1. Genus Rhyacophila Pictet 



Full-grown larva. Length 10— 24 mm. Head usually more or less 

 oblong; body slightly flattened or almost cylindrical. Pronotum with smooth 

 surface and a few secondary setae; forelegs slightly different from the 

 211 mid- and hind legs in size and form of the segments; anterior -angle and 

 medioanal setae of mesothorax, metathorax and abdominal segments well 

 developed; in primitive forms (as in the early stages), are long; they are 

 short and small in the higher forms. The anal legs have a long sword- 

 shaped process on sclerite "b" or, as in the young larvae of the whole genus, 

 such a process is absent. 



This is a large and complex genus; Dohler (1950:272—276) divided the 

 European species of the genus according to the larvae into 6 subgenera 

 which have also been recorded from the USSR (except one subgenus). As 

 only a small number of species of the genus is covered by Dohler' s 

 classification, we consider them as groups of species. Another two groups 

 of species were established in the USSR from material from the Asian part 

 of the Soviet Union. 



Mode of life and habitats. Brooks and rivulets with a rapid 

 current, on a solid (usually stony) bottom; predatory, with a few exceptions. 



Distribut ion. Throughout the USSR and also in Europe, Asia and 

 North America. This genus occurs rarely also in North Africa. 



Key to Groups of Species* 

 Full-grown larva 



1 (8). Sclerite "b" of anal legs with a long sword-shaped process 



posteriorly. 



2 (5). Tracheal gills with numerous filaments. 



3 (4). Gills forming a tuft, with a short stalk and numerous filaments . . 



1. Rhyacophila s. str. Dohl. (p. 219) 



4 (3). Gills conical, with a long stalk and filaments situated on one side . 



2. Hyperrhyacophila Dohl. (p. 239) 



5 (2). Gills with four filaments, or one filament, or gills absent. 



6 (7). Gill with four segmented filaments 



3. Pararhyacophila Dohl. (p. 242) 



7 (6). Gills with a single filament or absent 



4. Mesorhyacophila Lepn. (p. 248) 



8 (l). Sclerite "b" without sword-shaped process. 



9 (10). Gills forming a tuft 5. Paleorhyacophila Lepn. (p. 262) 



10 (9). Gills with a single filament or absent. 



11 (12). Gills with a single filament ... 6. Prosrhyacophila Dohl. (p. 265) 



12 (11). Gills absent 7. Hypo rhyacophila Dohl. (p. 275) 



* In the classification of the subgenera of Rhyacophila, Dohler (1950:272) considered the presence of 

 2 or 3 anterior-angle setae on the pronotum as one of the principal characters. We are not using this 

 character, because the number of anterior- angle setae in the notch of the pronotum is always 3 in 

 Rhyacophila: one primary and 2 secondary setae. One of the secondary setae may be almost as long 

 and dark as the primary seta, while the 2nd secondary seta is small, or both secondary setae are long but 

 not always as long as the primary seta. 



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