Daily activity patterns of host-seeking horse flies (Diptera: Tabanidae: Hybomitra spp.) in northern and southern Manitoba

Daily patterns of host-seeking activity by female tabanids were determined by hourly trapping (05.30-22.30 h) with Manitoba horsefly traps at Seven Sisters, Manitoba, Canada, 4 days a week, throughout the summer of 1988. Hybomitra epistates and H. pechumani were most active during late morning or midday; H. arpadi and H. zonalis in early afternoon; H. affinis, H. illota and H. lasiophthalma in late afternoon; H. nitidifrons nuda and H. lurida in early evening. The morning onset of tabanid flight activity usually was related to temperature, but the cessation of activity in the evening was related to temperature or light, depending on which was first to fall below threshold levels. Tabanid flight activity was generally low at temperatures below 20°C, although H. lasiophthalma and H. affinis occasionally were caught at 12°C. Little flight activity occurred at light intensity levels below 1000 lx regardless of temperature. At Churchill, Manitoba, where tabanids were trapped hourly from 27 July to 15 August in 1988, H. affinis and H. frontalis activity was low below 14°C, although some activity occurred at 6°C.