Abstract
The fauna and distribution of blackflies in Okayama Prefecture, Japan, were examined based on the collections of larvae and pupae from streams and adults flying around the collectors at 74 sites in spring of 1991. A total of 4,949 blackflies, [3,675 larvae (74.3% in total number), 1,259 pupae (25.4%) and 15 adults (0.3%)], were collected at 72 sites. These blackflies were classified into 23 species of three genera : Prosimulium Roubaud, Cnephia Enderlein and Simulium Latreille. Nine species, i.e. Prosimulium (Prosimulium) kiotoense, P (P.) yezoense, Cnephia (Stegopterna) mutata, Simulium (Nevermannia) aureohirtum, S. (N) konoi, S. (N.) mie, S. (Gomphostilbia) ogatai, S. (Simulium) japonicum and S. (S.) kawamurae were newly recorded from Okayama Prefecture. Further, five undescribed and / or unidentified spcies, e.g. E. sp. 2, S. sp. H, S. sp. O-1, S. sp. O-2 and S. (Helichiella) sp., were recognized. The most abundant species was S. (N) uchidai (22.9% in total number), followed by S. (S.) arakawae (19.7%), S. (S.) japonicum (18.8%), P. (P.) kiotoense (10.9%), S. (N) subcostatum (8.1%), S. (S.) suzukii (3.6%) and S. (Gnus) bidentatum (3.3%). The most widely distributed species was S. (N) uchidai (55 sites), followed by S. (S.) japonicum (44 sites), S. (N) subcostatum (32 sites), S. (S.) arakawae (26 sites), S. (Gn.) bidentatum (26 sites), S. (S.) rufibasis (22 sites), S. (O.) aokii (17 sites) and P. (P.) kiotoense (14 sites).
