The Creepy Crawlies Are Here to Stay: The Story of California’s Enormous Ant Hill

Have you ever woken up to a swarm of ants crawling across your floor and into your snack drawer? Well, you’re not alone! In fact, a sizeable portion of California suffers from the same ant-festation that we endure. California is home to the second largest ant colony in the entire world. It ranges about 900 km (600 mi), beginning in San Diego and ending just north of San Francisco.

Though we may try to protect our rooms, resistance is futile. No matter how high up our snacks are, no matter how much Raid we spray, they will find a way in. Nothing can stop the mighty, but tiny, force of the Linepithema humile, also known as the Argentine ant.

Complaining about these tiny pests has become a campus-wide pastime, and we like to think that they are devil incarnate, sent to our rooms to personally ruin our lives. However, these little guys are actually really interesting creatures, with a war-torn and bloody history.

And when they’re not eating our popcorn, we might come to appreciate them.  

Just outside Buenos Aires, where the Río Uruguay and Río Paraná rivers meet lies a floodplain. During each storm, the ant colonies that inhabit the area are forced up into the trees. After the storm, the different varieties of ants scurry back down, competing to rebuild colonies on the same land. This results in constant inter-colony fighting.

During each bloodbath, ants with the stronger, more ruthless genes live to procreate and pass on those genes, resulting in the creation of a hyper-violent Argentine ant.

Researchers suggest that in the late 19th century, these ants managed to climb aboard a steamboat that rolled into Buenos Aires. The first Argentine ant-festation was recorded in 1891 in New Orleans, and then, nearly a century ago, they were found way out in California. From there, the Argentine ants established the Californian supercolony.

But what makes these ants able to spread out in a way that other ants cannot? It started back in those flood plains, where only the most violent ants could survive. While other kinds of ants interbreed and take slaves into their colony, Argentine ants bred to be violent, killing or eating anything in their path. This particular species leaves no survivors and they never breed with other kinds of ants, therefore maintaining a pure genetic pool.

Because of this phenomenon, the Argentine ant has established colonies from San Diego to San Francisco, but members of the species are still able to identify each other. Ants use scent as a form of identification: when two ants meet, they use their antennae to smell the other one, determining whether it is a member of their colony. If it is a member of the same colony, nothing happens, but if it is a member of a different colony, then it becomes a fight to the death. (I watched a few videos of ant fights on YouTube. I was thoroughly disturbed.)

The genetic “purity” of the Argentine ant allows them to keep the same scent and stay united as a colony. And what is an ant to do after it has killed off everything in its path? Spread like mad!

And that is how we all wound up with thousands of tiny, extremely violent roommates.

Helena Shannon PO ‘18 is a cognitive science major from New York. One of her life goals is to own a small army of dachshund puppies.

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