In order to apply the ability of aquatic insects for water purification, we need fundamental knowledge of (1)ability of silk and nets of an individual of potential taxa to catch POM, (2)in situ POM amount and its composition of particles size, and (3)in situ community dynamics of the potential taxa. Among lotic aquatic insects, larvae of Chironomidae are frequently the most abundant and the most species-rich group in aquatic ecosystems. In our study, we focused on chironomids as potential taxa that can be used for water purification and investigated their in situ community dynamics in a representative river.