BUMBLEBEES DO NOT RESPOND TO VARIANCE IN NECTAR CONCENTRATION

Worker bumblebees (Bombus fervidus) were given repeated binary choices between two colors of artificial flowers with the same associated mea n nectar concentration ((X) over bar = 20%), but with different varian ces in nectar concentration. Flowers of one color, yellow or blue, rew arded a bee with 1 mu l of 20% sucrose solution (low-variance flower t ype) on each visit (p = 1) and flowers of the other color rewarded a b ee on each visit with 1 mu l of either 10% or 30% sucrose (p = 0.5; hi gh-variance flower type). Of the 10 bees tested, nine showed no prefer ence for either the high- or low-variance flowers (indifferent or risk -insensitive). This result is similar to honeybee responses to variati on in nectar concentration, despite differences in foraging ecology be tween bumblebees and honeybees. Flower-choice behaviour in the presenc e of variance in nectar concentration is a response to the expected co ncentration of the alternative flower types. Possible mechanisms of ri sk-sensitive foraging behaviour in bees are discussed.