Fig. 2

White and black scales. a, b Epi-illumination light micrographs of wing areas with white (area 2 of Fig. 1b) and black cover scales (area 3 of Fig. 1b). c, d Scanning electron micrographs of a white and a black scale, respectively. e Cross-sectional SEM image of a white scale showing the basic scale architecture with the lower lamina of thickness ~200 nm (arrowhead). f Reflectance spectra; spectrum 1 is from a white scale overlapping a white scale, and spectrum 2 is from a central area of a white scale above a black ground scale, as indicated in (a), while spectrum 3 is from a central area of a black scale above a black ground scale, as indicated in (b). g Scatterogram of a white scale. The red circles indicate directional angles of 5°, 30°, 60°, and 90°. Scale bars: a, b 100 μm, c-e 2 μm