Floral calcium oxalate crystals as foraging cues for honeybees
Houston Joost, Michael Amspoker, Brandi Silke, Harrington Wells
Artificial flower patches were used to test whether floral calcium oxalate crystals (which reflect UV light) affect honey bee (Apis mellifera) flower fidelity, and whether honey bees will use calcium oxalate crystals as reward-correlated foraging cues. Experiments presented bees with a floral dimorphism in a flower patch where a pattern representative of anthers was either coated or not coated with calcium oxalate, but where the flower colour in an experiment was always the same (blue, white, or yellow). Flowers were arranged randomly as to presence or absence of calcium oxalate and flower patches were changed periodically in each experiment so that flower position would not become a factor determining flower choice. Each experiment used a new set of naive bees that had not foraged on the artificial flowers before. Each bee extensively visited both flower types when rewards were identical in competing flower morphs. The presence of calcium oxalate thus did not increase a flower's attractiveness to foragers. However, when a reward difference (1 M vs. 2 M sucrose) existed between competing flower morphs, bees preferred the flower type offering the higher caloric reward. Bees thus used calcium oxalate as a reward-correlated visual cue to maximize net caloric gain while foraging.