Optomotor control of speed and height by free-flying Drosophila.

Abstract

ABSTRACT The optomotor reactions of Drosophila have been studied intensively, with the conclusion that in flight there are two main types of response. One of these controls the course of the animal by adjusting the relative amplitudes of the wingbeats on the two sides of the body. The other controls the total thrust produced by the wings (Gotz, 1968). Drosophila do not change the direction of the thrust produced relative to the body axis (Gotz, 1968; Vogel, 1966; David, 1978) but do change the distribution of their total power output between lift and thrust by changing the inclination of the body axis (David, 1978). This could not, however, be observed in tethered fliers on which previous work had been done. Nevertheless, it has been implied that free fliers alter only their lift, so that the control of power output is used only to control height (Gotz, 1972; Buchner, Gotz & Straub, 1978). Here I report some experiments on free-flying Drosophila hydei Sturtevant showing that speed (and hence thrust) as well as height (and hence lift) are controlled by optomotor reactions to features of the surroundings.