The Unlikely Warrior: The Argentine Ant Empire#

Alright, imagine this: pretty much everywhere you look on Earth, ants are having their own little wars. Nature gives them different tools for fighting – some have tough armor, others deadly stingers, or sharp chompers. But then there’s this one ant. It’s tiny, frankly not very impressive-looking, but get this – it runs the biggest ant empire ever built! We’re talking a colony that stretches across whole continents, fighting wars where millions of ants die.

Let’s meet this unexpected little fighter: Linepithema humile, the Argentine ant. (By the way, this whole story comes with some neat visuals, like a Kurzgesagt intro and background music).

Where It All Began: The Paraná River Floodplains#

So, our story starts way back in the floodplains around the Paraná River in South America. Think of it as a super crowded ant city, a real megalopolis. There were tons of different ant species scrapping for space – like fire ants and army ants – and right there among them was the pretty unimpressive Argentine ant.

These ants are tiny, only about 2 to 3 millimeters long. With their small mandibles (that’s their mouthparts), it’s a bit of a wonder they even survived mixed in with all those tougher, buffer ants!

Their homes weren’t anything special either. Argentine ant colonies could be anywhere from fairly small to really huge, and you’d find them in all sorts of spots:

• Under logs
• In loose leaf litter
• Even taking over the old homes of other ants

Their Secret Weapon: Sheer Numbers#

Back in their native home, Argentine ants were getting ready with their most effective tool against rivals: just having a massive amount of bodies.

You see, most ant species usually have just one queen making all the babies. But the Argentine ants decided to go all-in on numbers. For every 120 worker ants, there’s one queen, and she can lay up to 60 eggs a day. This means their colonies grow super fast, reaching millions or even billions of individuals.

Often, teams of queens and workers would branch off from the main group to start new colonies. But this strategy had a bit of a problem in their native South America. As colonies got bigger and made lots of offspring, little random changes (mutations) would pop up. New colonies would adapt to their local spots, and their DNA would slowly shift over generations. After a while, the ants that left the original colony would become more like distant cousins, and eventually, they’d start competing and fighting with their mother colony.

This is exactly how Argentine ants behaved in their native South American range. They were super cooperative and well-organized within their own colony, but they’d fight brutal wars against other Argentine ant colonies, as well as against other ant species. With tough opponents all around, the Argentine ant became incredibly aggressive, fighting hard for every tiny bit of land. But they could never really take over and dominate their neighbors back home.

The Big Change: Humans Show Up#

That all changed when humans came into the picture. We humans, being humans, started moving stuff all over the world, often by ship. And wouldn’t you know it, a few Argentine ant queens managed to sneak aboard one of these ships as stowaways. Their trip took them from South America all the way to places like Madeira and New Orleans.

Suddenly, these Argentine ants found themselves in a totally new place. Instead of being surrounded by fierce, deadly enemies, they found… well, mostly victims. Nobody they encountered could fight them off effectively.

Here’s a key point: because only a few queens were introduced to these new places, the resulting colonies had really low genetic diversity. On top of that, the introduced Argentine ants have this weird habit of killing off a huge chunk of their queens every year – up to 90%! Fewer queens and less genetic variation meant that as these colonies spread out, the ants that branched off weren’t seen as distant cousins anymore.

The Birth of Supercolonies#

The amazing result of this low genetic diversity and queen culling was that the new colonies didn’t become rivals; they became cooperating partners, forming what are called “supercolonies”. This is a very unusual tactic in the ant world; only a handful out of the 16,000 known ant species have ever developed supercolonies.

One supercolony that started on the West Coast of the USA became like a main base for the tiny ants’ global takeover. Today, the Argentine ant has spread and lives in the Mediterranean climate zones of six continents and on lots of islands. This one specific supercolony was incredibly successful, setting up linked locations – sort of like sister cities – in California, Europe, Japan, New Zealand, and Australia. Together, these formed one enormous, connected intercontinental megacolony of Argentine ants.

This makes their society the largest on Earth, with even more individuals than the human population!

Impact on Invaded Lands: Ecosystem Overhaul#

But their huge success came at a cost for the places they invaded. California is a prime example. The invading Argentine ants, in their push for more territory, have swarmed over and replaced a massive 90% of the native ant species there. This includes several types of native Californian carpenter ants.

Even though carpenter ant workers are giants compared to the Argentine ants, their colonies only have between 3,000 and 6,000 individuals. They simply stand no chance against an expanding supercolony that numbers in the billions.

Here’s how the Argentine ants attack:

• They wipe toxic chemicals on their victims.
• This irritates the enemy and marks them for other Argentine ants to target.
• When they attack in force, they literally wash over their victims.
• They cling onto opponents in groups.
• Then, they work together to pull apart their limbs.
• The key is that it doesn’t matter how many Argentine ants die; there are always more coming.

Once a native colony is overrun and wiped out, the Argentine ants do a few things:

• They feed on their victims’ brood (the young ants).
• They take over their home and territory.

The sheer numbers of Argentine ants also mean they can hunt down and eat so many different kinds of insects that, over time, some species completely disappear from the areas the ants control. Argentine ants aren’t interested in working alongside the local plants and animals; they just consume them and move on.

Troubles for Humans#

And if their next stop happens to be property belonging to us humans? Well, they’ll just rudely make themselves at home there too.

You might find them:

• Foraging in dumpsters
• Raiding bowls of pet food
• Sneaking into kitchens to claim leftovers

It’s not just our houses. Our gardens and farm fields also feel the impact of Argentine ants. They act like ranchers, looking after huge groups (or “hordes”) of aphids as if they were their cattle. The aphids feed on plants and produce a sweet liquid called honeydew. The aphids trade this honeydew with the ants in exchange for protection. Since the Argentine ants in their new homes don’t have a major enemy to worry about, the aphids thrive and, sadly, end up killing the plants they live on.

So, besides totally messing up the ecosystems they invade, they are also a big problem (a huge pest) for agriculture.

Challenges to the Empire: Civil War and Old Enemies#

But the Argentine ant’s seemingly unstoppable rule is starting to face some challenges. Parts of the massive supercolonies have started breaking off and forming their own separate empires. This has led to a brutal civil war among the Argentine ants themselves!

For example, out in San Diego County, the Lake Hodges Supercolony has been fighting against the Very Large Colony for years. This is a massive war happening along a constantly shifting front line that stretches for kilometers. It’s estimated that a staggering 30 million ants die in this one conflict zone every single year.

On other fronts, an old familiar face from the Paraná River floodplains has reappeared: Red imported fire ants. These tough fighters were accidentally introduced from their original home to the coast of Alabama. Not only are fire ants fierce and capable of handling Argentine ants, but they can also form supercolonies themselves!

So, the old wars from their distant home have now moved to foreign battlegrounds. In the southeastern US, the supercolonies of Argentine ants and red imported fire ants clashed fiercely. And guess what? The Argentine ants found themselves outgunned. The fire ants’ major workers are more than twice the size of the Argentine ants, and they come armed with venom-injecting stingers. Even though the Argentine ants fought hard, the fire ants were simply too much for them. After countless defeats, the red imported fire ant managed to wipe out the Argentine ant supercolony from much of the southeastern US.

The Future: Fighting On#

That’s one territory lost for the Argentine ants, but they aren’t about to give up. This incredible network of cooperating supercolonies is the biggest success they’ve ever had. They won’t just abandon it because of one setback.

They will stand their ground against any enemy that pops up, whether that fight is happening back on the Paraná River or on one of the giant battlefields they’ve created across the world.

(Background music gently fades)