Beetle fossils show their colors

Photo by Jordan Konell.

The fossils of beetles may open the door to understanding what exactly ancient organisms looked like.

Maria McNamara, a postdoctoral fellow in the Yale Department of Geology and Geophysics, used fossilized beetles to show how colors of insects have changed over time, adding to scientists’ understanding of ancient insects’ appearance. McNamara, with help from her colleagues at the Peabody Museum, the Department of Applied Physics and University College Dublin, studied the cuticles of fossilized beetle remains ranging from 15 million to 47 million years old.

Using electron microscopy, McNamara saw that the metallic colors of beetles was altered, demonstrating that fossilization changed the metallic color of the beetle.

The hue of a beetle depends on refraction of light within its exoskeleton. According to the study, the chemical makeup of the exoskeleton of the insect bends light waves to produce a metallic color. McNamara found that the fossils’ color had changed due to chemical processes. By studying the color of the fossilized beetles and analyzing how the refractive index has changed over time, McNamara and her team can now go backwards in time and identify the original colors of ancient beetles.

“In order to show the function, behavior and patterns of ancient organisms, we have to know what their original colors were,” McNamara said. “Now have a way to actually tell whether insect fossils were colored in the first place, and we can actually color in a lot more of the insect fossil records than we’ve been able to do previously.”

Studying the colors of the beetles might reveal their characteristics, such as their modes of communication and method of thermoregulation, McNamara added.

Derek Briggs, a geology and geophysics professor and director of the Peabody Museum of Natural History said that study opens up the possibility of investigating color in a range of fossil insects to determine when and why insect colors evolved.

Andrew Parker, a research leader at the Natural History Museum in London, said the findings show that animal coloring has mattered for millions of years, especially in the evolutionary race between predators and prey.

“The big question is, how far can we extend this scenario?” Parker said. “The answer is to the origin of eyes in a fast-moving predator that can have a major influence on the dynamics of an entire ecosystem.”

He added that scientists like McNamara are helping to fill in the gaps of the historical visual arms race.

Shuhai Xiao, a professor of geobiology at Virginia Tech, said the most promising part of the study is how it demonstrates that reflector structures, and thus colors, can change due to geological alteration during fossil formation.

McNamara’s next experiments will focus on examining fossils of other insects and comparing their patterns, he said.