In the watercourses of Tuva, the communities of amphibiotic insects, including black flies, caddisflies and stoneflies, are characterized by heterogeneity in the longitudinal profile of the rivers.
Highmountain, middlemountain, and lowmountain types of com munities are well distinguished.
The redistribution in the structure of domination conditioned by the gradi ent of biotopic characteristics in the altitudezonal regime is observed.
Trophic characteristics of the com munities also undergo changes.
A gradual replacement of ways to catch food, from scraping to predation in the upper reaches to collecting in the lower reaches, is caused by changes in the food base in watercourses. The larvae of amphibiotic insects feed on algae, detri tus, and small insects, selecting their food objects according to a size category.