Synonym(s): Solenopsis wagneri (Santschi, 1916)
Adult Description: Well known to most Texans, red imported fire ants (Solenopsis invicta) are small ants that live in colonies and consist of several types of adults: winged males, reproductives and worker ants. Workers are sterile females ranging in size from 3-6mm in length. Winged males, or "reproductives" live in the colony until their mating flight where they fly with the queen to establish a new colony, then die. Queens can attain greater sizes (9mm), especially when they are mature and producing eggs. Queens, winged males, and workers are reddish-brown in appearance, and look very similar to other Solenopsis species, including the Ginger ant Solenopsis geminata (native) and the Black Imported Fire ant Solenopsis richteri (invasive). Red Imported Fire ants are also notorious for their sting for which they are named. The stinger is obvious on the abdomen under close examination.
Larva Description: The larval stage typically lasts 6 to 12 days, and the pupal stage for 9 to 16 days. The larvae and pupae are small and a non-descript white color.
Host Plant: None
Ecological Threat: Any Texan who has walked through a field and seen dozens of red fire ant mounds knows the destructive power of the red imported fire ant. Not only are the mounds unaesthetic, but they can ruin lawns, and more ecologically important, they can displace native ants from their habitat. These native ants, including the Texas leaf-cutter ant, the harvester ant, as well as the carpenter ant are out-competed and even face hostility from red imported fire ants. This has led to a reduction in population numbers of all indigenous ants.
Birds, especially those that are ground-nesters such as the Bobwhite Quail are vulnerable to the Red Imported Fire Ant. The ants are notorious for eating newly-hatched chicks, or destroying unhatched eggs. Any unfortunate insect, lizard, bird, mammal, or amphibian that is unlucky enough to disturb a Red Imported Fire ant mound is sure to be attacked and are often killed. Red imported fire ants attack very quickly and in great numbers, as many humans who have accidentally stepped on a mound will attest.
In addition to their ecological effects on native fauna, humans are impacted economically by the Red Invasive Fire ant. Lawns, ranches, or other lands can be permanently altered by the Red Imported Fire ant because of their ability to build many mounds in a clustered area. It is not uncommon to see an entire field dotted with large Red Imported Fire ant mounds.
Biology: Red imported fire ants are prolific breeders and aggressive feeders, which makes them a successful invader. Mounds can be hundreds of thousands of individuals strong, and multiple queen colonies exist whose individuals can move between mounds freely which ultimately leads to an increase in the number of mounds that may be found within an area. Thus, Red Imported Fire ants are able to take over an area rather quickly by turning fields into homogeneous, desolate wastelands comprised of dozens of Red Imported Fire ants mounds. Most Texans have observed this phenomenon, possibly in their own backyard.
History: The red imported fire ant was introduced around the 1930's and has spread to infest more than 260 million acres of land in 9 southeastern states, including all or portions of Florida, Georgia, South Carolina, Tennessee, Alabama, Mississippi, Arkansas, Texas, and Oklahoma. This species has become very abundant, displacing many native ant species when abundant. It has the potential of spreading west and surviving in southern Arizona and along the Pacific coast north to Washington.
U.S. Habitat: In infested areas, colonies are common in lawns, gardens, school yards, parks, roadsides, and golf courses. Nests generally occur in sunny, open areas and are especially common in disturbed and irrigated soil. Red Imported Fire ant mounds are 4 to 24 inches tall and have no visible surface entrance. Mounds are accessed through subterranean tunnels that spoke out from the central mound. Non-Red Imported Fire ant mounds rarely exceed an inch or 2 in height. Red Imported Fire ant mounds have a fresh-tilled appearance, especially after a rain.
Native Origin: South America, specifically Brazil.
U.S. Present: Currently, the red imported fire ant has established in many U.S. states, especially those in the southeast, as far north as North Carolina. The ants are found all across Texas, and in California.
The red imported fire ant is found all across Texas, especially in the southern and southeastern counties.
Red Imported Fire ants look very similar to other Solenopsis species, including the tropical fire ant, S. geminata (native), and the black imported fire ant, S. richteri (invasive).
Managing the Red Imported Fire ant has proven difficult, as the ants are hearty and tough to eradicate. Presently, insecticides seem to be the best and most-recommended option. Spraying mounds, injecting mounds, bait-traps, colony poisons, pouring boiling water onto the mounds, or igniting mounds have all been tried with varying results.
Biological controls are still being investigated, but there is some hope that a natural enemy may be useful in eradication of this invasive pest.
If your property is overrun with Red Imported Fire ants, you should contact a professional exterminator rather than attempt a potentially fruitless (or dangerous) remedy yourself.
Adams CT, Plumley JK, Lofgren CS, Banks WA. 1976. Economic Importance of the red imported fire ant, Solenopsis invicta Buren. I. Preliminary investigations of impact on soybean harvest. Journal of the Georgia Entomologist Society II: 165-169.
Banks WA, Adams CT, Lofgren CS, Wojcik DP. 1990. Imported fire ant infestation of soybean fields in the southern United States. Florida Entomologist 73: 503-504.
Cohen PR. 1992. Imported fire ant stings: clinical manifestations and treatment. Pediatric Deteratology 9: 44-48.
Diffie S, Sheppard C. 1990. Impact of imported fire ants on Georgia Homeowners. In 1990 Imported Fire Ant Conference (Mispagel ME, editor) pp. 62-71. Texas A&M University, College Station, Texas.
Vinson SB, Sorenson, AA. 1986. Imported Fire Ants: Life History and Impact. The Texas Department of Agriculture. P. O. Box 12847, Austin, Texas 78711.
Dr. Jerry Cook, PhD. - Sam Houston State University - firstname.lastname@example.org