Natural Selections: Solenopsis invicta

Though they are little, they are fierce. Measuring a measly one-eighth to one-quarter of an inch long, fire ants have been known to burrow intricate mounds of tunnels, viciously defend their territory and ruin many a romantic picnic.

UNWELCOME HOME Hailing from South America, fire ants accidentally entered the U.S. through the port of Mobile in the early 1900s, hidden in soil used to weigh down ships and secure their cargo. The ants have since spread throughout the southeast. Oops, so sorry y’all!

EARTH INVADERS Since a mature colony can consist of 200, 000-plus fire ants, trying to control populations of the non-native species has become a pesky — and expensive — problem. It’s estimated their damage costs the U.S. close to $1 billion per year.

TUNNEL VISION Fire ants construct their nests primarily in sunny, open, grassy environments. The worker ants burrow tunnels through the soil, excavating the dirt and piling it just above the soil line to create heaping mounds of habitat, which vary in height based on weather temperature and rainfall. During cold, wet weather they build higher dunes to escape flood waters; in dry, warm conditions, they keep the colony lower and deeper in the soil where the earth is cooler. 

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HOME SECURITY SYSTEM When their territory is invaded (like when tennis shoes or puppy paws traipse on top of a mound), fire ants instinctively become aggressive, immediately attacking the perpetrator.

STING OPERATION When fire ants sting, they clamp their jaws down on their victims’ skin, releasing venom with a chemical called piperidine. Bite symptoms may include redness, itchiness, swelling and pain, as well as pus-filled blisters at the site of the bite. Those with an allergy to the venom may experience serious effects, such as difficulty breathing, rapid heartbeat and swelling of the throat. 

Expert Ant-ecdotes

At the age of only 13, former Mobilian and Pulitzer-prize-winning biologist E.O. Wilson reported the country’s first colony of fire ants — and the little guys have stuck with him ever since. He has been widely published on the topic. Here are a few of his musings.

  • “I was a senior in high school when I decided I wanted to work on ants as a career. I just fell in love with them and have never regretted it.” 
  • “There’s the question of, why did I pick ants, you know? Why not butterflies or whatever? And the answer is that they’re so abundant, they’re easy to find, and they’re easy to study, and they’re so interesting. They have social habits that differ from one kind of ant to the next.” 
  • “Each kind of ant has almost the equivalent of a different human culture. So each species is a wonderful object to study in itself.”
  • “I honestly can’t understand why most people don’t study ants. Ants have the most complicated social organization on earth next to humans.”
  •  “The work on ants has pro-foundly affected the way I think about humans.”

text by lawren largue • illustration by kelan mercer

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