Originating from Argentina’s flood plains and savannahs, red imported fire ants were accidentally brought to Alabama through a seaport in Mobile in 1930. Since then, they’ve spread throughout a quarter of the US.
Black imported fire ants are very similar in habitat and behavior to red imported fire ants. However, they’re limited to Alabama, Mississippi, and Tennessee.
Fire ants are fiercely competitive and perfectly suited to invasions. They’ve been spreading rapidly ever since they arrived in the US. This is why some people don’t remember encountering fire ants in childhood.
With people unknowingly aiding in their spread, fire ants have spread to over half the land of most southern states, are sporadically found in other parts of the US, and have even invaded Mexico, Taiwan, New Zealand, Australia, and China.
Due to the lack of natural competitors in the US, the fire ant seems to be here to stay. Read on to learn more about how it all started.
Where Did Red Imported Fire Ants Come From?
Although the red imported fire ant is a native fire ant to Brazil, the worker ants that invaded the US are genetically different. Studies show that they actually originate from the Paraguay River in Argentina.
Even so, the native ant species are much more numerous in the US than in South America. There are 10 to 100 times more fire ant populations in the US than in Argentina.
When they came to the US, fire ants found an escape from their natural enemies and a perfect temperate climate to aid their spread.
In South America, the southern fire ant competes for food and resources with other insects. One of the natural predators of the fire ant is the Pseudacteon, also known as the ant-decapitating fly.
These flies are incredibly specific with their host, only attacking fire ants. They quickly inject an egg into a fire ant, it grows inside the ant, and eventually emerges from the ant, decapitating it. They’re being considered a natural way to keep the US fire ant population in check, as they’ll simply die when no more fire ants are left.
How Were Fire Ants Transported to the US?
Fire ants weren’t brought to the US for research purposes like other invasive species. By the time biologist E.O. Wilson reported the first fire ant colony in Mobile, it had already been over a decade since the introduction of fire ants to the US.
Fire ants were transported as cargo stowaways or in the soil used as ballast to weigh the cargo ships down. There were likely only a dozen or so ants in the beginning, but their biology has allowed them to spread way beyond that, causing fire ant invasions.
The Spread Of Fire Ants Throughout The US
Once fire ants made it to the US, they found themselves in a land with no natural competitors. Fire ants are incredibly durable, tunneling into the ground when it’s too hot and making “living rafts” during floods.
By the time the USDA conducted the first fire ant survey in 1953, fire ants were already present in 10 different states. Today, fire ants have spread all across the Southern United States. See Where Do Fire Ants Live? (Most Infested Regions)
Fire ants have their own natural ways of spreading to new territories, such as calculated colony movement, mating flights, or “rafting” when floods occur. Fire ant queens have wings and can fly as far as 3 miles away. Even more, if the wind is assisting them.
However, we have played a much bigger role in the extensive and rapid spread of the fire ant than we think. The introduction of the fire ant coincides with the housing boom after World War 2.
The ants were transported from house to house through landscaping plants used at the time. The US government has tried to eradicate fire ants on a country-wide scale, spraying long-lasting pesticides throughout the southeastern US.
Unfortunately, these pesticides would kill wildlife like fish, birds, and other insects indiscriminately. Even worse, this eliminated many native species competing with the fire ant, making it much easier to spread.
Even today, we artificially transport fire ants to new locations via infested beehives, hay, or sod. Queens can go even longer distances if they land on cars.
Although we’ve researched and learned more about the fire ant, they’re still almost impossible to completely eradicate. Their spread continues, and the USDA predicts they’ll eventually reach the mid-Atlantic and the Pacific Northwest.
FAQ
Why Are They Called Imported Fire Ants?
Fire ants were brought to the US by accident. There are fire ants native to the southern US. Imported fire ants were brought into the US from Argentina, though “imported” implies that it was done on purpose.
How Do Fire Ants Survive Floods?
Fire ants not only survive floods; they can spread to new territories during floods. The ants hold onto each other, forming a “living raft.” They float until they hit a tree or dry ground, always keeping the queen and eggs in the middle of the raft for safety. They’re the only insects known to do this.
Are Fire Ants Considered Pests In Their Homeland?
Fire ants are considered pests in South America, but not nearly to the extent they are in the US. Fire ants native to South America are pests to the people there as much as fire ants native to the US are pests to us.
Final Thoughts
Fire ants cause about $6 billion per year in damage. They’re called Solenopsis invicta, or invincible, for a reason. They went from being totally unknown to one of the most widespread pests in the US.
Imported fire ants have rapidly spread throughout the southeastern US despite many efforts to stop them, and it seems like they’re here to stay.
As we continue to research new ways to eliminate imported fire ants, it’s important that we remember the havoc that a few members of non-native species can wreak on foreign land.
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