Small and Large Bumblebees Invest Differently when Learning about Flowers

Honeybees(1) and bumblebees(2) perform learning flights when leaving a newly discovered flower. During these flights, bees spend a portion of the time turning back to face the flower when they can memorize views of the flower and its surroundings. In honeybees, learning flights become longer when the reward offered by a flower is increased.(3) We show here that bumblebees behave in a similar way, and we add that bumblebees face an artificial flower more when the concentration of the sucrose solution that the flower provides is higher. The surprising finding is that a bee's size determines what a bumblebee regards as a low or high concentration and so affects its learning behavior. The larger bees in a sample of foragers only enhance their flower facing when the sucrose concentration is in the upper range of the flowers that are naturally available to bees.(4) In contrast, smaller bees invest the same effort in facing flowers whether the concentration is high or low, but their effort is less than that of larger bees. The way in which different-sized bees distribute their effort when learning about flowers parallels the foraging behavior of a colony. Large bumblebees(5,6 )are able to carry larger loads and explore further from the nest than smaller ones.(7) Small ones with a smaller flight range and carrying capacity cannot afford to be as selective and so accept a wider range of flowers.

Automated summary

Honeybees and bumblebees engage in learning flights when discovering a new flower, spending time facing the flower to memorize its surroundings. Larger bumblebees show increased flower facing behavior only when the flower provides a higher sucrose concentration, while smaller bees invest similar effort in facing flowers regardless of concentration. The distribution of effort when learning about flowers parallels the foraging behavior of a colony, with large bumblebees able to carry larger loads and explore further distances compared to smaller ones.