THE MUSCULAR SYSTEM. 247 



the Diptera belongs to the abdomen, because a spiracle is found upon 

 it, requires no refutation after the description given above of the 

 general situation of the spiracles. 



We must still make an observation upon the connection of the wings 

 together. I know but of two of all the orders of insects which exhibit an 

 apparatus for the connection of both the wings together, these are the 

 Hymenoptera and the Lepidoptera. 



In the Hymenoptera it consists of a row of minute booklets, which 

 are bent backwards, and are placed upon the anterior margin of the 

 posterior wing, and which fit to a small groove along the posterior 

 margin of the superior wing. 



In the Lepidoptera this apparatus is somewhat more complicated. 

 Giorna, who appropriates to himself the priority of this discovery, 

 although it was made thirty-seven years before him by De Geer *, 

 has, however, given the most detailed account of it f. There is found, 

 namely, at the base of the posterior wings of many of the crepuscular 

 and night moths, a spine projecting from the anterior marginal rib, 

 which is sometimes divided into several radiating branches. This spine 

 is enclosed by a hook placed upon the central main rib of the superior 

 wing, which surrounds the whole circumference of the spine, which passes 

 through it as through the eye of the needle, but which can freely move 

 itself to and fro within it. If the superior wing expands by means of 

 the spine, it draws the inferior wing with it, and both remain in 

 immediate connexion; a provision of nature which is rendered the more 

 necessary, as we shall see below, from the mesothorax being furnished 

 with large muscles of connexion and motion, which are entirely wanting 

 in the metathorax, so that the muscles which distend the superior 

 wings must act likewise upon the inferior ones. We find a similar 

 adaptation in the muscles of the Hymenoptera. 



II. THE MUSCULAR SYSTEM. 

 169. 



The muscles of insects, like those of the higher animals, consist of 

 two parts, viz. the tendon and the muscle. Under the name tendon 

 we understand the in general more compact, firmer, and uncontractile 



* Mm. pour servir a 1'Hist. des Insecles, t. i. p. 173. 

 f- Trans, of Linnsean Society, vol. i. No. 7. Lond. 1791. 



