Detection of bright and dim colours by honeybees

Honeybees, Apis mellifera, were trained to detect coloured disks with eithe r a strong or a weak intensity difference against the background. Green. bl ue. ultraviolet-reflecting white and grey papers were reciprocally combined as targets or backgrounds, providing strong chromatic and/or achromatic cu es. The behavioural performance of the honeybees was always symmetrical for both reciprocal target/background combinations of a colour pair, thus show ing that target detection is independent of whether the colour is presented as a background or as a target in combination with the other colour. Brigh t targets against dim backgrounds and vice versa were detected more reliabl y than dim target/background combinations. This result favours the general assumption that the detectability of a coloured stimulus increases with inc reasing intensity.