Red imported fire ant

The species name of the red imported fire ant, invicta, derives from Latin, and means "invincible" or "unconquered". The epithet originates from the phrase Roma invicta ("unconquered Rome"), used as an inspirational quote until the fall of the Western Roman Empire in 476 AD. The generic name, Solenopsis, translates as "appearance of a pipe". It is a compound of two Ancient Greek words, solen, meaning "pipe" or "channel", and opsis, meaning "appearance" or "sight". The ant is commonly known as the "red imported fire ant" (abbreviated as RIFA); the "fire ant" part is because of the burning sensation caused by its sting. Alternative names include "fire ant", "red ant" or "tramp ant". In Brazil, locals call the ant toicinhera, which derives from the Portuguese word toicinho (pork fat). ==Taxonomy==

specimen of S. invicta collected from Brazil The red imported fire ant was first described by Swiss entomologist Felix Santschi in a 1916 journal article published by Physis. In 1930, American myrmecologist William Creighton reviewed the genus Solenopsis and reclassified the taxon as Solenopsis saevissima electra wagneri at infrasubspecific rank, noting that he could not collect any workers that referred to Santschi's original description. In 1952, the S. saevissima species complex was examined and, together with nine other species-group names, S. saevissima electra wagneri was synonymised with S. saevissima saevissima. This reclassification was accepted by Australian entomologist George Ettershank in his revision of the genus and in Walter Kempf's 1972 catalogue of Neotropical ants. In 1972, American entomologist William Buren described what he thought was a new species, naming it Solenopsis invicta. Buren collected a holotype worker from Cuiabá in Mato Grosso, Brazil, and provided the first official description of the ant in a journal article published by the Georgia Entomological Society. He accidentally misspelled invicta as above the description pages of the species, although it was clear that invicta was the intended spelling because of the constant use of the name in the article. The type material is currently housed in the National Museum of Natural History, Washington, D.C. He states that Trager wrongfully classified S. wagneri as an unavailable name and cites S. saevissima electra wagneri as the original taxon. He concludes that S. wagneri is, in fact, the original name and has priority over S. invicta. Under the present classification, the red imported fire ant is a member of the genus Solenopsis in the tribe Solenopsidini, subfamily Myrmicinae. It is a member of the family Formicidae, belonging to the order Hymenoptera, an order of insects containing ants, bees, and wasps. Phylogeny The red imported fire ant is a member of the S. saevissima species-group. Members can be distinguished by their two-jointed clubs at the end of the funiculus in workers and queens, and the second and third segments of the funiculus are twice as long and broad in larger workers. Polymorphism occurs in all species and the mandibles bear four teeth. Hybridisation between the two ants occurs in areas where they make contact, with the hybrid zone located in Mississippi. Such hybridisation has resulted from secondary contact between these two ants several decades ago, when they first encountered each other in southern Alabama. Genetics Studies show that mitochondrial DNA variation occurs substantially in polygyne societies (nests with multiple queens), but no variation is detected in monogyne societies (nests with a single queen). Triploidy (a chromosomal abnormality) occurs in red imported fire ants at high rates (as high as 12% in non-reproductive females), which is linked to the high frequency of diploid males. The red imported fire ant is the first species shown to possess a green-beard gene, by which natural selection can favour altruistic behaviour. Workers containing this gene are able to distinguish between queens containing it, and those that do not, apparently by using odour cues. The workers kill queens that do not contain the gene. In 2011, scientists announced they had fully sequenced the red imported fire ant genome from a male. ==Description==

Red imported fire ant workers range in size from small to medium, making them polymorphic. Workers measure between . The head measures and is wide. In the larger workers (as in the major workers), their heads measure and wide. The antenna scapes measure and the thoracic length is . The head becomes wider behind the eyes with rounded occipital lobes present, and unlike the similar-looking S. richteri, the lobes peak further than the midline, but the occipital excision is not as crease-like. The scapes in major workers do not extend beyond occipital peak by one or two scape diameters; this feature is more noticeable in S. richteri. In medium-sized workers, the scapes reach the occipital peaks and exceed the rear border in the smallest workers. In small and medium workers, the head tends to have more elliptical sides. The head of small workers is wider out front than it is behind. Gastric spots are sometimes seen in larger workers, where they are not as brightly coloured as those in S. richteri. The gastric spot usually covers a small portion of the first gastric tergite. The thorax is concolorous, ranging from light reddish-brown to dark-brown. The legs and coxae are usually lightly shaded. The head has a consistent colour pattern in large workers, with the occiput and vertex appearing brown. Other parts of the head, including the front, genae, and the central region of the clypeus, are either yellowish or yellowish brown. The anterior borders of the genae and mandibles are dark-brown; they also both appear to share the same coloured shade with the occiput. The scapes and funiculi range from being the same colour as the head or shares the same shade with the occiput. Light-coloured areas of the head in small to medium-sized workers is restricted to only the frontal region, with a dark mark resembling an arrow or rocket being present. On occasion, nests may have a series of different colours. For example, workers may be much darker, and the gastric spot may be completely absent or appear dark-brown. Larvae measure . They show a similar appearance to S. geminata larvae, but they can be distinguished by the integument with spinules on top of the dorsal portion of the posterior somites. The body hairs measure with a denticulate tip. The antennae both have two or three sensilla. The labrum is smaller with two hairs on the anterior surface that are . The maxilla has a sclerotised band between the cardo and stipes. The labium also has a small sclerotised band. The tubes of the labial glands are known to produce or secrete a proteinaceous substance that has a rich level of digestive enzymes, which includes proteases and amylases that function as an extraintestinal digestion of solid food. The midgut also contains amylases, roteases and upases. The narrow cells in its reservoir have little to no function in secretion. The pupae resemble adults of any caste, except that their legs and antennae are held tightly against the body. They appear white, but over time, the pupa turns darker when they are almost ready to mature. Four larval instars have been described based on distinctive morphological characters. The larvae of the minor and major workers are impossible to distinguish before the final instar, when size differences become apparent. Upon pupation a wider head width difference between castes become more evident. Reproductive larvae are larger than worker larvae, and present discrete morphological differences in mouthparts. Fourth-instar larvae of males and queens can be differentiated based on their relative shape and body coloration, In incipient colonies, polymorphism does not exist, but instead they are