Top to bottom: A detail of the moth wing; electron microscope analysis; and a computer rendering of the moth's true color. Images: McNamara et al./PLoS Biology

In this exquisitely preserved fossil moth is a glimpse of life’s colors almost as they appeared 47 million years ago.

“Until now, we had no idea what colors ancient moths and butterflies had,” said Yale University paleogeologist Maria McNamara.

The fossils’ time-machined hues exist because moths and butterfly wings have what’s known as structural color. Rather than pigments, structural colors are created by light-warping nanoscale surface features; if fossilization occurs delicately enough, and the intervening eons are gentle, those structures can be reproduced and preserved indefinitely.

In one recent study, McNamara looked at the colors of ancient beetle fossils. But compared to the moth fossil, which she analyzed in a Nov. 15 Public Library of Science Biology paper, colorful ancient beetles are common. “There are loads of beetle fossils with some evidence of color, but this had never been found for a lepidopteran at all,” she said.

McNamara’s team used an electron microscope to photograph the moth fossil’s wing surface. Based on what’s known from similar structures in living moths and butterflies, the fossil should appear yellow-green rather than slightly yellow-blue, a difference likely caused by subtle structural changes during fossilization.

The moth is believed to be an extinct ancestor of modern-day forester moths, which possess a bright coloration that warns predators of their poisonous nature. The researchers suspect this moth was poisonous, too.

Image: McNamara et al./PLoS Biology

Citation: “Fossilized Biophotonic Nanostructures Reveal the Original Colors of 47-Million-Year-Old Moths.” By Maria E. McNamara, Derek E. G. Briggs, Patrick J. Orr, Sonja Wedmann, Heeso Noh, Hui Cao. PLoS Biology, Nov. 15, 2011.

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