width; the abdomen gradually tapers toward the 8th segment; the 8th seg- 

 ment is much smaller than the others. The anterior-margin setae of 

 segments 1—8 small and setuliform; anterior -angle setae of segments 1—7 

 situated in the middle of the segments, displaced posteriorly on segment 8, 

 brown and long; medioanal setae similar, broadly separated to the sides of 

 the segment; intermediate and lateral setae situated close together on 

 segments 1—7, small and light; anterior-angle seta long from segment 6 

 onward and is situated close to the anal setae; all 4 setae of segment 8 

 (as on segment 9) form a row at the sides of the segment; relatively thick 

 medioanal seta brown and short; thin lateral seta and especially the 

 yellowish intermediate seta longer than on the preceding segments. One of 

 262 the ventral setae (intermediate seta) long and brown, like the large dorsal 

 setae. 



Dorsal sclerite of segment 9 light brown, narrowed anteriorly into a 

 median process (Figure 279); a black anterior margin absent; sclerite 

 slightly dark anteriorly, pale yellow posteriorly, almost white in the middle, 

 with two large grayish dots at the sides; sclerite broader posteriorly than 

 anteriorly; posterior margin with widely separated groups of 4 setae near 

 the posterior angles; medioanal and angle setae long, reddish brown, thick 

 at the base, very thin at the end; intermediate and lateral setae situated 

 between them, short, light and very thin. 



The dorsolateral sclerite "b" of the anal legs (Figure 280) is light 

 yellow, with dark brownish scars formed by the oblique groove and the 

 groove perpendicular to it; basoventral hook of the sclerite slightly curved, 

 reddish, with a blackish brown triangular base; the ventral sclerite near 

 the hook forms a small sclerotized dot; the seta on it is thin and light; 

 distally and laterally, a small pointed process at the point of the sword- 

 shaped process of species of Rhyacophila s. str.; distal part of sclerite 

 brownish black in the middle; instead of the distodorsal tubercle, there is a 

 white, weakly sclerotized skin fold; both setae of the part (dorsal and 

 lateral seta) brown, strong and long; the former is longer (not shorter as in 

 Rhy a c o phila s. str.) than the adjacent short and thin seta of the baso- 

 dorsal part of the sclerite; such a length of the setae is observed also in 

 larvae of the 1st and 2nd stage of Rhyacophila s. str. Ventral sclerite 

 "c" small; its seta light and thin; lateral sclerite "c" large and yellow. 



Claw long; its basal part with a dark margin and a basodorsal blackish 

 brown, beak-shaped process which enters under the fold of the distal 

 sclerite "b" if the claw is flexed. Distal part of claw weakly curved; 

 dorsal and outer setae dark, more or less long; their basal part with the 

 long seta 1 and the shorter seta 2; the distal part bears seta 3 near the 

 transverse, membranous stripe; the long seta 5 is situated laterally near 

 the base; seta 6 is situated in the distal part; the short thin seta 4 is 

 situated near seta 8 in the middle; the light setae 7 and 8 are situated 

 ventrally; seta 7 short and thin; seta 8 reaches the end of the claw, curved 

 and thick. 



Mode of life and habitats. Brooks and rivulets with cool water 

 and a rapid current, on stony bottom. 



Distribution. USSR: Siberia, Altai, Sayans. 



280 



