This is a highly polymorphic species, with various sizes of workers within a single colony. The largest workers in the colony can be as much as ten times the size of the smallest workers.
The red imported fire ant is covered in long, bristly hairs and is identified by its red head and thorax and red and black abdomen.
The red imported fire ant is one of the worst ant pests in the U.S. in terms of human health, property damage, and environmental damage. Colonies may have several hundred thousand workers and dozens of queens, and workers very aggressively defend their nest with stinging. Nests are created in the soil and can be identified by the large mound of soil raised above the surface. They are very common in turf. Red imported fire ant nests may go as deep as eight feet in the soil, and produce mounds above ground that are three feet tall and two feet wide. When their mound is disturbed they will rapidly overwhelm the intruder and, on a chemical command, begin stinging simultaneously. Nests may be found in wall voids, rain gutters, bath traps, and under carpets, as well as in electrical equipment.
The workers are aggressive predators, feeding on any other insects they find as well as small mammals or birds, earthworms, frogs and lizards. They dramatically alter the natural habitat when they move into an area.
Males die after mating and the female creates a brood cell in the soil and deposits 10-15 eggs using her tubelike ovipositor. These hatch in seven to ten days and are fed by the queen. Within 15 days, pupae emerge and begin to forage for food. Within 30 days, larger workers emerge and the colony grows. The queen lives up to seven years and produces an average of 1,600 eggs per day throughout her life. A red imported fire ant colony can hold more than 250,000 ants.
Most red imported fire ant stings result in a raised welt that becomes a white pustule. If a person is allergic, however, he or she may experience a more grave reaction. Victims rarely receive a single sting; instead, a person typically receives many hundred stings simultaneously. Red imported fire ant colonies may contain numerous queens and have multiple satellite colonies. Up to 200 mounds per acre have been found.
Due to the large colony size, deep nests, and sensitivity to chemicals, baiting is a preferred method of control, and baits with an oil attractant appear most acceptable. Physical disturbance and flooding of the mounds do not work.