Laboratory analysis of flower constancy in foraging bumblebees: Bombus ternarius and B. terricola

Abstract

1. We established apparently normal foraging behavior in captive bumblebees utilizing artificial flowers. Syrup rewards of flowers visited were experimentally manipulated to correspond to nectar volumes found in flowers utilized in the field. 2. Bees became >90% flower-constant to either of two flower types (distinguished by color) when rewarded with 1.0 μl 50% sucrose at each visit to flowers of one color, while the others remained unrewarded. 3. Flower-constancy to 'blue' was achieved within 50 flower visits, but equal flower constancy to 'white' was achieved only after 250 flower visits. 4. While being trained to white flowers the bees increased their percent correct (rewarding) flower choice over consecutive foraging trips during the day, but decreased their performance overnight. 5. Bees trained to blue did not switch to white flowers even when the white were subsequently rewarded with more food than the blue. However, bees trained to white utilized blue flowers. 6. Most bees simultaneously presented with white flowers having six times greater syrup rewards than blue visited both in approximately equal proportions independent of flower density, while some individuals visited primarily blue flowers. 7. The laboratory experiments suggest that bumblebees, once conditioned, are relatively 'constant' foragers despite changes in resource availability. © 1977 Springer-Verlag.