occupied by monomorphic workers called "minims" or "nanitics". The average head-width in tested colonies increases during the first six months of development. In five-year-old colonies, the head width of minor workers decreases, but for major workers, the head-width remains the same. The total weight of a major worker is twice that of a minor worker when they first arrive, and by six months, major workers are four times heavier than minor workers. Once major workers develop, they can make up a large portion of the workforce, with as many as 35% being major workers in a single colony. As worker ants grow to larger sizes, the shape of the head changes, due to the head length growing at the same time as the total body length, and the head width may grow by 20%. The length of the antennae only grows slowly; the antennae may only grow 60% longer by the time the body doubles its length, thus the relative antennal length decreases by 20% as the length of the body doubles. All individual legs of the body are isometric with body length meaning that even when the length of the body doubles, the legs will also double. However, not all of the legs are the same length; the prothoracic portion accounts for 29% of leg length, the mesothoracic 31%, and the metathoracic 41%. The first two pairs of legs are of equal length to one another, whereas the final pair is longer. Overall, the morphological appearance of a worker changes dramatically when it grows larger. The head exhibits the greatest shape change and the height of the alinotum grows quicker than its length, where a height/length ratio of 0.27 in minor workers and 0.32 in major workers is seen. Due to this, larger workers tend to have a humped-shape and robust alinotum in contrast to smaller workers. No petiole segment exhibits any change in shape as the size of the body changes. The width of the gaster grows more rapidly than its length, where the width may be 96% of its length but increases to 106%. As with other insects, the direct communication between the tracheal system and tissues eliminates the need for a circulating fluid network to transport O2. Thus, red imported fire ants and other arthropods can have a modest circulatory system though they have highly expensive metabolic demands. The excretory system consists of three regions. The basal region has three cells found within the posterior portion of the midgut. The anterior and superior cavities are formed by the bases of four Malpighian tubules. The superior cavity opens into the lumen of the small intestine. The rectum is a large but thin-walled sac that occupies the posterior fifth of the larvae. The release of waste is controlled by the rectal valves that lead to the anus. Sometimes, the larvae secrete a liquid that consists of uric acid, water and salts. These contents are often carried outside by workers and ejected, but colonies under water stress may consume the contents. Flight muscle degeneration is initiated by mating and juvenile hormones, and prevented by corpus allatectomy. Histolysis begins with the dissolution of the myofibril and the slow breakdown of the myofilaments. Such dissolution continues until it reaches the only free Z-line materials, which would also disappear; only the nuclei and lamellar bodies remain. The glandular system contains four glands: the mandibular, maxillary, labial, and postpharyngeal glands. The functions of the other glands remain poorly understood. In one study discussing the enzymes of the digestion system of adult ants, lipase activity was found in the mandibular and labial glands, as well as invertase activity. The Dufour's gland found in the ant acts as a source of trail pheromones, although scientists believed the poison gland was the source of the queen pheromone. The neurohormone pheromone biosynthesis activating neuropeptide is found in the ant that activates the biosynthesis of pheromones from the Dufour's gland. The spermatheca gland is found in queens, which functions in sperm maintenance. Males appear to lack these glands, but those associated with its head are morphologically similar to those found in workers, but these glands may act differently. Hypoxia and hypercapnia can result from red imported fire ant colonies living in poorly ventilated thermoregulatory mounds and underground nests. Discontinuous gas exchange (DGE) may allow ants to survive the hypercapnic and hypoxic conditions frequently found in their burrows; Colonies living in unshaded and warmer sites tend to have a higher heat tolerance than those living in shaded and cooler sites. Metabolic rate, which indirectly affects respiration, is also influenced by environmental temperature. Peak metabolism occurs at about 32 °C. Metabolism, and therefore respiration rate, increases consistently as temperature increases. DGE stops above 25 °C, although the reason for this is currently unknown. Respiration rate also appears to be influenced significantly by caste. Males show a considerably higher rate of respiration than females and workers, due, in part, to their capability for flight and higher muscle mass. In general, males have more muscle and less fat, resulting in a higher metabolic O2 demand. While the metabolic rate is highest at 32 °C, colonies often thrive at slightly cooler temperatures (around 25 °C). The high rate of metabolic activity associated with warmer temperatures is a limiting factor on colony growth because the need for food consumption is also increased. As a result, larger colonies tend to be found in cooler conditions because the metabolic demands required to sustain a colony are decreased. ==Distribution and habitat==

Red imported fire ants are native to the tropical areas of central South America, where they have an expansive geographical range that extends from southeastern Peru to central Argentina, and to the south of Brazil. In contrast to its geographical range in North America, its range in South America is significantly different. It has an extremely long north–south range, but a very narrow east–west distribution. The northernmost record of the red imported fire ant is Porto Velho in Brazil, and its southernmost record is Resistencia in Argentina; this is a distance of about . In comparison, the width of its narrow range is about , and this is most likely narrower into southern Argentina and Paraguay and into the northern areas of the Amazon River basin. Most known records of the red imported fire ant are around the Pantanal region of Brazil. However, the interior of this area has not been examined thoroughly, but it is certain that the species occurs in favourable locations around it. The Pantanal region is thought to be the original homeland of the red imported fire ant; hydrochore dispersal via floating ant rafts could easily account for the far south populations around the Paraguay and Guaporé Rivers. The western extent of its range is not known exactly, but its abundance there may be limited. It may be extensive in easternmost Bolivia, owing to the presence of the Pantanal region. The northeastern regions of Argentina are the most credible guess where the invading ants originate. In Brazil, they are found in northern Mato Grosso and in Rondônia and in São Paulo state. The red imported fire ant and S. saevissima are parapatric in Brazil, with contact zones known in Mato Grosso do Sul, Paraná, and São Paulo. In Paraguay they are found throughout the country, and have been recorded in Boquerón, Caaguazú, Canindeyú, Central, Guairá, Ñeembucú, Paraguarí, and Presidente Hayes departments; Trager claims that the ant is distributed in all regions of the country. They are also found in a large portion of northeastern Bolivia and, to a lesser extent, in northwestern Uruguay. The red imported fire ant is able to dominate altered areas and live in a variety of habitats. It can survive the extreme weather of the