Return to Georgia Extension Service publications page.
The University of Georgia College of Agricultural & Environmental Sciences
Cooperative Extension Service
T. Don Canerday, Former Head, Extension Entomology
Fire ants are of tremendous concern to Georgians. Red imported fire ants were first reported in Georgia in the early 1950s. By 1987, they had spread to 143 of our 159 counties. Relatively mild winters and generally favorable conditions have contributed to their success.
At least three fire ant species are found in Georgia. Two are native to the state: the tropical fire ant, Solenopsis geminata Fabicius and the southern fire ant, Solenopsis exloni McCook. These ants are rarely seen any more, because they have largely been displaced by the more aggressive red imported fire ant, Solenopsis invicta Buren. This South American ant entered the United States at the port of Mobile, Alabama, in the 1930s and has now successfully invaded much of the South. It is difficult to distinguish between imported and native species. Positive identification should be made by a specialist familiar with all species. Contact your county Extension agent for information on submitting specimens for identification.
Fire ants look very much like ordinary house or garden ants. They're about one-eighth to one-fourth inch long and are reddish-brown to black. Fire ant colonies are dome-shaped mounds that may be one to two feet high. Mounds are often found in open areas such as lawns, pastures, along roadsides and unused cropland. Fire ants rarely build nests in heavily-shaded or frequently cultivated areas. Nests will contain ants of different sizes. Unlike most other ants, they will aggressively attack -- in mass -- anything that disturbs their mound.
The successful and rapid spread of the fire ant in the United States is due in part to their adaptability and high reproductive potential. Fire ants spread naturally through flights of queens at the rate of five to 12 miles a year. Most flights occur during late spring and summer, but some have been observed year-round in South Georgia.
The queen's flight range depends on wind speed, rainfall and temperature. Most queens land within a relatively short distance from the source, but distances of up to 12 miles have been documented; and it's suspected that the range may be greater.
Queens also spread by crawling, drifting downstream on or in logs, or traveling aboard machinery, cars, trucks or trains. An entire ant colony or nest can relocate through shipments of nursery stock or soil from an infested area.
It is a consensus that fire ants cannot survive in areas where minimum temperatures reach 10 degrees F for extended periods or in areas that receive less than 10 inches of rain a year. Heavy kill of fire ants may occur in the Piedmont Plateau of Georgia during harsh winters, but most colonies survive the winter in the Coastal Plain.
A fire ant colony consists of three castes (forms) -- queens, males and workers:
Queens -- fertile fire ant females are either winged, future queens that are virgin prior to the mating flight or wingless queens that shed their wings and lay eggs after mating. Most colonies have only one -- mated egg-laying female -- or queen.
Winged males that mate with the queens.
Worker ants are wingless and sterile females. Adult workers differ in size. Larger forms are called "major workers," the smaller forms are "minor workers." Older workers forage and defend the nest while younger workers care for the developing brood (eggs, larvae and pupae).
The virgin, winged forms are cared for by the workers until it is time to leave the colony (mound) and begin their mating flight. Both sexes fly directly from the mound surface or climb on nearby plants and take off. Once airborne, the female mates with a male in flight. The males dies soon after mating. The fertilized queens attempt to find suitable nesting sites, shed their wings and begin digging underground chambers in which to lay eggs. Only a small percentage of new queens successfully start a colony. One fire ant colony may produce three to five thousand queens per year.
The newly-mated queens select potential sites during flight and after landing. Selection is based on surface properties (moisture, soil type, topography and reflectance). This behavior results in colonies being established along roadsides and in playgrounds, shopping malls, housing developments, cemeteries, lawns, pastures and some croplands. Open, sunny areas appear to be preferred. Large colonies are often found nesting next to fence posts, power poles, stumps and other objects.
The queen lays 100 to 200 eggs during the first three to four weeks. Some eggs hatch in 8 to 12 days, and the remainder are eaten by the developing larvae. The queen later lays eggs continuously, and the larvae are tended by the earlier produced workers. The larvae pupate in 6-12 days and adults emerge in 9-16 days. The life cycle may be complete in three to six weeks, depending on environmental conditions. Mound building by newly-established colonies may not be conspicuous for six months after the young queen initiates egg laying.
