Structural Color in Nature: Basic Observations and Analysis

Some bird and insect species exhibit iridescent colors that originate from submicron microstructures. One example is a periodic stack of thin layers that selectively reflects light wavelengths with high efficiency through multilayer optical interference. However, the periodicity of the microstructure is not a unique factor in the coloration mechanism; other physical factors such as structural irregularities, large-scale structures, and pigmentation also contribute greatly to the coloration in natural examples. This chapter describes basic experimental and theoretical methods of studying structural color, mainly for those who are unfamiliar with this subject. The chapter discusses two insect species, the jewel beetle and Morpho butterfly, repeatedly rather than introducing many examples. It is emphasized in discussing these examples that additional factors are as important for the coloration as the periodicity in the microstructures.