South American rain forest, and in disturbed areas, nests are seen frequently alongside roads and buildings. In areas where water is present, they are commonly found around: irrigation channels, lakes, ponds, reservoirs, rivers, streams, riverbanks, and mangrove swamps. In particular, they are found in cultivated land, managed forests and plantations, disturbed areas, intensive livestock production systems, and greenhouses. This includes: urban gardens, picnic areas, lawns, playgrounds, schoolyards, parks, and golf courses. During winter, colonies move under pavements or into buildings, and newly mated queens move into pastures. Workers are only able to access their nests through a series of tunnels that protrude from the central region. Such protrusions can span up to 25 feet away from the central mound, either straight down in to the ground or, more commonly, sideways from the original mound. Constructed from soil, mounds are oriented so that the long portions of the mound face toward the sun during the early morning and before sunset. These ants also spend large amounts of energy in nest construction and transporting brood, which is related with thermoregulation. The brood is transported to areas where temperatures are high; workers track temperature patterns of the mound and do not rely on behavioural habits. Inside nests, mounds contain a series of narrow horizontal tunnels, with subterranean shafts and nodes reaching grass roots below the surface; these shafts and nodes connect the mound tunnels to the subterranean chambers. These chambers are about 5 cm2 (0.77 inch2) and reach depths of . The mean number of ants in a single subterranean chamber is around 200. Introductions Red imported fire ants are among the worst invasive species in the world. Some scientists consider the red imported fire ant to be a "disturbance specialist"; human disturbance to the environment may be a major factor behind the ants' impact (fire ants tend to favour disturbed areas). This is shown through one experiment, demonstrating that mowing and plowing in studied areas diminished the diversity and abundance of native ant species, whereas red imported fire ants found on undisturbed forest plots had only diminished a couple of species. In the United States, the red imported fire ant first arrived in the seaport of Mobile, Alabama, by cargo ship between 1933 and 1945. Arriving with an estimated 9 to 20 unrelated queens, the red imported fire ant was only rare at the time, as entomologists were unable to collect any specimens (with the earliest observations first made in 1942, preceded by a population expansion in 1937); the population of these ants exploded by the 1950s. Since its introduction to the United States, the red imported fire ant has spread throughout the southern states and northeastern Mexico, negatively affecting wildlife and causing economic damage. The expansion of red imported fire ants may be limited since they are almost wiped out during Tennessee winters, thus they may be reaching their northernmost range. However, global warming may allow the red imported fire ant to expand its geographical range. As of 2004, the ant is found in 13 states and occupies over 128 million hectares (1,280,000 km2, 494,000 mi2) of land, and as many as 400 mounds can be found on a single acre of land (988 mounds per acre). The United States Department of Agriculture estimates that they expand westward per year. The ants were believed to be present in shipping containers arriving at the Port of Brisbane, most likely from North America. Anecdotal evidence suggests fire ants may have been present in Australia for six to eight years prior to formal identification. The potential damage from the red imported fire ant prompted the Australian government to respond rapidly. A joint state and federal funding of A$175 million was granted for a six-year eradication programme. Following years of eradication, eradication rates of greater than 99% from previously infested properties were reported. The program received extended Commonwealth funding of around A$10 million for at least another two years to treat the residual infestations found most recently. In December 2014, a nest was identified at Port Botany, Sydney, in New South Wales. The port was quarantined, and a removal operation took place. In September 2015, populations originating from the United States were found at a Brisbane airport. Hundreds of millions of dollars have since been allocated to their eradication. In August 2023, the Invasive Species Council said that without additional funding, fire ants would probably spread into northern New South Wales and west, potentially into the Murray Darling Basin. Red imported fire ants have spread beyond North America. The Invasive Species Specialist Group (ISSG) reports the ant inhabiting at least three of the Cayman Islands. However, the sources the ISSG cited give no report about them on the island, but recent collections indicate that they are present. Red imported fire ants have been reported in India, Malaysia, the Philippines and Singapore. The reports in the Philippines most likely misidentified collected material as the red imported fire ant, as no populations have been found there. No geographic or climatic barriers prevent these ants from spreading further, thus it may spread throughout the tropical and subtropical regions of Asia. In Europe, a single nest was found in the Netherlands in 2002. Around 1980, red imported fire ants began spreading throughout the West Indies, where they were first reported in Puerto Rico and the U.S. Virgin Islands. Between 1991 and 2001, the ant was recorded from Trinidad and Tobago, several areas in the Bahamas, the British Virgin Islands, Antigua, and the Turks and Caicos Islands. Since then, red imported fire ants have been recorded on more islands and regions, with new populations discovered in: Anguilla, Saint Martin, Barbuda, Montserrat, Saint Kitts, Nevis, Aruba, and Jamaica. The ants recorded from Aruba and Jamaica have only been found on golf courses; these courses import sod from Florida, so such importation may be an important way for the ant to spread throughout the West Indies. Despite the spread of the red imported fire ant (S. invicta), S. geminata has a greater geographical range, but it can be easily displaced by S. invicta. Because of this, almost all of S. geminata's exotic range in North America has been lost and it has almost disappeared there. On roadsides in Florida, 83% of these sites had S. geminata present when the red imported fire ant was absent, but only 7% when it is present. This means that the ant can probably invade many tropical and subtropical regions where S. geminata populations are present. ==Behaviour and ecology==

