above group; as in Rhyacophila s. str.,the distodorsal seta of the basal 

 part of the sclerite is short and thin. Ventral plate of sclerite "c" small, 

 yellowish brown, with a short light seta; the lateral sclerite "c" 



is wide and rhomboidal, with a dark ventral 

 margin and a concave basal margin the angles 

 of which rest on the apex of the process of the 

 posterior margin of sclerite "b" and on the 

 base of the sword-shaped process. 



Claw (Figure 248) long and narrow, 

 resembling the claw of species of 

 Hyporhyacophila; all setae are more 

 or less long, seta 1 on the dorsal side of the 

 basal part longer and thicker than seta 2; 

 the outer seta 5 is also long and strong, 

 situated closer to the base of the claw; 

 median seta 4 situated near the margin of 

 the transverse membranous fold, near the 

 curved light ventral seta 8; seta 7 near the 

 base of the claw as long as seta 8; the 

 dorsal side of the distal part of the claw 

 with seta 3 near the transverse membranous 

 fold; seta 6 situated on the outer side, 

 slightly more distally; both setae strong, 

 dark and long. 



Mode of life and habitats. Small 

 mountain brooks and rivulets, clean channels 

 of lakes (Teplovsl Channel near Khabarovsk). 



Distribution. USSR : Altai, Say ans, 

 East Siberia, Far East. 



5. Group P al e o r hy a c o ph i 1 a Lepneva 

 Lepneva, 1963:68. 



248 



FIGURE 249. Rhyacophila hokkai- 

 densis Iwata. Full-grown larva, dorsal 



Distribution. USSR 

 Territory. In addition, Japan, North America 



Full-grown larva. Length 16.5— 19.0 mm. 

 Head oblong, with a dark dorsal pattern and 

 with indistinct spots ventrally; left mandible 

 without teeth; right mandible with 2 distal 

 teeth; a small toothlike process at the base 

 of the distal part of the blade. Pronotum 

 with a dark figure in the middle. Thoracic 

 gills absent; abdominal gills tufted, present 

 on segments 1—8. Sclerite "b" of the anal 

 legs without sword- shaped process. 



Mode of life and habitats. 

 Brooks, including mountain brooks with a 

 stony bottom and a low temperature. 

 Sakhalin, probably also in the Maritime 



262 



