 workers break off from the parent colony and start a new mound nearby. This process in polygynous colonies can accounts for much higher mound density which sometimes approaching 1,000 mounds per acre.
Different sized worker adults. Image courtesy of USDA Archives.
One of the identifying characteristics of an imported red fire ant colony is the earthen nest or mound. This mound is a cone-shaped dome with a hard crust. They averages 1 ½ feet in diameter and 8-inches in height. In heavy clay soils they can exceed 3-feet in height and 4 1/2 feet diameter. There are usually no external openings in the mound; but tunnels a few inches below the surface tunnels radiate several feet from the mound allowing foraging workers access to the colony. These mounds serves several functions: They act as a flight platform for nuptial flights and to raise the colony above ground in excessively wet soil while protecting it above ground from intruders and rain. They also serve as a passive solar collector to supply warmth to the colony during the cold winter months.
Mound of red imported fire ant. Image courtesy of USDA Archives.
In areas with hot, dry summers these mounds may not be maintained or may not be formed at all. In a dark, protected site with sufficient moisture and an adequate supply of food, fire ants will nest in a wide variety of locations (e.g. rotten logs, walls of buildings, under sidewalks and roads, in automobiles, in dried cow manure).
Fire ants are omnivorous, feeding on almost any plant or animal material; although dead and living insects seem to be their preferred food. In rural habitats, they have a major impact on ground nesting animals (birds, reptiles, mammals). Studies have shown that once established in a new area there is typically a minimum of a two-fold reduction in the populations of field mice, snakes, turtles and other vertebrates and a maximum of a total elimination of some species. Fire ants also feed on plants attacking young saplings and seedlings, destroying buds and developing fruits and have