Diurnal activity patterns of Glossina brevipalpis and G austeni (Diptera: Glossinidae) in South Africa, with reference to season and meteorological factors.

Studies on the diurnal and seasonal availability of Glossina brevipalpis Newstead and G. austeni Newstead to stationary targets were conducted in north-eastern KwaZulu-Natal, South Africa. G. brevipalpis showed a bimodal, and occasionally trimodal, partly crepuscular cycle. Periods of the availability of flies to stationary, odour-baited targets (here referred to as diurnal "activity" patterns) were mainly early in the morning and late afternoon until dark, especially at dawn and dusk. The main diurnal activity period was the late afternoon peak, which occurred during the 1-2 h before sunset until dark. The amplitude of the morning and afternoon peaks seemed to be mainly modulated by temperature. This species was also active throughout the remainder of the day, depending on the season. Glossina austeni was day-active and activity seemed to increase with increasing temperature and decreasing relative humidity (RH). The species remained available to targets throughout the day, but during the hottest part of the day the diurnal pattern decreased somewhat, resulting in a U-shaped but still more or less unimodal pattern. The diurnal pattern was strongly modulated by ambient temperature, although seemingly more by a combined temperature-RH effect. Both species' availability to targets ceased after dark, although night activity was observed on various other occasions. The use of artificial refuges for G. brevipalpis and G. austeni as a possible means of escaping climatic extremes is briefly discussed and speculated on.