Red imported fire ants are extremely resilient and have adapted to contend with both flooding and drought conditions. If the ants sense increased water levels in their nests, they link together and form a ball or raft that floats, with the workers on the outside and the queen inside. The brood is transported to the highest surface. They are also used as the founding structure of the raft, except for the eggs and smaller larvae. Before submerging, the ants will tip themselves into the water and sever connections with the dry land. In some cases, workers may deliberately remove all males from the raft, resulting in the males drowning. The longevity of a raft can be as long as 12 days. Ants that are trapped underwater escape by lifting themselves to the surface using bubbles which are collected from submerged substrate. Owing to their greater vulnerability to predators, red imported fire ants are significantly more aggressive when rafting. Workers tend to deliver higher doses of venom, which reduces the threat of other animals attacking. Due to this, and because a higher workforce of ants is available, rafts are potentially dangerous to those that encounter them. Necrophoric behaviour occurs in the red imported fire ant. Workers discard uneaten food and other such wastes away from the nest. The active component was not identified, but the fatty acids accumulating as a result of decomposition were implicated and bits of paper coated with synthetic oleic acid typically elicited a necrophoric response. The process behind this behaviour in imported red fire ants was confirmed by Blum (1970): unsaturated fats, such as oleic acid, elicit corpse-removal behaviour. Workers also show differentiated responses towards dead workers and pupae. Dead workers are usually taken away from the nest, whereas the pupae may take a day for a necrophoric response to occur. Pupae infected by Metarhizium anisopliae are usually discarded by workers at a higher rate: while 47.5% of unaffected corpses are discarded within a day, for affected corpses this figure is 73.8%. Red imported fire ants have negative impacts on seed germination. The extent of the damage, however, depends on how long seeds are vulnerable for (dry and germinating) and by the abundance of the ants. One study showed that while these ants are attracted to and remove seeds which have adapted for ant dispersal, red imported fire ants damage these seeds or move them in unfavourable locations for germination. In seeds given to colonies, 80% of Sanguinaria canadensis seeds were scarified and 86% of Viola rotundifolia seeds were destroyed. Small percentages of longleaf pine (Pinus palustris) seeds deposited by workers successfully germinate, thus providing evidence that red imported fire ants help the movement of seeds in the longleaf pine ecosystem. Elaiosome-bearing seeds are collected at a higher rate in contrast to nonelaiosome-bearing seeds and do not store them in their nests, but rather in surface trash piles in the mound vicinity. Foraging and communication (Helianthus annuus) Colonies of the red imported fire ant have tunneling surfaces that protrude out of the surfaces where workers forage. These areas of protrusion tend to be within their own territory, but greater ant colonisation can affect this. Tunnels are designed to allow effective body, limb and antennae interactions with walls, and a worker can also move exceptionally fast inside them (more than nine bodylengths per second). The holes exit out of any point within the colony's territory, and foraging workers may need to travel half a metre to reach the surface. Assuming the average forager travels 5 m, over 90% of foraging time is inside the tunnels during the day and rarely at night. Workers forage in soil temperatures reaching and surface temperatures of . Workers exposed to temperatures of are at risk of dying from the heat. The rate of workers foraging drops rapidly by autumn, and they rarely emerge during winter. This may be due to the effects of soil temperature, and a decreased preference for food sources. These preferences only decrease when brood production is low. In the northern regions of the United States, areas are too cold for the ant to forage, but in other areas such as Florida and Texas, foraging may occur all year round. When it is raining, workers do not forage outside, as exit holes are temporarily blocked, pheromone trails are washed away, and foragers may be physically struck by the rain. The soil's moisture may also affect the foraging behaviour of workers. Foraging workers become scouts and search solely for food outside the surface, and may subsequently die two weeks later from old age. Workers communicate by a series of semiochemicals and pheromones. These communication methods are used in a variety of activities, such as nestmate recruitment, foraging, attraction, and defence; for example, a worker may secrete trail pheromones if a food source it discovered is too large to carry. These pheromones are synthesized by the Dufour's gland and may trail from the discovered food source back to the nest. The components in these trail pheromones are also species-specific to this ant only, in contrast to other ants with common tail pheromones. The poison sack in this species has been identified as being the novel storage site of the queen pheromone; this pheromone is known to elicit orientation in worker individuals, resulting in the deposition of brood. Red imported fire ants can distinguish nestmates and non-nestmates through chemical communication and specific colony odours. Workers prefer to dig into nest materials from their own colony and not from soil in unnested areas or from other red imported fire ant colonies. One study suggests that as a colony's diet is similar, the only difference between nested and unnested soil was the nesting of the ants themselves. Therefore, workers may transfer colony odour within the soil. Queen-derived cues are able to regulate nestmate recognition in workers and amine levels. However, these cues do not play a major role in colony-level recognition, but they can serve as a form of caste-recognition within nests. Workers living in monogyne societies tend to be extremely aggressive and attack intruders from neighbouring nests. In queenless colonies, the addition of alien queens or workers does not increase aggression among the population. Diet Red imported fire ants are omnivores, and foragers are considered to be scavengers rather than predators. The ants' diet consists of dead mammals, arthropods, insects, earthworms, vertebrates, and solid food matter such as seeds. However, this species prefers liquid over solid food. The liquid food the ants collect is sweet substances from plants or honeydew-producing hemipterans. Arthropod prey may include dipteran adults, larvae and pupae, and termites. The consumption of sugar amino acid is known to affect recruitment of workers to plant nectars. Mimic plants with sugar rarely have workers to feed on them, whereas those with sugar and amino acids have considerable numbers. The habitats where they live may determine the food they collect the most; for example, forage success rates for solid foods are highest in lakeshore sites, while high levels of liquid sources were collected from pasture sites. Specific diets can also alter the growth of a colony, with laboratory colonies showing high growth if fed honey-water. Colonies that feed on insects and sugar-water can grow exceptionally large in a short period of time, whereas those that do not feed on sugar-water grow substantially slower. Colonies that do not feed on insects cease brood production entirely. Food distribution plays an important role in a colony. This behaviour varies in colonies, with small workers receiving more food than larger workers if a small colony is seriously deprived of food. In larger colonies, however, the larger workers receive more food. Workers can donate sugar water efficiently to other nestmates, with some acting as donors. These "donors" distribute their food sources to recipients, which may also act as donors. Workers may also share a greater portion of their food with other nestmates. In colonies that are not going through starvation, food is still distributed among the workers and larvae. One study shows that honey and soybean oil were fed to the larvae after 12 to 24 hours of being retained by the workers. The ratio distribution of these food sources was 40% towards the larvae and 60% towards the worker for honey, and for soybean oil this figure was around 30 and 70%, respectively. Red imported fire ants also stockpile specific food sources such as insect pieces rather than consuming them immediately. These pieces are usually transported below the mound surface and in the driest and warmest locations. This species engages in trophallaxis with the larvae. Regardless of the attributes and conditions of each larva, they are fed roughly the same amount of liquid food. The