Effect of pre-wintering and wintering temperature regimes on weight loss, survival, and emergence time in the mason bee Osmia cornuta (Hymenoptera: Megachilidae)

Osmia cornuta adults require exposure to wintering temperatures followed by incubation in the to emerge. We studied winter survival, weight loss, emergence time, and post-emergence longevity O. cornuta exposed to a variety of pre-wintering and wintering treatments. Few bees emerged after to wintering durations <30 days. Maximum survival and longevity were obtained with wintering of 90-150 days. Time to emergence following incubation declined with increasing wintering and increasing wintering temperature. Pre-wintering treatment had a dramatic effect on bee fitness. pre-wintered for 15 days lost less weight, had higher survival and lived longer than bees pre-wintered 45 or 75 days. In general, larger bees were more likely to survive the winter and lived longer than smaller We discuss the relevance of these results to survival in wild O. cornuta populations and the of populations used in orchard pollination.