Temperature shapes oviposition site selection and post-oviposition egg transport in an insect with parental care

Depositing eggs in an area with adequate temperature is often crucial for mothers and their offspring, as the eggs are immobile and therefore cannot avoid exposure to sub-optimal temperatures. However, the importance of temperature on oviposition site selection is less clear when mothers have the capability to avoid these potential adverse effects by both moving their eggs after oviposition and providing other forms of egg care. In this study, we addressed this question in the European earwig, an insect in which mothers care for the eggs during several months in winter and often move them during this period. Using 60 females from two Canadian populations (St John's and Harvey station) set up under controlled thermal gradients, we demonstrated that earwig females both select oviposition sites according to temperature and move their eggs after oviposition to reach warmer environmental temperatures. While this set of behavioural thermoregulation is present in the two studied populations, its modality of expression was population-specific: St John's females explored greater ranges of temperatures before oviposition, laid their eggs in warmer areas, and moved their eggs quicker toward warm locations. Overall, our study reveals that earwig females have evolved both pre-and post-oviposition behavioural strategies to mitigate the risks inherent to tending eggs during winter. More generally, it also reveals that egg care and egg transport do not prevent behavioural thermoregulation via oviposition site selection and highlights the diversity of behaviours that insects can adopt to enhance their tolerance to global climate change.