The species composition in dragonfly larvae of ten types of habitat situated at two sites in a Mediterranean irrigation canal was investigated by sampling these habitats at five dates in 1990 and 1991. A total of 28 species were found to be developing in the canal. Out of these 28 species, 19 were found in the larval stage and the rest during additional collections of exuviae along the water course. The types of habitat could be separated into five groups of different community structure. The distribution and larval densities of the most frequent species are described and niche selection discussed. It is stated that structural diversity is the main reason for high species diversity in the canal. It is suggested that this irrigation canal is a good example for consistency of human utilization and species richness of running waters.