238 THE AMERICAN NATURALIST.  [Vou. XXXII. 
In the nymph of Nemoura (Fig. 8) we have not observed a 
costal trachea. The subcosta is forked in the typical manner, 
and vein Scz2 anastomoses with vein X:. The radius is reduced, 
the radial sector being only two-branched; it is probable that 
this reduction came about by the coalescence outward of vein 
R2 with R, and of vein R4 with Æ;. The media is reduced in a 
similar way. The cubitus is typical, but in the fore wing sev- 
Fic. 8.— Wings of Nemoura, nymph. 
eral cross-veins have been developed between its branches, and 
also between it and the media; the strengthening of this region 
of the fore wing is quite characteristic of the Plecoptera. The 
anal veins are typical in the fore wing, but in the hind wing the 
second and third anal veins are each forked.! 
1 There is a striking similarity between the anal areas of the Plecoptera and the 
Orthoptera; throughout both these orders the first anal vein remains simple in both 
wings, but the second and third anal veins are forked when this part of the wing 
is expanded. z 
