Fig. 6: The role of dominant wavelength vs. contrast in mosquito visual attraction.

a Spectral reflectance of 660 nm (R-Hue), black, and gray objects used in the experiments: Gray 9.5, 6.5, 4.5, 4.0, 2.5, and 1.5, with Weber contrast values of −0.17, −0.30, −0.05, −0.10, −0.20, −0.24, −0.27, and −0.28, respectively. b Spectral reflectance of 496 nm and 510 nm objects used in the experiments: Gw-T1, Gw-T3, Gc-T1, Gc-Hue, G-S1, and G-S2, with Weber contrast values of −0.18, −0.11, −0.17, −0.20, −0.25, and −0.27, respectively. c, d Occupancy maps showing the distribution of female mosquitoes in the wind tunnel (top and side views) during CO₂ delivery in presence of the 660 nm (R-Hue) and Grey2.5 objects (c), or 510 nm (G-S2) and Grey1.5 objects (d); both the 510 nm and Grey1.5 objects have the same levels of contrast with the background (Weber Contrasts of −0.27). e Mean preference indices for the 660 nm vs. gray objects with different levels of contrast with the background. The Grey1.5 object (Weber Contrast value of −0.28) was not significantly different from 0 (one-sample two-tailed t-test: P = 0.07) and was subsequently used in experiments in (f) (blue arrow). f The Grey1.5 object was significantly more attractive than most of the 510 nm objects (one-sample two-tailed t-test: P < 0.001, ***), although the darkest 510 nm object (G-S2; Weber Contrast = −0.27) was not significantly different from 0 (one-sample two-tailed t-test: P = 0.66))(n = 10,098–15,578 trajectories for each tested object). g As in (c), occupancy maps showing the distribution of trajectories around the 660 nm and dark 510 nm objects. h Mean preference indices for 660 nm vs. dark 510 nm objects, and 496 nm vs. dark 452 nm or dark 510 nm objects. Mosquitoes significantly preferred the 660 nm and 496 nm objects over the dark chromatic objects (510 nm and 452 nm)(one-sample two-tailed t-test: P < 0.0001). For (e, f and h), boxplots area the mean (line) with 95% confidence interval (shaded area), and asterisks denote P < 0.001 (one-sample t-test) (n = 7191–27,717 mosquito trajectories for each tested object).