Temporal range: Early Oligocene–Recent
Fire ants are several species of ants in the genus Solenopsis. They are, however, only a minority in the genus, which includes over 200 species of Solenopsis worldwide. Solenopsis are stinging ants, and most of their common names reflect this, for example, ginger ants and tropical fire ants. Many of the names shared by this genus are often used interchangeably to refer to other species of ant, such as the term red ant, mostly because of their similar coloration despite not being in the genus Solenopsis. Both Myrmica rubra and Pogonomyrmex barbatus are common examples of non-Solenopsis ants being termed red ants.
None of these names apply in all countries nor to all species of Solenopsis, nor only to Solenopsis species; for example the colloquial names for several species of weaver ants in the genus Oecophylla in Southeast Asia include "fire ants" because of their similar coloration and painful bites; the two genera, however, are not closely related. Wasmannia auropunctata is another unrelated ant commonly called the "little fire ant" due to its potent sting.
The bodies of mature fire ants, like the bodies of all typical mature insects, are divided into three sections: the head, the thorax, and the abdomen, with three pairs of legs and a pair of antennae. Fire ants of those species invasive in the United States can be distinguished from other ants locally present by their copper brown head and thorax with a darker abdomen. The worker ants are blackish to reddish and their size varies from 2 to 6 mm (0.079 to 0.236 in). In an established nest these different sizes of ants are all present at the same time.
Solenopsis spp. ants can be identified by three body features—a pedicel with two nodes, an unarmed propodeum, and antennae with 10 segments plus a two-segmented club. Many ants bite, and formicine ants can cause irritation by spraying formic acid; myrmecine ants like fire ants have a dedicated venom-injecting sting, which injects an alkaloid venom, as well as mandibles for biting.
A typical fire ant colony produces large mounds in open areas, and feeds mostly on young plants and seeds. 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 bite only 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, a sensation similar to what one feels when burned by fire (hence the name), and the after-effects of the sting can be deadly to sensitive people. Fire ants are more aggressive than most native species, so have pushed many species away from their local habitat. One such species that Solenopsis ants parasitically take advantage of are bees, such as Euglossa imperialis, a nonsocial orchid bee species, from which the ants enter the cells from below the nest and rob the cell's contents. These ants are renowned for their ability to survive extreme conditions. They do not hibernate, but can survive cold conditions, although this is costly to fire ant populations as observed during several winters in Tennessee, where 80 to 90% of colonies died due to several consecutive days of extremely low temperatures.
Fire ants have been known to form mutualistic relationships with several species of Lycaenidae and Riodinidae butterflies. In Lycaena rubidus, the larvae secrete a fluid that is high in sugar content. Fire ants bring the larvae back to the nest, and protect them through the pupal stage in exchange for feeding on the fluid. In Eurybia elvina, fire ants were observed to frequently construct soil shelters over later instars of larvae on inflorescences on which the larvae are found.
Fire ants nest in the soil, often near moist areas, such as river banks, pond shores, watered lawns, and highway shoulders. Usually, the nest will not be visible, as it will be built under objects such as timber, logs, rocks, or bricks. If no cover for nesting is available, dome-shaped mounds are constructed, but these are usually only found in open spaces, such as fields, parks, and lawns. These mounds can reach heights of 40 cm (16 in), but can be even higher on heavier soils, standing at 1.0 m (3 ft 3 in) in height and 1.5 m (4 ft 11 in) in diameter. 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).
Fire ants are resilient and can survive floods. During Hurricane Harvey in Texas in 2017, clumps of fire ants, known as rafts, were seen clumped together on the surface of the water. Each clump had as many as 100,000 individual ants, which formed a temporary structure until finding a new permanent home.
Fire ants dig tunnels efficiently using about 30% of the population of the colony, thereby avoiding congestion in tunnels.
