Red Imported Fire Ant, Solenopsis invicta Buren (Insecta: Hymenoptera: Formicidae: Myrmicinae)

Red Imported Fire Ants are from South America and are native to the floodplains of the Paraguay River in Brazil, Paraguay and Northern Argentina.

Like all ants, thier bodies are divided into four main sections. The head is the first section, followed by the large mesosoma, the small petiole and postpetiole, and finally the gaster. The head carries the antennae and mouthparts, the three pairs of legs are attached to the lower surface of the mesosoma and the gaster terminates with a defensive structure. Although the mesosoma and gaster appear to correspond to the thorax and abdomen of most other insects, this is not the case. The rear section of the mesosoma, the propodeum, is actually the first abdominal segment, the petiole is the second segment and the postpetiole, when present, the third segment. The gaster is composed of the remaining segments of the abdomen.

Workers consist of many sizes (polymorphic) between 2.4 to 6 mm (1/8 to 1/4 in). The mandible has four distinct teeth and the antennae are 10-segmented, ending in a two-segmented club. A sting is present at the tip of the gaster. Body color is usually red to brown in color with a black gaster.

Red Fire Ant colony mounds are built of soil and are seldom larger than 46 cm (18 in) in diameter. Nests have no obvious entry or exit holes on top of them. When a mound is disturbed, large numbers of ants emerge aggressively to bite and sting the intruder. A white pustule usually appears the next day at the site of the sting.

The lifespan of RIFA workers depends on their size. Minor workers may live 30 to 60 days, media workers 60 to 90 days, major workers 90 to 180 days, and queens may live two to six years. Complete lifecycle from egg to adult takes between 22 and 38 days. Mating flights are the primary means of colony propagation, secondarily, budding can occur in which a portion of a colony becomes an autonomous unit. Mating flights usually occur midday on a warm (>74°F/24°C), sunny day following rain. Mating occurs during flight and the males die soon after mating.

The three types of workers are all sterile females and serve to perform tasks necessary to maintain the colony. The diet of foraging workers consists of dead animals, including insects, earthworms, and vertebrates. Workers also collect honeydew and will forage for sweets, proteins, and fats in homes.

Colonies may contain single queens (monogyne colonies) or multiple queens (polygyne colonies). In the latter, workers are not aggressive towards neighbouring colonies.

The Red Imported Fire Ant has become a major agricultural and urban pest wherever it has colonised. Soybean crops, citrus, corn, okra, bean, cabbage, cucumber, eggplant, potato, sweet potato, peanut, sorghum, and sunflower have all suffered considerable damage. They also reduce ground-nesting populations of lizards, rodents and birds.

After a heavy rain, colonies may move to higher ground or inside homes to take refuge from saturated soil.

If you are stung by a fire ant:

Apply a cold compress to relieve the swelling and pain.

Gently wash the affected area with soap and water and leave the blister intact as it may become infected if broken

People who are allergic to insect stings should seek medical attention immediately. On rare occasions, fire ant stings can cause severe acute allergic reaction (anaphylaxis)

If you find any nest, DO NOT TOUCH IT. Report it to your local authority (e.g. Department of Primary Industries and Fisheries Call Centre on 13 25 23 in Australia)

Further Information:

Windaroo Valley High: http://wvhigh.eq.edu.au/curriculum/fireants/index.html

CSIRO: http://www.ento.csiro.au/science/ants/myrmicinae/solenopsis/solenopsis.htm

Qld Department of Primary Industries: http://www2.dpi.qld.gov.au/fireants/

Teacher's Guide: http://www.cdfa.ca.gov/phpps/pdep/rifa/mm/Posters/TeachersGuide.pdf

Glossary of Ant Anatomy: http://homepage.mac.com/aenictus/g1.html