(unlike in many other species, e. g., in Rh. nar vae and apparently also 

 in Rhyacophila sp. "y") forms a trapezoidal, posteriorly tapering sclerite 

 which is thickened at the margin; it is directed downward toward the claw, 

 resembling the articulation of sclerite "b" and the claw in Philopotamidae; 

 there is a curved notch at the end of the distal part of "b"; distodorsal 

 tubercle absent; 2 setae laterally, near the dorsal margin of the sclerite; 

 they are dark, very long, directed posteriorly and situated at the sides of the 

 276 claw; distal seta in the middle short and strong. Basoventral plate of 



section "b" absent; ventral seta displaced to the ventrodistal part of section "b." 

 Sclerite "c" consists of a ventral plate; a lateral plate absent; seta short 

 and thin. 



275 



FIGURES 307. Rhyacophila obscura Mart. Dorsal sclerite of abdominal 

 segment 9 and anal legs 



Basal part of claw (Figure 308) shorter than distal part; as in several 

 species of the group Hy porhyaco phila (sibirica, narvae and 

 others), it is without ventral spinules. Seta 1 and seta 2 small, setae 3, 5 

 and 4 very long, situated on the outer and inner side of the basal part; 



296 



