Floral preferences of bumblebees ( Bombus edwardsii) in relation to intermittent versus continuous rewards

Worker bumblebees, Bombus edwardsii, preferably feed from artificial flowers yielding the same (continuous) reward on each visit rather than from flowers yielding variable (intermittent) rewards, even though the long-term expectation of reward is the same at each type of flower. However, variation in degree of preference among individual bees is high. Preferences after long foraging experience correspond closely to early preferences. Rate of flower visitation increases as mean reward increases, and may accelerate preference formation. Preferences are discussed in light of processes thought to control learning in honeybees. From these findings we propose that reward variance and expected time between reinforcements be considered as constraints in models of optimal foraging behaviour.