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Solenopsis geminata (Fabricius)
Julian R. Yates III, Extension Urban Entomologist
Victoria Tenbrink, Research Associate
Arnold H. Hara, Entomologist
College of Tropical Agriculture and Human Resources, University of Hawaii
Fire ants feed on grass seeds that they gather and store in granaries of their large, centralized nest systems, which often extend 5 feet into the ground. They also tend honeydew producing homoptera and feed on arthropods, sweets, meats, and fats. Lewis (1912) describes the beneficial quality of their feeding on a great number of pest insects.
Solenopsis geminata inhabits the tropics worldwide. In mainland United States they are found from Texas to South Carolina and Florida. The species was well established in Hawaii by the 1870's (Reimer et al., 1990).
Fire ants tend honeydew producing homoptera, especially mealybugs. This increases pest populations and the incidence of disease vectored by homoptera. This is also one of a number of ant species that damage plastic drip irrigation tubing by chewing new holes and enlarging the existing ones (Chang & Ota, 1990).
Fire ants get their name from the fiery pain caused by their stings. Other ant species with similar stinging behavior are also known by this name. The average victim has multiple stings because each fire ant can administer several stings, and numerous ants may attack a person when the colony is disturbed. The sting can produce an immediate, intense pain. This is followed by a wheal. Within 12 to 24 hours a pustule may appear surrounded by a red halo, or a swollen, painful area which begins to itch. In three to eight days, the purulent material is absorbed or a small disc of skin sloughs off, leaving a smooth, pink area. This persists for several weeks and scar tissue may form. Often, pustular lesions are in a circular pattern. First aid treatment includes washing the sting area with soap and water and using an antiseptic, especially after a pustule is broken. No other treatment is recommended for dermal symptoms. In the event of a severe, systemic allergic reaction, a physician should be contacted immediately.
Fire ants undergo complete metamorphosis. Colonies are individually established by newly mated queens following a mating flight. During warm months these winged individuals are found in large numbers in mature colonies. Mating takes place 300 to 800 feet in the air. Newly mated queens seek moist areas, normally within one mile of the mother colony. If the female lands on a suitable site, she sheds her wings and digs a small burrow in the soil, usually under a leaf, rock, or small crevice. She excavates a small chamber at the end of the burrow and seals it.
Fire ants prefer food with high protein content, but will feed on almost anything, plant or animal.
The queen lays 10 to 15 eggs in the initial cluster. By the time they hatch in 8 to 10 days, she has laid 75 to 125 more eggs. She then stops laying eggs until the first brood is mature in two weeks to a month.
Larvae emerge from the eggs as soft, legless grubs. The queen feeds the young larvae with regurgitated oils. The last larvae stage, in addition to receiving liquid food, is also fed solid foods. The larvae have enzymes which digest the food, which is regurgitated to adult ants who are not able to digest protein by themselves. These digested proteins are also fed to the queen to stimulate egg production.
The pupae develop in the nest, and are tended by workers.
Newly emerged adults spend several days to weeks taking care of eggs, larvae, pupae, and the queen. These small workers, called "miners", open the burrow to locate food, feed the queen and the new larvae, and begin construction of the mound. As they age, they become reserves, who groom the larvae, defend the colony, build and maintain the mound, and bring back food discovered by the foragers, the oldest ants. Foragers lay a chemical trail for the reserves to follow when a food supply is found.
Fire ants are ground nesting ants, preferring sunny, open areas or partially shaded ones. In sugarcane, they move their nests to the perimeter of the field when the canopy closes and shades the ground (Chang & Ota, 1990). They are most prevalent in drier areas, where they replace the big-headed ant, Pheidole megacephala; but they are also found in wet areas around Hilo, where they colonize fields of perennial ornamentals, such as red ginger. Besides tending aphids and mealybugs in these fields, they are a nuisance because of their fiery sting. Colonies, often initiated by a solitary, fertile queen, may eventually consist of a few queens, many winged males, winged virgin females, a gradation in size of soldiers and workers, and all stages of immature forms.
Biological control agents, such as mites and nematodes, have demonstrated some promise, but their effectiveness requires more investigation.
There are mechanical devices available; however, their effectiveness has not been documented. Before installing drip irrigation, check on the ant resistance of the materials and design.
Fire ants can be controlled by using ant baits, soil drenches and/or contact insecticides. Special baits can be used as a broadcast treatment and/or applied around individual mounds. Special aminohydrozone and fenoxycarb baits are available specifically for fire ants.
Several residual pesticides are registered in some states as soil drenches, including chlorpyrifos, bendiocarb, diazinon, carbaryl and acephate. The drench can be applied with low-pressure spray equipment. Generally, the mixture is applied on the top and around the outside of the mound. Then the mound is opened and the mixture poured directly inside. Aerosol formulations of chlorpyrifos are available to be injected into the mound using a special long, perforated tube.
A year-round fire ant control program may be needed if the surrounding area is heavily infested or if a small area, such as a residence is being treated.
A soap-pyrethroid dip with agitation will dispose of workers infesting flowers. The solution must penetrate tight areas. Packing house perimeters should be monitored for ant activity and treatment undertaken when necessary.
Anonymous. 1987. Fire ants, Solenopsis spp. National Pest Control Association Technical Release 2/18.
Berger, J. 1990. Fire ants--the southern menace. Pest Management Quarterly. Whitmire Research Laboratories. 9: 8-10.
Chang, V. & A. K. Ota. 1990. Ant Control in Hawaiian Drip Irrigation Systems. In Applied Myrmecology. R. K. Vander Meer, K. Jaffe, & A. Cedeno, Ed. Westview Press: San Francisco.
Holldobler & Wilson. 1990. The Ants. Belknap Press: Cambridge.
Lewis, L. V. 1912. A few notes on Solenopsis geminata. Proc. Hawn. Entomol. Soc. 2(4): 175-178.
Reimer, N., J. W. Beardsley, & G. Jahn. 1990. Pest Ants in the Hawaiian Islands. In Applied Myrmecology. R. K. Vander Meer, K. Jaffe, & A. Cedeno, Ed. Westview Press: San Francisco.
Smith, E. H. & R. C. Whitman. 1992. NPCA Field Guide to Structural Pests. NPCA.
Yamada, E. 1982. Ants. In Vector Control Manual. Vector Control Branch, Hawaii State Department of Health: Honolulu.