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. Last Updated: 07/27/2016

Southern Europe Yields Gigantic Colony of Ants

WASHINGTON -- A supercolony of ants has been discovered stretching more than 5,000 kilometers from the Italian Riviera along the coastline to northwest Spain.

It's the largest cooperative unit ever recorded, according to Swiss, French and Danish scientists, whose findings appear in Tuesday's issue of Proceedings of the National Academy of Science.

The colony consists of billions of Argentine ants living in millions of nests that cooperate with one another.

In Argentina, typical ant behavior -- defending boundaries, ripping off the legs and heads of enemies and spurting out toxic chemicals -- leaves piles of wartime casualties and colonies about the size of suburban lots.

By contrast, the Californian and European transplants share what amounts to a peace dividend. Instead of using resources for war, the peaceniks spend time looking for food and nurturing teeming numbers of young. The result: massive supercolonies of ants that don't fight even though they are unrelated.

Scientists on both continents are having a difficult time explaining just why these ants are so nice to each other. The amiable behavior among distant strangers contradicts a basic idea of evolutionary biology called kin selection theory -- the notion that gallant behavior should only persist among related individuals because helping your kin helps perpetuate the genes you share.

Cooperating allows the colonies to develop at much higher densities than normally would occur, eliminating some 90 percent of other types of ants that live near them, said Laurent Keller of the University of Lausanne, Switzerland.

The researchers concluded that ants in the supercolony were all close enough genetically to recognize one another, despite being from different nests with different queens.

Researchers determine if ants from different areas are part of the same supercolony by pairing them in miniature gladiatorial bouts in the lab. Members of the same supercolony occasionally tap each other with their antennae but tend to peacefully coexist. Members from different colonies, however, rise up on their rear legs and bite each other to shreds.

The huge numbers of Argentine ants in California -- too many even for scientists to estimate -- swamp the armies of larger native ants, kill rival queens, take over nest sites and munch on all available food. Their success has meant trouble for coastal horned lizards, which are starving as their accustomed food -- native ant species -- disappears. The lizards won't make a meal of the bitter-tasting Argentines.

Richard Fell, an entomologist at Virginia Polytechnic Institute, said Argentine ants have been known to form large colonies -- the size of several city blocks, for example -- but he had not heard of any as large as that cited in the report.

"It may be that certain ant colonies will bud off, form satellites and remain connected with one main colony," he suggested.

The Argentine ants were accidentally introduced to Europe around 1920, probably in ships carrying plants, Keller said in an e-mail interview.

The European researchers said that in addition to the main supercolony of ants they found a second, smaller but also large colony of Argentine ants in Spain's Catalonia region. (AP, LAT)