Optimizing Laboratory Rearing of a Key Pollinator, Bombus impatiens

SIMPLE SUMMARY: Rearing insects in captivity is critical for both research and commercial purposes. One group of insects that stands out for their ecological and scientific importance are bumble bees. However, most research studies with bumble bees rely on commercial colonies due to the challenges associated with initiating colonies in the laboratory. This limits the ability to study the early stages of the colony life cycle and the ability to control for variables such as colony age and relatedness. To overcome these challenges, we tested several aspects related to the solitary phase of the North American bumble bee species, Bombus impatiens. In this species, queens emerge by the end of the season, mate, and enter a winter diapause. They then initiate a colony the next spring. We examined the optimal age for mating and how the timing of CO(2) narcosis (a technique used to bypass diapause) and social cues post-mating affect queen egg laying. We demonstrate an optimum age for mating in males and females and the importance of worker and pupa presence to egg laying in queens. Overall, our findings indicate that the laboratory rearing of bumble bees can be improved by reducing challenges associated with rearing queens during the solitary phase. ABSTRACT: Bumble bees are key pollinators for wild and managed plants and serve as a model system in various research fields, largely due to their commercial availability. Despite their extensive use, laboratory rearing of bumble bees is often challenging, particularly during the solitary phase queens undergo before founding a colony. Using a literature survey, we demonstrate that most studies rely on commercially available species that are provided during the colony’s social phase, limiting study on early phases of the life cycle and the ability to control for colony age and relatedness. Laboratory rearing is challenging since the queen solitary phase is less understood compared to the social phase. To overcome this barrier, we examined several aspects related to the queen solitary phase: the effect of age on likelihood of mating, how the timing of CO(2) narcosis post-mating (a technique to bypass diapause) affects egg-laying, and whether different social cues affect the success of colony initiation. Our data show an optimum age for mating in both sexuals and decreased egg-laying latency in the presence of workers and pupae. The timing of CO(2) narcosis did not significantly affect egg laying in queens. These findings can be incorporated to improve bumble bee rearing for research purposes.