Studies on the Bionomics and Control of the Horse Flies Attacking the Grazing Japanese Cattle

I. Diurnal Biting Activity and Habitat Segregation of the Horse Flies

Abstract

The diurnal biting activity and habitat segregation of 3 tabanid-flies attacking livestock were observed on 3 days, from July 24 to Aug. 4, 1967, in grazing land of Kyoto. A pair of steers were tied to a tree or pole all day long in 3 places; A: watering place surrounded by a growth of oaks and elms, B: resting place situated about midway between A and C, and C: feeding place, 117m northwest of A, and the undergrowth was composed mainly of silvergrass and bracken. Of the 7 species of the horse flies occurring in this land, the whitishmaculate horse fly, Tabanus mandarinus SCHINER, was dominant in A, and the giant horse fly, T. chrysurus LOEW, was dominant in C. In fine weather there were 2 peaks in the number of biting flies, one was in the morning, the air temperature being about 27°C and the other in the late afternoon when the daylight intensity decreased rapidly. The biting activity, therefore, seemed to be regulated mainly by the diurnal changes of temperature and daylight intensity. Both giant and common (T. trigonus COQUILLETT) horse flies were found to be more attracted to black-setose steers than to the brown-setose ones. The former fly fed predominantly on the back, while the latter on the belly. The smallest mandarinus was found on the legs and neck. The segregation of these horse flies resulted from their variable preferences for the setigerous parts of the steer's body according to their headlengths including the proboscis, and also to the intensity of illumination. There was also evidence of ecological coaction between the closely related species, chrysurus and trigonus.