548 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.xxxvi. 



tral end of the muscle inserted upon this disk is attached to the an- 

 terior edge of the metacoxa in beetles. This is probably the principal 

 muscle concerned in bending the wing toward the body. 



The third axillary (J, J Ax, longitudinal shading). — This sclerite 

 serves principally as a means of folding the anal region of the wing. 

 When the fourth is absent it articulates directly to the posterior 

 notal wing process. It nearly always presents a scoop-like muscle 

 process on the side next the body at right angles to its long axis. 

 The muscle inserted upon this turns the third axillary on its axis and 

 thus causes a folding of the anal region of the wing. In the beetles 

 this muscle is attached by a ligament first to a smaller accessory 

 sclerite. The outer edge of the third axillary is alwaj^s connected 

 with the bases of the anal veins; frequently the latter are fused with 

 it by a common flexible chitinous base. 



The fourtli axillary (4, JtAx., transverse shading). — AVhoii this 

 small sclerite is present it forms the posterior hinge plate of the wing, 

 iritervening between the posterior notal wing process {PNP) and the 

 third axillary. 



Tlie median flates {phligue shading In hroken lines). — These lie 

 between the l)ase of the radius {R) and the third axillary. They are 

 variously developed but are principally associated with the bases of 

 the media, llie cubitus, and the first anal when the latter is separated 

 from the other anals. Often one of them is fused with the third 

 axillary and sometimes none of them is present. 



TJie axillary tnoxhraiic {A.rM). — This is specially developed along 

 the anal margin of the wing base where it is Ijordered by the axillary 

 cord. It nearly always forms an ample expansion here, Ijut in the 

 wings of flies and the eh'tra of beetles it forms large folded lobes. 

 These are called the s(jiiain<t' or alida' in the Diptera (212, Al). The 

 similar membranous lobes under the elytra of some beetles (131, Al) 

 are certainly the same things as the alula' of Di[)tera. Comstock 

 and Xeedham (1898) have already suggested this and cited the mar- 

 ginal cord-like structures (131, AxC) arising from the posterior 

 angles of the scutellum as evidence. 



Axillary cord {AxC). — This is the corrugated cord-like thicken- 

 ing along the posterior margin of the axillary memljrane. The jjair, 

 one on each side, originate froui tlie posterior lateral angles of the 

 notum, and are thus valuable nuirks in determining the limits of this 

 l^late when the latter is obscured by close connection with the parts 

 following. 



The lolng veins {C, Sc, R, M, Ou, A). — Most of these are connected 

 or associated in a very definite and constant manner with the sclerites 

 of the wing base. The latter are certainly a valuable asset in the 

 identification of the veins in the different orders. Comstock and 

 Xeedham (1898, 1899), however, have left little to be said on this 



