The Invasion of Argentine Ants

From a suburban sidewalk in southern California, Jad and Robert witness the carnage of a gruesome turf war. Though the tiny warriors doing battle clock in at just a fraction of an inch, they have evolved a surprising, successful, and rather unsettling strategy of ironclad loyalty, absolute intolerance, and brutal violence.

David Holway, an ecologist and evolutionary biologist from UC San Diego, takes us to a driveway in Escondido, California where a grisly battle rages. In this quiet suburban spot, two groups of ants are putting on a chilling display of dismemberment and death. According to David, this battle line marks the edge of an enormous super-colony of Argentine ants. Think of that anthill in your backyard, and stretch it out across five continents.

Argentine ants are not good neighbors. When they meet ants from another colony, any other colony, they fight to the death, and tear the other ants to pieces. While other kinds of ants sometimes take slaves or even have sex with ants from different colonies, the Argentine ants don’t fool around. If you’re not part of the colony, you’re dead.

According to evolutionary biologist Neil Tsutsui and ecologist Mark Moffett, the flood plains of northern Argentina offer a clue as to how these ants came to dominate the planet. Because of the frequent flooding, the homeland of Linepithema humile is basically a bootcamp for badass ants. One day, a couple ants from one of these families of Argentine ants made their way onto a boat and landed in New Orleans in the late 1800s. Over the last century, these Argentine ants wreaked havoc across the southern U.S. and a significant chunk of coastal California.

In fact, Melissa Thomas, an Australian entomologist, reveals that these Argentine ants are even more well-heeled than we expected - they've made to every continent except Antarctica. No matter how many thousands of miles separate individual ants, when researchers place two of them together - whether they're plucked from Australia, Japan, Hawaii ... even Easter Island - they recognize each other as belonging to the same super-colony.

But the really mind-blowing thing about these little guys is the surprising success of their us-versus-them death-dealing. Jad and Robert wrestle with what to make of this ant regime, whether it will last, and what, if anything, it might mean for other warlike organisms with global ambitions.

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