\ 



THE WINGS OF TRICIIOPTERA 



309 



320, a) is given off, which extends to the margin of the wing. The humeral 

 vein is present in its usual position. 



The radius of the fore wing is typical; the radial fork is quite near the 

 base of the wing; and the radial sector is dichotomously four-branched. 

 The media is also typical, being dichotomously four-branched. 



The cubitus and the first anal vein coalesce at the base, where they 

 traverse the cubito-anal sulcus. From the point where these two veins 

 separate vein Cu extends in an oblique direction towards media, which it 

 nearly reaches, and then making a bend extends in a longitudinal direction 

 to the outer margin of the wing. It is of the typical two-branched form. 



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2d A islA Oi2 ^"' 

 Fig. 320. — Wings of Rhyacophila fiisctda. 



The basal part of the free portion of vein Cu appears very much like a 

 cross-vein. This appearance is accentuated by the fact that a serial vein 

 has been developed, which consists of three parts, the basal part of media, a 

 short cross-vein connecting media and vein Cu (Fig. 320, pa), and the 

 longitudinal part of vein Cu. This results in the longitudinal part of vein 

 Cu appearing to be a nearly direct continuation of the stem of media. The 

 short cross-vein connecting media and cubitus corresponds to the posterior 

 arculus of those orders in which an arculus is developed. 



The separate portion of the first anal vein is a direct continuation of vein 

 Cu -|- I St A and extends in the bottom of the cubito-anal fold to the margin 

 of the wing. The outer portions of the second anal vein and of two 

 branches of the third anal vein coalesce, forming a single vein, which ends 



