SEM Images of butterfly wing scales

The beautiful and sometimes irridescent colours displayed by butterflies have their origin in the fine microstructure of the scales on their wings. Butterfly and moths have wings covered with thousands of tiny scales arranged in regular arrays much like roof tiles on a house. The upper surface of a single scale is shown in one of these images photographed with a scanning electron microscope. As the magnification is increased, finer and finer detail is resolved and it is beleived that the regular ridges and spacings on the scales act like diffraction gratings and scatter incident light, splitting it up into diiferent colours depending on the width of the spacings and the angle of incidence of the light. This, combined with wavelength selective absorption by pigments in the scales, gives rise to the many varied colours. These spacings and structures vary with different species of butterfly. Scientists have studied these subjects in an attempt to reproduce them artificially and engineer optical coatings with similar properties.