A Fluctuating Thermal Regime Improves Long-Term Survival of Quiescent Prepupal Megachile rotundata (Hymenoptera: Megachilidae)

The alfalfa leafcutting bee Megachile rotundata (F.) is the primary pollinator for alfalfa seed production. Under standard management conditions, the alfalfa leafcutting bee develops to the diapausing prepupal stage undereld conditions, after which they are cold-stored at a static temperature until the following spring, when temperatures are raised and development resumes. Wehave assessed the effects of a auctuating thermal regime (FTR) during overwintering cold storage, where bees were exposed to a daily 1 h pulse of 20 degrees C, and compared viability and insect quality to bees stored under a static thermal regime. Our results demonstrate that implementing an FTR protocol dramatically increases the survival of cold-stored alfalfa leafcutting bees, effectively extending their shelf-life into the subsequent growing season. These ndings could substantially ameliorate signicant obstacles that restrict the more widespread use of this important pollinator, such as the biological constraints that restrict its use in early blooming crops, and yearly auctuations in bee prices that add signicant nancial uncertainty to end users. This study also strengthens a growing body of evidence that indicates FTR protocols are superior to static thermal regime protocols for insect cold storage.