1. Genus Hydropsyche Pictet 



Full-grown larva. Length 15— 20 mm, Head dorsally with a dark lyre- 

 shaped figure, with or without a pattern of light spots. Left mandible with 

 a penicillus in the middle. Posterior margin of mesonotum with a large 

 curved black spot in the middle; metanotum with a large spot. Four anal 

 gills. Anal legs posteriorly with a tuft of black, strong setae. 



Pupa. Length 8—14 mm. Antennae almost reaching end of body or 

 slightly longer. Mandibles finely serrated, with several large denticles. 

 Postsegmental plates of abdminal segment 3 with 2 rows of small, anteriorly - 

 directed denticles. Anal rods divided into 2 small lobes posteriorly. 



Mode of life and habitats. Running water of various types; 

 living on the bottom or on wood. 



Distribution. Throughout the European and Asian parts of the 

 USSR. In addition, Europe, North America, Asia; genus little represented 

 in Africa and Australia. 



Key to Species 

 Full-grown larva 



480 



1 (2). Frontoclypeus mainly light, milk-white on the background of the 



lyre-shaped figure; light background sometimes constricted in 



the middle; length 14— 15 mm 1. H. ornatula McL. (p. 548) 



2 (l). Head completely dark dorsally, or with a pattern of light spots 



which are sometimes indistinct. 



3 (4). Length 14— 15 mm; closely related to H. ornatula; frontoclypeus 



dark, divided into an anterior and posterior spot which are not 



always distinct; sometimes with 3—4 spots 



2. H. guttata Pict. (p. 559) 



4 (3). Length 18— 20mm. Head with distinct but very variable pattern; 



4—9 light spots on the dark head. 



5 (12). Not more than 5 light spots on dark figure of head. 



6 (7). Dots of lateral sclerites of head dark and distinct; median spot 



on mesonotum large; anterior margin straight in the middle, 

 forming an obtuse angle laterally; large distinct, dark dots anterior 



to the spot and in its lateral arcs; length 16— 17 mm 



6. H. instabilis Curt. (p. 572) 



7 (6). Dots of lateral sclerites of head less dark or pale. 



8 (9). Anterior margin of median black spot of mesonotum straight; dots 



lateral to spot small; length 18— 20 mm 



5. H. saxonica McL. (p. 571) 



9 (8). Anterior margin of median black spot curved. 



10 (ll). Large dots near median spot at posterior margin of mesonotum 



absent; median spot of metanotum small; its posterior margin 

 almost straight, without serration or with only 1 or 2 serrations 

 3. H. angustipennis Curt. (p. 559) 



11 (l0). Large dots near median spot at posterior margin of mesonotum 



indistinct and pale; spot of metanotum slightly larger; posterior 

 margin with numerous serrations . . . 4. H. pellucidula Curt. (p. 568) 



547 



