Experimental warming dramatically changes survival and growth of an autumn- and winter-active ground-dwelling beetle

• We focused on the ground-dwelling beetle active in autumn and winter. • Survival of adult beetles decreased only in females under high temperature. • Larger female adults were more likely to survive regardless of temperature. • Larval survival also decreased under high temperature. • Larval growth was accelerated under high temperature. Insects are one of the animal groups that experience global declines associated with climate warming. Because insects provide important ecosystem functions, understanding their responses to warming is essential. However, previous studies on responses of insects to warming have overwhelmingly focused on species active and reproducing in spring and summer. Consequently, effects of global warming and heat stress on autumn- and winter-active insect performances are poorly understood. To address this gap, we conducted temperature-manipulated rearing experiments using the ground-dwelling beetle, Synuchus cycloderus Bates (Coleoptera). It is considered as an autumn-breeding univoltine species and the larvae are active and grow during winter. It may have ecological roles in nutrient cycles and food chain in winter. To examine the effects of temperatures on adult and larval survival, and on larval growth and gene expression, we set two rearing temperature conditions: a control (14°C for adults; 5°C for larvae) and a heat treatment (control + 5°C). Survival of adult beetles decreased only in females under high temperature. Larger female adults were more likely to survive regardless of temperature conditions, whereas body size had no effect on male adult survival. Larval survival decreased under high temperature, although larval growth and expression of genes related to development were accelerated. These findings suggest that the population of S . cycloderus could be at risk of decline due to global warming. Moreover, in comparison with studies on beetles active in spring and summer, our results suggest that autumn- and winter-active insects may be especially vulnerable to climate warming.