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To reproduce and to transmit disease, female mosquitoes must obtain blood meals and locate appropriate sites for egg laying (oviposition). While distinct sensory cues drive each behavior, humidity contributes to both. Here, we identify the mosquito's humidity sensors (hygrosensors). Using generalizable approaches designed to simplify genetic analysis in non-traditional model organisms, we demonstrate that the ionotropic receptor Ir93a mediates mosquito hygrosensation as well as thermosensation. We further show that Ir93a-dependent sensors drive human host proximity detection and blood-feeding behavior, consistent with the overlapping short-range heat and humidity gradients these targets generate. After blood feeding, gravid females require Ir93a to seek high humidity associated with preferred egg-laying sites. Reliance on Ir93a-dependent sensors to promote blood feeding and locate potential oviposition sites is shared between the malaria vector Anopheles gambiae and arbovirus vector Aedes aegypti. These Ir93a-dependent systems represent potential targets for efforts to control these human disease vectors., Competing Interests: Declaration of interests P.A.G. is a co-inventor on patent WO2017196861A1 (WIPO PCT; pending; inventors: Z. Knecht, P. Garrity, L. Ni) “Methods for modulating insect hygro- and/or thermosensation.” This patent proposes using members of the ionotropic receptor family as targets for strategies to disrupt hygro- and thermo-sensation in insects. W.J.L. and P.A.G. are co-inventors on patent application PCT/US2021/052374, “Sterile organisms, methods of making, and methods of use thereof.” This patent includes methods for genetic manipulations in non-traditional model organisms., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Mosquito-borne diseases such as malaria, Zika virus, and dengue virus are a menace to the human population. Although many mosquito species are not attracted to humans and do not feed on blood, human-biting female mosquitoes are strongly attracted to people and use chemosensory cues to identify a suitable host for a blood meal. Mosquitoes need blood components to reproduce, rendering them excellent vectors for blood-borne diseases. The three genera ( Culex , Anopheles , and Aedes ) responsible for most of these diseases find hosts by using their peripheral sensory organs. These organs include the antennae, maxillary palps, and proboscis. All three contain diverse populations of highly sensitive neurons that express sensory receptors that can detect odorants, temperature, chemicals, and tastants. Although these organs are essential to the host-seeking behavior that results in biting, their small size and thick outer cuticle can hinder typical histochemical analyses. Here, we briefly review the role the peripheral sensory organs play in mosquito behavior. Then, we introduce how to investigate their gene expression profiles using immunohistochemical and RNA in situ approaches for both whole-mount and frozen-section preparations., (© 2023 Cold Spring Harbor Laboratory Press.)

Mosquitoes transmit pathogens that kill >700,000 people annually. These insects use body heat to locate and feed on warm-blooded hosts, but the molecular basis of such behavior is unknown. Here, we identify ionotropic receptor IR21a, a receptor conserved throughout insects, as a key mediator of heat seeking in the malaria vector Anopheles gambiae Although Ir21a mediates heat avoidance in Drosophila , we find it drives heat seeking and heat-stimulated blood feeding in Anopheles At a cellular level, Ir21a is essential for the detection of cooling, suggesting that during evolution mosquito heat seeking relied on cooling-mediated repulsion. Our data indicate that the evolution of blood feeding in Anopheles involves repurposing an ancestral thermoreceptor from non-blood-feeding Diptera., (Copyright © 2020 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.)