Competition between fixed and moving stripes in the control of orientation by flying Drosophila

ABSTRACT. The direction in which Drosophila hydei Sturtevant flew in response to the movement of a striped pattern beneath them was biased along a direction parallel to the long axis of a stationary stripe between them and the pattern. This was not due to the flies reacting to the movement of the ends of the stripes along the long edges of the stationary one, since a stationary stripe above the flies, not between them and the pattern, similarly biased their flight direction. It was due instead to an optomotor turning reaction induced by the edges of the stationary stripe as the flies were led towards or away from it by their turning and speed control reactions to the moving stripes.