Effects of Extended Prepupal Storage Duration on Adult Flight Physiology of the Alfalfa Leafcutting Bee (Hymenoptera: Megachilidae)

The alfalfa leafcutting bee, Megachile rotundata (F.), is a solitary, cavity-nesting bee and is the primary pollinator for alfalfa seed production. Bee management practices include cold storage during the prepupal stage. Fluctuating thermal regimes during cold storage increases survival of cold storage and allows a doubling of the cold storage period with no decrease in survival. However, survival, characterized as successful adult emergence, is not qualitative. In this study, we determined whether extended storage affects adult bee respiration or flight physiology. We overwintered bees for a single winter (current management protocol) or for 12 mo longer (extended storage). We used resting and tethered flight metabolic rates and resting critical PO2 (the oxygen partial pressure below which metabolism can no longer be sustained) as indices of adult bee quality. We found no significant differences in body mass, resting or flight metabolic rates, or critical PO2 between the two groups. Together these data indicate that extended storage of M. rotundata produces bees of similar respiratory capacity and flight ability. These findings could increase the use of M. rotundata as an alternative pollinator, allowing for extended storage to time adult emergence with early blooming crops.