Fig. 1: Olfactory gating of mosquito color preference.

a The Ae. aegypti eye. Image courtesy of Alex Wild (with permission). b Spectral reflectance of behaviorally important objects for Ae. aegypti females: human skin (brown line); flower (Platanthera obtusata; green line) and within a small puddle filled with Ae. aegypti larvae (blue line). Lines are mean; shaded area around the mean is the ±sem (n = 6–10). c Wind tunnel system with real-time tracking system, odor and visual stimulation. d Heat map of the CO₂ plume in the wind tunnel. e Example of individual trajectories (top: [x-,y-axes], bottom: side view [x-,z-axes]). The arrows represent the start of a trajectory; circles are the visual objects. f Heat (occupancy) maps showing the distribution of female mosquitoes without (left panels) and with CO₂ delivery (right panels) while in presence of a white and a red objects (top), or white and green objects (bottom). Plots shows the top and side views of the tunnel working section. g Reflectance of the visual stimuli used in the experiments, as quantified using a spectrophotometer and calibrated with a white Spectralon standard. Different colored traces correspond to the different stimuli. h Relative flight activity between the different phases of the experiments (pre-, CO₂ and post-CO₂) for black and white circles (n = 12) and color and white circles (n = 51). There were no significant differences when the tested visual object was black vs. objects of different wavelengths (Kruskal–Wallis test, df = 1, Chi-sq = 0.01, P = 0.92), although for both groups CO₂ significantly elevated the number of flying mosquitoes compared to the filtered Air treatment (P < 0.002). i Mean preference index for the test object vs. the control (white) object. There was a significant effect of color on the attraction to the tested object (Kruskal–Wallis test, Preference index ~ pair of visual stimuli used: df = 8, Chi-sq = 597.23, P < 0.0001). Several hues were significantly more attractive than the control, white object (one-sample two-tailed t-test: ***: P < 0.001). Boxplots are the mean (line) with 95% confidence interval (shaded area) (n = 25,529; 17,729; 53,786; 23,694; 34,343; 31,037; 32,257; 24,774; 42,595; 20,929; and 48,198 mosquito trajectories for the all-white, all-black, black-and-white, Bv-T2, Bw-, Gw-T1, Gc-, YGc-, Yw-, O- and R-Hue treatments, respectively).