15 - Hidden habitats: microclimate heterogeneity drives mosquito resilience and control outcomes in the Desert Southwest

Abstract: Mosquitoes are ectothermic organisms, meaning their body temperature closely matches that of their surrounding environment. Consequently, local microclimate conditions influence not only their survival and reproduction but also the toxicity of insecticides. By integrating microclimate field measurements with manipulative laboratory experiments, we aim to elucidate how local habitat conditions affect mosquito biology and control.

Since June 2024, we have been recording temperature and humidity in typical mosquito resting habitats across Arizona, an arid region characterized by hot summers, mild winters, and two distinct rainy seasons. According to macroclimate datasets commonly used in mosquito and disease modeling, mosquitoes in Arizona often experience temperatures that exceed both their optimal and lethal limits. Yet they continue to thrive in this desert environment. Our measurements reveal substantial variation among microhabitats, with some sites being 10–20°C cooler during the warmest parts of the day for much of the year. These habitats appear buffered from daily thermal fluctuations, a pattern also reflected in relative humidity values, which remain higher and more stable than those recorded at nearby weather stations.

When replicating representative microclimate conditions in the laboratory to assess the combined effects of temperature and humidity on insecticide toxicity, we found that the efficacy of deltamethrin was influenced by both temperature and relative humidity, whereas malathion toxicity was affected only by temperature. Our ongoing research underscores that reliance on standard meteorological data is inadequate for accurate risk assessment, as it fails to capture localized microclimate heterogeneity that is critical for understanding and managing mosquito populations and the diseases they transmit.