Iridescent Insects From Cretaceous Found in Amber

Chinese scientists report on wasps and beetles trapped in amber and found in Myanmar still displaying bright colors after 99 million years

Ruth Schuster
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A cuckoo wasp.
Insect of colors: The cuckoo wasp todayCredit: RudiSteenkamp
Ruth Schuster

Insects trapped in amber when dinosaurs were ascendant displayed beautiful iridescent coloration, scientists from the National Natural Science Foundation of China reported in Proceedings of the Royal Society B this week.

The scientists, led by Cai Chenyang, associate professor at the Nanjing Institute of Geology and Palaeontology of the Chinese Academy of Sciences, studied 35 pieces of amber with insects mined in northern Myanmar. The area has become a rich source of prehistoric life trapped in resin dripping from conifers in the prehistoric tropical rainforest, they report.

The iridescent insects date to the mid-Cretaceous 99 million years ago. The specimens include cuckoo wasps with metallic bluish-green, yellowish-green, purplish-blue or green colors on the head, thorax, abdomen and legs – about the same as cuckoo wasps extant today, Cai says. Cuckoo wasps earned their name by being parasitic: they lay their eggs in host nests (such as bee hives). Their larvae eat the host’s larvae and when they’re done doing that, they eat the food the unwitting host provides for its deceased young. At least they are gorgeous.

The scientists also discovered blue and purple beetles and a metallic dark green soldier fly. Whether or not you can stand insects, these are beautiful.

99-million year old cuckoo wasps in Myanmar amber from the mid-Cretaceous
99-million year old cuckoo wasps in Myanmar amber from the mid-CretaceousCredit: NIGPAS

Prior peeks into the past afforded by amber include a feathered dinosaur’s tail (a very small dinosaur), a baby frog, scorpions, a spider caught attacking a wasp, and a flea with the plague. But the preservation of color in the newly reported ones is incredibly rare.

How did these bugs keep their color for 99 million years while other specimens lose their hues during the amber immurement process? Because the color molecules were integral to the insects’ exoskeleton.

“The type of color preserved in the amber fossils is called structural color. It is caused by microscopic structure of the animal’s surface,” Nanjing Institute Prof. Pan Yanhong, a specialist on palaeocolor reconstruction, explains following analysis by electron microscope. “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.”

Structural coloration can serve for camouflage, thermoregulation or attracting mates. Apparently some things never change.

Diverse structural-colored insects in mid-Cretaceous amber from northern Myanmar
Diverse structural-colored insects in mid-Cretaceous amber from northern MyanmarCredit: NIGPAS
caption
captionCredit: NIGPAS

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