The RIFA is the most notorious of the two species of the fire ants found in Florida. Its less common cousin is the tropical or native fire ant. Native to central South America, the RIFA has also established itself throughout the world. It was first introduced from Brazil either into Mobile, Alabama or Pensacola, Florida during 1933 and 1945. By 2008, infestations were established in Alabama, Arkansas, California, Florida, Georgia, Louisiana, Maryland, Mississippi, New Mexico, North Carolina, South Carolina, Oklahoma, Tennessee, Texas, and Virginia.
RIFA’s usually builds mounds that are no larger than 18 inches in diameter. When their mound is disturbed, they immediately emerge aggressively to bite and sting the intruder. By the next day after a bite, a white pustule will appear at the site of the sting.
RIFAs have varying life spans that run from 30 days up to 180 days. The breakdown is:
Minor workers: 30 to 60 days
Median workers: 60 to 90 days
Major workers: 90 to 180 days
The queen will live from two to six years. It takes between 22 and 38 days to go from egg to adult.
Minor workers, also called minims, are small due to the fact that the queen limits their nutrients. These are the workers that first burrow out and start foraging for food to feed the queen and new larvae. At the same time, they begin construction of the mound. Within a month, the mound is growing in size and larger workers are being produced. The colony reaches several thousand workers within six months and the mound can be seen in a field or lawn. When colonies reach this size, they are mostly minor workers containing only a few median and major workers. All three types of workers are sterile females and severe only to perform tasks necessary to maintain the colony. A mature RIFA colony typically contains 80,000 workers but can grow as large as 240,000 workers. Only the queen is the producer of eggs. She can produce 1,500 eggs per day.
RIFA’s diet of the foraging workers consists of dead animals, such as insects, earthworms, and vertebrates. Workers will collect honeydew and forage for sweets, proteins, and fats in homes. At times, they are attracted to piles of dirty laundry.
A sting from a RIFA possesses venom of an alkaloid nature and exhibits potent neurotoxic activity. With approximately 95% of the venom composed of the alkaloids, this is what causes both pain and the white pustule. In hypersensitive individuals, the remaining venom containing an aqueous solution of proteins, peptides, and other small molecules produce an allergic reaction. Since RIFA’s both bite and sting, only the sting is responsible for the pain and pustule.
Since their introduction, they have become a major agricultural and urban pest causing both medical and environmental harm. Crops damaged by the RIFAs include soybean, citrus, corn, okra, bean, cabbage, cucumber, eggplant, potato, sweet potato, peanut, sorghum, and sunflower. Losses occur when the RIFA interfere with the root system of the plant. State and federal agencies have spent more than $250 million in total in order to control or eradicate the RIFA. Private agencies and individuals spend between $25 and 40 million per year for chemical pesticides.
Current, research is leading the way for the introduction of natural enemies. The microsporidian protozoan, Thelohania solenopsae, and the fungus, Beauveria bassiana are two hopeful pathogens. From South American, two parasitoid files, the Pseudacteon tricuspis, and Pesudacteon curvatus have been introduced into the southern states. Both of these flies will decapitate worker ants in the final stages of larval development. One other parasitic ant being investigated is the Santschi. It invades RIFA colonies and replaces the queen to take control of the colony.