Fig. 2.
Spectral reflectance curves of the perianth of Ophrys heldreichii (dark violet), the artificial perianth (dark pink) and the background (green) as a function of wavelength. In a, mean reflectance of the flower perianths is given (NO. heldreichii = 19, NBackground = 5, see text). b shows the mean reflectance of O. heldreichii presented with the standard deviation of the mean to visualise the variation within the species. c The colour loci of Ophrys heldreichii (dark violet), the artificial perianth (pink) and major food plants (grey shades) represented in the colour hexagon model (Chittka 1992). The large circle denotes 0.1 hexagon units around the centre. The grey line indicates the loci of pure spectral lights at background intensity. Colour distances in the hexagon space are calculated as the Euclidean distance between two loci (Chittka 1992)