Pronotum (Figure 694, A) with a narrow dark brown stripe along suture 

 in sharp contrast to light background; posterior part with several large 

 dark dots. Transverse suture of mesonotum (Figure 694, B) replaced by a 

 ridge and a row of dark dots; anterior part with large and small dots in 

 each half; posterior part with a whitish median stripe and with rows of 

 4—5 dark dots lateral to it; groups of dots laterally. Metanotum with small 

 oblique tergites with fine dots. 



Lateral row of gills on segment 2 only. 



Tergite of segment 9 indistinct, light, slightly dark in middle of anterior 

 part, with indistinct dots; setae of posterior margin as in M.angustata. 



Number and arrangement of gills of M, s u b m a r g i n a 1 i s 



Segment 



Dorsal 



Pleural 



Ventral 



1 



4 







2 



4 



2 (1) 



3 



3 



4 





3 



4 



3 





3 



5 



3 





3 



6 



3 





3 



7 



3 





2 



Sclerite "b" of anal legs light yellow, the 4 black posterior-margin setae 

 (3 dorsal and 1 lateral) shorter and thinner than in M. angu s t at a ; sides 

 with thin, dark, secondary setae; a short, black, spine- shaped seta near 

 median margin, in contrast to M. albicans (Figure 695). 



Case shield-shaped, as in M.angustata and M, a lb i c an s ; ventral 

 side of tube less convex (Figure 696). 



Mode of life and habitats. Littoral of lakes, on a bottom of sand 

 or sand with silt, open littoral and among vegetation, at a depth of 1— 4 m; 

 sublittoral and upper profundal at a depth of 4— 10 m. 



Distribution. Northern, northwestern, and central parts of the 

 European USSR; Eastern Siberia, the Amur Region (isolated specimens). In 

 addition, Finland, Sweden. 



2. Genus Molan nod e s McLachlan 



Full-grown larva. Length 11— 12 mm. Head mainly dark. Frontoclypeus 

 wider and relatively larger than in Molanna. Pronotum entirely dark. 

 Mesonotum with distinct transverse suture. Claw of hind legs modified, long, 

 almost as long as tarsus. 



535 



