The attractive iridescent green of the Indonesian Papilio palinurus butterfly is not generated by chemical pigments but by special concavities of 4-10 microns in diameter located in two-dimensional arrays in the wing scales. The optical image was captured by using an optical microscope (magnification 200) together with a digital pocket camera. Note that concavities act as secondary punctual light sources and the image is affected by the optical aberrations of the lens.
> Download hi-res image
—Jose M. Medina, University of Minho, Portugal; and José A. Diaz, University of Granada, Spain