The purpose of this experiment was to examine the species and activity of horseflies found in Sambe Pasture. The experiment was carried out in the pasture, Oda City, Shimane Prefecture from August 1 to September 4.
Horse-flies were caught with an insect-net during half an hour from 9 in the morning and from 3 in the afternoon. The horseflies were 6 species, Tabanus mandarinus, T. kinoshitai, T. rufidens, T. trigonus, T. chrysurus and Atylotus horvathi. Among them, T. mandarinus were the most in number, twice the total of the other five.
As for T. mandarinus, they flew on to the cattle in a larger number in the afternoon than in the morning. There was no difference about the other five species.
It is generally said that horse-flies appear most in July and August. During this experiment, T. trigonus, T. chrysurus, T. mandarinus and T. rufidens were seen more early in August and A. horvathi late in August and September. The number of T. kinoshitai had no difference during the experiment period.
Of all the species of flies, there were a greater number on fine or high temperatured days and a fewer on rainy or low-temperatured days.