rate of trophallaxis may increase with larval food deprivation, but such increase depends on the size of each larva. Larvae that are fed regularly tend to be given small amounts. To reach satiation, all larvae regardless of their size generally require the equivalent of eight hours of feeding. Predators A number of insects, arachnids, and birds prey on these ants, especially when queens are trying to establish a new colony. While in the absence of defending workers, the fire ant queens must rely on their venom to keep off competitor species. Other invertebrates that prey on red imported fire ants are earwigs (Labidura riparia) and tiger beetles (Cicindela punctulata). Many species of ants have been observed attacking queens and killing them. Apparently, the venom of fire ant queens is chemically adapted to rapidly subdue offending competitor ants. C. insana ants are known to be effective predators against founding queens in studied areas of Northern Florida. The pressure of attacks initiated by C. insana increase over time, causing queens to exhibit different reactions, including escaping, concealment, or defence. Most queens that are attacked by these ants are ultimately killed. Ants can attack queens on the ground and invade nests by stinging and dismembering them. Other ants such as P. porcula try to take the head and gaster, and C. clara invade in groups. Also, certain ants try to drag queens out of their nests by pulling on the antennae or legs. Small, monomorphic ants rely on recruitment to kill queens and do not attack them until reinforcements arrive. Aside from killing the queen, some ants may steal the eggs for consumption or emit a repellent that is effective against red imported fire ants. Parasites, pathogens and viruses Flies in the genus Pseudacteon (phorid flies) are known to be parasitic to ants. Some species within this genus, such as Pseudacteon tricuspis, have been introduced into the environment for the purpose of controlling the imported fire ant. These flies are parasitoids of the red imported fire ant in its native range in South America, and can be attracted through the ants' venom alkaloids. One species, Pseudacteon obtusus, attacks the ant by landing on the posterior portion of the head and laying an egg. The location of the egg makes it impossible for the ant to successfully remove it. The larvae migrate 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 head to its body. The fly pupates in the detached head capsule, emerging two weeks later. P. tricuspis is another phorid fly that is a parasitoid to this species. Although parasitism pressures by these flies do not affect the ants' population density and activity, it has a small effect on a colony population. The strepsipteran insect Caenocholax fenyesi is known to infect male ants of this species and attack the eggs, and the mite Pyemotes tritici has been considered a potential biological agent against red imported fire ants, capable of parasitising every caste within the colony. Bacteria, such as Wolbachia, has been found in the red imported fire ant; three different variants of the bacteria are known to infect the red imported fire ant. However, its effect on the ant is unknown. Solenopsis daguerrei is a reproductive parasite to red imported fire ant colonies. A large variety of pathogens and nematodes also infect red imported fire ants. Pathogens include Myrmecomyces annellisae, Mattesia spp., Steinernema spp., a mermithid nematode, Vairimorpha invictae, which can be transmitted via live larvae and pupae and dead adults and Tetradonema solenopsis, which can be fatal to a large portion of a colony. Individuals infected by Metarhizium anisopliae tend to perform trophallaxis more frequently and have an enhanced preference to quinine, an alkaloid substance. Phorid flies with Kneallhazia solenopsae can serve as vectors in transmitting the disease to the ants. Weakening the colony, infections from this disease are localised within the body fat, with spores only occurring in adult individuals. The mortality of an infected colony tends to be greater in contrast to those that are healthy. The toxicity from antimicrobial property of volatiles produced by the ants can significantly reduce the germination rate of B. bassiana within the colony. A virus, S. invicta 1 (SINV-1), has been found in about 20% of fire ant fields, where it appears to cause the slow death of infected colonies. It has proven to be self-sustaining and transmissible. Once introduced, it can eliminate a colony within three months. Researchers believe the virus has potential as a viable biopesticide to control fire ants. Two more viruses have also been discovered: S. invicta 2 (SINV-2) and S. invicta 3 (SINV-3). Polygynous colonies tend to face greater infections in contrast to monogynous colonies. Multiple virus infections can also occur. Lifecycle and reproduction Nuptial flight in red imported fire ants begins during the warmer seasons of the year (spring and summer), usually two days after rain. The time alates emerge and mate is between noon and 3:00pm. Nuptial flights recorded in North Florida have, on average, 690 female and male alates participating in a single flight. Males are the first to leave the nest, and both sexes readily undertake flight with little to no preflight activity. However, workers swarm the mound excitedly stimulated by mandibular glands within the head of the alates. As mounds do not have holes, workers form holes during nuptial flight as a way for the alates to emerge. This behaviour in workers, elicited by the pheromones, includes rapid running and back-and-forth movements, and increased aggression. Workers also cluster themselves around the alates as they climb up on vegetation, and in some cases, attempt to pull them back down before they take flight. Chemical cues from males and females during nuptial flight attract workers, but chemical cues released by workers do not attract other nestmates. It also induces alarm-recruitment behaviour in workers which results in a higher rate of alate retrieval. Males fly at higher elevations than females: captured males are usually above the surface, whereas the females are only above the surface. A nuptial flight takes place for roughly half an hour and females generally fly for less than before landing. About 95% of queens successfully mate and only mate once; some males may be infertile due to the testicular lobes failing to develop. In polygyne colonies, males do not play a significant role and most are, therefore, sterile; one of the reasons for this is to avoid mating with other ant species. This also makes male mortality selective, which may affect the breeding system, mating success and, gene flow. Ideal conditions for a nuptial flight to begin is when humidity levels are above 80% and when the soil temperature is above . Nuptial flights only occur when the ambient temperature is . Queens are often found 1–2.3 miles from the nest they flew from. Colony founding can be done by an individual or in groups, known as pleometrosis. This joint effort of the co-foundresses contributes to the growth and survival of the incipient colony; nests founded by multiple queens begin the growth period with three times as many workers when compared to colonies founded by a single queen. Despite this, such associations are not always stable. The emergence of the first workers instigates queen-queen and queen-worker fighting. In pleometrotic conditions, only one queen emerges victorious, whereas the queens that lost are subsequently killed by the workers. The two factors that could affect the survival of individual queens are their relative fighting capabilities and their relative contribution to worker production. Size, an indicator of fighting capacity, positively correlates with survival rates. However, manipulation of the queen's relative contribution