Daily patterns of host-seeking activity by female tabanids were determined by hourly trapping (0530–2230 hours) with Manitoba horse fly traps at Seven Sisters, Man., 4 days a week, throughout the summer of 1988. Hybomitra epistates (Osten Sacken) and H. pechumani Teskey and Thomas were most active during late morning or mid-day; H. arpadi (Szilady) and H. zonalis (Kirby) in early afternoon; H. affinis (Kirby), H. illota (O.S.), and H. lasiophthalma (Macquart) in late afternoon; H. nitidifrons nuda (McDunnough) and H. lurida (Fallen) 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 either 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, Man., where tabanids were trapped hourly from 27 July to 15 August in 1988, H. affinis and H. frontalis (Walker) activity was low below 14°C, although some activity occurred at 6°C.