Fig. 5: The effect of achromatic contrast on mosquito attraction to visual objects.

a Occupancy map of the distribution of female mosquitoes in the wind tunnel (top and side views) during CO₂ delivery in presence of a white and a light gray object (Weber Contrast: −0.05). b As in a, except the gray object has a higher contrast (−0.23). c Relative flight activity between the different phases of the experiments (pre-, CO₂ and post-CO₂). Mosquitoes exhibited similar flight activities across all tested visual objects (Kruskal–Wallis test, df = 1, Chi-sq = 3.24, P = 0.07). d Mean preference indices for the test (gray, or black) vs. control object (white) with 95% confidence interval (n = 12,764; 27,537; 37,085; 28,644; 36,050; 25,896; and 21,514 mosquito trajectories for the white, grey9.5, grey6.5, grey4.5, grey4.0, grey2.5, and black treatments, respectively). Object contrast had a significant effect on the attraction to the tested object (Kruskal–Wallis test: Preference Index~contrast tested object, df = 5, Chi-sq = 634.16, P < 0.001). All gray objects were significantly more attractive than the control, white object (one-sample tw-tailed t-test, **: P < 0.01, ***: P < 0.001) except for the lightest gray object (−0.05), which was not more attractive (one-sample t-test: P = 0.33).