Reprinted by permission from Fluttering Friends, newsletter of the Sarasota County Butterfly Club, May 2016

In April I attended a lecture at New College of Florida to learn from Professor Natalia Dushkina why butterfly wings, such as the Morpho, have gorgeous, iridescent colors. Did you know that the Morpho can be seen flying 3 to 5 miles away in a forest? I didn’t. But I will never forget the time I saw it flying ten feet in front of me in Panama – and the amused reaction of the locals to my outcry “Morpho, Morpho, Morpho!” Just a butterfly, right?

With an audience of about 50 people (amazing, considering it was 4 pm on a Friday) Prof. Dushkina discussed the composition of opals, labradorite (another gorgeous stone), feathers (such as peacocks), and butterfly wings. Scientists discovered that they all contain bio microstructures which interact with light to produce structural colors that are iridescent. Structural colors are non-pigment colors that originate from the scattering of light from microstructures. Pigments absorb light, while structural colors are produced by interaction of light with the structure of the substance. In short, pigments can be extracted from the colored tissues by appropriate chemical reagents, while structural colors are not produced by pigments and are not affected by chemical treatment of the structure creating the color.

At various angles, a peacock’s feather or an opal or the wings of the Morpho butterfly appear to change color. The different levels of the layers and their rough composition are keys for light to diffract.

The Morpho butterfly is a perfect example. Simply put, the tops of the scales in its wing have non-uniform heights of parallel ridges. When seen under a scanning electron microscope, the butterfly’s wing has an amazing structure that resembles a forest of equidistant stems/ trunks (like pine trees), resting upon a semi-curved ground – actually tubules – all that help scatter light to produce the fascinating Morpho iridescent blue color.

So what are some other examples of animals with structural colors? Do you know about the Japanese Beetle, the eating machine that is a serious pest of about 200 species of plants? The elytra (forewing) of this beetle are iridescent copper-colored. Another insect is the Emerald Ash Borer, a green jewel beetle native to eastern Asia that feeds on ash species. Scientists were able to develop a female model of the Emerald Ash Borer with realistic elytra using knowledge of structural colors. They mass produced these fake females with an electrical charge released on contact and placed them strategically out in the field, which then attracted male Emerald Ash Borers. As soon as the male landed, ZAP! It was electrocuted.

The knowledge gained from the discovery of bio microstructures led to the development of nacreous* paints, fabrics, and cosmetics. (*Nacreous – from Nacre: mother of pearl, produced by some mollusks as an inner shell or outer coating of pearls. Strong, resilient, and iridescent.) Remember when metallic colors on cars came out in the mid 1990s? The development of those metallic paints was a result of this scientific inquiry!

The next time you admire the shimmering colors of iridescent butterflies – or your car’s sparkly paint job – you now know why it is so captivating. All that glitters – or is nacreous – is not gold!

Professor Natalia Dushkina of Millersville University in Pennsylvania is from Bulgaria and speaks several languages fluently.

Professor Dushkina is coauthor of the chapter: “Structural colors” Natalia Dushkina and Akhlesh Lakhtakia, In: Lakhtakia, A. & R. J. Martín-Palma (eds.), Engineered biomimicry. Elsevier, Waltham , MA (2013), pp. 267-303.

by Karen Anthonisen Finch

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