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Ouch! OUCH! That HURTS!
By Dr. Stuart Mitchell
Lacking natural predators and parasites has sanctioned a vigorous, unimpeded arrival and radiation of Fire ants, Genus: Solenopsis, Subfamily: Myrmicinae, Family: Formicidae, Order Hymenoptera, and human reaction, Ouch! OUCH! That HURTS! Indigenous to Central and South American tropical regions and now invasive to temperate regions of North America, this pestiferous species is the Red Imported Fire ant (RIFA), Solenopsis invicta.
Colonially polymorphic, worker ants are 0.12 to 0.24 inches in length while colonially polygyne, queens are 0.27 inches. Polygyne colonies produce smaller workers (a negative correlation, number of queens and average worker ant size). With a copper-brown head and body as well as darker gaster, ants have three body characteristics.
- Antennae of 10 segments with a two-segmented club
- A pedicel with two nodes
- A propodeum (first abdominal segment constricted posteriorly to form the articulation of the petiole)
Communication is via chemical secretions and stridulation (sound created by rubbing or drumming one body part against another). Under the risk of attack from adjacent ant colonies, worker ant adults are infamous for their aggressive behavior while young Fire ants, with not yet fully developed exoskeletons and stingers, “play dead.” Workers are notorious for attacking people, companion animals and production animals, damaging crop grains, girdling trees, and damaging electrical equipment.
Fire ants may not survive the winter when temperatures go below -0.4°F or when annual rainfall is less than 10 inches (absent irrigation). Semi-permanent formicariums consist of loose mounds with open craters for ventilation.
- As many as 600 mounds/acre
- Up to 500,000 ants/colony
- In the U.S., the Red Imported Fire ant is medically significant
- Within endemic areas, 30-60% of urban populations are stung annually
- Ants use mandibular leverage to curve the abdomen and insert stinger (sting repeatedly)
- Venom contains piperidine alkaloids producing a burning sensation, followed by itching, and within hours a whitish sterile pustule (not caused by infection)
- Secondary infection results from scratching
- Venom contains 1% protein that can cause anaphylaxis in hypersensitive persons
As part of a state of the art, cyclic IPM program, professional product, area-wide applications render excellent Red Imported Fire ant elimination. A bait formulation is quite effective as foraging behavior is domesticated, delivering a systemically lethal dose to the ant population.
A predatory Phorid fly is now released in Florida and other locations, demonstrating potential biological control. Eggs are placed on Fire ants by Phorid flies. The larvae emerge, invading the head of the ant. The brain is consumed and the ant’s head decapitates allowing emergence of the fly. This overall process interferes with ant foraging, reducing competitive success over native ant species.
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