no 



brownish, and moderately long, both much shorter than the posterior apical 

 ventral seta. Posterior seta of femur situated subventrally near the distal 

 margin, long, brown; distoventral seta brownish, long, shorter than the 

 posterior seta; basoventral seta in form of light, large spine; both setae 

 situated close together in middle of segment. 



Dorsal process of abdominal segment 1 low; lateral processes larger, 

 situated more ventrally. 



Lateral line extending from middle of segment 2 to beginning of segment 

 8, thin, consisting of very fine hairs. Ventral elliptical areas on segments 

 2—3. Gills absent or rudimentary and dorsal, barely visible, postsegmental 

 on abdominal segment 2. 



Tergite of abdominal segment 9 (Figure 180) light, whitish, indistinct, 

 with dense, small, pinkish spinules; 2—3 large dots without spinules laterally; 

 setae brown, medioanal setae relatively thin, moderately long, anterior- angle 

 setae situated apically on the sides, slightly longer, intermediate and 

 lateral seta short, thin; a similarly thin, slightly brownish seta between 

 the median setae; a brown, moderately long seta lateral to the median 

 setae; a small, light seta sometimes present among the spinules near the 

 dots. 



Sclerite "b" of anal legs whitish yellow, with reddish brown distal 

 stripe laterally and ventrally; surface densely spinulose, as on sclerite 

 "c"; setae reddish brown, median and the neighboring seta long, lateral 

 seta moderately long, ventral seta short, thick; inner margin with short, 

 brown subapical seta. Sclerite "c" light yellowish, with broad reddish 

 brown outer margin; seta light, small. 



Claw chestnut brown at the base, with dark reddish brown distal part; 

 setae 1, 2, 3, and 6 light brown, seta 6 small, thin, other setae light; 

 chaetotaxy as in the species just described. 



Case 12— 16 mm long, curved, made of coarse, loosely attached sand 

 grains, grains on the ventral surface no smaller than on the dorsal surface 

 (Figure 181); larger sand grains on sides of anterior part; oblique, anterior 

 opening, posterior opening closed by membrane with a central hole. 



Pupa. Pupal case shorter than larval case, anterior opening closed by 

 sievelike membrane loosely covered with sand grains, similar posterior 

 membrane with several small holes. 



Mode of life and habitats. Open shore of Lake Baikal, at a 

 depth of 2— 6 m, rarely 10 m, usually on sandy or sandy-stony bottom, rarely 

 on stones, sometimes among vegetation; it avoids silt and does not occur 

 on silt bottom. 



Distribution. USSR: Lake Baikal. Not known outside USSR. 



2. Tribe Ap at an i i n i Ulmer 



Full-grown larva. Length 5— 12 mm. Sclerites of head rough, spinulose. 

 Submentum with2 small, not always distinct, sclerites ventrally. Anterior 

 margin of pronotum without the comb of large spines characteristic for the 

 Baicalinini. Dark spot in posterior angle of mesonotum always large, 

 distinct, position constant. Apical ventral part of fore trochanter and baso- 

 ventral part of femur with large, hairlike chaetoids directed distally, as 



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