INTERNAL ANATOMY OF INSECTS. 187 
wings have their attachment in the anterior portion of 
the alitrunk 8 ; in the Coleoptera, in the posterior* ; and 
in the Libellidina, those of the anterior wincrs 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 11 . 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 £: 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. d Ibid. c. i. 440. 
e Ibid. 444. f Ibid. 445. c. iii. 359. 
g Ibid. c. ii. 332. c. iii. 359. »• Ibid, c. i. 445. 
' Ibid. c. iv. 78. 
