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A single mega-colony of ants has colonised much of the world, scientists have discovered.

Argentine ants living in vast numbers across Europe, the US and Japan belong to the same inter-related 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.

What's more, people are unwittingly helping the mega-colony stick together.

Argentine ants (Linepithema humile) were once native to South America. But people have unintentionally introduced the ants to all continents except Antarctica.

These introduced Argentine ants are renowned for forming large colonies, and for becoming a significant pest, attacking native animals and crops.

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.

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.