Billions of ants from Argentina have created the Earth's biggest "super organism" in Europe, a network of communicating worker ants spanning more than 3,700 miles.
The invading ants are in millions of nests in a supercolony stretching from northern Italy, through the south of France to the Atlantic coast of Spain, in what is thought to be the largest co-operative unit of individual organisms.
The Argentine ant first appeared in southern Europe in the Twenties and wherever it went it managed to push out the 20 or so indigenous species of European ant. Now scientists think they know why.
Ants of the same species from different nests are usually highly aggressive towards each other, but the Argentine invader does not seem to share this aggressiveness between neighbouring ants.
For that reason, an unprecedented degree of co- operation between worker ants from neighbouring nests has grown into a fully fledged supercolony extending from Italy to Spain. The Argentine immigrant has thus been able to concentrate on fighting its indigenous rivals with great success.
Laurent Keller, professor of ecology at the University of Lausanne in Switzerland, whose research is published today in the Proceedings of the National Academy of Sciences, said entomologists had never before recorded such a huge supercolony of ants.
"A collection of colonies acting as one can be described as a supercolony. It is very unusual because ants are usually highly aggressive," Professor Keller said.
The Argentine ant, Linepithema humile, has become one of the most persistent pests in southern Europe, raiding domestic kitchens and protecting crop pests such as aphids against chemical attack from farmers. "People have tried to treat them with pesticides but the best you can do is limit their numbers," Professor Keller said.
There is one ray of hope on a gloomy horizon. A second, smaller supercolony of Argentine ants has been identified in the Catalan region of Spain around Barcelona and the Lausanne scientists say these Argentine ants are happy to make war on their compatriots.
Professor Keller said he hoped to identify the signals that triggered aggression between Argentine ants to foment strife and insurrection within the main supercolony.
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