Scientists classify fire ants as ground-nesting ants. The ants usually make their nest in sunny areas. Scientists suspect this is so the sun can heat the nest under the soil.
Fire ants often place their nest next to a sidewalk, a driveway, or a building foundation. Scientists think that this is so the ants can use the reflected heat from the concrete during the winter. Fire ants often nest beside the pavement of roads and parking lots. This habit may be a reason the fire ants have been able to survive in areas that have severe winters.
When the fire ants make their nest, they dig tunnels that extend deep into the ground. During the day, ant workers move the queen and the immature ants up and down in the tunnels. This way they are able to maintain a constant temperature.
In rainy or cold weather, the workers often build a mound of soil above the nest. The mound allows the queen to get out of the damp tunnels. The mound absorbs the sunlight, so it is often warm on winter days.
In areas where fire ants are common, scientists think there can be hundreds of fire ant colonies per acre. Since the workers forage in the grass, homeowners are often unaware that the fire ants have invaded their yard. When the mounds appear, many homeowners assume that the fire ants arrived that day. In fact, the ants had probably been there for some time.
As fire ant colonies mature, their mounds often grow very large. These large mounds have been known to damage farm equipment.
In residential areas, fire ants often make nests under slabs of homes. They use bath traps or cracks in the slab to get into the home to find food or water. Homeowners are surprised to find fire ants coming out of the wall behind the tub. The ants also use weep holes in brick exteriors to enter homes from their mound beside the foundation.
Fire ants seem to be attracted to electrical devices. They move into transformers and other equipment. The ants often cause short circuits and overheating. There have been blackouts of cities that were caused by fire ant nesting.