In the longitudinal continuum of the Kupa River the vegetation cover and substrate type were the important environmental factors influencing the spatial differences in the biomass and community composition. Of total macroinvertebrate biomass, a significantly greater percentage of trichopterans was found on boulder and cobble substrata covered with moss (54.3% on boulders, 55.8% on cobbles) than on substrata covered with periphyton (9.9% on boulders, 14.8% on cobbles). In the potamal, trichopterans were markedly reduced (<2.5% of total macroinvertebrate biomass) on gravel substrata.
A comparison of the Shannon diversity index values suggested that for trichopteran species diversity the substrate type was a more influential factor than vegetation cover. On the other hand, multidimensional scaling analysis showed that trichopteran community composition was related more significantly to vegetation cover and river area than to substrate type.
In the rhithral the vegetation cover was an important factor influencing the functional feeding group composition of trichopterans. The spatial distribution of scrapers and filtering collectors depended significantly on the vegetation cover associated with substrate type, and shredder trichopterans were related to vegetation cover only. Predatory trichopterans made up 17–65% of total predator biomass, and in the rhithron area they were correlated significantly only with vegetation cover. On gravel substrata in the potamal, vegetation cover did not affect the spatial distribution of shredder and collector‐filterer trichopterans significantly.