68 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL, 8o 



wing is simpler in wings with a small anal area, but is essentially 

 the same in all insects. 



In the Dermaptera and the Coleoptera the distal parts of the flexed 

 wings are mechanically folded transversely in order that the wings 

 may be concealed beneath the shorter elytra. The various types of 

 this folding in the wings of Coleoptera have recently been described 

 by Forbes (1926). 



The positions of the axillaries relative to one another in the flexed 

 wing are quite dififerent from those which they have in the extended 

 wing. The extension of the wing involves a restoration of the axil- 

 laries to a horizontal plane, in which the sclerites again assume their 

 former relations. The key to the transposition from one state to the 

 other is in the position of the second axillary. If this sclerite is 

 forcibly depressed, all the axillaries go back to the horizontal plane, 

 and the wing is necessarily spread. The depression of the second 

 axillary is evidently accomplished by the contraction of the subalar 

 muscle (fig. 30 A, /-'), since the subalar sclerite is closely connected 

 with the ventral i)late (f ) of the second axillary. The epimeral muscle 

 of the coxa (fig. 26 B, F), therefore, in the adult insect (fig. 30 A) 

 becomes the posterior extensor of the zving (Straus-Dvirckheim, 

 Bauer). The final, complete extension of the wing is probably 

 brought about by the contraction of the basalar muscles (fig. 30 A, 

 E, E'), since the basalar sclerite, or corresponding lobe of the epi- 

 sternum, is in intimate connection with the anterior angle of the wing 

 base. The basalar muscles are, therefore, the anterior extensors of 

 the zving. Their function in this capacity, however, is sometimes 

 difficult to demonstrate. 



The wings in extension are ready to be acted upon by the indirect 

 muscles of elevation and depression. These are principally the longi- 

 tudinal and oblique dorsal muscles, and the vertical tergo-sternal 

 muscles. The last (figs. 28, 29, 30 B, C), by contraction, flatten the 

 arch of the tergum (T), and the movement in the edges of the latter, 

 bearing downward on the bases of the wings mesad of the pleural 

 fulcra, gives the up-stroke to the distal parts of the wings (fig. 30 B), 

 The longitudinal dorsal muscles (A) now act as antagonists to the 

 verticals, since by their contraction they pull upon the two ends of the 

 tergum and restore the curvature of the latter. The upward move- 

 ment in the lateral tergal margins gives the down-stroke to the wings 

 (fig. 30 D). The function of the oblique dorsal muscles (fig. 28, B) 

 is not clear in all cases. Ordinarily these muscles appear to be acces- 

 sory to the longitudinals; in the Diptera (fig. 34 D, B), however. 



