Presegmental plates present on segments 4—7, postsegmental plates 

 on segments 3—5; the plates are light brown, rounded and thick; spinules 

 small, dense and numerous. Their numbers are as follows: 3rd:32; 

 4th:25+ 55; 5th:45+ 36; 6th:36; 7th:22. 



End of abdomen of female pupae blunt; segments 9 and 10 indistinctly 

 separated; 10th segment of male pupae with two lateral lobes; sheaths of 

 the lower appendages broad and long, slightly flattened, obliquely truncate; 

 penis tapering (Figure 198). 



The pupa is situated in a cavelike, ventrally open case consisting of 

 coarse, small stones with sand grains between them (Figure 199); there 

 are numerous openings between the mineral particles which are connected 

 by strands of tissue (Figure 200); the pupa lies in a thick brown cocoon with 

 ends that are attached to the case at one point (Figure 201 ). 



Mode of life and habitats. Rapidly running brooks and rivulets, 

 on the lower surface of stones in cool water. 



Distribut ion. Northwest, west and southwest of the European USSR, 

 and also Europe. 



2. Rhyacophila obliterata McLachlan 



Mackereth, 1954:149-150, Figures 1, 3. - Kachalova, 1957:1 75-1 78, 

 Figures 1—3. 



Full-grown larva. This species is closely related to Rh. septentrio- 

 nis. Length 16— 18 mm. Head (Figure 202) oblong, broader anteriorly 

 than in Rh. septentrionis; it widens slightly and gradually posteriorly; 

 sides of head appear almost parallel; in dorsal view the lateral margins of 

 the head are less uniformly rounded posteriorly than in Rh. septentrio- 

 nis. Dorsal and lateral stripes of head distinct; between them a small, 

 darker area with light spots at the base of setae 15 and 16. Dorsal stripes 

 blackish brown in the anterior part, almost black near the frontal sutures; 

 dots on them indistinct; posterior part of the stripes less dark; dark dots 

 distinct; the difference in color between the anterior and posterior parts of 

 the stripes is more sharply marked in Rh. obliterata than in Rh. sep- 

 tentrionis. Lateral stripes with distinct dark dots. 



Pronotum (Figure 203) with broad black posterior margin; the median 

 dark field with two dots posteriorly; the large lateral field with numerous 

 distinct dots; space between both fields darker than the yellowish brown 

 ground color. 



The claw of the anal legs has ventral tubercle at the base of seta 8 and 

 two spines in its distal part; the tubercle and spines are slightly smaller 

 than in Th. septentrionis but are clearly marked. 



Mode of life and habitats. Brooks under stones. 



Distribution. North and northeast of the European part of the USSR, 

 it extends into the northwest of West Siberia (Obdor Tundra); rare; north 

 Central Europe. 



3. Rhyacophila cupressorum Martynov, larva nova 



Full-grown larva. Length 18— 20 mm. Ground color of sclerites yellowish 

 white. Dark spot in posterior part of frontoclypeus less broad, more 



227 