Queens, males and workers
Fire ant queens, the reproductive females in their colony, also are generally the largest. Their primary function is reproduction. Typically, a fire ant queen will seek to establish a new colony following a nuptial flight, wherein it will use its special venom to paralyze offending competitors, in the absence of workers for defense. Fire ant queens may live up to seven years and can produce up to 1,600 eggs per day, and colonies will have as many as 250,000 workers. The estimated potential life span is around 5 years and 10 months to 6 years and 9 months. Young, virgin fire ant queens have wings (as do male fire ants), but they often cut them off after mating. Although, occasionally a queen will keep its wings after mating and through her first year.
Male fire ants mate with queens during a nuptial flight. After a male has successfully inseminated a queen, he will not get accepted back to the mother colony, and will eventually die outside the nest.
The other roles in an ant colony are usually undertaken by workers. Fire ant workers are haphazardly divided into different size classes, namely minima, minor, media, and major workers. The major ants are known for their larger size and more powerful mandibles typically used in macerating and storing food items (i.e. as repletes), while smaller workers take care of regular tasks (the main tasks in a colony are caring for the eggs/larvae/pupae, cleaning the nest, and foraging for food). However, Solenopsis daguerrei colonies contain no workers, as they are considered social parasites.
Although most fire ant species do not bother people and are not invasive, Solenopsis invicta, known in the United States as the red imported fire ant (or RIFA), is an invasive pest in many areas of the world, including the United States, Australia, China and Taiwan. The RIFA was believed to have been accidentally introduced to these countries via shipping crates, particularly with Australia when they were first found in Brisbane in 2001. These ants have now since been spotted in Sydney for the first time. They were believed to be in the Philippines, but they are most likely to be misidentified for Solenopsis geminata ants.
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 $750 million in damage annually to agricultural assets, including veterinarian bills and livestock loss, as well as crop loss. Over 40 million people live in RIFA-infested areas in the southeastern United States. It is estimated that 30–60% of the people living in fire ant-infested areas of the US are stung each year. RIFA are currently found mainly in subtropical southeastern USA states including Florida, Georgia, South Carolina, Louisiana, Mississippi, Alabama, and parts of North Carolina, Virginia, Tennessee, Arkansas, Texas, Oklahoma, New Mexico, and California.
Since September 2004, Taiwan has been seriously affected by the red fire ant. The US, Taiwan and Australia all have ongoing national programs to control or eradicate the species, but with the exception of those in Australia, none have been especially effective. In Australia, there is an intensive program costing A$175 million, although the fire ant has remained despite efforts. By July 2013, multiple sites west of Brisbane were confirmed, including the Lockyer Valley, Muirlea and Goodna. According to a study published in 2009, it only took seventy years for the lizards in parts of the United States to adapt to the ant's presence—they now have longer legs and new behaviors that aid them in escaping from the danger.
Sting symptoms and treatment
The venom of fire ants is mainly (>95%) composed of oily alkaloids structurally derived from piperidine (also known as solenopsins) mixed with a small amount of toxic proteins. Fire ant stings are painful, characterised by a local burning sensation, followed by urticaria. The sting site typically swells into a bump within hours, which can cause further pain and irritation, especially following several stings at the same place. The bump may develop into a white pustule within 24–36 hours which can become infected if scratched, but will spontaneously flatten within a few days if left alone. The pustules are obtrusive and uncomfortable while active and, if they become infected, may cause scarring. Some people may become allergic to the venom, and if untreated, may become increasingly sensitive to the point of experiencing anaphylaxis following fire ant stings, which requires emergency treatment. Management of an emergency visit due to anaphylaxis is recommended with the use of adrenaline. It has been demonstrated that, whilst pustule formation results from the injected venom alkaloids, allergy to fire ant stings is caused solely by venom allergenic proteins.
