fire ant

This page is about stinging ants in the genus Solenopsis. For the aggressive red weaver ants sometimes called "fire ants" in Southeast Asia please see Oecophylla smaragdina.

Fire ant
Solenopsis queens and workers
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda subphylum= Uniramia
Class:	Insecta
Order:	Hymenoptera
Suborder:	Apocrita
Family:	Formicidae
Subfamily:	Myrmicinae
Tribe:	Solenopsidini
Genus:	Solenopsis Westwood, 1840
Species
S. conjurata S. daguerrei S. fugax S. invicta S. molesta S. richteri S. solenopsidis S. wagneri S. xyloni  many more, see text

Fire ants are a variety of stinging ants with over 280 species worldwide. They have several common names including ginger ants and tropical fire ants (English), aka-kami-ari (Japanese), fourmis de feu (French), Feuerameisen (German), mod-kun-fai (Thai), and Langgam (Filipino).

Appearance

S. conjurata worker

The bodies of fire ants, like all insects' bodies, are broken up into three sections: the head, the thorax, and the abdomen, with three pairs of legs and a pair of antennae. Fire ants can be distinguished from other ants by their copper brown head and body with a darker abdomen. The worker ants are blackish to reddish, and their size varies from 2mm to 6 mm (0.12 in to 0.24 in). These different sizes of the ants can all exist in the same nest.

Solenopsis sp. ants can be identified with three body features - a pedicel with two nodes, an unarmed propodium, and antennae with 11 segments and a two segmented club.

Behavior

A typical fire ant colony produces large mounds in open areas, and feeds mostly on young plants, seeds, and sometimes crickets. Fire ants often attack small animals and can kill them. Unlike many other ants, which bite and then spray acid on the wound, fire ants only bite to get a grip and then sting (from the abdomen) and inject a toxic alkaloid venom called Solenopsin, a compound from the class of piperidines. For humans, this is a painful sting, it hurts, a sensation similar to what one feels when burned by fire—hence the name fire ant—and the aftereffects of the sting can be deadly to sensitive individuals. The venom is both insecticidal and antibiotic. Researchers have proposed that nurse workers will spray their brood to protect them from microorganisms.

Fire ants nest in the soil, often near moist areas, such as river banks, pond edges, watered lawns and highway edges. Usually the nest will not be visible as it will be built under objects such as timber, logs, rocks, pavers, bricks, etc. If there is no cover for nesting, dome-shaped mounds will be constructed, but this is usually only found in open spaces such as fields, parks and lawns. These mounds can reach heights of 40 cm (15.7 in).

Colonies are founded by small groups of queens or single queens. Even if only one queen survives, within a month or so the colony can expand to thousands of individuals. Some colonies may be polygynous (having multiple queens per nest).^[1]

Roles

A queen is generally the largest individual in the colony. The primary function of the queen is reproduction; she may live for 6-7 years and produce up to 1,500 eggs per day. Many fire ant colonies will have more than one queen.

Males / Drones

Males mate with the queen ant for the purpose of producing baby ants. Their lifespan is approximately three days.

Workers

The workers are sterile females who build and repair the nest, care for the young, defend the nest, and feed both young and adult ants. The worker ants also go find supplies to build the nest.

Introduced species

Although most fire ant species do not bother people and are not invasive due to biological factors, Solenopsis invicta, commonly known as the Red imported fire ant (or RIFA) is an invasive pest in many areas of the world, notably the United States, Australia, the Philippines, China and Taiwan. The RIFA was accidentally introduced into the United States due to a South American cargo ship coming to an Alabama port in the 1930's, but now infests the majority of the Southern and Southwestern United States.^[2]

In the US, the FDA estimates that more than US$5 billion is spent annually on medical treatment, damage, and control in RIFA-infested areas. Furthermore, the ants cause approximately US$750 million in damage annually to agricultural assets, including veterinarian bills and livestock loss as well as crop loss.^[3] Over 40 million people live in RIFA-infested areas in the southeastern United States.^[4] Between 30 and 60% of the people living in fire ant infested areas are stung each year.^[5] Since September 2004, Taiwan has been seriously affected by the red fire ant. The US, Taiwan and Australia all have ongoing national efforts to control or eradicate the species, but, other than Australia, none have been especially effective. In Australia an intensive program costing A$175 million has, at February 2007, eradicated 99% of fire ants from the sole infestation occurring in South East Queensland.

