Spectral preferences of mosquitos are altered by odors

Vision underlies many important behaviors in insects generally and in mosquitos specifically. Mosquito vision plays a role in predator avoidance, mate finding, oviposition, locating vertebrate hosts and vectoring disease. Recent work has shown that when sensitized to CO2, the visual responses of Aedes aegypti are wavelength dependent, but little is known about how other olfactory stimuli can modulate visual responses. The visual cues associated with flowers, vertebrate hosts or oviposition sites differ substantially and it is possible that odors might prime the mosquito visual system to respond to these different resources. To investigate the interplay of olfactory and visual cues, we adapted previously used wind tunnel bioassays to use quasi-monochromatic targets (390-740 nm) created with novel LED synthesizers. We coupled these visual targets with CO2 and the odors representative of vertebrate hosts, floral nectar or oviposition sites and assessed responses via 3D tracking of female mosquitos. When CO2 alone was present, we observed a lower preference for wavelengths in the green portion of the visible spectrum with a gradual increase as wavelengths moved towards the violet and red ends of the spectrum. However, when odors associated with both flowers and oviposition sites were present, we observed significant increases in mosquito preference for green (475-575 nm) stimuli. In contrast, when vertebrate host odor was present, we saw increased preference for stimuli across the entire visible spectrum. These odor shifts in mosquito spectral preferences suggest these preferences are not fixed and shift depending on the behavioral context.