Scientists turn a brown butterfly purple—in just six generations

The starting material. A year later, and the wing was predominantly purple.

Yale

For most forms of life, coloration is synonymous with the presence of a pigment that absorbs some wavelengths and reflects others. But butterflies and birds are different. Their wings and features have incredibly fine, microscopic features that can help channel light and create interference patterns that enhance some wavelengths while suppressing others.

Now, researchers have tested just how readily these complex optical systems can evolve. In just six generations of selection, they took a brown butterfly and shifted it to a rich, purple color.

Turning a "brown bush" purple

The species chosen for this work was Bicyclus anynana, an African species that also goes by the name of "squinting brown bush." As the name implies (and the image above shows), the majority of its pigmentation is brown, with a few prominent eye spots.