INNATE COLOR PREFERENCES OF FLOWER VISITORS

Freshly emerged flower visitors exhibit colour preferences prior to in dividual experience with flowers. The understanding of innate colour p references in flower visitors requires a detailed analysis, as, on the one hand, colour is a multiple-signal stimulus, and, on the other han d, flower visits include a sequence of behavioural reactions each of w hich can be driven by a preferential behaviour. Behavioural reactions, such as the distant approach, the close-range orientation, the landin g, and the extension of mouthparts can be triggered by colour stimuli. The physiological limitations of spectral sensitivity, the neuro-sens ory filters, and the animals' different abilities to make use of visua l information such as brightness perception, wavelength-specific behav iour and colour vision shape colour preferences. Besides these receive r-based factors, there are restrictions of flower colouration due to s ender-based factors such as the absorption properties of floral pigmen ts and the dual function of flower colours triggering both innate and learned behaviour. Recordings of the spectral reflection of coloured o bjects, which trigger innate colour preferences, provide an objective measure of the colour stimuli. Weighting the spectral reflection of co loured objects by the spectral composition of the ambient light and th e spectral sensitivity of the flower visitors' photoreceptors allows t he calculation of the effective stimuli. Perceptual dimensions are kno wn for only a few taxa of flower visitors.