FIGURE 167. Potamobionts: larvae of Br achy cent rus subnubilus in the 

 current (A), nets of Neureclipsis bimaculata larvae in river plant thickets 

 (B), eggs of Hydropsyche ornatula (C) 



122 



Potamobionts which occur in the Volga: Hydropsyche ornatula, 

 Neureclipsis bimaculata and Brachycentrus subnubilus 

 are also found in the Oka; H. ornatula predominates; Leptocerus 

 annulic ornis, which occurs in lakes, is found also on the banks of the 

 Oka; the fauna of plant thickets is more abundant than in the Volga. In 

 addition to the aforementioned potamobionts, there are Agraylea multi- 

 punctata, Ecnomus tenellus and Phryganea striata (Lepneva, 

 1925:124-127; Zhadin, 1940:866-892). 



The same caddis fly fauna of the Volga was also found throughout the 

 Kama before its pollution: (Hydropsyche ornatula, H. guttata, 

 Neureclipsis bimaculata, Brachycentrus subnubilus); 

 some of these species are still present in some parts of that river. 

 Hydropsyche ornatula is distributed everywhere in parts of the river 

 not silted or polluted; 265 specimens per m were found above Okhansk in 

 1938, and 332 specimens per m were found on stable bottom near Okhansk 

 in autumn 1939 (Bening, 1928:270-272; Gromov, 1949:130; 1950:45-46; 

 1951:115; Lepneva, 1928a:25). Caddis flies completely disappeared, or their 

 numbers decreased markedly in some localities, after the obstruction and 

 pollution of the river (Gromov, 1954:9—10). 



The potamobionts Hydropsyche ornatula, Neureclipsis 

 bimaculata and Brachycentrus subnubilus predominated in the 

 large tributaries of the Volga and Kama, e. g.,the Mologa, Sheksna, Sura, 



113 



