracic tergum, is none other than 

 Burmeister's humerus. I shall give reasons for thinking that 

 Burmeister's view is the correct one*. The anterior portion of 

 the dorsal surface is formed by a rectangular plate, the anterior 

 angles of which are cut off by the humeri. In front it extends 

 almost to the margin of the cephalothoracic foramen, its central 

 portion being only separated therefrom by the narrow ring of the 

 prothorax. Behind the humeri it extends the whole breadth of 

 the dorsal surface, and is bounded behind by a straight transverse 

 suture just in front of the articulation of the wings. From the 

 circumstance that this piece is distinctly marked off from the fol- 

 lowing portion by a very evident external furrow and internal 

 ridge, and, moreover, from the fact that it lies wholly in front of 

 the articulation of the wings, I believe that it is the homologue 

 of that part which in the Coleoptera especially is seen to occupy 

 a similar position, viz. the praescutum, though in this order, as 

 illustrated chiefly in the metathorax, it is bent inward to form the 

 mesophragma. Following the prsescutum is the large dorsal plate, 

 the scutum, to which, as in all other insects, the wings are attached ; 

 and this is again followed by the prominent and subtriangular scu- 

 tellum, to which belong the alulets. These parts are shown in 

 my figure 1, Plate I. 



We will now look at the thorax from a lateral point of view as 

 illustrated in Plate I. fig. 6. We here notice first the parts 

 already mentioned, and in addition the following, viz. first, the 

 anterior spiracle immediately behind the humerus, which is fol- 

 lowed by a large subquadrangular plate, bounded in front by the 

 spiracle, above by the prsescutum, beneath by the sternum, and 

 behind by a smaller plate to be presently described. Mr. Lowne 

 (I. c.) has called this piece the episternum ; but although its rela- 

 tion to the sternum would seem to justify this appellation, there 

 are yet circumstances which seem to me decidedly to remove it 

 from the piece so designated by Audouin. It will be noticed 

 that, like the prsescutum, it is wholly and entirely anterior to the 

 wing-socket, the latter being situate behind its superior posterior 

 angle ; and in this important respect it differs entirely from the piece 

 which in all the Coleoptera I have been enabled to identify with 

 Audouin' s episternum. It appears to me probable that this plate is 



* Postea, p. 22. 



