ARTHROPODA—INSECTA. 423 



ing from the siibcosta to the costa near the humeral angle of the 

 wing; (2) the radio-medial cross-vein (Fig. 1725, r-m) connect- 

 ing radius and media, usually near the center of the wing; (3) 

 medio-ciihital cross-vein (Fig. 1725, m-cii) connecting the media 

 and cubitus usually near the center of the wing; (4) the medial 

 cross-vein (Fig. 1725, m) , connecting the second and third medial 

 branches, and (5) the arculus (Fig. 1725, ar), connecting radius 

 and cubitus near the base of the wing, the media appearing to 

 arise from it but in reality forming the anterior part of it, the 

 remainder being formed by a strong cross-vein from the cubitus 

 to the angle in the bent media (ex. Odonata, Fig. 1752, b). 



Fjg, 1725. Diagram of veins and cells of the fore-wing of an adult Cicada. C, 

 costa ; Sc, subcosta ; /^, radius ; M, media ; Cu, cubitus ; A, anal vein. The cells 

 are named according to the veins bounding them in front, cv, cross veins ; ar, arculus ; 

 r-/;/, radio-medial cross vein ; m, medial cross vein ; m-cu, medio-cubital cross vein. 

 (After Comstock and Needham.) 



The cells formed by the bounding veins are designated accord- 

 ing to the principal vein which bounds them anteriorly. In the 

 basal part of the wing, the cells are bounded by the stems of the 

 principal veins, and are designated accordingly, cells R, M, Cu, 

 A, etc. (see Fig. 1725). In the anterior part of the wing, how- 

 ever, where the bounding veins are the branches, these give their 

 names to the cells. Thus we have cells M^, M^, M.,, M^, Cu^, 

 etc. When cross-veins unite branches, as in the case of the median 

 cross-vein, Fig. 1725, m, we may have ist M^, and 2d, M^. In the 

 cicada wing (Fig. 1725) the radial cells are also divided into 

 1st R.,, 2d R., etc. When two branches coalesce, the cells between 



