The distribution pattern was compared among the caddisfly larvae of the family Rhyacophilidae by examining the various larval communities covering a total basin of the Ohta River, Japan. A total of 15 species were collected, among which the distribution range and the mean was remarkably different for any environmental parameter. Rhyacophila bilobata, R. shikotsuensis and R. sp. RF showed a narrow range and small standard deviation for distance from riverhead, river width and valley area. Each parameter was standardized, and cluster analysis was performed on the basis of the means of 8 parameters for distribution of each species. A cluster, involving R. bilobata, R. clemens and R. sp. RK, all primitive, was estimated to have adapted to high altitude, steep riverbed slope, small-scale, oligotrophic and low-temperature waters. Another cluster, involving R. nigrocephala and R. yamanakensis, both derivative, was estimated to have adapted to low altitude, loose slope, large-scale, eutrophic and high-temperature waters. Besides, R. kawamurae, a species of Nigrocephala group, participated in an Apsilochorema sutshanum-cluster whereas R. nigrocephala, another species of the same group, constructed a R. nigrocephala-cluster. These suggest that the original habitat of the ancestral species be headwaters, that strongly restricting factors be different among species and that there be some habitat-partitionings among the sibling species.