flashes of orange and metallic blue shifting and changing in the morning air; Waves of sunlight descend on the scales of their wings and scatter the colors like prisms.
The Texas Butterfly Festival has come and gone, but the shimmering colors of a butterfly’s wing still reverberate through the minds of our endless fan club.
Monarchs, malachites, bay fritillates, Mexican bluewings, blue morphos—they all wear a distinctive color scheme that sets them apart from the crowd. Butterfly lovers can quickly identify butterflies by their unique markings.
But do we know how they get their colour?
Butterflies have a complex anatomy filled with chemoreceptors for taste and smell on their feet and all over their bodies.
Each part is a new journey through the mind of nature.
The wings themselves have clever multitasking grouping for several purposes: veins pump fluid across the wings to collect heat, use coloration as camouflage, to warn off predators, to signal to other members of their species and to attract mates.
Colors come from two sources: pigmentation and scales.
Most people understand pigmentation pretty well, says Professor Matthew Terry, assistant professor in the Department of Biology at the University of Texas Rio Grande Valley, but butterfly wing scales have a much more interesting type of structure and function.
The scales, which are made of a carbohydrate called chitin, refract different bands of light creating constant changes in colors and patterns like a kaleidoscope, pieces of color that split off, come together, and rotate again.
He said, “Refraction is something similar to what we get in a prism where white light is split into its components.” “You can do it through different planes like in a glass prism. It can also happen through very small regular structures. These are almost like a ladder but on a micro level. Light is basically split into different wavelengths, which is basically what iridescence is” .
Now, that’s cool enough, but it just gets better.
A complex tapestry of disciplines–physics, chemistry, and biology to name a few– emerges in a feat of engineering far deeper than any peer-reviewed study.
“With refraction, if you change the angle, you see the different colors kind of play,” Terry said. “A place that was once green, you change the angle, and it looks red or yellow. This is iridescence and not just a reflection of light.”
The hard science described here hardly touches on the strength of a butterfly.
Besides the science of metrology and refraction, there is the passion, nuance, and familiarity that touches everyone.
In the online publication KQED, author Jenny Oh describes the work of Nipam Patel, a professor in the Department of Molecular and Cellular Biology at the University of California, Berkeley. A 2014 article cites Patel’s study of thousands of tiny cells, known as scales, on a butterfly’s wings.
She wrote “From a distance, rows and rows of scales look like vivid patterns adorning a butterfly’s wings. But up close, each scale is like a dab of paint in a Pointillist painting.”
You write that some butterfly scales are colored with dyes. Others, however, rely on what’s called “structural color,” which is the production of color through subtle microshapes that reflect and bend light. The color blue is often created by refracted light, as most animals cannot produce this color as a pigment.
How light is refracted, Terry said, depends on the specific structures of the individual scales.
“It’s going to depend on the distance between those little structures that cause the iridescence, how wide those areas are, and how wide these organs are,” he said. “You’re also likely to see a mixture of pigmentation and iridescence. You might see a base color that doesn’t change much, but the over the top effect, you can have both at the same time.”