Crop storage of pollen and its functional significance in the solitary bee, Melissodes rustica (Hymenoptera: Apidae)

Crop dissections of female Melissodes rustica (Say) in northwest Arkansas revealed that on the last collecting trip of the day large amounts of pollen are carried back in the crop, suggesting that this is a feeding trip, providing resources for self-maintenance. Females returning to burrows in the middle of the day do not carry large amounts of pollen or nectar in their crops. Females arriving at their burrows without scopal pollen on the final trip of the day spend more time in their burrows prior to their last trip and have shorter last trips than females carrying scopal pollen at the same time. Foraging females may make pollen and nectar-loading decisions based on whether or not they have an active brood cell in which they can deposit externally-carried scopal pollen. As an important part of self-feeding, the last trip of the day is a potentially critical aspect of nesting energetics.