How do butterfly wings become so vivid and colorful?

Chuck Bednar for redOrbit.com – Your Universe Online
Butterflies are some of nature’s most beautiful creatures, with the shiny blue Morpho butterfly standing out as among the most spectacular. But how do the colors and patterns featured on their wings evolve? Researchers from the University of California, Berkeley intend to find out.
According to KQED, Nipam Patel, a professor in the Bay Area university’s Molecular & Cell Biology Department, is in the process of studying the thousands of tiny cells on their wings, known as scales. While from a distance, the rows of scales look like vivid patterns, up close they more closely resemble a dab of paint or a single tile in a mosaic, he explained.
Each scale represents an individual unit of color, and each is “a single cell,” said Patel, who recently published a study detailing his work in the journal Developmental Biology. “As far as cells go, they are huge, much larger than the typical cells in our bodies. A human blood cell is about 10 microns in size – a pretty typical size for a cell in our bodies. A butterfly scale is…a huge one, about 50 microns across and 200-250 microns long.”
While some butterfly scales are colored by pigments, others rely on a phenomenon known as “structural color,” which involves the production of hues by elaborate nanoscale shapes that bend and reflect light. Among the butterfly species that utilize this phenomenon is the Morpho, a stunning blue butterfly typically found in South America, Mexico and Central America.
A Morpho butterfly is “a master of nanoscale light bending,” according to Gwen Pearson of Wired.com. Its scales, which are essentially made from the same sugars that make up the rest of the creature’s skeleton, reflect wavelengths of light in order to create its appearance. Essentially, it gets it shine from detailed nanostructures of longitudinal ridges and crossbeams, she said.
As part of its research earlier this year, Patel’s lab examined the developing wings of a pupa, the stage bridging the gap between caterpillar and butterfly. They found that two types of cells were involved: scale cells and socket cells, which anchor the scale cells to the wing’s membrane.
In caterpillars, these are perfectly ordinary cells, but early on in the pupal stage, they begin to organize themselves in rows that correspond to where the wing will eventually grow. This process begins when the transitional phase is approximately seven percent complete. Scale cells go on to form strings of proteins known as f-actins that serve as the framework.
When the metamorphosis is a little more than one-fourth complete, it is possible to see both cells and ribbed bundles of actin beginning to form, Pearson explained. Scale cells create and assemble a lattice of actins that will form the template for the rest of the scale, and by the time the process in nearly two-thirds complete, those protein bundles will start to disappear. Eventually, the scale cell dies and leaves behind a finished scale that hardens once it emerges.
“What’s cool about this work is that in contrast to the way people currently mimic naturally occurring structural colors – by using industrial processes deposit layers of heavy metals by electricity that’s expensive and energy-intensive – butterflies and moths have evolved a way to create these stunning colors with a string of sugar molecules,” Ryan Null, a graduate student in Patel’s lab, told KQED.
“The genetic program controlling the creation of the nanostructures is elegant, robust and done in a way that is not hazardous to the life of the animal,” he added. “If we can figure out how the butterflies do what they do, we have the potential to apply what we learn to a vast array of problems like creating cars that have their ‘paint’ grown from the surface of their sheet metal, vivid cosmetics that are inherently safe for use with minimal testing, and even making solar cells more efficient.”