Flower Color Choices by Bumble Bees : Evidence Against Innate Preferences for Blue or Yellow in Bombus Impatiens

Abstract

Global change is predicted to result in warmer and more variable temperatures, which may impact insect learning. Learning is critical to social insects, like bumble bees, where colony success relies on worker memory. We used a foraging arena to investigate whether bumble bee (Bombus impatiens) learning is influenced by temperature. We wanted the bees to learn that yellow flowers had a higher reward (50% sugar) than blue flowers (25% sugar). Bee colonies were connected to a training arena with half-blue, half-yellow flowers with ad-libitum nectar for one week, then individual workers were removed from the training arena to be tested in the foraging arena. Before foraging, bees were starved for six hours, then introduced to the foraging arena and allowed to forage for 10 minutes on two subsequent days. We recorded the color of the first flower visited, the duration foraging on both high- and low-reward flowers, and the number and type of each flower, per foraging visit. In total, we tested nine temperature combinations of 18, 25, and 32°C across days 1 and 2. As a control, we also evaluated whether bees had an innate preference for blue or yellow flowers when floral reward was equal (both 50% sugar).