Fire ant

Fire ant
File:Fire ant queens 3589.JPG
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Insecta
Order:	Hymenoptera
Suborder:	Apocrita
Family:	Formicidae
Subfamily:	Myrmicinae
Tribe:	Solenopsidini
Genus:	Solenopsis Westwood, 1840
Species
More than 280 species and subspecies, see text

Fire ants, sometimes referred to as simply red ants, are stinging ants of which there are over 280 species worldwide.

Appearance

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 2 mm to 6 mm (0.12 in to 0.24 in). These different sizes of the ants can all exist in the same nest. In Australia, detection and identification in order to deliver eradication of the tramp ant pest the red imported fire ant (S. invicta) is complicated in Queensland by its resemblance to another long-standing invasive species, the "coastal brown" (Pheidole megacephala).

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 (piperidine). For humans, this is a painful sting, 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). It has been observed that a colony can have over 100 queens.

Malaysian fire ant nest inside a leaf

In the Klang Valley of Malaysia, fire ants build nests in leaves by folding the leaf sideways and downwards over itself, with the queen inside, and then excreting a sticky white substance with which they bond and seal the fold. The excretion is also used inside the folded leaf to cover the queen and the eggs, like a kind of translucent duvet. The ants guard the nest and fiercely attack intruders.

Roles

Queens

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 1500 eggs per day. Many fire ant colonies will have more than one queen (potentially at least 100).

Males

The male ant's only function is to mate with the queen and continue the species with his genes. Once done mating, the males continue on with their search for another queen.

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. they will attack intruders and rape them.

Introduced species

Further information: Red imported fire ant and invasive subspecies

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 via Brazilian cargo entering the port of Mobile, Alabama, in the 1930s but now infests the majority of the Southern and Southwestern United States.

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. 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 South East Queensland.

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. They can be very irritating and painful 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. The pustules are unattractive and uncomfortable while active and, if the bite 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. 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), alcohol, bleach, a whipped mixture of egg whites and salt (spread over the affected skin for 30 minutes, removes the pain).
• Oral medicines: antihistamines

For patients who experience severe or life threatening allergic reactions to fire ant insect stings, visit a doctor or hospital immediately as these reactions can result in death.

Other names

In Spanish, fire ants are known as hormiga colorada (red ant) or hormiga brava (fierce ant). In Portuguese, they are called formiga de fogo (fire ant) and formiga lava-pé (wash foot ant).

References

• Bert Hölldobler and Edward O. Wilson (1990). The Ants. Cambridge: Belknap Press of Harvard University Press. ISBN 3-540-52092-9.
• "Areawide suppression of Fire Ants using baits and Biological Control" (PDF). USDA. 2003. Retrieved 2006-10-25. {{cite journal}}: Cite journal requires |journal= (help) Details use of Phorid flies

External links

• Biology, Control, and Management of Imported Fire Ants in North America at www.eXtension.org
• Queensland Government Department of Primary Industries Fire Ants Homepage