In just 70 years, according to a new study, lizards in parts of United States have developed longer legs and new behaviors to escape the ants, which can kill the lizard in under a minute.^[6]

Symptoms and first aid

A human leg three days after coming in brief contact with a fire ant colony

The venom of a fire ant sting causes stinging and swells into a bump. This can cause much pain and irritation at times, especially when stung repeatedly by several at once. The bump often forms into a white pustule, which is at risk of becoming infected if scratched; however, if left alone, it will usually go down within a few days. The pustules are unattractive and uncomfortable while active and, if the sting sites become infected, can turn into scars. Additionally, some people are allergic to the venom and, as with many allergies, may experience anaphylaxis, which requires emergency treatment.^[7] An antihistamine or topical corticosteroids may help reduce the itching.

First aid for fire ant bites includes external treatments and oral medicines.

• External treatments: a topical steroid cream (hydrocortisone), or one containing aloe vera. Also, regular toothpaste can be a quick and simple relief. A simple solution of half bleach and half water applied immediately to the area can reduce the pain, itching and, perhaps, pustule formation.^[8]

• Oral medicines: antihistamines.

Patients who experience severe or life threatening allergic reactions to fire ant insect stings should visit a doctor or hospital immediately upon contact as these reactions can result in death. These more severe reactions include severe chest pain, nausea, severe sweating, loss of breath, serious swelling, or slurred speech.^[9]

Other names

In Spanish, fire ants are known as hormiga colorada/roja (red ant) or hormiga brava (fierce ant). In Puerto Rico there is a native, very small and slow-moving kind of fire ant called abayarde. In Portuguese, they are called formiga de fogo (fire ant) and formiga lava-pé (wash foot ant).

Natural predators

Phorid flies, or Phoridae, are a family of small, hump-backed flies resembling fruit flies; two species in this family (Pseudacteon tricuspis and Pseudacteon curvatus) are parasitoids of the red imported fire ant in its native range in South America. Some 110 species of the genus Pseudacteon, or ant-decapitating flies, have been described. Members of Pseudacteon reproduce by laying eggs in the thorax of the ant. The first instar larvae migrates to the head, then develop by feeding on the hemolymph, muscle tissue, and nervous tissue. After about two weeks, they cause the ant's head to fall off by releasing an enzyme that dissolves the membrane attaching the ant's head to its body. The fly pupates in the detached head capsule, requiring a further two weeks before emerging.^[10]

Pseudacteon flies have been widely introduced throughout the southern United States, starting with Travis, Brazos, and Dallas counties in Texas, as well as Mobile, Alabama, where the ants first entered North America.

Species

This species list is incomplete.

See also

• Ant stings

Footnotes

References

• Bert Hölldobler and Edward O. Wilson (1990). The Ants. Cambridge: Belknap Press of Harvard University Press. ISBN 3-540-52092-9. 
• (PDF) Areawide suppression of Fire Ants using baits and Biological Control. USDA. 2003. http://www.ars.usda.gov/fireant/publications/brochure_2003.pdf. Retrieved 2006-10-25.  Details use of Phorid flies
• ITIS: Solenopsis species list (2001)
• Treatment of Fire Ant Bites
• Medical Treatment of Fire Ant Bites

External links

Wikimedia Commons has media related to: Solenopsis

• Biology, Control, and Management of Imported Fire Ants in North America at www.eXtension.org
• The Alabama Fire Ant Management Program
• Queensland Government - Department of Primary Industries Fire Ants Homepage
• Fire Ant Gene Sequence database
• Fireants building a lifeboat to save the queen - Video