Abstract
Observations were made on the horse fly, Tabanus iyoensis Shiraki, at Nakanokouchi, Toyama Prefecture, in early fall of 1968, using the collection methods with dry ice light traps and insect nets. The results were as follows : 1. Carbon dioxide gas was found to have a remarkable attracting effect on the female horsefly and large numbers of them could be collected in the dry ice traps shown in Fig. 3. Remarkable increases were seen in the number collected in the trap with dry ice during the daytime from 10 a.m. to 7 p.m. in comparison with the control trap without dry ice. 2. No consistent differences were seen between the numbers collected in the traps covered with black or white sheets. 3. The horse fly was observed to be attracted to electric light (fluorescent lamp, green and blue light) in the evening. 4. Their flight activity was found to be enhanced by the movement of a vehicle, and by waving of insect nets. Large numbers of the horse-fly could be collected with the insect net particularly in early morning and at dusk. 5. Preliminary studies on the population density and the flight range of this species of horse-flies were conducted by the mark and release method, in which about 1 and 5 percent of the population were recaptured with the dry ice traps and the insect nets at the two trials. 6. The flight and the biting activity of the horse-fly were observed in the temperature range of 20°to 26℃ and during the daytime under illumination of 10 to 1, 000 lux, but not at temperatures below 15℃ nor in complete darkness. In this connection, their activity was found to be the highest in the morning and at dusk in midsummer, and at the daytime in the autumn season.
