182 INTERNAL ANATOMY OF INSECTS. 
of support of the humerus*; the depressors being at- 
tached immediately to the wings without it, and the leva- 
tors within it, with this sole difference, that they are con- 
nected to the internal extremity of the base of the wing 
by the intervention of a cupule terminating in a tendon ; 
all are disposed perpendicularly to the arms of the levers 
on which they act, and all incline more or less out- 
wards, the one to dilate, and the other to contract the 
trunk>. It may be observed in general, that in insects 
formed upon the jirst type, the great action of these mus- 
cles is the dilatation and contraction of the alitrunk, the 
main tendency of which is to depress and raise the wings °. 
I shall add here a few words upon the attachment of the 
wing-muscles in the different Orders: but first I must re- 
quest you to read what I have said on.the partitions and 
chambers of the alitrunk in a former letter?. In most 
insects of the first type, the depressors are longitudinal 
dorsal muscles that have their posterzor point of attach- 
ment in the metaphragm (costale Chabr.); but the anterior 
varies :—in those that have elytra, tegmina, or hemelytra, 
the muscles for them seem to be contained in the cham- 
ber, varying in size, that lies between the prophragm and 
mesophragm ; and the anterior point of attachment of their 
depressor muscles is the mesophragm: they are also at- 
tached in some to the metathorax or back of the poste- 
rior portion of the alitrunk®. The levator muscles in 
Coleoptera, at least in the cockchafer, by a long tendon 
have their posterior attachment in the lower part of the 
* Chabrier Analyse,28. Sur le Vol des Ins. c.i. 445. Vou. II. p- 619. 
» Analyse ubi supr. “ Sur le Vol des Ins. c. i. 448. c. ii. 336, 
4 Vor. II. p. 58e@—. * Chabr. Ibid, c. i. 443, ii, 316, 332. 
