Fire ants, known for their painful stings, are an invasive species. While primarily associated with the warmer climates of the southern United States, their presence can extend into more northern regions. Although not widely established across Illinois, isolated encounters with certain fire ant species have been reported.
Current Status in Illinois
The Red Imported Fire Ant (Solenopsis invicta) and Southern Fire Ant (Solenopsis xyloni) are the main species. These ants are not broadly established throughout Illinois, largely due to the state’s colder winter temperatures, which they typically cannot tolerate for extended periods. However, their potential range extends to the southernmost tip of Illinois, where conditions can be more favorable.
Fire ants primarily arrive in new areas through human-assisted transport. They can hitchhike on contaminated materials like nursery stock, sod, baled hay, or soil-moving equipment from infested regions. Federal and state agencies, including the Illinois Department of Agriculture, implement quarantine programs and monitor for new infestations. These efforts minimize the spread of these pests into non-infested areas of Illinois.
Recognizing Fire Ants
Identifying fire ants involves observing their physical characteristics and distinct behaviors. Adult fire ants are typically reddish-brown to black and range from 1/8 to 1/4 inch long. Worker ants within the same colony vary in size. They also possess a segmented body with two distinct nodes, or bumps, between their thorax and abdomen, and have elbowed antennae.
Their nests, or mounds, are another identifier. Fire ant mounds are often irregularly shaped piles of loose soil, lacking a visible central opening on top, unlike many other ant species. These mounds sometimes reach heights of 18 to 24 inches and are frequently found in sunny, open areas like lawns or fields. When disturbed, the ants exhibit aggressive behavior, swarming out rapidly and running up any vertical surface to sting repeatedly. This aggressive, upward-climbing response distinguishes them from many native ant species in Illinois, such as pavement ants or odorous house ants, which do not sting or swarm in the same manner.
Responding to Fire Ant Encounters
If you encounter fire ants or suspect a sting, immediate action manages the reaction. For stings, gently wash the affected area with soap and water, then apply a cold compress to reduce swelling and pain. Over-the-counter antihistamines can alleviate itching, and hydrocortisone cream may soothe the irritation. In cases of severe allergic reactions, such as difficulty breathing, swelling of the face or throat, or a rapid heartbeat, seek immediate medical attention.
Avoid disturbing fire ant mounds, as this will provoke a mass attack and multiple stings. If you suspect a fire ant infestation in Illinois, contact your local University of Illinois Extension office or the Illinois Department of Agriculture. These organizations assist with proper identification and advise on management strategies. Homeowners can deter fire ants by inspecting new plants or nursery stock, maintaining a clean yard, sealing cracks and gaps in foundations, and ensuring proper drainage.