Colonies one year or older will likely contain in excess of 100 thousand workers. Strong, mature colonies may contain as many as 300 thousand workers.
Mound development and size is influenced by soil type and colony size. Generally, mounds are 12 inches or more in diameter and height. However, mounds in excess of two feet and diameter and height are not uncommon in Georgia.
The underground nest is a series of interlocking galleries, tunnels and chambers that may go one to five feet or more in the ground, depending on soil type, age and colony size. Tunnels just below the soil surface extend several yards out from the mound, with regular exits where the ants come out to search for food.
Most nests contain only one egg-laying queen. A small percentage of nests recently found contained multiple, functional queens. Workers in multiple-queen colonies are smaller and lighter in color, and the mounds are often smaller and closer together. Multiple-queen colonies usually contain 20 to 60 queens.
Since fire ants exist in many habitats -- field and vegetable crops, nurseries, orchards, vineyards, hay fields, parks, lawns -- there is little question that they are pests. That they are a significant economic pest of agriculture has not been adequately documented. Ants may cause damage to very young plants, ripe fruits and berries. They occasionally attack young, unprotected animals, such as newborn calves and pigs and newly-hatched quail, poultry or ground-nesting birds and young rabbits. It is unlikely that this occurs to any great extent, and available date do not support the conclusion that fire ants are an important economic pest of crops, livestock or wildlife.
Mounds on farms can cause damage to combines and other machinery, hinder mowing operations, and reduce land values in heavily-infested areas. Ants can interfere with harvesting operations because their sting is quite painful. Farmers can also lose valuable time during seeding, fertilizing and harvesting operations.
There is limited data indicating that large numbers of fire ants may reduce soybean yields. Conversely, since the fire ant's primary diet includes insects, ticks and other small invertebrates, they are often highly beneficial.
For the most part, fire ants are a "people pest," because they often occupy the same areas where we work, live and play. It is estimated that about 40 million people are in potential conflict with fire ants, almost on a daily basis.
Fire ants are so named because their venom induces a painful, fiery sensation. When disturbed, fire ants are very aggressive. The ant grips the skin with its mandibles or jaws and stings its victim several times in a circular pattern around the point of mandible attachment. Because of the ant's aggressive nature and capacity for multiple stings, an attack usually results in several stings.
Some people who are stung experience only local reaction and temporary discomfort but, in most, a swollen red area will occur followed by a sterile pustule within 24 hours. Although the venom is bactericidal, secondary infections due to scratching may occur.
Reaction to fire ant stings is similar to reaction to the stings of bees, wasps, hornets and yellow jackets. The overwhelming majority of fire ant stings are medically uncomplicated, but evidence shows that people hypersensitive to fire ants are more likely to be hypersensitive to other venomous insects.
A small percentage of people stung -- probably less than .5 percent -- experience a systemic anaphylactic reaction. These reactions occur within minutes of a sting and vary in severity. Some individuals may require hospitalization, and the reaction may be life-threatening. One author cites 17 deaths due to fire ant venom.
Anyone stung and displaying marked symptoms of hives, weakness, dizziness, wheezing, shortness of breath or confusion should be given immediate medical attention.
Currently, there is no single, universal solution to the fire ant problem. However, there are a number of options available. Before attempting any control measure, consider all the available methods for achieving the most satisfactory results. Not controlling fire ants is one option, particularly where they do not directly interfere with humans or their activities.
Selection of a control option, pesticide and method of application should be determined by factors such as location of mounds, number to be treated, potential for human exposure to ants and chemical used, and (obviously) risk of chemical contamination.
Your county Extension agents can help you select the best management strategy for your particular situation.
The University of Georgia and Ft. Valley State College, the U.S. Department of Agriculture and counties of the state cooperating. The Cooperative Extension Service offers educational programs, assistance and materials to all people without regard to race, color, national origin, age, sex or disability.
An Equal Opportunity Employer/Affirmative Action Organization Committed to a Diverse Work Force
Issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, The University of Georgia College of Agricultural and Environmental Sciences and the U.S. Department of Agriculture cooperating.
Gale A. Buchanan, Dean and Director