Mimicking Atmospheric Flow Conditions to Examine Mosquito Orientation Behavior

Mosquitoes are known vectors for many infectious diseases, including malaria and West Nile virus. One of the most notorious species is Aedes aegypti, also known as the yellow fever mosquito, which in addition to its namesake also carries other diseases including dengue fever and chikungunya. Recently, the species has been the focus of intense interest due to the role females A. aegypti play in the transmission of the Zika virus. Such new mosquito-borne diseases have been increasing in number due to anthropogenic disturbances and climate change, and in the face of this challenge, the host-seeking behavior of female mosquitoes is viewed as a target for disruption in the disease transmission cycle. Thus, experiments that expand our understanding of the orientation strategies used by mosquitoes may lead to drastic improvements in mosquito control. Much of the work which has been performed on mosquito orientation has involved field and laboratory bioassay methodologies, including suction trapping (field), landing on humans/traps in large semi-field cages, entrance of flying mosquitoes into a trap or port, hand-in-box assays, and close-range orientation assays [1, 2, 6, 7, 8]. While these studies have produced valuable information regarding effective cues, the flow conditions in these studies are not always reported and/or well-characterized, placing limits on our understanding of the influence of atmospheric flow conditions upon mosquito orientation behavior. In order to better simulate odor dispersion and plume structures encountered by mosquitoes in natural settings, wind tunnel tests are often employed [4]. However, previous work utilized either laminar flows — which lack the fluctuations and multi-scale characteristic of the highly turbulent atmospheric boundary layer — or turbulent flows generated by passive grids — which generate only small scale turbulent fluctuations [3]. Even if the grid-generated turbulence matches the turbulence intensities found in mosquitoes’ natural habitats, the time and length scale effects of larger and slower flow features on the scalar dynamics have essentially been ignored. Further, as evidenced by unique orientation behaviors that are observed only in lab settings, studies suggest that the host-finding behavior of mosquitoes is affected not only by the odor composition but also by the characteristics of the flow environment [5].