First aid for fire ant stings includes external treatments and oral medicines. There are also many home remedies of varying efficacy, including immediate application of a solution of half bleach and half water, or aloe vera gel – the latter of which is also often included in over-the-counter creams that also include medically tested and verified treatments. External, topical treatments include the anesthetic benzocaine, the antihistamine diphenhydramine, and the corticosteroid hydrocortisone. Antihistamines or topical corticosteroids may help reduce the itching and will generally benefit local sting reactions. Oral medicine include antihistamines. Severe allergic reactions to fire ant stings, including severe chest pain, nausea, severe sweating, loss of breath, serious swelling, and slurred speech, can be fatal if not treated.
Phorid flies, or Phoridae, are a large family of small, hump-backed flies somewhat smaller than vinegar 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 develops 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, emerging two weeks later.
Pseudacteon flies appear to be important ecological constraints on Solenopsis species and they have been introduced throughout the southern United States, starting with Travis, Brazos, and Dallas counties in Texas, as well as south central Alabama, where the ants first entered North America.
The Venus flytrap, a carnivorous plant, is native only to North and South Carolina in the United States. About 33% of the prey of the Venus flytrap are ants of various species. They lure their prey with a sweet sap. Once the prey has entered the trap and within about three seconds has touched two or three "trigger hairs," bristles on the surface of the trap, the leaf closes around the prey, confining it behind the "teeth" on its perimeter, and digests it. The majority of ants that are captured include non-native RIFAs, and three other species of ants. Other carnivorous plants, such as sundews (Drosera) and various kinds of pitcher plants also trap many ants.
Key natural enemies of fire ants also include other ant species which will attack prospective queens during the nest founding period, when there is an absence of workers to defend the emergent colony. Frequent competitors of fire ant founding queens include other Solenopsis thief ant species, and some invasive pest species, such as the tawny crazy ant, and the black crazy ant.
A number of entomopathogenic fungi are also natural enemies of fire ants, such as Beauveria bassiana and Metarhizium anisopliae. The latter is commercially available for the biological control (as an alternative to conventional pesticides) of various pest insects, and a new proposed technology has increased its shelf life and efficiency against fire ants.
The genus Solenopsis contains over 200 species. Not all species included in the genus are known as fire ants, but most are small slow-moving ants which are unable to sting, called thief ants. "True" fire ants are but a group of about 20 species of Solenopsis which are larger, and will viciously sting in swarms whenever disturbed. Some of the most studied species include:
- Bolton, B. (2014). "Solenopsis". AntCat. Retrieved 20 July 2014.
- Reins, Dusty. "Species: Pogonomyrmex barbatus - Red Harvester Ant". Wildcat Bluff Nature Center. Archived from the original on 2 April 2015. Retrieved 30 December 2014.
- "Wasmannia auropunctata". Hawaiian Ecosystems at Risk project (HEAR). Retrieved 9 July 2015.
- "Fire ant identification". Department of Agriculture, Fisheries and Forestry (Queensland Government). 30 July 2013. Retrieved 30 December 2014.
- "Red Imported Fire Ant - UC Statewide IPM Program". University of California Agriculture & Natural Resources. 25 April 2014. Retrieved 30 December 2014.
- Yi, GB; McClendon, D; Desaiah, D; Goddard, J; Lister, A; Moffitt, J; Meer, RK; deShazo, R; Lee, KS; Rockhold, RW (2002). "Fire ant venom alkaloid, isosolenopsin A, a potent and selective inhibitor of neuronal nitric oxide synthase". International Journal of Toxicology. 22 (2): 81–6. doi:10.1080/10915810305090. PMID 12745988. S2CID 23324548.
- Drees, Bastiaan M. (December 2002). "Medical Problems and Treatment Considerations for the Red Imported Fire Ant" (PDF). Texas A&M University (Texas Imported Fire Ant Research and Management Project). Retrieved 30 December 2014.
- Roberts, R. B.; Dodson, Calaway H. (1967). "Nesting biology of two communal bees, Euglossa imperialis and Euglossa ignita (Hymenoptera: Apidae), including description of larvae". Annals of the Entomological Society of America. 60 (5): 1007–1014. doi:10.1093/aesa/60.5.1007.
