Colour preferences in relation to the foraging performance and fitness of the bumblebee Bombus terrestris

Bumblebee (Bombus terrestris) colonies showed significant variation in their unlearned preference for violet (bee UV-blue) over blue (bee blue) flowers. Bumblebee colonies with a higher average innate preference for violet (over blue) in the laboratory harvested more nectar per unit time under field conditions. Although this correlation was strong (rs = 0.82), it narrowly missed statistical significance at the 5% level (p = 0.089), but was significant at the 10% level. This increase in foraging performance appears to make evolutionary sense because, on average, violet flower species contain around four times the amount of sugar (in nectar) as flowers of any other colour in the local area. Interestingly, although colonies with a stronger preference for violet were more effective at nectar foraging, this increase in colony food availability was not predictably translated into investment in fitness, quantified as gyne (new queen) production.