Legions of legionary ants have also spread across Europe


ZoologyLegions of legionary ants have also spread across Europe

A 35-million-year-old fossil shows that these destructive colonies, never seen on our continent, took over before they disappeared.

This eyeless army ant is 3 mm in size and found in amber.

Zosiak et al. 2022, Museum of Comparative Zoology, Harvard University; President and Fellows of Harvard College

About 270 species of army ants currently live in the Eastern Hemisphere and about 150 in North and South America. Unlike other ant lineages, these have wingless queens capable of laying millions of eggs per day, while their nomadic colonies temporarily occupy nests between stages of the journey, sometimes comprising millions of ants up to 100 meters long. And they attack their prey en masse, with such ferocious efficiency that they can cause… 500,000 casualties per day.

But it is surprising that they are not in Europe today. A fossil discovery shows this wasn’t always the case. Trapped in amber for 35 million years, that is, in the Eocene, this individual rested for almost 100 years in a drawer of the Museum of Comparative Zoology at Harvard University (USA). Christine Zosiak, who was researching ants preserved in amber, came across the specimen, which she labeled a common ant, but soon realized it wasn’t.

Named after Perseus

Sosia and his colleagues discovered that unlike most ant species, this insect has eyes, sharp jaws, a single pelvis, and a large gland that secretes protective fluids necessary for life. “New Science”. They named him Dissimulatorylus Perseus, Named after Perseus, who defeated Medusa without looking her in the eye, using the reflection of her shield. It is the first army ant fossil discovered in Europe and the second in the world.

Thus, before disappearing in the last 50 million years, army ants were almost certainly present throughout continental Europe. “At the time the fossils formed, Europe was warmer and wetter than it is today and may have provided better habitat for ancient army ants,” said Philip Barton, senior author of the paper. “Biology Letters”. “However, Europe has undergone several cooling cycles over the millions of years since the Eocene, which may have been inhospitable to these tropical-adapted species.”

Combined indiscriminate attacks

The specimen found is 3 mm. It is a worker. “Army ant workers attack swarms and participate in hunting other insects and vertebrates. Because these army ants are blind, they use chemical interactions to coordinate with each other to take larger prey,” explained Christine Sosiak. “Eurekalert”. “This worker may have strayed far from its fellow hunters and become enmeshed in the sticky tree resin that eventually solidified and sealed the ant we see today.”

“This discovery is the first physical evidence of an Eocene army ant syndrome, establishing that the traits of these specialized predators predate the ancestors of some army ants, such as Dorylus,” Barton said.

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