INTERNAL ANATOMY OF INSECTS. 189 
the part of both diaphragm and ribs a : but in the Libcl- 
lidina, as in birds, these muscles are placed on each side 
of the point of support of the humerus 15 ; 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 cupule terminating in 
a tendon ; all are disposed perpcndiadarly 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 the Jirst 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 6 . In most insects of the first type, the depressors 
are longitudinal dorsal muscles that have their posterior 
point of attachment in the metaphragm [costalc Chabr.) ; 
but the anterior varies : — in those that have elytra, teg- 
mina, or hemelytra, 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 Chabricr 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. 01 7. 
e Analyse ubi supr. rt Sur le Vol des Ins. c. i. 448, c. ii. 330. 
L Vol. III. p. 57».- ' Chabr. Ibid. c. i. 443. ii. 310, 332. 
