Colour preferences of flower-naive honeybees

Flower-naive honeybees Apis mellifera L. flying in an enclosure were tested for their colour preferences. Bees were rewarded once on an achromatic (grey, aluminium or hardboard), or on a chromatic (ultraviolet) disk. Since naive bees never alighted on colour stimuli alone, a scent was given in combination with colour. Their landings on twelve colour stimuli were recorded. Results after one reward (“first test”) were analysed separately from those obtained after few rewards (“late tests”).

1. After pre-training to achromatic signals, bees preferred, in the first test, bee-uv-blue and bee-green colours. With increasing experience, the original preference pattern persisted but the choice of bee-blue and bee-green colours increased.
2. Neither colour distance of the test stimuli to the background or to the pre-training signal, nor their intensity, nor their green contrast, accounted for the colour choice of bees. Choices reflected innate preferences and were only associated with stimulus hue.
3. Bees learned very quickly the pre-trained chromatic stimulus, the original colour preferences being thus erased.
4. Colour preferences were strongly correlated with flower colour and its associated nectar reward, as measured in 154 flower species.
5. Colour preferences also resemble the wavelength dependence of colour learning demonstrated in experienced bees.