Observations on the orientation of tsetse flies (Glossina pallidipes) to wind‐borne odours

Observations of the upwind flight of Glossina pallidipes Austen near a source of host odour show that in the absence of a visual target the insects tend to overshoot the odour source in fast, low flight. There is no sign of the crosswind ‘casting’ flight which characterizes the behaviour of moths under similar circumstances, except that a 180d̀ turn is executed to bring the tsetse flies back to the vicinity of the odour source in downwind flight. This may be followed by a second overshoot and another 180d̀ turn before the insects alight within a metre or so of the source. The results indicate that the orientation of tsetse flies to host odour may involve a step‐wise approach to the odour source, providing an opportunity for assessment of wind direction when the insects are at rest between successive bursts of flight.