Flies actively integrate cross-modal visual cues while tracking the terminated ethyl butyrate plume. (A) After flies were 'visually' dragged near the odor nozzle, the ethyl butyrate plume was turned on and terminated after 3 seconds. The arena pattern was set to high contrast vertical stripes. Flies could no longer track the ethyl butyrate plume upon switching to a grayscale pattern after 12 seconds from the start of the experiment. Shown are 5 exemplar individual flight trajectories. (B) Plume deviation, a metric used to assess quality of plume tracking, was computed when the grayscale pattern was switched on and compared to the extent of plume deviation when the arena displayed high-contrast visual stripes. The two values were found to be significantly different (t-test p < 0.01). n = 20 flies.