Scientists Discover 'Exceptional' 44-million-year-old Caterpillar Preserved in Amber

Researchers have identified a previously unknown species of ancient caterpillar preserved in amber from 44 million years ago.

The find has been described as "exceptional" by the team who discovered it, a group from the Bavarian State Collection of Zoology (BSCZ) in Munich, Germany, Deutsche Welle reported.

The 0.2-inch-long specimen was identified in amber from the Baltic Sea region in northern Europe. It is the larva of a large butterfly species that has been dubbed Eogeometer vadens.

Axel Hausmann, lead author of a Scientific Reports study describing the new species, said this was the first caterpillar from a large butterfly species to be found preserved in an ancient block of amber from the Baltic.

"Caterpillar finds in amber are rarities in any instance, and this is the first ever large butterfly fossil to be found in Baltic amber," Hausmann told Deutsche Welle. "This may be due to the nocturnal activity of most caterpillars."

This caterpillar likely became trapped in resin from a tree which eventually hardened into amber over millions of years. The scientists say that resin would be runnier than normal in direct sunlight or warmer daytime temperatures.

This could be part of the reason why amber caterpillar finds are rare. A runnier liquid is more likely to trap an unsuspecting creature. But at night time—when most caterpillars are active—temperatures are cooler, thus the resin will be thicker and stickier.

The delicate bodies of butterflies and caterpillars also mean that they do not preserve in amber very well.

According to the study, Eogeometer vadens belongs to the butterfly family called Geometridae, which is unknown from Baltic amber. The Baltic region is home to the largest deposit of amber in the world.

Eogeometer vadens
An image of Eogeometer vadens preserved in amber. Fischer et al./Scientific Reports

Caterpillars from this family are unusual compared to those from other butterfly groups because they only have two or three pairs of legs, instead of five—the most common number. This reduced number of legs means they walk in an unusual manner.

Geometridae is one of the three largest butterfly families, containing around 23,000 different species. Most species from this family live on trees and shrubs.

The latest finding will provide insights into the evolutionary processes that took place during the Eocene Period (56 to 33.9 million years ago) long after the initial spread of flowering plants, according to the researchers.

This is not the first time in recent months that scientists have announced the discovery of a new species from specimens preserved in amber.

A study published last month identified microscopic ancient creatures—dubbed "mold pigs"—in 30-million-year-old amber. The specimens that the authors of the study found represent not only a new species, but an entirely new family of invertebrates—animals without backbones.

And in May, scientists identified a new, tiny species of millipede in 99-million-year-old amber from the southeast Asian nation of Myanmar.