Fig. 2.

Short-, medium- and long-wavelength receptor responses to the average color of leaves, petals and flower centers. From each of the 53 images in our multispectral database, we selected areas that contained leaves (34 images), petals (52 images) and areas where the nectar and the stamens/carpels can be found (centers, 38 images). From each area, we randomly chose 1000 pixels for estimating the average reflectance spectrum (practically, the color) of each flower part. Finally, we estimated the photoreceptor responses of the bee eye to each leaf, petal and center of each flower species. The dots represent the individual receptor responses, the black lines indicate their means and the gray areas depict the standard deviations. For all areas, the responses of the long-wavelength receptors are the largest and they have the smallest standard deviations (Mean ± SD, leaves: S = 0.36 ± 0.25, M = 0.40 ± 0.21, L = 0.48 ± 0.11; petals: S = 0.68 ± 0.18, M = 0.68 ± 0.23, L = 0.70 ± 0.11; centers: S = 0.27 ± 0.24, M = 0.39 ± 0.28, L = 0.53 ± 0.17)