INTERNAL ANATOMY OF INSECTS. 189 



the part of both diaphragm and ribs 3 : but in the Libel- 

 lulina, as in birds, these muscles are placed on each side 

 of the point of support of the humerus 5 ; the depressors 

 being attached immediately to the wings without it, and 

 the levators within it, with this sole difference, that they 

 are connected to the internal extremity of the base of 

 the wing by the intervention of a ctipule terminating in 

 a tendon ; all are disposed perpendicularly to the arms 

 of the levers on which they act, and all incline more or 

 less outwards, the one to dilate, and the other to contract 

 the trunk . It may be observed in general, that in in- 

 sects formed upon thejirst type, the great action of these 

 muscles is the dilatation and contraction of the alitrunk, 

 the main tendency of which is to depress and raise the 

 wings d . I shall add here a few words upon the attach- 

 ment of the wing-muscles in the different Orders : but 

 first I must request you to read what I have said on the 

 partitions and chambers of the alitrunk in a former let- 

 ter e . In most insects of the first type, the depressors 

 are longitudinal dorsal muscles that have their posterior 

 point of attachment in the metaphragm (costale Chabr.) ; 

 but the anterior varies : in those that have elytra, teg- 

 mina, or hemetytra, the muscles for them seem to be con- 

 tained in the chamber, varying in size, that lies between 

 the prophragm and mesophragm ; and the anterior point 

 of attachment of their depressor muscles is the meso- 

 phragm : they are also attached in some to the metatho- 

 rax or back of the posterior portion of the alitrunk f . 



a ChabrieY^Analyse, 28. The latter part of this passage is copied 

 from a MS. note of the author's in my copy. W. K. 

 b Chabrier Analyse, Ibid. Sur le Vol des Ins. c.i.445. VOL. III. p. 617. 

 c Analyse ubi supr. d Sur le Vol des Ins. c. i. 448, c. ii. 336. 



e VOL. III. p. 579.- t Chabr. Ibid. c. i. 443. ii. 316, 332. 



