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ZoologyArmies of legionary ants have also swept over Europe
A 35 million year old fossil shows that these devastating colonies that were not found on our continent had nevertheless conquered it before disappearing.
This eyeless army ant measures 3 mm and was found in amber.
Sosiak 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 travel that take the form of bivouacs, sometimes involving million ants spanning 100 meters. And they attack their prey en masse, with formidable efficiency since they can cause… 500,000 victims per day.
Yet they are surprisingly absent in Europe today. The discovery of a fossil shows that this was not always the case. Trapped in amber for 35 million years, that is to say in the Eocene, this individual rested for almost 100 years in a drawer of the Museum of Comparative Zoology at Harvard University (USA). Christine Sosiak, who was researching ants preserved in amber, came across this specimen that was labeled as a common ant, but soon realized that was not the case.
Named after Perseus
Sosiak and his colleagues figured out that, unlike most ant species, this insect had no eyes, sharp jaws, a single waist segment and a large gland that would have secreted the protective fluids necessary for life. underground, explains the «New Scientist». They named him Persuasive dissembler named after Perseus who defeated Medusa without looking her in the eye, but using the reflection of her shield. This is the first army ant fossil discovered in Europe and the second such fossil found in the world.
Military ants therefore existed, certainly throughout continental Europe, before disappearing over the last 50 million years. “At the time the fossil formed, Europe was warmer and wetter than it is today and may have provided an ideal habitat for ancient army ants,” said Phillip Barden, senior author of the article published in «Biology Letters». “Europe has, however, undergone several cooling cycles over tens of millions of years since the Eocene, which may have been inhospitable to these tropic-adapted species.”
Coordinated Blind Attacks
The discovered specimen measures 3 mm. It was a worker. “Army ant workers participate in raiding swarms, hunting other insects and even vertebrates. Because these army ants are blind, they use chemical communication to stay coordinated with each other in order to take down large prey,” explained Christine Sosiak in «Eurekalert». “This worker may have strayed too far from her fellow hunters and got caught in sticky tree resin, which eventually solidified and encased the ant as we see it today.”
“This finding is the first physical evidence of Eocene army ant syndrome, establishing that the characteristics of these specialized predators were in place even before the ancestors of some army ants like Dorylus,” Barden said.