Fig. 3. Halteres encode faster rotations whereas the visual system is responsive to slower rotations along all three functional axes. The mean amplitude of the sinusoid fit to averaged wingbeat amplitude (WBA) data ± S.E.M. is plotted against the peak angular velocity for visual (open circles) and mechanical (filled circles) stimuli. The amplitude of WBA modulation is plotted in relative units and represents the difference between left and right WBA for roll and yaw, and the sum of the left and right WBA for pitch. For mechanical pitch, roll, and yaw, the number of flies (N) is 9, 10 and 10, respectively. For visual pitch, roll and yaw, N=11, N=10 and N=12, respectively, except for the leftmost two data points of roll, N=7, and the leftmost datum of pitch, N=6, which were measured in a separate experiment.