271 Anal legs (Figure 296) long; dorsolateral sclerite "b" light brown, 

 with dark brown grooves; mediodorsal part of the sclerite with large 

 indistinct dots. Basoventral hook absent and replaced by a blackish 

 brown dark spot, resembling the base of the hook in other species; 

 the small basoventral sclerite with setae also absent; large ventral seta 

 displaced to the middle of the segment; lateral part of sclerite "b" with a 

 dark distal process in place of the sword-shaped process of Rhyaco- 

 phila s. str. (also in other species of Hy p o r hy ac o phi 1 a); distodorsal 

 part of sclerite small, the high distal tubercle with a dark apex and 2 very 

 long blackish brown setae which are longer than the claw; seta in the 

 middle of the sclerite situated near the end of an oblique groove (as in 

 Rh. s ib i r i c a), shorter and thinner than the setae of the distal part, as in 

 larvae of Rhy ac o phi 1 a s. str. 



Claws narrow, with a long, almost straight basal part; dorsal seta 1 of 

 this part strong and dark, longer than the thin and much smaller seta 2; 

 lateral seta 5 situated in the middle of the basal part; it is the longest seta 

 of the claw; median seta 4 situated near seta 8, short and thin; ventral 

 setae 7 and 8 light, large and curved; seta 3 in the distal part of the claw 

 situated dorsally, dark and strong; seta 6 situated more distally and 

 shorter than seta 3. 



Mode of life and habitats: Cool brooks and rivulets, on stony 

 bottom. 



Distribution. USSR: East Siberia, Khabarovsk Region and Maritime 

 Territory. Not recorded outside the USSR. 



4. Rhyacophila obscura Martynov, larva nova 



Full-grown larva. Length 11 — 12 mm (Figure 297). Head dark, chestnut 

 brown, oblong, flattened dorsally, especially anteriorly. Lateral anterior- 

 margin seta light and curved, situated lateral to the frontal suture; inter- 

 mediate seta in the angle of the sclerite short; unlike in many species of 

 Hy po rhy a co phi la, the median seta is straight and long; anterior frontal 

 seta light and recumbent; the small middle seta situated near the curvature 

 of the frontal sutures; posterior frontal seta dark and long; seta 9 dark and 

 long; seta 7 also large, slightly smaller; seta 11 situated at the base of 

 seta 9, short and thin; seta 10 is small and light, situated lateral to the eye; 

 setae 14 and 12 situated posterior to the eye, almost of the same length; 

 seta 13 small and light; setae 15 and 16 thin and short, situated one behind 

 the other; seta 17 very small; seta 8 short; seta 18 slightly smaller; both 

 setae strong. 



Labrum (Figure 298) relatively small; dorsal sclerite light brown, 

 rugose in some places; setae 1 are unusually long for a species of 

 Rhy a c o phi la, light and crossed; seta 2 shorter and straight; setae 4 

 situated at the sides of the median notch, straight and short; seta 3 light 

 and recumbent; seta 6 long, situated on the surface of the sclerite; seta 5 

 similarly large, situated near the margin. 



Mandibles (Figure 299) short, with large, pointed, distal teeth; they 

 resemble in this respect the larva of Rhyacophila sp. "y" described 

 by Krawany (1935:245); upper blade of the left mandible also with a large 



291 



