Abstract
The blackflies fauna was surveyed at 68 stream sites in Tochigi Prefecture, Japan, in April-May 1983. A total of 2,794 larvae and 993 pupae belonging to 20 species were collected from 61 sites in Tochigi. The predominant species were Simulium uchidai (21% of the total), S. japonicum (21%) and Prosimulium yezoense (11%). The widely distributed species were S. japonicum (56%), S. uchidai (49%), S. subcostatum (45%) and S. suzukii (30%). Six species (S. iwatense, P. yezoense, S. japonicum, S. subcostatum, S. uchidai and P. kiotoense) were collected from the low land (lower than 500m above the sea level) to the high land (higher than 1,000m).
