These ants get their common name from their ability to inflict especially painful bites and stings. The two most important species are the southern fire ant and the red imported fire ant. The southern fire ant is a native species and ranges from California to southern South Carolina to northern Florida. The red imported fire ant is from central Brazil and is found in the southeastern United States, from Virginia through Texas.
Native fire ants rarely become structural pests. The red imported fire ant (RIFA) and black imported fire ant have spread to more than 13 southern and western states and continue to expand their range. These ants cause serious medical, agricultural and property damage. The RIFA is very aggressive and will sting repeatedly, especially when their colony/mound is disturbed.
Fire ants typically nest outdoors in sunny areas of exposed soil or lawns. If untreated, fire ant infestations may reach 30–100 single-queen mounds per acre, containing up to 80,000 ants. Over time, colonies may “link,” creating super colonies of up to 250,000 ants. Mounds are rounded and range from a few inches to several feet across. Each mound has several tunnels just under the soil surface extending out several feet. After rain, nests in sandy soil are rebuilt with sponge-like surfaces. When disturbed, fire ant workers pour out of their mound and aggressively attack the offender.
Colonies generally have their own territories. They forage in established trails. Red imported fire ants will sometimes nest in areas of exposed soil within buildings (e.g., bath traps). They also build outside nests adjacent to foundation walls and slabs. Fire ants are attracted to electrical junction boxes and air conditioners. They also nest in gas and water meter boxes and follow pipes into the building.