Bumble Bees (Hymenoptera: Apidae) Assess Pollen Availability in Anemonopsis macrophylla (Ranunculaceae) through Floral Shape

Workers of the bumble bees Bombus honshuensis Pérez and B. diversus Smith visit flowers of Anemonopsis macrophylla (Ranunculaceae) for pollen. Their visitation patterns suggest that they use age-related morphological differences in the flowers to discriminate in favor of young, pollen-rich flowers. This ability allows the bees to select well-rewarding flowers rapidly without alighting. Discriminatory behavior has previously been demonstrated in bees among nectar flowers; such flowers often also provide pollen. This study shows that pollen availability in itself can be a significant component in determining bee behavior.