188 INTERNAL ANATOMY OF INSECTS. 
The other wing-muscles are of a secondary description, 
and auxiliary to the above. Their office is to extend 
and close the wings : so that though the denomination 
of extensor will suit the former, that of flexor is not so 
proper for their antagonists ; their office being not so 
much to bend, as to bring back the wing to its station of 
repose. The folding of certain wings, as those of Coleo- 
ptera, Dermaptera, the Vespidee, &c, seems more the 
function of the abdomen than of the wing-muscles ; this 
you may easily see, as I have often done, if you attend 
to any Staphylinus, when after alighting from flight it 
proceeds to fold up its wings under the elytra. Perhaps 
the term retractor might not be inapplicable to the mus- 
cles in question. Both these and the extensors are usu- 
ally small slender muscles, but sometimes numerous*. 
They are larger in the Colcoptcra, Lcpidoptera, and saw- 
flies 5 . The muscles that open and shut the elytra of 
Colcoptcra, and probably ofHctcrojrtcrousHemiptcra, and 
which also aid their movements during flight, are very 
slender c . With regard to the attachment and insertion 
of the wing-muscles, it is according to two very distinct 
types, one of which appertains to insects in general, and 
the other is peculiar to the Libellulina. In insects in 
general, the principal muscles for flight have not their 
insertion in the wings, but act upon their bases by the 
intervention of small long pieces. The depressors oc- 
cupy the middle and upper region of the alitrunk, and 
are inserted anteriorly and posteriorly upon the concave 
surfaces of two transverse horny semi-partitions, adapted 
by their elasticity to dilate the trunk — and thus acting 
n Chabr. Sur le Vol des Lis. c. i. 415, 442. c. iv. 80. 
" Ibid. c. i. 442. c Ibid. 439 -. 
