Structural color of Morpho butterflies

Structural color is caused by wavelength-selective scattering of light by microscopic features, such as those on the scales of some insects. The brilliant blue displayed by some male Morpho butterflies is a classic example of this phenomenon. In this paper, experiments used to distinguish structural color from color due to pigmentation are reviewed. A simple electromagnetic model is developed for the structural scattering from Morpho butterfly scales, and the blue color and iridescence normally seen for these butterflies are predicted by this model. The analysis is based on topics usually discussed in courses on electromagnetism and optics and can be used as an example to supplement classroom discussions of these topics.