Observations on the behaviour of tsetse flies (Glossina morsitans orientalis Vanderplank and G. pallidipes Austen) during an attempt to concentrate breeding around cattle.
The following is substantially the authors' summary. Investigations on the diurnal activity and seasonal distribution of Glossina morsitans orientalis Vanderplank [cf. RAE B 55 270] and G. pallidipes Aust. [cf. 49 54], with or without the presence of cattle as a permanent food supply, were carried out in the Zambezi Valley, Rhodesia, during 1965-67. Flies landing on one of three oxen tethered close together were caught, marked and released between 05.00 and 18.30 hours. More males than females of G. m. orientalis were caught off the oxen, but females of G. pallidipes were more abundant than males. The sex ratio of adults emerging from pupae was close to 50: 50 in both species. Results from weekly sampling in four different vegetation communities indicated that flies were evenly distributed throughout the bush between January and August, while riverine mopane (Colo-phospermum mopane) generally contained larger numbers of both species during the hot dry months [cf. 55 270]. No other difference between the vegetation communities could be detected except that there appeared to be a higher percentage of females in the riverine mopane than in the other communities during August-October. G. m. orientalis was not active below 13-14°C or G. pallidipes below 16°C, and the first captures each day of both species appeared to be related to the minimum daily temperature. Activity was not detected before dawn or after dusk [cf. 32 162; 53 242]. The pattern of diurnal activity varied from season to season and also between the two species except from September to November. Trials involving a grid of eleven tethered oxen and a 5-acre paddock containing a herd of fifteen animals showed that the presence of a permanent food supply did not result in the concentration of flies nor did it affect the seasonal fluctuations in their numbers.