Combining thermopreference (T<i><sub>p</sub></i>) and CO<sub>2</sub>-gated heat-seeking assays, we studied the thermal <i>preferendum</i> and response to thermal cues in three <i>Culex</i> mosquito species exhibiting differences in native habitat and host preference (e.g., biting cold and/or warm-blooded animals). Results show that these species differ in both T<i><sub>p</sub></i> and heat-seeking behavior. In particular, we found that <i>Culex territans</i>, which feed primarily on cold-blood hosts, did not respond to heat during heat-seeking assays, regardless of the CO<sub>2</sub> concentration, but exhibited an intermediate T<i><sub>p</sub></i> during resting. In contrast, <i>Cx. quinquefasciatus</i>, which feeds on warm blooded hosts, sought the coolest locations on a thermal gradient and responded only moderately to thermal stimuli when paired with CO<sub>2</sub> at higher concentrations. The third species, <i>Cx. tarsalis</i>, which has been shown to feed on a wide range of hosts, responded to heat when paired with high CO<sub>2</sub> levels and exhibited a high T<i><sub>p</sub></i>. This study provides the first insights into the role of heat and CO<sub>2</sub> in the host seeking behavior of three disease vectors in the <i>Culex</i> genus and highlights differences in preferred resting temperatures.
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