- Walter R. Tschinkel (2006). The Fire Ants. Cambridge: Belknap Press of Harvard University Press. p. 89. ISBN 978-0-674-02207-2.
- Horvitz, Carol C.; Turnbull, Christine; Harvey, Donald J. (1987-07-01). "Biology of Immature Eurybia elvina (Lepidoptera: Riodinidae), a Myrmecophilous Metalmark Butterfly". Annals of the Entomological Society of America. 80 (4): 513–519. doi:10.1093/aesa/80.4.513. ISSN 0013-8746.
- Watt, Loren (2001). "Lycaena rubidus". Animal Diversity Web.
- Lockley, Timothy C. "Imported Fire Ants". University of Minnesota (IPM World Textbook). Archived from the original on 30 December 2014. Retrieved 30 December 2014.
- Kintz-Early, Janet; Parris, Leslie; Zettler, Jennifer; Bast, Josh (September 2003). "Evidence of polygynous red imported fire ants (Hymenoptera: Formicidae) in South Carolina". Florida Entomologist. 86 (3): 381–382. doi:10.1653/0015-4040(2003)086[0381:EOPRIF]2.0.CO;2. Retrieved 30 December 2014.
- "Floating fire ants form rafts in Houston floodwaters". BBC. London. August 2017. Retrieved 30 August 2017.
- Gorman, James (2018-08-16). "The Secret to Ant Efficiency Is Idleness". The New York Times. ISSN 0362-4331. Retrieved 2019-01-17.
- Fox, Eduardo G.P.; Wu, Xiaoqing; Wang, Lei; Chen, Li; Lu, Yong-Yue; Xu, Yijuan (February 2019). "Queen venom isosolenopsin A delivers rapid incapacitation of fire ant competitors". Toxicon. 158: 77–83. doi:10.1016/j.toxicon.2018.11.428. PMID 30529381. S2CID 54481057.
- Vinson, S.B.; Sorenson, A.A. (1986). Imported Fire Ants: Life History and Impact. P. O. Box 12847, Austin, Texas 78711: The Texas Department of Agriculture.CS1 maint: location (link)
- Tschinkel, Walter R. (1987). "Fire Ant Queen Longevity and Age: Estimation by Sperm Depletion" (PDF). Annals of the Entomological Society of America. 80 (2): 263–266. doi:10.1093/aesa/80.2.263. Retrieved 30 December 2014.
- "Texas Imported Fire Ant Research and Management Project". fireant.tamu.edu. Retrieved 2019-04-13.
- Fox, Eduardo Gonçalves Paterson; Pianaro, Adriana; Solis, Daniel Russ; Delabie, Jacques Hubert Charles; Vairo, Bruno Cunha; Machado, Ednildo de Alcântara; Bueno, Odair Correa (2012). "Intraspecific and Intracolonial Variation in the Profile of Venom Alkaloids and Cuticular Hydrocarbons of the Fire Ant Solenopsis saevissima Smith (Hymenoptera: Formicidae)". Psyche: A Journal of Entomology. 2012: 1–10. doi:10.1155/2012/398061. ISSN 0033-2615.
- Briano, Juan A.; Calcaterra, Luis A.; Wojcik, D.P.; Williams, D.F.; Banks, W.A.; Patterson, R.S. (1997). "Abundance of the Parasitic Ant Solenopsis daguerrei (Hymenoptera: Formicidae) in South America, a Potential Candidate for the Biological Control of the Red Imported Fire Ant in the United States". Environmental Entomology. 26 (5): 1143–1148. doi:10.1093/ee/26.5.1143. Retrieved 30 December 2014.
- Ascunce, M. S.; Yang, C.-C.; Oakey, J.; Calcaterra, L.; Wu, W.-J.; Shih, C.-J.; Goudet, J.; Ross, K. G.; Shoemaker, D. (24 February 2011). "Global Invasion History of the Fire Ant Solenopsis invicta". Science. 331 (6020): 1066–1068. Bibcode:2011Sci...331.1066A. doi:10.1126/science.1198734. PMID 21350177. S2CID 28149214.
