2. Genus Hyd atophyl ax Wallengren 



Full-grown larva. Large, 19 — 32 mm, or medium-sized. Resem.bling 

 Potamophylax in coloration of head, pronotum and mesonotum, and in 

 form and chaetotaxy of legs. Anterior median tergites of metathorax 

 fused. Dorsal process of abdominal segment 1 present. Dorsal, lateral, 

 or ventral presegmental gills on abdominal segment 2 absent. Tergite of 

 abdominal segment 9 usually with only 2 — 3 secondary setae. 



Case made of detritus, usually large pieces, with longitudinally arranged 

 rods projecting anteriorly and posteriorly; sand grains rarely present in 

 anterior part. Case 30 — 65 mm long, including rods. 



Mode of life and habitats. Clear brooks and rivulets with cool 

 water. 



Distribution. Northwestern part of the European USSR, Siberia, 

 Far East, Kamchatka, Sakhalin. In addition, Europe, North China, Japan, 

 North America. 



Key to Species 

 Full-grown larva 



1 (4). Siberia, Far East. 



2 (3). Length 22 — 26 mm; head with distinct, large dots; mesonotum 



with contrasting pattern including a light, wide, median stripe 

 which continues in whitish, median area of anterior median 

 tergite of metathorax; legs of variegated color, with black distal 

 cross-stripes on tibiae and tarsi, and less distinct, but also 

 dark cross-stripes on trochanters and femora; case made of 

 detritus, sometimes bulky, 30 — 40 mm long, sometimes with 

 sand grains among detritus, rarely a large part made of sand 



grains; Siberia, Far East, Kamchatka 



2. H. nigrovittatus McL. (p. 343) 



3 (2). Larger, 30 — 32 mm long; head with large and small dots; light, 



median stripe of mesonotum less marked, dark dots in anterior 

 third near suture; anterior tergite of metathorax brownish yel- 

 low; legs not variegated, brown cross-stripes only on tarsi; 

 case made entirely of detritus, bulky, usually of large particles 



of wood, 40 — 50 mm long; Maritime Territory 



1. H. magnus Mart. (p. 338) 



4 (1). Northwestern and part of western territory of the European 



USSR; mesonotum with broad, light median area; legs without 

 distinct cross-stripes; case made of coarse detritus, bulky, 



with rough surface, 30 — 50 mm long 



3. H. infumatus McL. (p. 348) 



337 



