Fig. 9. Both the visual and wind stimuli shaped fly orientation. The orientation predicted by a preference for wind is indicated by the blue bars and that predicted by FOC orientation is indicated by the red bars. Each row represents a change in the location of the FOC with the bottom row corresponding to the orientation behavior measured while the visual arena was dark. Numerical values above and to the right of the labeled panels are mean preference indices ±s.d. Orientation could, in general, be described as a compromise between the two competing stimuli with orientation being increasingly biased towards the wind with increasing wind velocity, and increasingly favoring the FOC with increasing expansion velocity.