Red imported fire ants do not live in Minnesota. The species requires warm climates and cannot survive Minnesota’s winters. Their established range stays in the southern United States, roughly from Texas to the Carolinas and down through Florida. If you’ve been stung by an ant in Minnesota or spotted a mound that looks suspicious, you’re almost certainly dealing with a native species that resembles fire ants.
Why Fire Ants Can’t Survive in Minnesota
Red imported fire ants need sustained warm temperatures to maintain their colonies. They thrive in the Southeast, where mild winters let colonies persist year-round. Minnesota’s prolonged freezing temperatures kill colonies before they can establish. Even with occasional warm shipments bringing stray fire ants into northern states through nursery stock or soil, those ants don’t survive long enough to reproduce and spread.
The University of Minnesota Extension states it plainly: fire ants do not occur in the upper Midwest. Climate modeling consistently places Minnesota well outside the zone where fire ant colonies could overwinter, even accounting for warming trends.
What You’re Probably Seeing Instead
Minnesota has several native ant species that look and behave enough like fire ants to cause confusion. The most common culprit is the field ant.
Field ants (genus Formica) build prominent dirt mounds in lawns and fields, which is the main reason people mistake them for fire ants. They come in black, brown, red, or combinations of those colors, and workers range from about 1/8 to 1/4 inch long. A colony will have both larger and smaller workers. Field ants can bite and will spray formic acid into the wound, which stings, but their bites are far less painful than a true fire ant sting and don’t produce the distinctive blisters fire ants cause.
European fire ants are another species that sometimes turns up in Minnesota and neighboring states. Despite the name, they’re a different genus from the red imported fire ant and behave differently. They nest in moist soil, mulch, and garden debris rather than building the large, hard-crusted mounds associated with southern fire ants. Their stings hurt but are mild compared to their southern relatives.
Carpenter ants are also common across Minnesota. They’re larger, typically black, and nest in wood rather than soil. They don’t sting at all, though they can deliver a noticeable bite.
How to Tell the Difference
The easiest way to rule out true fire ants is the sting itself. A red imported fire ant locks its jaws onto your skin, then pivots its body to sting repeatedly in a circular pattern, sometimes delivering seven or eight stings at once. This creates a distinctive ring of welts that turn into small white blisters (pustules) within a day. Those blisters last seven to 10 days. If you were stung by an ant in Minnesota and didn’t develop that pattern of fluid-filled blisters, it wasn’t a fire ant.
Mound shape matters too. Red imported fire ant mounds are dome-shaped, can reach 18 inches tall, and have no visible entry hole on top. Field ant mounds are flatter, more irregular, and often built around grass or debris. If you can see ants entering through the top of the mound, it’s not a fire ant colony.
What a Real Fire Ant Sting Does
For context on why the distinction matters: real fire ant stings cause an immediate burning sensation followed by itchy welts, often arranged in that circular pattern. Most people develop only a local reaction, where the area around the sting swells, reddens, and blisters. A sting on your calf might cause your entire lower leg to swell for a couple of days.
In rare cases, people experience a systemic reaction affecting the whole body. Symptoms can include stomach cramps, nausea, vomiting, a swollen tongue, or difficulty breathing. Anaphylaxis from fire ant stings is uncommon but possible, particularly in people with known insect venom allergies. These severe reactions require immediate emergency care.
What to Do If You Suspect Fire Ants
If you genuinely believe you’ve found fire ants in Minnesota, possibly from a recent shipment of plants, soil, or landscaping materials from the South, the Minnesota Department of Agriculture wants to hear about it. Reporting is straightforward:
- Online: Use the MDA’s reporting form at their “Report a Pest” page, where you select the species from a dropdown menu and attach photos.
- Email: Send photos and a description of the location to reportapest@state.mn.us.
- Phone: Call 1-888-545-6684 and leave a message with your name, location, and what you found.
- App: Download the free EDDMapS app for iOS or Android to submit a report with photos directly from your phone.
Before handling any unfamiliar ant, wear gloves. If you can safely capture a specimen, place it in a sealed plastic bag and freeze it. Take close-up photos with a coin next to the ant for scale, and note the exact address or GPS coordinates where you found it. The MDA uses these reports to track potential introductions and respond before a population could take hold.
In nearly every case, the ant will turn out to be a native field ant or another common Minnesota species. But reporting is still worth doing, because catching a hitchhiker colony early, before it has any chance to spread, is exactly how states outside the fire ant range keep it that way.