2018 年 69 巻 2 号 p. 55-60
In order to control adult blackflies in the upper reaches of the Ukawa River in Kashiwazaki City, Niigata Prefecture, the present study was conducted on the species composition and densities of adult female blackflies attracted to humans at a total of 22 sites in four areas in the upper reaches of the Ukawa River Basin from June to October in 2013. A total of 2,195 individual adult blackflies were captured from all sampling sites during the investigation periods. The average number of blackflies per site was 11.0 individuals/2 investigators·10 minutes. Noda was the highest capture area where we could collect 13.5 individuals/2 investigators·10 minutes, followed by the Joujou Area. The fewest captures were in the Ukawa Area (8.9 individuals/2 investigators·10 minutes). The dominant species was Simulium (Simulium) arakawae Matsumura, 1915 (397 total individuals, 99.5%), followed by Simulium (Simulium) oitanum (Shiraki, 1935) (2, 0.5%). The daily biting activity of female adult blackflies observed every two hours from 6:00 to 20:00 at four areas on August 10, 2013 peaked at 16:00–18:00 (range from 62.5 to 89.1%, average±S.D. 75.0±11.0%).