Solenopsis spp. workers are polymorphic, physically differentiated into more than two forms (Holway et al. 2002). Their total body length ranges from 3 to 5mm long. The body is an orange to brown colour and the head is brown. Major workers are characterised by the following traits: head almost square, posterodorsal margin distinctly convex in frontal view; mandibles robust, each with a strongly convex outer margin and 4 blunt teeth on the masticatory margin; mandibular teeth obscure in some individuals; clypeus with a pair of longitudinal carinae; eyes rather small, each with more than 20 facets; anterior ocelli often present; antennal scapes reaching nearly to posterior border of head; antennal club longer than the 3rd to 9th antennal segments combined; legs, mesosoma and gaster with numerous erect hairs. Minor workers are characterised by the following traits: head almost square in frontal view; mandibles 4-toothed; antennal scapes reaching posterior margin of head; clypeus with a pair of longitudinal carinae; posterolateral corners of propodeum carinate, the carinae reaching the dorsal surface of the propodeum; subpetiolar process absent.

Please click on AntWeb: Solenopsis geminata for more images and assistance with identification. The AntWeb image comparison tool lets you compare images of ants at the subfamily, genus, species or specimen level. You may also specify which types of images you would like to comare: head, profile, dorsal, or label.
Please see PaDIL (Pests and Diseases Image Library) Species Content Page Ants: Tropical Fire Ant for high quality diagnostic and overview images.

Please follow this link for a fully illustrated Lucid key to common invasive ants [Hymenoptera: Formicidae] of the Pacific Island region [requires the most recent version of Java installed]. The factsheet on Solenopsis geminata contains an overview, diagnostic features, comparision charts, images, nomenclature and links. (Sarnat, 2008)

Some ants are thought to be invasive largely due to their colony structure and social characteristics. Uniclonal colonies are characterised by the inclusion of a multiple number of nests (polydomy) and by the co-operation of the workers to provide for many queens (polygyny). This confers many advantages for the survival and reproduction of an ant colony. In contrast ants with a monogynous monodomous colony structure (with workers attending to a single queen and nest) are less able to colonise a new location rapidly (McGlynn 1999). \r\n
In introduced regions tropical fire ants may be either multiclonal, with workers defending one queen and exhibiting high intranest aggression, or uniclonal. In the latter case workers lack internest aggression and work co-operatively as a supercolony to recruit new food items quickly. As a consequence ants are more likely to reach high local densities and dominate entire habitats (Ness and Bronstein 2004; McGlynn 1999).

Solenopsis geminata undergoes the following metamorphosis. Eggs are laid by the queen that will hatch to produce soft larvae, which are feed from regurgitated oils produced by the queen. During the last larvae stages, the larvae are feed solid foods, as opposed to only receiving liquid nutrients. Apparently the larvae are able to digest various proteins (due to their production of specific digestive enzymes) that cannot be digested by worker ants. The products of digestion are regurgitated by the larvae to passed along to the queen, in whom they stimulate the production of eggs. The larvae then develop into pupae, which are tended by workers. Newly emerged small adult workers spend several days to weeks taking care of eggs, larvae, pupae, and the queen. They open the burrow (in order to locate and gather food sources), feed the queen and the larvae, and construct the nest. Older workers groom the larvae, defend the colony, help to build and maintain the nest and carry back to the nest nutrients obtained from food sources. The oldest ants, the foragers, scavenge for food sources and lay chemical trails for the reserves to follow (back and forth from a food sources).

Solenopsis geminata is classified as a “hot climate specialist” as it resides only within hot arid regions. Native habitats in cold climates are unsuitable for successful colonisation by S. germinata. However it may survive in climate-controlled buildings, greenhouses or other human dwellings and infrastructure. In such cases, although its capacity for local spread is restricted its continued presence facilitates long distance dispersal to locations more suitable for establishment (McGlynn 1999; Holway et al. 2002). \r\n
Like many other invasive ants the topical fire ant will more readily invades disturbed habitats such as forest edges or agricultural crops (Ness and Bronstein 2004). For example, in Kakadu National Park, Australia, infestations of this ant were found only at sites located near areas frequented by humans, including within the grounds of a tourist complex. The ant did not penetrate the surrounding undisturbed savanna habitat, despite the production of alates (winged ants) that enabled sufficient dispersal into such areas (Hoffmann and O’Connor 2004). A study conducted in coffee plantations in Costa Rica by Perfecto and Vandermeer (1996) showed S. geminata abundance decreased with increasing shade conditions. The authors stipulate this to be a direct affect of the increased abundance of other ant species in shaded habitats (and the increased competitive pressure) rather than the light variable itself.

During warm months winged individuals are found in large numbers in mature colonies. New colonies are individually established by solitary fertile queens following a mating flight. Queens seek moist areas within a few kilometres of the parent colony. Once a suitable site is found the female sheds her wings and digs a small burrow into the soil and seals it. She will lay around 10 to 15 eggs each day for up to 10 days after which she will stop laying eggs until the workers are mature (which may take two weeks to a month). The colony may eventually consist of a few queens, many winged males, winged virgin females and a group of soldiers and workers in graduating sizes. Colony “budding” may occur, resulting in the outwars radiation of a colony.

