A supercolony of ants has been discovered stretching over 3,000 miles from the Italian Riviera along the coastline to northwest Spain. It's the largest group of ants ever recorded, according to Swiss, French and Danish scientists. The colony consists of billions of Argentine ants living in millions of nests, and they all cooperate with one another.
Normally, ants from different nests fight with each other. But the researchers think the ants in the supercolony are all close enough genetically to recognize one another as part of the same family, despite being from different nests with different queens.
Cooperating allows the colonies to develop at much higher densities than normal, eliminating 90 percent of the other types of ants that live near them, says Laurent Keller of the University of Lausanne, Switzerland.
The Argentine ants were accidentally introduced to Europe around 1920, probably in ships carrying plants. Richard D. Fell, an entomologist at Virginia Polytechnic Institute, says Argentine ants have been known to form large colonies the size of several city blocks, but he hadn't heard of any as large as this. "It may be that certain ant colonies will bud off, form satellites and remain connected with one main colony," he says.
In addition to the supercolony of ants, the researchers found a second colony of Argentine ants in Spain's Catalonia region that is slightly smaller. When ants of the two supercolonies were placed together they fought to the death, while ants from different nests of the same supercolony showed no aggression towards one another.
"It is interesting to see that introduction in a new habitat can change social organization," says Keller. "In this case, this leads to the greatest cooperative unit ever discovered."
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