Bombus lucorum visits open flowers, collects honeydew and "steals" nectar, forages in exposed habitats, collects pollen without nectar and is relatively uninfluenced by the presence of bees of other sp. B. hortorum is restricted to long-corolla-tubed flowers and unadapted psychologically for collecting pollen without nectar or for "stealing". B. pratorum visits mainly open flowers, forages in sheltered habitats, and is aggressive to other spp. B. agrorum visits flowers of intermediate corolla-tube length, forages in sheltered habitats later in the season than pratorum, and is retiring in its behavior to other spp.