Heat tolerance in tropical moths varies with micro-climate, life stage and larval feeding strategy

Understanding heat tolerance variation and its drivers is crucial for predicting climate change impacts on biodiversity. While most studies focus on adults and macro-climate effects on heat tolerance, how micro-climate shapes heat tolerance variation across life stages and feeding strategies remain largely untested. We quantified heat tolerance (critical thermal maximum: CTmax) variation in 35 species of moth larvae (caterpillars) within a seasonal tropical forest. For 17 species, we were also able to measure the CTmax of adults. We tested how seasonal macro-climate and life stage-specific micro-climate drove CTmax variation across life stages, and how feeding strategy-specific micro-climate drove CTmax variation in caterpillars. We found strong seasonal effects, with caterpillars and adults exhibiting higher CTmax in the hot season. Caterpillars exhibited higher CTmax than conspecific adults in the cool season, but this pattern was reversed in the hot season. Shelter-building caterpillars experiencing cooler micro-climates exhibited lower CTmax than free-living caterpillars. Our study highlights the complex drivers of heat tolerance and the importance of micro-climate in shaping heat tolerance variation across life stages and feeding strategies.