to worker production had no correlation with survival rate. A single queen lays around 10 to 15 eggs 24 hours after mating. A colony can grow exceptionally fast. Colonies that housed 15–20 workers in May grew to over 7,000 by September. These colonies started to produce reproductive ants when they were a year old, and by the time they were two years old, they had over 25,000 workers. The population doubled to 50,000 when these colonies were three years old. At maturity, a colony can house 100,000 to 250,000 individuals, but other reports suggest that colonies can hold more than 400,000. Polygyne colonies have the potential to grow much larger than monogyne colonies. Several factors contribute to colony growth. Temperature plays a major role in colony growth and development; colony growth ceases below 24 °C and developmental time decreases from 55 days at temperatures of 24 °C to 23 days at 35 °C. Growth in established colonies only occurs at temperatures between 24 and 36 °C. Nanitic brood also develops far quicker than minor worker brood (around 35% faster), which is beneficial for founding colonies. Colonies that have access to an unlimited amount of insect prey are known to grow substantially, but this growth is further accelerated if they are able to access plant resources colonised by hemipteran insects. In incipient monogyne colonies where diploid males are produced, colony mortality rates are significantly high and colony growth is slow. In some cases, monogyne colonies experience 100% mortality rates in the early stages of development. The life expectancy of a worker ant depends on its size, although the overall average is around 62 days. Minor workers are expected to live for about 30 to 60 days, whereas the larger workers live much longer. Larger workers, which have a life expectancy of 60 to 180 days, live 50–140% longer than their smaller counterparts, but this depends on the temperature. However, workers kept in laboratory conditions have been known to live for 10 to 70 weeks (70 days to 490 days); the maximum recorded longevity of a worker is 97 weeks (or 679 days). The queens live much longer than the workers, with a lifespan ranging from two years to nearly seven years. Queens also exert control over the production of sexuals through pheromones that influence the behaviours of workers toward both male and female larvae. Monogyny and polygyny There are two forms of society in the red imported fire ant: polygynous colonies and monogynous colonies. Polygynous colonies differ substantially from monogynous colonies in social insects. The former experience reductions in queen fecundity, dispersal, longevity, and nestmate relatedness. Polygynous queens are also less physogastric than monogynous queens and workers are smaller. Understanding the mechanisms behind queen recruitment is integral to understanding how these differences in fitness are formed. It is unusual that the number of older queens in a colony does not influence new queen recruitment. Levels of queen pheromone, which appears to be related to queen number, play important roles in the regulation of reproduction. It would follow that workers would reject new queens when exposed to large quantities of this queen pheromone. Moreover, evidence supports the claim that queens in both populations enter nests at random, without any regard for the number of older queens present. There is no correlation between the number of older queens and the number of newly recruited queens. Three hypotheses have been posited to explain the acceptance of multiple queens into established colonies: mutualism, kin selection, and parasitism. The mutualism hypothesis states that cooperation leads to an increase in the personal fitness of older queens. However, this hypothesis is not consistent with the fact that increasing queen number decreases both queen production and queen longevity. Kin selection also seems unlikely given that queens have been observed to cooperate under circumstances where they are statistically unrelated. Therefore, queens experience no gain in personal fitness by allowing new queens into the colony. Parasitism of preexisting nests appears to be the best explanation of polygyny. One theory is that so many queens attempt to enter the colony that the workers get confused and inadvertently allow several queens to join it. Monogyne workers kill foreign queens and aggressively defend their territory. However, not all behaviours are universal, primarily because worker behaviours depend on the ecological context in which they develop, and the manipulation of worker genotypes can elicit change in behaviours. Therefore, behaviours of native populations can differ from those of introduced populations. In a study to assess the aggressive behaviour of monogyne and polygyne red fire ant workers by studying interaction in neutral arenas, and to develop a reliable ethogram for readily distinguishing between monogyne and polygyne colonies of red imported fire ants in the field, monogyne and polygyne workers discriminated between nestmates and foreigners as indicated by different behaviours ranging from tolerance to aggression. Monogyne ants always attacked foreign ants independently if they were from monogyne or polygyne colonies, whereas polygyne ants recognised, but did not attack, foreign polygyne ants, mainly by exhibiting postures similar to behaviours assumed after attacks by Pseudacteon phorids. Hostile versus warning behaviours were strongly dependent on the social structure of workers. Therefore, the behaviour toward foreign workers was a method of characterising monogyne and polygyne colonies. Most colonies in the southeastern and south-central US tend to be monogynous. The monogynous red imported fire ant colony territorial area and the mound size are positively correlated, which, in turn, is regulated by the colony size (number and biomass of workers), distance from neighbouring colonies, prey density, and by the colony's collective competitive ability. In contrast, nestmate discrimination among polygynous colonies is more relaxed as workers tolerate conspecific ants alien to the colony, accept other heterozygote queens, and do not aggressively protect their territory from polygyne conspecifics. These colonies might increase their reproductive output as a result of having many queens and the possibility of exploiting greater territories by means of cooperative recruitment and interconnected mounds. A social chromosome is present in the red imported fire ant. This chromosome can differentiate the social organisation of a colony carrying one of two variants of a supergene (B and b) which contains more than 600 genes. The social chromosome has often been compared to sexual chromosomes because they share similar genetic features and they define colony phenotype in a similar way. For example, colonies exclusively carrying the B variant of this chromosome accept single BB queens, but colonies with both B and b variants will accept multiple Bb queens only. Differences in another single gene can also determine whether the colony will have single or multiple queens. Relationship with other animals Competition When polygyne forms invade areas where colonies have not yet been established, the diversity of native arthropods and vertebrates declines greatly. This is evident as populations of isopods, mites and tumblebug scarabs decline significantly. They can also significantly alter the populations of many fly and beetle families, including: Calliphoridae, Histeridae, Muscidae, Sarcophagidae, Silphidae, and Staphylinidae. Despite this, one review found that certain insects may be unaffected by red imported fire ants; for example, the density of isopods decreases in red imported fire ant infested areas, but crickets of the genus Gryllus are unaffected. There are some cases where the diversity of certain