THE THORAX. 81 



such excrescences upon the mesonotum (Clilellarid'). The prominences 

 upon the surface of the mesonotum (for example, in Cimbex, Sircx, 

 Tabanus, Asilus, &c.) arise from the insertion of the muscles ; the 

 furrows which separate them correspond with similar ridges upon the 

 interior, which the bundles of muscles embrace. A great partition, of a 

 horny substance, separates superiorly the cavity of the second thoracic 

 segment from the first ; it descends from the upper side of the dorsal 

 piece, in greater or less distension, and likewise serves for the insertion 

 of the muscles of the back. Kirby and Spence call it PROPHRAGMA. 

 At its superior edge the membrane is affixed, which unites the first and 

 second segments. 



77- 



The SCAPULAE are contiguous to the mesonotum (PI. IX., &c., D, D). 

 On each side, in front, close to the mesonotum, they assist to form the 

 articulating socket of the superior wings (pteropega, Kirby and Spence), 

 and they here contract themselves, that they may pass into the cavities 

 of the prothorax in those orders which have a distinctly separated pro- 

 thorax, and with their opposite wing they pass down the sides of the 

 mesothoracic segment. They consequently fall into two divisions, 

 which may be distinguished as the anterior and posterior wings of the 

 scapulffi (ala scapulae anterior et posterior). Beneath and beyond the 

 posterior wings of the scapulae, in the Coleoptera, is found the spiracle 

 of the second thoracic segment ; it is entirely covered by it, which 

 explains why it has been hitherto overlooked. Straus- Durckheim dis- 

 covered it, and has distinctly shown its situation*. My attention being 

 thus drawn to it, I have fully convinced myself of its constant presence 

 in the Coleoptera, by numerous investigations. In the orders with an 

 unseparated prothorax, this part appears to diminish in compass as well 

 as in importance ; at least we never clearly discern a distinctly sepa- 

 rated scapula, but peculiar pieces, analogous by their situation, doubt- 

 lessly represent them, although with an altered function. As such we 

 consider the patagia and tegulce of the Lepidoptera and Hymenoptera ; 

 they are both decidedly the same part, and are also seated precisely at 

 the same place, but differ in their mode of attachment, the tegula of 

 the Hymenoplera being affixed to the mesonotum above the wing, and 

 the patagium of the Lepidoptera beneath it, to that part which we 



* C'onsid. (Jen., PI. VII. fip. 6, II. 

 G 



