Fossils are typically rather dull in appearance. Both the pigments and the fine structural details that give many animals their color rarely survive the ravages of times.
There are, however, exceptions.
Thanks to a treasure trove of ancient amber fossils recovered from amber mine in northern Myanmar, scientists are gaining new insights into the aesthetics of 99-million-year-old insects, according to a study published Wednesday.
“The amber is mid-Cretaceous, approximately 99 million years old, dating back to the golden age of dinosaurs,” lead researcher Cai Chenyang, associate professor at the Nanjing Institute of Geology and Palaeontology of the Chinese Academy of Sciences, said in a news release.
“It is essentially resin produced by ancient coniferous trees that grew in a tropical rainforest environment. Animals and plants trapped in the thick resin got preserved, some with life-like fidelity,” Chenyang said.
Researchers recovered 35 different amber fossils, many of which contained cuckoo wasps. The ancient wasps boast a color profile remarkably similar to modern cuckoo wasps — a mix of metallic bluish-green, yellowish-green, purplish-blue and green colors.
Scientists also observed amber fossils featuring blue and purple beetle species and a metallic dark-green soldier fly.
“We have seen thousands of amber fossils but the preservation of color in these specimens is extraordinary,” said Huang Diying, NIGPAS professor.
Researchers detailed their discovery this week in the journal Proceedings of the Royal Society B.
“The type of color preserved in the amber fossils is called structural color. It is caused by microscopic structure of the animal’s surface,” said Pan Yanhong, a professor at NIGPAS and an expert in palaeocolor reconstruction. “The surface nanostructure scatters light of specific wavelengths and produces very intense colors. This mechanism is responsible for many of the colors we know from our everyday lives.”
To better understand why some amber fossils preserve colors, while others don’t, researchers cut through the exoskeleton of two of the newly discovered, brilliantly colored amber wasps, as well as a duller specimen.
Electron microscopy revealed the exoskeleton nanostructures on the two colorful wasps were perfectly preserved, while the integrity of the duller specimen’s exoskeleton was compromised — its finer details severely degraded.
Previous studies suggest the colors created by nanostructure light-scattering help insects camouflage themselves. The ancient cuckoo wasps were parasitic wasps, laying their eggs in the nests unrelated bees and wasps. Camouflage would have been paramount.
“At the moment we also cannot rule out the possibility that the colors played other roles besides camouflage, such as thermoregulation,” Cai said.