Red mason bee (Osmia bicornis) thermal preferences for nest sites and their effects on offspring survival

Ectotherms usually require a narrow range of thermal conditions for development; thus, parentalselection of oviposition sites is crucial. In a field experiment, we investigated female solitary red mason bee (Osmiabicornis) preferences for potential nest site temperatures and their effects on offspring development. The resultsshowed that bees detected and avoided nest sites with high temperatures (28$^{\circ}C$) and often chose cooler (24$^{\circ}C$) orambient temperatures (average 18-20$^{\circ}C$). This is a protective behaviour because offspring survival decreases withincreasing nest temperature, mostly due to mortality at the egg stage. Elevated temperatures also led to weight loss inadult bees. However, hot nest temperatures appeared to deter adults or kill parasite larvae, as the highest numbers ofparasites were observed in unheated nests. We concluded that choosing the proper temperature for nests is animportant element in bee life strategies, especially in warming environments.