Indoor microclimate shapes resting patterns of Anopheles funestus in south-eastern Tanzania

Abstract Background Indoor resting patterns of malaria vectors are changing, potentially driven by housing design including roofing materials, wall construction and associated indoor thermal and humidity-steered microclimates. This study quantifies how microclimatic gradients shape the resting choices of Anopheles funestus in southeastern Tanzania, testing whether different indoor zones create distinct thermal and humidity niches that influence mosquito microhabitat selection. Methods Between November 2024 and January 2026, thirteen sentinel houses, representing variation in house materials, roofing (metal or grass thatched), and wall material (bricks or mud) were sampled three times a week. In each house, mosquitoes were collected from indoor bottom, mid and top section using Prokopack aspirators. Sampling occurred in the morning (6:00–9:00h) or afternoon (12:00–15:00h). Indoor temperature and relative humidity were recorded at 30-minute intervals. Associations between house materials and zone, microclimate and resting behaviour were analysed using mixed-effect models. Results Across 153 sampling days, 1,910 An. funestus were collected. Most of these rested near the bottom house-section (40%), while the top-section had the smallest proportion (27%) ( p  = 0.012). Brick-walled houses had 80% higher abundance than mud-walled houses (p < 0.001), and grass-thatched houses had a 52% higher mosquito abundance than metal-roofed houses ( p  = 0.002). Indoor thermal microhabitats matched mosquito resting patterns, as both temperature and humidity varied between house materials and zones. The strong negative correlation between temperature and relative humidity ( r = -0.738) limited the explanatory value of relative humidity, whereas the weaker correlation between temperature and absolute humidity enabled separation of temperature and humidity effects on resting behaviour. Abundance of resting An. funestus was associated with the joint interaction of mean temperature (\(\:\stackrel{-}{T}\)), temperature fluctuations (\(\:{T}_{\text{r}\text{a}\text{n}\text{g}\text{e}}\)), and absolute humidity (\(\:\stackrel{-}{\text{A}\text{H}}\)), with highest abundance near \(\:\stackrel{-}{T}\)=32.7°C and \(\:\stackrel{-}{\text{A}\text{H}}\)=16.4 g/m³, and for minimal temperature fluctuations ( T range ≈0°C). Conclusion The joint interaction between mosquito abundance, resting stratification and environmental variables (temperature and humidity) explains indoor resting patterns of An. funestus . These highlight the importance of incorporating indoor microclimatic heterogeneity into vector control strategies where housing improvements could alter indoor suitability for mosquito resting, survival, and malaria transmission.