Flower handling efficiency of bumble bees: morphological aspects of probing time.

The time required for a bumble bee to visit a flower is affected by the length of the bee's glossa and its body weight, and by the depth of the flower and the volume of nectar it contains. Probing time is comprised of two components: access time and ingestion time. Access time increases linearly with flower depth, but ingestion time varies with flower depth only in flowers deeper than the length of the bee's glossa, due to a decline in the rate of ingestion of nectar. Probing time therefore increases gradually with increasing depth for flowers shallower than the bee's glossa, but beyond that depth it increases much more rapidly. The relation of probing time to flower depth influences the foraging efficiency and choice of flowers by bumble bees.