Relationships among environmental factors, ecological parameters of aquatic insect communities, and occurrences of chironomid species were examined in mountainous streams in the Chugoku Region. A significant negative relationship was observed between water quality and larval density of Polypedilum tamasemusi. A significant positive relationship was observed between taxonomic diversity and feeding style diversity of aquatic insect communities. Larval densities of Polypedilum tamasemusi and Tvetenia tamaflava also showed significant positive and negative relationships, respectively, with taxonomic diversity. Similarly, larval density of Polypedilum takaoense showed a significant negative relationship with lifestyle diversity. Furthermore, significant positive relationships were observed between the larval densities of Neobrillia longistyla and Polypedilum tamasemusi, and Tvetenia tamaflava and Virgatanytarsus arduennensis, suggesting that the same factor determines the larval occurrence.　　

These results suggest the possibility of some chironomid species as promising indicators of biological and physicochemical conditions in mountain streams.