Moths were Highly Colourful 47 Million Years Ago, say Biologists

A newly discovered 47 million year old fossilized moth reveals that prehistoric moths were highly colorful specimens, and not at all like modern day moths that we see every evening hovering around outdoor lights today.

Computer rendering of the moth’s true colour


The remains of several moth species were found in the Messel oil shale in west central Germany which is well known for yielding well-preserved intricate fossils. The specimens belonging to a group called lepidopterans, which also includes butterflies, is also giving scientists insights into how the moths used escaped their predators millions of years ago.

Colour had a purpose

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

“They were probably using the coloru for the same kind of function, to hide themselves when they were resting, but as a warning signal when they were feeding” she added. “When you look at these fossils today in air, their wings look a blue-green colour. But we were able to work out that originally, their wings were more of a yellow-green colour.”

The researchers used electron microscopes to photograph the moth fossil’s wing surface to determine how the structure would have scattered light and hence work out the colour of the moths. Based on knowledge of similar structures in living moths and butterflies, the fossil should appear yellow-green rather than slightly yellow-blue. The change in colour was likely to have been caused by subtle structural changes during fossilization.

Camouflage

The change in colour may well have been part of an advanced camouflage system, to enable the moths to blend in with leaves and grass whilst resting. This is likely as the colour was not iridescent – that is to say it looked the same from any angle.

The fossils’ colours have been preserved because moths and butterfly wings contain “structural colour” which is not created by pigments but rather by the organization of an organism’s tissues (“light-warping nanoscale surface features”) which can if sufficiently well preserved be reconstructed.
Other scientists have suggested that the bright colours could also have been useful for courtship and communication.

The discovery conveys a lot of information about the moths’ lives, said McNamara.

Warning to predators

Modern butterflies with the same colours contain toxic cyanide in their tissues. So it is likely that the yellow-green may have also served as a warning to predators that the moths were poisonous just like the modern day forester moth.
The scientists believe that the discovery could shed light on the function and evolution of colours as well as on the colours of many long-extinct creatures, such as birds, fishes, and other insects.

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