- Murphy, Damien (13 December 2014). "Red fire ants will make thongs a thing of the past". Sydney Morning Herald. Retrieved 30 December 2014.
- "'Aggressive' red ants found at Sydney port". The Australian. Australian Associated Press. 8 December 2014. Retrieved 30 December 2014.
- Wetterer, James K. (2013). "Exotic spread of Solenopsis invicta (Hymenoptera: Formicidae) beyond North America". Sociobiology. 60: 53–63. doi:10.13102/sociobiology.v60i1.50-55.
- McDonald, Maggie (February 2006). "Reds Under Your Feet (interview with Robert Vander Meer)". New Scientist. 189 (2538): 50.
- Solley, GO; Vanderwoude, C; Knight, GK (3 June 2002). "Anaphylaxis due to Red Imported Fire Ant sting". The Medical Journal of Australia. 176 (11): 521–3. doi:10.5694/j.1326-5377.2002.tb04548.x. PMID 12064982. S2CID 33650493. Retrieved 30 December 2014.
- Oi, David H. (25 June 2008). "Public health significance of Urban Pests" (PDF). World Health Organization Technical Report. Pharaoh ants and fire ants. p. 175. Retrieved 30 December 2014.
- Condon, Matthew (27 July 2013). "Queensland launched a war against the fire ant invasion, but 12 years later, they're still on the march". The Courier Mail. Retrieved 30 December 2014.
- McCarthy, John; Williams, Brian (25 July 2013). "Mayors warn fire ants are dominating in south east Queensland as infestations double". The Courier Mail. Retrieved 30 December 2014.
- Bryner, Jeanna (26 January 2009). "Lizards' Dance Avoids Deadly Ants". Live Science. Retrieved 30 December 2014.
- Fox, Eduardo Gonçalves Paterson (2014), "Venom Toxins of Fire Ants", Venom Genomics and Proteomics, Springer, Dordrecht, pp. 1–16, doi:10.1007/978-94-007-6649-5_38-1 (inactive 31 May 2021), ISBN 9789400766495, retrieved 2018-12-07CS1 maint: DOI inactive as of May 2021 (link)
- dos Santos Pinto, José R. A.; Fox, Eduardo G. P.; Saidemberg, Daniel M.; Santos, Lucilene D.; da Silva Menegasso, Anally R.; Costa-Manso, Eliúde; Machado, Ednildo A.; Bueno, Odair C.; Palma, Mario S. (2012-09-07). "Proteomic View of the Venom from the Fire Ant Solenopsis invicta Buren". Journal of Proteome Research. 11 (9): 4643–4653. doi:10.1021/pr300451g. ISSN 1535-3893. PMID 22881118.
- deShazo RD, Butcher BT, Banks WA (1990). "Reactions to the stings of the imported fire ant". New England Journal of Medicine. 323 (7): 462–6. doi:10.1056/NEJM199008163230707. PMID 2197555.
- Diaz, Bruno L.; Machado, Ednildo A.; Atella, Georgia C.; Araujo, Maria F. C.; Araujo, Almair Ferreira de; Poublan, Luiz E.; Gama, Diogo; Monteiro, Ana Paula; Fox, Eduardo G. P. (2018-09-26). "The allergic response mediated by fire ant venom proteins". Scientific Reports. 8 (1): 14427. Bibcode:2018NatSR...814427Z. doi:10.1038/s41598-018-32327-z. ISSN 2045-2322. PMC 6158280. PMID 30258210.
- Lee, Jason; Betschel, Stephen (2013). "A case of the first documented fire ant anaphylaxis in Canada". Allergy, Asthma & Clinical Immunology. 9 (1): 25. doi:10.1186/1710-1492-9-25. PMC 3711928. PMID 23837799.
