Mummified bees 3,000 years ago are found in cocoons – 08/28/2023 – Science

A research team was combing the southwest coast of Portugal in 2019 looking for signs of how its ecosystem had changed over time. They came across a surprising and unexpected scene: bees that were mummified in underground sarcophagi almost 3,000 years ago.

An unlikely series of events conspired to preserve this swarm of helpless pollinators over millennia. Whatever happened, it was “an unfortunate night for hundreds of adult bees who were about to leave their cocoons,” said Carlos Neto de Carvalho, paleontologist and scientific coordinator at UNESCO’s Naturtejo Global Geopark in Portugal.

These were not typical European bees in a hive, but members of a group called the Eucera. Bees spend most of their lives gestating underground and eating pollen left behind by their mothers, only emerging for a few weeks when their favorite plant blooms.

Considering the clues, Carvalho and his colleagues deduced that the bees probably died a sudden death.

“Hundreds of bees preserved in their nests just before leaving means that something catastrophic has happened to them on what is now the sunny coast of Portugal,” he said.

The team described their discovery last month in the journal Papers in Palaeontology and came up with a hypothesis about what killed the buried bees.

Bees have evolutionary staying power, and their ancestors are known to have lived on Earth for over 120 million years. They have withstood violent climate changes and thrived wherever a flowering plant could grow.

But finding fossilized bee bodies is rare — unlike turtle bones preserved in layers of sediment.

“The exoskeleton of bees (and insects in general) is made of chitin, a biopolymer similar to cellulose that rapidly decomposes after the animal dies,” Carvalho wrote in an email.

What bees usually leave behind are traces of fossils or trace fossils – imprints frozen in time of bodies, abandoned or active nests or old burrows.

The cocoons the team discovered were lined and sealed with a silk-like thread produced by the mother bee. That yarn was a waterproof organic polymer – a blend of materials and structural engineering – that promoted the preservation of bees indoors.

Carvalho said this “organic mortar” protected the cells from the environment, saving the delicate chitin from bacterial activity and decomposition.

Sealed in their cocoons, the bees mummified, preserving their body shape and distinctive features. The team used X-ray microcomputed tomography – a type of CT scan that captures detailed images of tiny things like insects – to examine the mummified bees without destroying their protective cocoons.

“I think what makes this study so exciting is that you have the bee and you can see that it belongs to the Eucerini tribe, which are the long-horned bees,” said Bryan Danforth, an entomologist at Cornell University who was not involved in the study.

“If you look at the CT scan image, you can see the long antennae, so you know it’s a male.”

Usually, determining what created a fossilized brood cell is tricky. “There are other animals that burrow into the ground and can create something like a bee nest,” Danforth said.

This find, he added, is “the first trace fossil that actually contains the bee within it.”

As for what killed the insects, the researchers considered flooding or a prolonged drought that could have limited the food supply. But the pollen stored in the cells showed the team that the bees had plenty of food (meaning they didn’t starve).

Their hypothesis, instead, is climate change.

“We presume that a sudden drop to freezing temperatures that early spring was responsible for the massive death at ground level,” Carvalho said.

While this nest is an example of localized mass death, it could also be a reminder of how bees persevered in the face of changing weather conditions. There are more than 25 species of Eucera bees living in different habitats in Portugal.

“We hope that this discovery will bring us more information about how these animals became resistant to climate change”, said Carvalho. “The Eucera bee mummies can therefore be considered a message of hope in this world of climate chaos that we are living in.”