Most recently reviewed by: Janet Hurley & Pat Porter (2018)
Common Name(s): fire ant, Red Imported Fire Ant
Pest LocationUrban Structural, Landscape Ornamental
Fire ant workers are polymorphic and range in size, 1/16 inch to 1/4 inch. They are black, reddish brown or red and black. The waist (pedicel) has two nodes. Antennae are 10-segmented and end in a two-segmented club. Queen ants are larger (3/8 inch) and will drop their wings after mating.
Alates or reproductives are also found within the colony. They are larger than workers and have wings (3/8 inch).
Red imported fire ants produce hills or mounds in open areas where the colonies reside. Colonies occasionally occur indoors and in structures such as utility housings and tree trunks. Disturbance of mounds results in a rapid defensive response by worker ants, which quickly run up vertical surfaces.
There are three other species of fire ants that are native in Texas (the tropical fire ant, Solenopsis geminata Fabricius; the southern fire ant, S. xyloni McCook; and the desert fire ant, S. aurea Wheeler) and a number of other native ants.
Origin and Distribution
Fire ants infest the eastern two-thirds of Texas. Fire ants are omnivorous, but their primary diet consists of insects and other invertebrates. Predatory activities of fire ants suppress populations of ticks, chiggers, caterpillars and other insects. Predatory activity attributes to wildlife reductions in some areas.
Habitat & Hosts
Mouthparts are for chewing and sipping. Only the last larval stage can ingest solid food particles. Sieve plates in the mouths of worker ants prevent ingestion of food particles.
Sterile female fire ant workers can sting repeatedly; they first bite, and while holding on to the skin with their jaws, inject venom with stingers at the end of their abdomens; unique venom produces a fire-like burning sensation and most people react by developing a whitish pustule or fluid-filled blister at the site of the sting after a day or two; some people are hypersensitive to stings and should be prepared for a medical emergence if stung; most people can tolerate multiple stings but may have problems with secondary infections at the sites of the stings. Fire ants are considered to be medically important pests of people, pets, livestock and wildlife; they can also be damage crops such as corn, sorghum, okra, potatoes, sunflowers and others by feeding on seeds, seedlings and developing fruit.
Fire ants exhibit complete metamorphosis. Eggs hatch in eight to 10 days and larvae develop through four instars (or molts) before pupating. Development requires 22 to 37 days, depending on temperature. Fire ants are social insects, and each colony contains one or more queen ants. Queen ants can produce about 200 eggs per day. A “mature” colony can contain over 200,000 ants along with the developmental and adult stages of winged black-colored male and reddish-brown female ants called “reproductives.” These ants stay in the colony until conditions exist for their nuptial flight.
ManagementIf you live in the State of Texas, contact your local county agent or entomologist for management information. If you live outside of Texas, contact your local extension for management options.
Outside, colony mounds can be found anywhere from open areas in yards, gardens and pastures to areas adjacent to buildings, sidewalks, plants and other structures. Imported fire ants are predators/scavengers on many things, including insects, seeds and wildlife. In buildings, watch for ants trailing, and follow the trail to the nest. They usually nest outside.
Broadcast applications of an Insect Growth Regulator (IGR) bait containing methoprene or pyriproxifen; or non-IGR products containing abamectin, indoxacarb, hydramethylnon or spinosad, can be applied in the spring and fall for continued control. IGR baits may be applied to turfgrass areas during spring or summer vacations. For fast control of problem mounds, apply a non-IGR bait or contact insecticide to mounds. Baits are most effective when fire ants are actively foraging, i.e., when temperatures are between 70 and 90 degrees F.
Liquid, granular, dust or aerosol contact insecticide treatments may be used to eliminate individual mounds.
Surface-applied, slow-acting, long-residual, contact insecticides such as pyrethroids or fipronil where maximum suppression is desired can also be used. Remember to use caution when making these applications and to keep students and staff out of the area until these products have been watered into the soil and the application area has dried.
Faster acting toxicant baits such as hydramethylnon, indoxacarb or spinosad should be applied around colonies or mounds that extend under sidewalks or other pavement areas.
Barrier treatments using contact insecticides around perimeter walls may reduce the number of ants foraging indoors if an immediate problem exists.
Pyrethrum sprays may be applied to ant entry points only in emergency situations where fast control is needed and caulking or sealing is not possible.
Always read and follow the label. The label is the law. Pesticides must be used in accordance with federal, state and local regulations. Applicators must have proper credentialing to apply pesticides and should always wear personal protective equipment (PPE) as required by the pesticide label during applications. All labels and Material Safety Data Sheets (MSDS) for the pesticide products authorized for use in the IPM program should be maintained on file.
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