MAY FLIES AND MIDGES OF NEW YORK 



21 



of the venation are easily learned, and afford a ready clue to the 

 relationships. Eaton says, " Unstable in minutiae, so closely is 

 the essential plan of the neuration adhered to -by nearly related 

 mayflies that the general facies of the wing is an inuportant aid 

 to their classification, affording characteristics as easily recog- 

 nizable as the style of branching in the case of trees." 



By reference to figs.l, 2 or 3, or any of the wing figures of the 

 plates, it will be observed that there are three nearly parallel 

 veins extending along the front or costal margin of the wing, 

 costa (C), subcosta (8c), and radius (RJ. These three are fol- 

 lowed by three forking veins that occupy the greater part of the 

 wing area, the radial sector (Rs), the media (M) and the cubitus 

 (Cu). The middle one of these, the media, forking usually far- 



Fig. 2 Wings of Callibaetis 



ther outward than the others and being more constant in form, 

 is one of the best landmarks of the wing. All that lies between 

 it and vein R is radial sector, which, in the fore wings of may- 

 flies, is entirely detached from the radius and functions as a 

 separate vein. The only place in the series where there is likely 

 to be any difficulty in recognizing the media is in the few genera 

 closely allied to Baetis (see fig.2) in which both the media and 

 the 'Cuibitus are apparently simple ; but it will be readily observed 

 by carefully noting the number and relation of the longitudinal 

 veins that the hinder branch of the fork of these two veins is 

 detached/ and appears as an independent sector standing on the 

 hinder side; the relative lengths of these veins enable one to recog- 

 nize them all, even when detached, or when, through shifting of 

 cross veins at their bases, they appear to have formed attach- 

 ments of a contradictory sort (see vein Cu 2 in pl.8, fig.9). These 