insect and arthropod species increase in areas where red imported fire ants are present. Red imported fire ants are important predators on cave invertebrates, some of which are endangered species. This includes harvestmen, pseudoscorpions, spiders, ground beetles, and pselaphid beetles. The biggest concern is not the ant itself, but the bait used to treat them because this can prove fatal. Stock Island tree snails (Orthalicus reses) are extinct in the wild; predation by red imported fire ants is believed to be the major factor in the snail's extinction. Arthropod biodiversity increases once red imported fire ant populations are either reduced or eradicated. Interactions between red imported fire ants and mammals have been rarely documented. However, deaths of live-trapped animals by red imported fire ants have been observed. Mortality rates in eastern cottontail (Sylvilagus floridanus) young range from 33 to 75% because of red imported fire ants. It is believed that red imported fire ants have a strong impact on many herpetofauna species; scientists have noted population declines in the Florida kingsnake (Lampropeltis getula floridana), and eggs and adults of the eastern fence lizard (Sceloporus undulatus) and six-lined racerunner (Aspidoscelis sexlineata) are a source of food. Because of this, eastern fence lizards have adapted to have longer legs and new behaviours to escape the red imported fire ant. Additionally, another lizard species, Sphaerodactylus macrolepis are also a target of the fire ants' and have developed tactics to fend them off, such as tail flicks. Adult three-toed box turtles (Terrapene carolina triunguis), Houston toad (Anaxyrus houstonensis) juveniles, and American alligator (Alligator mississippiensis) hatchlings are also attacked and killed by these ants. Despite this mostly-negative association, one study shows that red imported fire ants may be capable of impacting vector-borne disease transmissions by regulating tick populations and altering vector and host dynamics, thereby reducing transmission rates not only to animals, but to humans as well. Mortality rates have been well observed in birds; there have been instances where no young have survived to adulthood in areas with high fire ant density. Many birds including cliff nesting swallows, ducks, egrets, quail, and terns have been affected by red imported fire ants. Ground nesting birds, particularly the least tern (Sterna antillarum), are vulnerable to fire ant attacks. The impact of red imported fire ants on colonial breeding birds is especially severe; waterbirds can experience a mortality rate of 100%, although this factor was lower for early-nesting birds. Brood survival decreases in American cliff swallows (Petrochelidon pyrrhonota) if they are exposed to foraging workers. Songbird nest survival decreases in areas with red imported fire ants present, but survival rates in white-eyed vireo (Vireo griseus) and black-capped vireo (Vireo atricapilla) nests increase from 10% to 31% and 7% to 13% whenever fire ants are not present or when they are unable to attack them. Red imported fire ants may indirectly contribute to low brood survival in the Attwater's prairie chicken. It was first thought that the ants were linked to the decline of overwintering birds such as the loggerhead shrike (Lanius ludovicianus), but a later study showed that ant eradication efforts using the pesticide Mirex, which was known to have toxic side effects, was largely to blame. Red imported fire ants are strong competitors with many ant species. They have managed to displace many native ants which has led to a number of ecological consequences. However, studies show that these ants are not always superior competitors that suppress native ants. Habitat disturbance prior to their arrival, and recruitment limitations, are more plausible reasons why native ants are suppressed. Between Tapinoma melanocephalum and Pheidole fervida, the red imported fire ant is stronger than both species but shows different levels of aggression. For example, they are less hostile towards T. melanocephalum in contrast to P. fervida. Mortality rates in T. melanocephalum and P. fervida when fighting with red imported fire ants are high, being 31.8% and 49.9% respectively. The mortality rate for red imported fire ant workers, however, is only 0.2% to 12%. The imported crazy ant (Nylanderia fulva) exhibits greater dominance than the red imported fire ant and has been known to displace them in habitats where they encounter each other in. Larger colonies of pavement ants (Tetramorium caespitum) can destroy red imported fire ant colonies, leading entomologists to conclude that this conflict between the two species may help impede the spread of the red imported fire ant. Individuals infected by SINV-1 can be killed faster than healthy individuals by Monomorium chinense. This means that ants infected with SINV-1 are weaker than their healthy counterparts and more than likely will be eliminated by M. chinense. However, major workers, whether they are infected or not, are rarely killed. In areas it is native to, the red imported fire ant is still a dominant species and coexists with 28 ant species in gallery forest gaps and ten species in xerophytic forest grassland, winning most aggressive interactions with other ants. However, some ants can be co-dominant in areas where they coexist such as the Argentine ant, where they compete symmetrically. Workers regularly engage in food competition with other ants, and can suppress the exploitation of food resources from honeydew-producing hemipterans (specifically from Phenacoccus solenopsis) from native ants; however, red imported fire ants are unable to eliminate T. melanocephalum completely although they consume a higher proportion of food. Instead, the two ants may peacefully coexist and share the honeydew. When encountering neighboring fire ants, workers may take on death-feigning behaviours to avoid them with success. However, such behaviour is only seen in young workers, as older workers either flee or fight back when threatened. As mentioned, red imported fire ants and Argentine ants compete with each other. Mortality rates vary in different scenarios (i.e. mortality rates in colony confrontation is lower than those confronting each other in the field). Major workers can also withstand more injuries to their bodies, thus increasing the mortality rate of Argentine ants. For an Argentine ant colony to successfully wipe out a monogyne colony of 160,000 workers, the colony would need 396,800 workers. A colony that has reduced in size due to successful bait treatment are prone to predation by Argentine ants. The ants may play a vital role in removing weakened fire ant colonies, and they may also be important in slowing the spread of these fire ants, especially in heavily infested Argentine ant areas. Despite this, Argentine ant populations in the southeastern United States have declined following the introduction of the red imported fire ant. Red imported fire ants may reduce butterfly numbers due to eggs and caterpillar predation and have been linked to butterfly species declines including Schaus swallowtails (Papilio aristodemus). Mutualism with each other Red imported fire ants have formed a relationship with an invasive mealybug, Phenacoccus solenopsis. Colony growth is known to increase if ants have access to resources produced by P. solenopsis, and the population density of these mealybugs is significantly higher in areas where red imported fire ants are present (the spread of P. solenopsis in areas it is not native is attributed to the presence of the ants). As well as that, the life expectancy and reproductive rate of P. solenopsis both increase. These mealybugs may even be transported by workers back to their nest. Predation of P. solenopsis decreases due to tending workers interfering with the predation and parasitism by natural enemies. Mealybugs are preyed on by the lady beetle (Menochilus sexmaculatus) and are hosts of two parasites (Aenasius bambawalei and ) if there are no ants present, but this is different if ants are present. Lady beetles are less frequently seen on plants with red imported fire ants, and the rate of "mummy" nymphs is significantly lower. This is clearly evident as scientists observed that cotton aphid (Aphis gossypii) populations, and the predation of sentinel bollworm eggs, increased in areas with red imported fire ant presence. Red imported fire ants have developed a mutual relationship with another mealybug (Dysmicoccus morrisoni). The ants promote the colony growth of D. morrisoni through protection, covering the colonies up with debris and collecting the honeydew they secrete. ==Toxicology==

