The imported fire ant is native to South America and was brought to the US in the early 1900s. Cargo ships delivering goods to South America used soil from Brazil and Argentina as ballast for their return trip. The soil was unloaded in Mobile, AL, where fire ants were first identified as an exotic pest in the US.

While the mound of dirt at the base of this tree may seem unassuming, it’s home to thousands of fire ants.

Photo Credit: Megan Bame

Once you learn to recognize fire ant mounds, they’re easy to spot, even from a distance.

Photo Credit: Megan Bame

It’s a common misconception that fire ants are large, red ants. But these are not fire ants. Imported fire ants actually closely resemble harmless, native, black ants. Most are 1/8-inch long, with the front portion of the body being a reddish-brown and the back portion a solid black.

The key to identification is the fire ants’ unmistakable mound.

In addition to being their home, the fire ants’ mound also serves as a battlefield, where these aggressive pests attack their unsuspecting victims. Those who aren’t familiar with fire ant mounds would assume the mound was just an exposed area of crusted-over soil. There’s no obvious entry hole like those found in native black ant mounds, and those built in clay are usually symmetrical and dome-shaped. Once you learn to recognize what a fire ant mound looks like, though, the red clay soil and the relatively large area a mound covers actually makes them easy to spot, even from a distance.

Fire ant mounds are most often found in undisturbed locations such as the base of a tree, a flower bed or along the edge of a sidewalk, but they can also be found in the middle of a lawn. The pests themselves prefer warm, southern exposures and are most active when the temperature is between 70-85 degrees F. They’re still present in the heat of summer and chill of winter – they’ve simply retreated deep within the mound for a more moderate temperature during those times.

Fire ants only attack if their mound is disturbed. To test a suspect mound, use a small stick or pencil to poke a single hole in the soil. Leave the stick in there, but hold it by the end. Native black ants are confused and unorganized if their mound is disturbed, so if, within seconds, you see ants climbing the stick and scurrying over the top of the mound, you’re witnessing the organized attack of fire ants. When that happens, be sure to release the stick before the ants reach your hand!

These aggressive pests release pheromones that call other colony members to attack. The fire ant secures itself by biting, then it swivels in a circular pattern, stinging its victim multiple times. It injects a venom that’s different from bee or wasp venom, resulting in a unique pustule filled with cloudy, sterile liquid over a red base.

Most people aren’t allergic to fire ant stings, but those who are may have a severe reaction, including dizziness, nausea, swelling, hives or shock. The allergy isn’t detected until a person has been attacked, and though uncommon, an anaphylactic reaction may occur at the first exposure to fire ants. The normal reaction is approximately an hour of stinging pain followed by itching as the pustules heal.

Natural progression is responsible for most new occurrences of fire ants, though they may be accidentally introduced to an area by relocation of infested soil or plant material. The US Department of Agriculture is tracking their “progress” but has conceded that there are no effective means of eradication. Fire ants are known to be present in all of the southeastern states. Once they arrive, we must learn to coexist with them.