NO. I 



INSECT THORAX — SNODGRASS 



6i 



by the z'cins and cross-veins; the thin intervening spaces, or cells, are 

 occupied by the iiieiiibninc of the wing. The wing base contains a 

 number of small sclerites, the axillarics, or ptcralia (fig. 27, Ax). 

 At the base of the anterior margin of the wing there is usually a 

 thickening, the tcgula (Tg), commonly having the form of a small 

 hairy pad, but sometimes developed into a large flat lobe overlapping 

 the base of the wing. The rear margin of the basal membrane of the 

 wing is' generally corrugated and thickened, forming a posterior liga- 

 ture of the wing, the axillary cord (AxC). The wing is held in 



Fig. 2y. — Diagrammatic structure of the wing base and its articulation with 

 the tergum. 



A, anal veins ; ANP, anterior notal wing process ; lAx, first axillary ; 2 Ax, 

 second axillary ; sAx, third axillary ; AxC, axillary cord ; C, costa ; Cmi, first 

 branch of cubitus ; Cm;, second branch of cubitus ; D, flexor muscle of third 

 axillary ; M , media ; m, in', median plates of wing base ; PNP, posterior notal 

 wing process ; R, radius ; Sc, subcosta ; T, tergum ; Tg, tegula. 



various positions when at rest, but with most insects it can be flexed 

 posteriorly against the sides of the body. When extended it is capable 

 of a free up-and-down motion, and of a slight rotary motion on its 

 long axis. The posterior part, or anal area, of the wing in some 

 insects when flexed can also be folded or plicated along the lines of 

 the veins. In two orders of insects the distal part of the wing can 

 be variotisly folded. 



The nomenclature of the wing veins given in figure 2^ is that of 

 Comstock and Needham, except that the vein ordinarily called " first 

 anal" is represented as a proximal branch of the cubitus. (See 

 Imms, 1924, fig. 28). A study of the wing base shows that this vein 



