We report cases of Simuliidae and Chironomidae living on Lachlania nymphs (Ephemeroptera). This is the first record of these associations in South America. Simulium exiguum (pupae and larvae), Simulium cuasiexiguum (larvae), Cricotopus sp. (larva) and Rheotanytarsus sp. (larva) were found associated with Lachlania nymphs. We believe that all of these associations can be classified as opportunistic (or casual) attachment.
aquatic insects; neotropical region; association; black fly; mayfly
