Figure 4.

Spectral tuning of the scale reflectance. (a) Absorbance spectra of single wing scales immersed in a refractive index liquid. The wing scales contain different compositions of two different absorbing pigments (see also table 1). (b) Reflectance spectra of the wings measured with an integrating sphere. Most birdwings are green, with maximal reflectance at approximately 550 nm, but the blue-coloured O. urvillianus has a reflectance peaking at approximately 490 nm and the orange O. croesus reflects maximally at approximately 660 nm.