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 Jlexor 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 oPcertain wings, as those of Coleo- 

 ptera, Dermaptera, the Vespidce, &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 Coleoptera, Lcpidoptera, and saw- 

 flies 5 . The muscles that open and shut the elytra of 

 Coleoptera,nnd probably ofHeteropterousHemiptera, 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 



a Chabr. Sur Ic Vol dcs Ins. c. i. 415, 442. c. iv. 80. 

 b Ibid. c. i. 442. c Ibid. 439 -. 



