"Majoring" and "Minoring" by Foraging Bumblebees, Bombus Vagans: An Experimental Analysis

Abstract

On their first 2 foraging trips out of the hive, young Bombus vagans workers visited, on the average, 4 or 5 different kinds of rewarding as well as unrewarding flowers, and few of each kind in succession. But, after 3—7 foraging trips, most of the bees specialized on jewelweed, which was the most numerous flower available with high nectar reward. When jewelweed specialists became numerous, and the food rewards in jewelweed declined, the bees resampled the reward spectrum. They again visited, and continued to visit, at least 3—4 different kinds of flowers on successive foraging trips in an enclosure where patch size was limited. Flowers in open inflorescences (aster, goldenrod) were handled appropriately from the start, but handling accuracy at zygomorphic flowers (jewelweed, turtlehead) was initially 40—50% at the first 10 flowers encountered, and increased to >90% in 60—100 flower visits. It is concluded that the most important problem faced by foraging bees attempting to enhance food intake is that of assessing the resources, which often change rapidly. Individual bees specialize on flowers yielding rewards that are "perceived" to exceed some minimum. However, the difference between perceived and actual rewards is, in part, determined by handling skills that are affected by foraging experience. Thus, optimal foraging in the bees must be explored from the perspective of long— rather than short—term energy balance.