Figure 3

Geometrical characteristics of cross-plume transits in male M. sexta moths seeking a pheromone source in a laboratory wind tunnel. (Top) Up/down-stream excursions, Δ x, plotted against lateral excursions, Δ y, for all observed transits (n=458). A linear regression (blue line, slope = -0.38, intercept = 15.0) is highly significant (p≪0.01) but explains little of the variance (r ²=0.07). (Middle) Log of the transformed course angle, \(\phi ^{*}=\frac {\pi }{2|\phi |}-1\), plotted against l o g(Δ y). The analysis leading to Equation 4 predicts a linear relationship between these quantities. A regression (blue line, slope = -0.45, intercept = 3.18) is highly significant (p≪0.01) and explains a substantial part of the variance (r ²=0.43). (Bottom) Lateral excursion, Δ y, plotted against course angle, |ϕ|. The solid blue curve represents Equation 3 with parameters emerging from the regression, q=0.225 and c ₁=0.0416. To illustrate effects of parameter variation on this functional form, Equation 3 is plotted with c ₁ increased and decreased by a factor of 2 (dot-dashed blue lines) and with q increased and decreased by a factor of 1.5 (dashed blue lines). Also shown in all three plots are medians (solid red lines) and 25th and 75th percentiles (dashed red lines) of binned data.