Earth News on the Beeb:

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 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.

These ants rubbed antennae with one another and never became aggressive or tried to avoid one another.

In short, they acted as if they all belonged to the same colony, despite living on different continents separated by vast oceans.

The most plausible explanation is that ants from these three super-colonies are indeed family, and are all genetically related, say the researchers. When they come into contact, they recognise each other by the chemical composition of their cuticles.

"The enormous extent of this population is paralleled only by human society," the researchers write in the journal Insect Sociaux, in which they report their findings.

How's they do it? No banksters, for starters. And I'm guessing they're able to keep their parasites under control.

NOTE Via Yves.