Fig. 1

The great purple emperor butterfly, Sasakia charonda (male). a, b, c, f Dorsal views. d, e Ventral views. a, d UV images. b, c, e, f RGB images. a, b, d, e Normal illumination. c Oblique illumination (angle of incidence of ~ 45°). f Illumination from below, showing transmitted light. Scale bar: 2 cm. g, h Reflectance spectra measured with a bifurcated probe. i Absorbance spectra (normalized at the long-wavelength peak) of pigments extracted from wing pieces cut from an orange-yellow area on the forewing (#3) and from a red spot on the hindwing (#4). The numbers 1–6 in g-i correspond to the numbered areas in b and e; the number 7 in e corresponds to Fig. 3p-t