Types of Ants :: Red Imported Fire Ants :: Printer-Friendly Version
Ant Origin & Distribution
There are several different fire ant species in the United States, some of native origin and others introduced from other parts of the world. They include the black imported fire ant (origin: South America), the tropical fire ant (origin: native), the southern fire ant (origin: native), and the red imported fire ant (origin: South America). Black imported fire ants are usually limited to areas of Tennessee, Alabama and Mississippi. The red imported fire ant is by far of greatest importance as a pest, and will therefore be described in the most depth.
Red imported fire ants originated in the lowlands of Brazil and were introduced into the United States between 1933 and 1945 in Mobile, Alabama. Most likely they were introduced when soil from Brazil was dumped at the Mobile port. Since then, they have continued to spread to parts of Alabama, Arkansas, California, Florida, Georgia, Louisiana, Mississippi, New Mexico, North Carolina, Oklahoma, South Carolina, Tennessee, Texas and Puerto Rico. They are occasionally found in Arizona, Kentucky and Virginia. The arid environment of western Texas and cold northern climates impede their spread westward and northward, but outbreaks in uninfested states may occur due to movement of infested soil in nursery stock and other materials by commerce. Potential spread may occur where average minimum temperatures are above 10°F and annual rainfall greater than 10 inches or in irrigated areas. Federal quarantines are designed to restrict movement of infested materials such as soil, sod, potted plants, plants with soil attached, and hay from infested areas to uninfested areas of the country.
Ant Identification
Workers of red imported fire ants are polymorphic, which means a single colony will contain workers of different sizes ranging from 1/8" to 1/4" in length. They appear an almost uniform dark reddish brown in color but closer inspection reveals a darker shiny gaster. People often recognize red imported fire ants simply by their dome shaped mounds and the protective behavior of workers pouring out of disturbed mounds to attack and sting intruders.
Ant Biology
As with all ants, red imported fire ants have a life cycle that includes egg, larval, pupal and adult stages-known as complete metamorphosis. Mature colonies produce thousands of winged male and female swarmers (called alates) that may swarm several times during a year from spring to fall. In their mating flights, swarmers may reach heights of several hundred feet and disperse over several miles. New queens land, lose their wings and typically tunnel into soil to start new colonies. Sometimes many queens may be seen clustered together in cracks and crevices on the ground or under objects before starting their nests.
Nests are typically started in sunny areas and may occur in open areas of exposed soil or lawns or next to structural components on the ground such as concrete, pavement, tree bases, fence posts, air conditioners or utility service boxes. Infested electrical equipment can be damaged and lead to short circuits. Queens may also land on buildings with flat roofs, sometimes many stories high, and start colonies that infest the building from the top down. Indoor nests may be in wall voids, bath traps, under carpets and in crawl spaces. A typical nest is a dome shaped mound sometimes as large as 18" in height and 24" in diameter, although mound structure will vary somewhat by soil type. Some nests may have no obvious mound such as those in mulched areas or where the tops of mounds are removed by mowing in lawns.
Depending on the region, red imported fire ant colonies may have a single queen (monogyne) or multiple queens (polygyne). Where single queen colonies occur, the density of mounds tends to be lower (30-40 per acre) due to the territorial nature of the workers. Where multiple queen colonies occur, the workers are not territorial and hundreds of mounds can occur within an acre. Queens can lay hundreds of eggs per day and a mature colony containing 200,000 to 300,000 workers can develop within a year or two. Once a mature colony has been established swarmers are produced to begin the cycle once again. In multiple queen colonies new colonies may also be produced by budding in which queens, workers and brood leave one nest to start another.
Ant Habits
By far the most notable characteristic of red imported fire ants is their stinging behavior. People, pets and other animals unknowingly disturb their mounds and are quickly covered with stinging ants. Deaths have occurred either from allergic reactions to the venom or from other complications in which individuals incapable of getting the ants off of them receive hundreds of stings. Red imported fire ant venom is unique in the insect world as it produces an immediate and painful stinging, burning sensation. Later, white pustules will form on the skin at the site of the sting. Over 40 million people live in areas infested by the red imported fire ant in the southeastern United States. An estimated 14 million people are stung annually.
Red imported fire ants may quickly move their whole colony if conditions are unfavorable or if the mound is disturbed. It is not uncommon to see mounds pop up within a few feet of a mound that received a poor and ineffective insecticide or pesticide treatment. Red imported fire ant workers are voracious foragers that exploit many different food sources. Workers are often seen trailing along driveways, sidewalks, street curbs, patios and along foundation walls. There may also be trails leading from the nest to visible food sources on the ground, such as sweets, oils and dead insects. Trails may lead into structures from the ground up, sometimes several stories high or from the roof down if nests are located on flat roofs.
Where their numbers are high, red imported fire ants may negatively impact local animal diversity. In these areas, other ant species, invertebrates and vertebrates, such as ground nesting birds, suffer and are sometimes eliminated due to the red imported fire ant. These ants may also attack and kill livestock, especially poultry, and can even damage certain crops. Their nesting behavior can damage electrical equipment such as air conditioners and utility service boxes as well as roadways and airport runways where they may cause potholes.
Ant Control
If you think you might have red imported fire ants infesting your property or your home, it's imperative that you contact a certified and licensed pest control professional to inspect the situation and confirm identification.
Experts will advise against do-it-yourself options, because ineffective attempts to control red imported fire ants may also have negative health-oriented consequences. Improper do-it-yourself options may result in killing a few ants, while the rest of the colony simply relocates to other areas around and inside the structure. It is much more efficient and cost-effective to have a trained set of eyes identify the correct ant species and recommend effective treatment options specific to an individual infestation.