Flight densities of adult black flies (Diptera: Simuliidae) and control strategies in the Betsumata area, upper Ukawa River, Niigata Prefecture, Japan

The blood-sucking habits of female black flies are responsible for considerable deleterious effects on humans and their economic welfare. With the aim of controlling black flies in the upper reaches of the Ukawa River in Kashiwazaki City, Niigata Prefecture, Japan, the present study was conducted to determine the flight densities of adult black flies by using sticky-board traps with dry ice set over 24 hours at 30 sites in the Betsumata area from June to October 2021 with citizen cooperation. The results were that a total of 4,232 individual adult black flies were captured from all sampling sites during the investigation period. The month in which the most black flies were captured was August 28–29, with 1,496 individuals, followed by October 23–24 with 1,434 individuals. The average number of black flies per site was 28.2 individuals/trap during the investigation periods. Many black flies tended to be captured around the Jojoimogawa River and around the mountains which surround the Betsumata area, while the density of black flies in rice paddies was low. It was presumed that the place of emergence and the resting/hiding place did not match. It is important to take measures against black flies in their resting/hiding places.