Blood-feeding mosquitoes are a leading threat to global public health-vectoring dangerous infections including Zika, dengue, and malaria. Mosquitoes identify and target hosts for blood meals by using visual, thermal, and chemical cues. Here we describe an assay for measuring odor-based host-preference behavior-that is, the preferential approach toward one host over another based on differences in the volatile compounds they emit. The assay can be adapted for use with diverse odor sources, from live animals and their breath to odor-scented sleeves with controlled amounts of CO2 Mosquitoes in this assay fly upwind to within 30 cm of the odor source and then enter a small trap. We therefore believe this assay best replicates medium- to short-range host-seeking, when females approach and are preparing to land on a host animal. We also find that relative response in a two-choice test shows less trial-to-trial variation than the absolute number of responsive mosquitoes, which appears more sensitive to exogenous factors such as rearing conditions. This assay has been used to better understand mosquito host-seeking decisions, which can provide fundamental insight into the brain and behavior as well as information useful for the design of novel vector control strategies.
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