When the Morpho butterfly rests on a leaf, the underside of its wings show an earthy brown colour. Yet when it flies, its wings give off a shimmering, iridescent blue sheen.
(The Independent) – This video from Deep Look explains how the glieming blue is effectively an optical illusion. The brown colours are created by pigments on the Morpho butterfly’s wings – i.e. they are physically brown.
But the blue on top is created by something called “structural colour” – i.e. it’s not really there. When the tiny scales of the wings are removed and observed under a microscope one can actually see they are white.
The tiny ridges on each of these scales helps to refract the light into almost perfect wavelengths that appear to give off the same blue shade. This same process occurs in feathers, a beetle’s elytra (shell) and even in the human eye. The human eye doesn’t contain any blue pigment as such, but rather the particles within it refract the light in a similar way to the butterfly’s “scales”.