The pollinating efficiency of honeybee and bumblebee visits to flowers of the runner bean Phaseolus coccineus L.
The pollinating value of bees on temporarily uncaged runner beans was determined from the set on flowers known to have been visited by these insects, compared with the set on unvisited and hand-pollinated flowers. Bee-visited and hand-pollinated flowers produced more pods than unvisited flowers. Bumble bees of all species, when they entered the mouth of a flower, were not significantly more efficient pollinators per visit than honeybees. Multiple visits did not improve set. Bombus hortorum and B. agrorum visits resulted in a greater pod set in one year than in the other. Flowers robbed by the short-tongued B. terrestris and B. lucorum, and subsequently by honeybees, produced fewer pods than those visited in the normal way, and not significantly more than unvisited flowers. Author