Invasive ants are typically have a generalised feeding regime, able to gain nutrition from a variety of sources including grains, seeds, arthropods, decaying matter and/or vegetation (Holway et al. 2002; Ness and Bronstein 2004). Specialised feeders such as army ants, which prey on other social insects, are less likely to be successful in introduced regions as the range of potential prey is smaller (McGlynn 1999).
the diet of S. geminata includes a high proportion of seeds (Holway et al. 2002). It feeds and gathers grass seeds, storing them in “granaries” in their large nests (which may extend a metre and a half into the ground). They also tend honeydew producing homoptera and feed on arthropods (including a number of insect pests). S. geminata prefers food with a high protein content but will feed on almost anything, including many human foods rich in carbohydrates or fats. S. geminata possess a venomous sting that gives it an ability to subdue relatively large invertebrate prey, and even small vertebrates (Holway et al. 2002).

Argricultural areas with fire ant infestations are a potential source of infestation (with a high risk of spread associated with such areas due to the movement of produce).Movement of materials out of any fire ant infested areas in any form of transportation risks spread of the ant.Spread into new countries via the trade of materials infested with fire ants may be the cause of new introductions of such ants into a country.Fire ants may infest potplants, meaning the movement of plants out of infected areas carries a high risk potential in terms of dispersing the ant to new locations.The movement of vegetative material or soil associated with agricultural land infested by fire ants may result in the introduction of ants into new areas.Within the world heritage site of Kakadu National Park, Australia, S. geminata and Pheidole megacephala were detected only at sites located near areas frequented by humans (including a t

Please read Invasive ants impacts for a summary of the general impacts of invasive ants, such as their affect on mutualistic relations, the competitive pressure they impose on native ants and the effect they may have on vulnerable ecosystems. \r\n
S. geminata presents a grave threat to conservation values where it invades native communities. In terms of ecosystem disruption there is evidence that S. geminata reduces populations of native butterfly eggs and larvae on Guam (SPREP). It is also known to have the potential to devastate native ant populations (McGlynn 1999). S. germinata may consume some myrmecochorous seeds, but there is conflicting evidence; it certainly does not usually bury myrmecochorous seeds and will ingest the elaisome without dispersing the seed. It may have negative effects on some plant life, for example, it excludes ants that disperse the seeds of the plant Calathea ovandensis and defend the plant from herbivorous arthropods (Ness and Bronstein 2004).
Because S. germinata tends honeydew producing insects it may instigate population explosions in populations in insects such as mealybugs or other crop pests. This also results in an increase in the incidences of any plant disease transmitted by such pests. For example, in Northern monsoonal Australia it is now a major domestic and agricultural pest. It is known to chew through plastic tubing, and because of this may cause great damage to irrigation systems.\r\n
Fire ants are most notorious for their stinging behaviour. They respond rapidly and aggressively to any disturbance of the colony or to a food source. A single fire ant can sting repeatedly and will continue to do so even after their venom sac has been depleted. Initially, the sting results in a localized intense burning sensation (hence the name \"fire\" ant). This is followed the reddening and swelling of the surrounding skin tissue. In some people the sting may cause a severe, systemic allergic reaction.

Preventative measures: Effective quarantine measures, continuous monitoring, and immediate response upon finding newly established populations may be more effective than attempting to eradicate established species. The early detection of ant infestations is essential for cost-effective successful eradication and to prevent the formation of large uncontrollable infestations. In Kakadu National Park, Australia, detection was facilitated by the conspicuous soil workings and waste piles of the ant, which differs from those of native ant species. In addition, visual inspection could be achieved by easy means as ants rapidly recruited to any food source, regardless of the lack of specialised attractants. Following the eradication of this ant from the park all major tourist stops along the roads leading to the park were inspected for ants in order to reduce the risk of re-invasion (Hoffmann and O’Connor 2004).

\r\nThe Pacific Ant Prevention Programme is a proposal prepared for the Pacific Plant Protection Organisation and Regional Technical Meeting For Plant Protection. This plan aims to prevent the red imported fire ant and other invasive ant species with economic, environmental and/or social impacts, entering and establishing in or spreading between (or within) countries of the Pacific Region.

A detailed pest risk assessment for the eight species ranked as having the highest potential risk to New Zealand (\r\nAnoplolepis gracilipes, Lasius neglectus, Monomorium destructor, Paratrechina longicornis, Solenopsis geminata, Solenopsis richteri, Tapinoma melanocephalum, Wasmannia auropunctata) was prepared as part of 'The invasive ant risk assessment project', Harris et al. 2005., for Biosecurity New Zealand by Landcare Research.
The Invasive ant risk assessment for Solenopsis geminata can be viewed at Solenopsis geminata risk assessment\r\n
Please see Solenopsis geminata information sheet for more information on biology, distribution, pest status and control technologies.\r\n

Chemical: Chemical control of S. geminata is very easy using baits laced with the active constituent, hydramethylnon (Notes on the control of Solenopsis spp.).
Small infestations of S. geminate can be eradicated by the application of chemicals such as hydramethylnon (for example, applied as the commercially available formicide Amdro®). Hydramethylnon is a stomach toxicant spread between individuals in a colony by trophylaxis. The toxin is highly soluble and harms aquatic invertebrates. Care must be taken when considering its use in ecologically sensitive areas, irrigated areas or near natural water ways. The toxin must also be applied during dry weather to ensure success. Most ants killed within 24 h and the toxin is passed to the queens, usually effectively killing the whole colony. It has been used widely in the Northern Territory of Australia for the control of the tropical fire ant and has successfully eradicated infestations of the ant in Kakadu National Park, Australia (Hoffmann and O’Connor 2004).