BUMBLE BEE LEARNING AND FLOWER MORPHOLOGY

The time required for naive bumble bees to learn flower handling skills was compared among nine plant species with flowers of varying morphological complexity. Learning was measured as the time to reach a criterion of 80% correct flower visits, and as the rate at which naive bees improved their flower handling efficiency relative to experienced bees. On shallow, cup-shaped flowers with exposed nectar and on most long-tubed flowers with an open entrance, all naive bees located the nectary on their first attempt. On these relatively simple flowers, naive bees reached the learning criterion after a few minutes and took 3-10 min to approach the handling efficiency of experienced bees. On more complex flowers, with nectar concealed in a closed tube or in an unusual location, 55-71% of bees failed to find the nectar on their first visits. Bees that did find concealed nectar took 5-30 min to reach the learning criterion and 20-60 min to approach the handling efficiency of experienced bees. In general, morphologically complex flower designs took bees longer to learn than open-tubed or cup-shaped designs. However, specific predictions about the relative difficulty of learning to handle flowers could not be made from general flower morphology. Variation among bees in reaching the learning criterion was associated with individual age and size, although much of the variation was unexplained. Previous experience with simple flowers of one plant species decreased subsequent learning on other species with simple flowers but not on species with complex flowers. © 1994 The Association for the Study of Animal Behaviour.