The effects of commercial propagation on bumble bee (Bombus impatiens) foraging and worker body size

Bumble bees (Bombus spp.) have been commercially propagated for over three decades. As the environmental conditions experienced by commercial bumble bees differ greatly from those experienced by wild bumble bees, commercial rearing of bumble bees may cause phenotypic changes. Here, we compare the foraging behavior and size of worker bumble bees (Bombus impatiens) from commercial and wild colonies. For this experiment, we measured worker body size, recorded if the workers returned with pollen, and examined the contents of pollen loads via microscopy. We found that, while commercial and wild bumble bees foraged on similar communities of flowers, wild bumble bees returned to colonies with purer pollen baskets (higher proportion of the most common species) and were more likely to return to the colony with pollen than their commercial counterparts. Commercial bumble bees were also smaller than wild bees. Our work highlights differences between commercial and wild bumble bees, in addition to raising important unanswered questions about the mechanism and drivers of these differences.