As bumblebees buzz around, their body temperatures tend to be warmer than 30°C. In this infrared image, the brighter the region the higher the temperature, such as on the bumblebee’s upper back.
According to new lab experiments, the bees prefer warm flowers and can learn color cues to finding them. A majority of bumblebees chose to visit the warmer of two otherwise identical feeders that differ by 4°C or more, report Lars Chittka of Queen Mary, University of London and his colleagues. Artificial flowers of different colors but the same temperature attracted bees about equally. However, when researchers coordinated either pink or purple color with warmth, bees preferred the warm-color flower. Insect preference for warmth may have influenced the evolution of flower characteristics, say the researchers in the Aug. 3 Nature.