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One type of South American ant is spreading around the world and is living in huge super-colonies．Not only that but these natural fighters seem to know they are family according to the latest scientific findings．
Over the years the light brown Argentine ant has moved to other parts of the globe possibly by hiding in people's suitcases and in cargo(货物)．This hasn't always been a good thing since the insects can destroy local plants and affect what animals in that area eat．
Ants are fierce fighters．They protect their territory(领地)from outsiders including other types of ants and insects．But Argentine ants though they live on separate continents are rather friendly towards each other when they come together scientists say．
There are three known super-colonies of Argentine ants．In Europe one super-colony is located along the Mediterranean Sea．It is believed to be 3 700 miles long．Another super-colony is located in California．It covers about 560 miles．The third super-colony is on the west coast of Japan．
Scientists have discovered that the insects in the three super-colonies share similar chemical composition(成分)．This helps them recognize one another．To prove this the scientists matched each super-colony with ants from a different colony in a similar part of the world．The Mediterranean ant colony couldn't get along with a smaller one from Spain．And the ants from the west coast of Japan couldn't get along with those from another area in Japan．But when the ants from the three super-colonies came together they acted like old friends greeting each other by rubbing antennae(摩擦触角)to say hello．
The scientists think that the Argentine ant super-colonies are one big family．Because they have similar chemical composition the scientists believe they are genetically related．The ants recognize each other by the chemical composition of their outer shells．