During 1980-1981, 1500 larvae of 19 species were collected. Distribution of the species along the river and similarity of the sampling stations were analyzed. For this purpose, both Sokal & Michener’s qualitative index and related dendrogram, and factorial analysis of the relative abundance of the species were applied. The former gives linear variation of station similarity in relation to reciprocal distances between stations, while more complex relations among the sampling stations are shown by the latter. The relation between water quality and presence of the species along the river makes the authors conclude that dragonflies may be used as ecological indicators.