Argentine ants living in vast numbers across Europe, the US and Japan belong to the same interrelated colony, and will refuse to fight one another. The colony may be the largest of its type ever known for any insect species, and could rival humans in the scale of its world domination.
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In Europe, one vast colony of Argentine ants is thought to stretch for 6,000km (3,700 miles) along the Mediterranean coast, while another in the US, known as the ‘Californian large’, extends over 900km (560 miles) along the coast of California. A third huge colony exists on the west coast of Japan.
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While ants are usually highly territorial, those living within each super-colony are tolerant of one another, even if they live tens or hundreds of kilometres apart. Each super-colony, however, was thought to be quite distinct. But it now appears that billions of Argentine ants around the world all actually belong to one single global mega-colony.
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The team selected wild ants from the main European super-colony, from another smaller one called the Catalonian super-colony which lives on the Iberian coast, the Californian super-colony and from the super-colony in west Japan, as well as another in Kobe, Japan.

Ants from the smaller super-colonies were always aggressive to one another. So ants from the west coast of Japan fought their rivals from Kobe, while ants from the European super-colony didn’t get on with those from the Iberian colony.
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But whenever ants from the main European and Californian super-colonies and those from the largest colony in Japan came into contact, they acted as if they were old friends.