Fire ant
Fire ants are several species of ants in the genus Solenopsis, which includes over 200 species. 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 common names apply to all species of Solenopsis nor exclusively to species of Solenopsis; for example, several species of weaver ants of the genus Oecophylla in Southeast Asia are colloquially called "fire ants" because of their similar coloration and painful bites, but the two genera are not closely related. Wasmannia auropunctata is another unrelated ant more commonly called the "little fire ant" due to its potent sting.
Appearance
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. 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; myrmicine ants like fire ants have a dedicated venom-injecting sting, which injects an alkaloid venom, as well as mandibles for biting.
Behavior
A typical fire ant colony produces large mounds in open areas, and feeds mostly on young plants, insects and seeds. Fire ants often attack small animals such as small lizards 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 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, 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, but can be even higher on heavier soils, standing at in height and 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.
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. Ants clumped in this way will recognize different fluid flow conditions and adapt their behavior accordingly to preserve the raft's stability.
Fire ants dig tunnels efficiently using about 30% of the population of the colony, thereby avoiding congestion in tunnels.
Queens, males and workers
Queen
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, but they often cut them off after mating. Occasionally, a queen will keep its wings after mating and through its first year.Males (drones)
Male fire ants mate with queens during a nuptial flight. After a male has successfully inseminated a queen, the male will not get accepted back to the mother colony, and will eventually die outside the nest.Workers
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, while smaller workers take care of regular tasks. However, Solenopsis daguerrei colonies contain no workers, as they are considered social parasites.Invasive species
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, 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 in the case of Australia.In Australia, RIFA ants were first identified in the Port of Brisbane in 2001, although a strategic review of the Australian RIFA eradication program published in 2021 suggested that RIFA ants may have been present but undetected in Australia as early as 1992. As of November 2023, the invasion of fire ants is restricted to an area of 7000 km2 in South East Queensland that includes Brisbane, with the colonised area bordering the state of New South Wales, with incursions reported in northern NSW on a regular basis. Outside of this region, as of 2023, there have been seven other incursions that have had to be eradicated, with all incursions linked to ports and airports, including in Gladstone, the Port of Botany near Sydney, and the Port of Fremantle, Western Australia. Elsewhere, fire ants have been frequently intercepted on incoming cargo in ports and airports across Australia. Of particular concern, Australian researchers predict that the entire country is able to provide suitable habitat for RIFA colonization, with the exception of highland Tasmania and the Snowy Mountains. In the 21-year time period between 2001 and 2022, the commonwealth and state governments of Australia spent a combined AU$644m in their attempts to eradicate RIFA ants. In 2015, the Australian National Red Imported Fire Ant Eradication Program National Fire Ant Eradication Program was set up and received AU$411m of funding. For the time period of 2023-2027, funding of AU$593m has been agreed. Despite the funded plan and a degree of success in the eradication of RIFA not seen elsewhere in the world, some Australian experts warn that the government on a national and state level may be moving too slowly given the size of the threat.
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 $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 warmer US states in the south-east of the country including Florida, Georgia, South Carolina, Louisiana, Mississippi and Alabama, but extend to include 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. According to a study published in 2009, it took only 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.
Solenopsis invicta is the most famous species in this genus, especially in the US, however several other species are similarly dangerous and invasive, such as Solenopsis geminata, which has invaded most of the tropical countries, wreaking havoc in medical systems, especially in unprepared countries and islands.