Red Imported Fire Ants (RIFA), native to South America, have been confirmed in Missouri, though they are not widely established across the state like they are in the deep South. They were first reported in 2009, with a confirmed colony found in Kennett in the southeastern Bootheel region. While the state is not considered fully infested, sporadic detections occur, often linked to the movement of materials like nursery stock, sod, or hay imported from states where fire ants are common. Missouri’s cold winters generally prevent the long-term survival and widespread colonization of this tropical species, meaning their presence is typically transient or limited to isolated pockets in the warmer southern counties.
Current Status and Geographic Spread
Missouri is situated at the northern edge of the Red Imported Fire Ant’s potential range, resulting in sporadic, rather than permanent, establishment. The highest risk of finding a colony is in the far southern parts of the state, particularly the Bootheel region, which borders established populations in Arkansas and Tennessee. The primary method of introduction is accidental transport via human activity from southern quarantine areas.
The Missouri Department of Agriculture (MDA) and the University of Missouri Extension actively monitor for new infestations to prevent widespread establishment. When a colony is confirmed, immediate eradication efforts are implemented. State officials caution those importing agricultural products from the South to inspect materials carefully for fire ant presence.
Key Identification Markers
Distinguishing the Red Imported Fire Ant (Solenopsis invicta) from native Missouri ants is important for accurate reporting and safety. The workers of this species are reddish-brown to dark brown, ranging from about 1/8 to 1/4 inch long, with varying sizes within the colony. RIFA workers have a two-segmented petiole, or “waist,” and their antennae have ten segments that end in a two-segmented club.
The most recognizable sign of fire ant presence is the characteristic mound structure they build. These nests are dome-shaped piles of loose, fine soil up to a foot in diameter, often found in open, sunny areas like lawns and pastures. A distinguishing feature is the absence of a central opening, as the ants enter and exit through underground tunnels. When disturbed, these ants respond with aggression, swarming immediately to defend their colony.
Handling Encounters and Stings
If you encounter a suspected fire ant mound, do not disturb it, as the ants are aggressive and will swarm to sting any intruder. If stings occur, quickly move away from the area and gently brush the ants off the skin and clothing to prevent multiple stings. The venom injected causes an immediate, intense burning sensation, which is how the species earned its name.
To treat the stings, wash the affected area with soap and water, then apply a cold compress to reduce swelling and pain. Within 24 to 48 hours, a localized, fluid-filled white pustule or blister will form at the sting site. Do not scratch or break these pustules, as this can lead to secondary bacterial infection. Taking an over-the-counter antihistamine or applying hydrocortisone cream can help manage itching and minor localized reactions.
Immediate medical attention is necessary if you experience signs of a severe allergic reaction, such as difficulty breathing, swelling of the throat or face, chest pain, or widespread hives. If you confirm a fire ant colony on your property, report the sighting to the Missouri Department of Agriculture or your local University of Missouri Extension office. Because RIFA is an invasive pest, control and eradication efforts are often regulated and tracked by state agencies.