Mosquitoes Use Vision to Associate Odor Plumes with Thermal Targets

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Recent evidence suggests that thermal attraction is gated by the presence of CO2 [6McMeniman C.J. Corfas R.A. Matthews B.J. Ritchie S.A. Vosshall L.B. Multimodal integration of carbon dioxide and other sensory cues drives mosquito attraction to humans.Cell. 2014; 156: 1060-1071Abstract Full Text Full Text PDF PubMed Scopus (259) Google Scholar], although this conclusion was based experiments in which the actual flight trajectories of the animals were unknown and visual cues were not studied. Using a three-dimensional tracking system, we show that rather than gating heat sensing, the detection of CO2 actually activates a strong attraction to visual features. This visual reflex guides the mosquitoes to potential hosts where they are close enough to detect thermal cues. By experimentally decoupling the olfactory, visual, and thermal cues, we show that the motor reactions to these stimuli are independently controlled. Given that humans become visible to mosquitoes at a distance of 5–15 m [16Bidlingmayer W.L. Hem D.G. The range of visual attraction and the effect of competitive visual attractants upon mosquito (Diptera: Culicidae) flight.Bull. Entomol. Res. 1980; 70: 321-342Crossref Scopus (38) Google Scholar], visual cues play a critical intermediate role in host localization by coupling long-range plume tracking to behaviors that require short-range cues. Rather than direct neural coupling, the separate sensory-motor reflexes are linked as a result of the interaction between the animal’s reactions and the spatial structure of the stimuli in the environment.