INTERNAL ANATOMY OF INSECTS. 187 



wings have their attachment in the anterior portion of 

 the alitrunk a ; in the Coleoptera, in the posterior b ; and 

 in the Libellulina, those of the anterior wings are con- 

 fined to the anterior portion, and those of the posterior 

 pair to the posterior c . The muscles for flight in gene- 

 ral differ from others by their mass, length, and colour ; 

 the bundles of fibres are very distinct, strong, and pa- 

 rallel; their direction is uniform, according to the motion 

 they are to produce ; their fibres are either attached to 

 the solid parts to be moved, or to cupules, but they never 

 terminate in a tendon ; the muscles are perfectly inde- 

 pendent of each other, and the wings can be moved by 

 them separately d . As to their denomination and kind 

 the principal ones are the levators and depressors, which 

 with respect to the trunk, as was before observed, are 

 constrictors and laxators. The levator muscles form 

 several distinct bundles in Coleoptera, Lepidoptera, &c.; 

 in the Diptera there are three e ; in the Libellulina they 

 seem to be single, are all environed with a blackish pel- 

 licle, with numerous aerial vesicles, symmetrically ar- 

 ranged, filling the interstices f . The most common 

 number is a levator to each wing; there are often, how- 

 ever, as in the cockchafer and the dragon-fly, two de- 

 pressors s : but in the Hemiptera, Lepidoptera, and saw- 

 flies (Serrifera) amongst the Hymenoptera, the secondary 

 wings have distinct levators, but not depressors h ; the 

 other insects of that Order have only a pair of each '. 



a Chabr. Sur le Vol des Ins. c. i. 415. b Ibid. 



c Ibid. c. iii. 344. t. viii./. 8, 9. A Ibid. c. i. 440. 



e Ibid. 444. { Ibid. 445. c. iii. 359. 



g Ibid. c. ii. 332. c. iii. 359. h Ibid. c. i. 445. 



1 Ibid. c. iv. 78. 



