basal spine blunt, much smaller than apical; posterior seta situated slightly 

 distal to basal spine. Ventral setae of mid-femur (Figure 438, B) situated 

 basally, strong, black, basal seta longer than apical; trochanter posteriorly 

 with 5 secondary setae in apical and 3 in basal part. Ventral setae of hind 

 femur (Figure 438, C) situated in distal part, strong and black as on the 

 midlegs, apical seta moderately long, basal seta shorter; trochanter with 

 a secondary seta in distal and basal part. 

 Gills on segments 2 — 7. 



Number and arrangement of gills ofA.lapponicus 



Segment 



Dorsal 



Pleural 



Ventral 



2 



2 

 3 



2 



9 



2 

 2 



3 



3-2 

 3 



2 



2 



2 

 3 



4 



2 

 2 



1 





2 

 2 



5 



2-1 

 1 







2 



2 



6 



1(0) 

 1(0) 







2 

 1 



7 









2-1 

 1(0) 



250 



Tergite of abdominal segment 9 grayish brown, with indistinct punctation 

 at anterior margin; setae black; medioanal seta longer than anterior-angle 

 seta; intermediate and lateral seta thin, the former moderately long; one 

 thin, moderately long seta between medioanal setae; one secondary seta 

 on surface. 



Sclerite "b" of anal legs brownish; distal and median setae as in 

 A.amurensis, surface with 4—5 secondary setae. Sclerite "c" with blackish 

 margin. Claw with 2 dorsal denticles of different length. Larval case as 

 in Figure 439. 



Mode of life and habitats. On stones among vegetation, in 

 littoral zone of lakes (Lake Teletskoe), near banks of rivers and in parts 

 with a slow current (Abakan, Biya, Lena). 



Distribution. Northern and northeastern parts of the European USSR, 

 Western and Eastern Siberia. 



2. Tribe S t e no p hy 1 a c i n i Schmid 



Full-grown larva. Length 20 — 32 mm. 



Pattern on head and thoracic sclerites mainly punctate, without stripes 

 or spots; when present, spots are pale and indistinct. 



Gills single on segments 2 — 7, usually absent from segment 8. 



313 