- Javors, M.A.; Zhou, W.; Maas, J.W.; Han, S.; Keenan, R.W. (1993-01-01). "Effects of fire ant venom alkaloids on platelet and neutrophil function". Life Sciences. 53 (14): 1105–1112. doi:10.1016/0024-3205(93)90546-F. ISSN 0024-3205. PMID 8396703.
- Talcott, Patricia A.; Peterson, Michael E. (2013). Small animal toxicology (3rd ed.). St. Louis, Mo.: Elsevier. pp. 584–585. ISBN 978-1455707171. Retrieved 30 December 2014.
- "Fire Ant Bites". American Osteopathic College of Dermatology. Retrieved 30 December 2014.
- "Insects and Scorpions". Centers for Disease Control and Prevention and The National Institute for Occupational Safety and Health. 22 October 2008. Retrieved 11 April 2008.
- Prahlow, JA; Barnard, JJ (June 1998). "Fatal anaphylaxis due to fire ant stings". The American Journal of Forensic Medicine and Pathology. 19 (2): 137–42. doi:10.1097/00000433-199806000-00007. PMID 9662108. S2CID 39162329.
- Ehrenberg, Rachel (18 September 2009). "Venom attracts decapitating flies". Science News. Retrieved 30 December 2014.
- Porter, Sanford D.; Graham, L. C. “Fudd”; Johnson, Seth J.; Thead, Larry G.; Briano, Juan A. (June 2011). "The Large Decapitating Fly (Diptera: Phoridae): Successfully Established on Fire Ant Populations in Alabama". Florida Entomologist. 94 (2): 208–213. doi:10.1653/024.094.0213.
- Ellison, DM; Gotelli, NJ (2009). "Energetics and the evolution of carnivorous plants—Darwin's 'Most Wonderful plants in the world'". Journal of Experimental Botany. 60 (1): 19–42. doi:10.1093/jxb/ern179. PMID 19213724.
- Greenberg, Les; Kabashima, John N.; Allison, Clinton J.; Rust, Michael K.; Klotz, John H.; Hurvois, Jean-Pierre; Paine, Timothy D. (2008-11-01). "Lethality of Red Imported Fire Ant Venom to Argentine Ants and Other Ant Species". Annals of the Entomological Society of America. 101 (6): 1162–1168. doi:10.1603/0013-8746-101.6.1162. ISSN 0013-8746. S2CID 83922482.
- Siebeneicher, Stacy R.; Bradleigh^Vinson, S.; Kenerley, Charles M. (1992-05-01). "Infection of the red imported fire ant by Beauveria bassiana through various routes of exposure". Journal of Invertebrate Pathology. 59 (3): 280–285. doi:10.1016/0022-2011(92)90133-O. ISSN 0022-2011.
- Angelone, Steven; Bidochka, Michael J. (2018-07-01). "Diversity and abundance of entomopathogenic fungi at ant colonies". Journal of Invertebrate Pathology. 156: 73–76. doi:10.1016/j.jip.2018.07.009. ISSN 0022-2011. PMID 30017951.
- Qiu, Hua-Long; Fox, Eduardo G. P.; Qin, Chang-Sheng; Zhao, Dan-Yang; Yang, Hua; Xu, Jin-Zhu (2019-07-01). "Microcapsuled entomopathogenic fungus against fire ants, Solenopsis invicta". Biological Control. 134: 141–149. doi:10.1016/j.biocontrol.2019.03.018. ISSN 1049-9644.
- Pitts, James P.; Camacho, Gabriela P.; Gotzek, Dietrich; Mchugh, Joseph V.; Ross, Kenneth G. (April 2018). "Revision of the Fire Ants of the Solenopsis saevissima Species-Group (Hymenoptera: Formicidae)". Proceedings of the Entomological Society of Washington. 120 (2): 308–411. doi:10.4289/0013-8718.104.22.1688. ISSN 0013-8797. S2CID 91162352.
- Bert Hölldobler and Edward O. Wilson (1990). The Ants. Cambridge: Belknap Press of Harvard University Press. ISBN 978-3-540-52092-4.