Many species of Hydropsychidae which live mainly in mountain streams 

 show the greatest development in large rivers in the plains. They are 

 found almost throughout the profile of the river. 



They use the dense tufts at the anterior margin of the labrum to clean 

 their capturing nets which are clogged by detritus; this enables the species 

 in large rivers in the plains to tolerate the water turbidity during floods in 

 spring, summer and autumn; respiration is ensured by the tracheal gills 

 on the sides and ventral surfaces of the larva. 



The structures of the larvae of Psychomyiidae (Tinodes, Psycho - 

 my ia), are found on the surface of the solid water bottom or on wood in 

 rivers and brooks in the plains, as are also those of the larvae of Lepto- 

 c e r u s and the nets of the larvae of Neureclipsis bimaculata. 

 The larvae of Neureclipsis, with their delicate structures, find optimal 

 conditions in small rivers in the plains with a moderate current, where they 

 often occur in large numbers in plant thickets; they place their nets on the 

 stalks and leaves of Potamogeton perfoliatus or other plants in the 

 current. 



When the current is slower or disappears in calm parts of running water 

 bodies or in stagnant water, the bottom and its soil change; hard soil is 

 112 replaced by loose debris and deposits; in stagnant water, hard bottoms are 

 areas of stony or clay bottom on the open littoral of lakes, wood fragments 

 and macrophytes; loose bottoms are detritus deposits, sandy soils and slime 

 deposits. 



Conditions in the open, stony littoral washed by breakers resemble 

 conditions on the stony bottom of a running water body; this enables some 

 lithorheophiles which entered from running water to settle in these regions, 

 where they live on stones together with other species of the lascustrine fauna. 



In lakes Onega and Ladoga, these species are represented by Rhya- 

 cophila nu b i 1 a, Poly c ent r opu s flavomaculatus, Hydro- 

 psyche an gu st ip enni s, species of Apatania, Potamophylax 

 stellatus; species of Chaetopteryx and Leptocerus, etc., in Lake 

 Teletskoe are represented by Apatania stigmatella, Dicosmoecus 

 palatus, Anisogamodes flavipunctatus, Annitella obscurata, 

 Lepidostoma hirtum. 



Detritus -covered bottom is the only type of loose soil in stagnant water 

 bodies which is widely inhabited by caddis flies; the life of lithophiles on 

 detritus may be considered as life on small fractions of woody soil; as 

 lithophiles living on stones may be found on large boulders, rocks, rock 

 fragments, screes or pebbles, larvae living on wood may be found on large 

 pieces of wood (tree trunks or large branches) or on coarse and fine wood 

 detritus; the latter rarely consists of only wood and is usually mixed with 

 leaves, conifer needles or partly decomposed parts of aquatic plants, 

 especially reeds, sedge, Tr i o di a, horsetail or riparian plants. 



Life on a detritus bottom is closely connected with life among macro- 

 phytes; it results in the construction of cases covered with large particles 

 of detritus (sometimes also with green plant fragments or sand grains and 

 mollusk shells), as for example, in the following species: Limnophilus 

 (L. flavicornis, L. politus, L. rhombicus, L. marmoratus, 

 L. stigma, etc.). 



A large group of phytophages and detritophages is closely associated 

 with green plants, in stagnant or slowly running water bodies. Some of these 



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