Mosquito heat seeking is driven by an ancestral cooling receptor

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.