The toxicology of red imported fire ant venom has been relatively well studied. The venom is important to the ant, enabling it to capture its prey and to defend itself. Some 14 million people are stung annually in the United States, who may suffer reactions ranging from mild eczema to anaphylactic shock. Most common reactions to fire ant stings are a burning sensation at the sting site, followed by urticaria and pustule formation. Some victims may develop a more serious allergic reaction which can be life-threatening. The venom is mainly composed of insoluble alkaloids with a minor watery phase containing some 46 proteins of which four are reported as allergens. Effective immunotherapy is available. ==Relationship with humans==

As pests Because of their notoriety and invasive behavior, red imported fire ants are considered pests. In the United States, the Food and Drug Administration estimates more than $5 billion is spent annually on medical treatment, damage, and control in infested areas. In Texas alone, red imported fire ants caused $300 million in damages for livestock, wildlife and public health. Approximately $36 per American household, and more than $250 million has been spent to control and eradicate red imported fire ants. Private agencies spend $25 to $40 million on pesticides annually. Red imported fire ants thrive in urban areas, especially in backyards, golf courses, parks, recreational areas, school grounds, and street verges, in which their presence may deter outdoor activities. If they enter homes or properties, they can harm pets if they are caged, penned, tied or cannot escape. Additional damage by mounds can be inflicted on trees, yard plants, and pipes; some structures may also collapse. Colonies may migrate into human homes after heavy rain to take refuge from saturated soil. As a result, red imported fire ants can destroy electrical equipment. This is known as magnetism, where scientists have identified internal magnetic materials which may play a role in orientation behaviors. They are known to chew through electrical insulation which causes damage to electric motors, irrigation lines, pumps, signal boxes, transformers, telephone exchanges, and other equipment. Colonies aggregate near electrical fields and are capable of causing short circuits or interfering with switches and equipment such as air conditioners, computers, and water pumps. They are also known to infest airport landing areas and traffic lights. In agriculture The red imported fire ant is a significant agricultural pest in areas where it is not native. They are capable of damaging crops, and they threaten pastures and orchards. The mounds themselves can destroy agricultural equipment such as irrigation systems and damage machinery during harvest time. The ants are known to invade soybean crops causing lower yields, and could cause $156 million in losses for soybean crops in the southeastern United States. Reports from Georgia and North Carolina claim that 16.8 to 49.1 kg/ha of soybeans could not be harvested due to interference from fire ant mounds; combine harvesters skipped over the mounds preventing the crops from being harvested, and farmers raised the cutter bars on their combine harvesters to avoid impacting the mounds. The feeding behaviour of red imported fire ants can result in significant damage to many other crops, including: beans, cabbage, citrus, corn, cucumber, eggplant, okra, peanut, potato, sorghum, sunflower, and sweet potato. The ants also interfere with plants' root systems and feed on young growth. Despite its pest status and notoriety, the red imported fire ant can be beneficial. The ant is an effective insect predator, so it may serve as a biological agent against other pest species, especially in sugarcane fields. Pest insects the ant kills include: boll weevils (Anthonomus grandis) in cotton crops, sugarcane borers (Diatraea saccharalis) in sugarcane fields, horn flies (Haematobia irritans) in manure, velvetbean caterpillars (Anticarsia gemmatalis) in soybeans, and whiteflies that are found in greenhouses. A number of studies indicate that red imported fire ants do not interfere or attack insects of economic importance in cotton fields, which has resulted in many farmers in the southeastern regions of the United States viewing red imported fire ants as beneficial. However, some scientists have suggested that the beneficial status of the red imported fire ant is hard to predict when geography, plant size, season, soil moisture and the use of insecticides are not considered. These factors may lower the efficacy of red imported fire ants as pest control agents. Another factor is that workers are indiscriminate and kill beneficial insects such as predators that eat horn flies and other pests in pastures and predators of aphids and scale insects. They also reduce the efficacy of parasitic wasps against pest species by eating the larvae and pupae. Control In comparison to other ant species like Anoplolepis gracilipes, which rapidly take over areas they have been contained in, red imported fire ants are fairly easy to control. The first proposals to controlling the ant occurred in 1957 when the United States Congress authorised an eradication program using federal and state funding. Research on the ant and its biology has been continuous after the establishment of an eradication program, and many chemicals were used to eliminate them. However, scientists discovered that these insecticides were killing native fauna, and the Environmental Protection Agency subsequently outlawed them. Some scientists even questioned whether the ants were pests or not. Today, it is unlikely that the red imported fire ant will be eradicated in areas such as the United States. Populations can be managed properly if an integrated approach is used. Some scientists have considered using the ants' natural enemies against it; this includes Kneallhazia solenopsae and B. bassiana. Phorid flies have also been viewed as potential biological agents, as they can reduce foraging activity in red imported fire ants and affect population levels. However, they are unable to affect colony growth rate. In addition, parasitic ants, parasitic wasps, mites, other pathogens, nematodes, and fungi have been considered to be potential biological agents. Others suggest that populations can be maintained or reduced by manipulating several ecological factors. Several baits have been used to control populations. Mounds are destroyed in a matter of weeks if baits are used on them. Baits are considered to be effective and simple to use against red imported fire ants, in comparison to drenching, dusting, or fumigating. They are sprinkled onto the mound then the ants take and consume them. Certain baits such as growth regulator baits, and boric acid-sucrose water baits, benefit native fauna and low concentrations are usually required to kill a colony. Others baits used against red imported fire ants include Amdro, Ascend, hydramethylnon, indoxacarb, and Maxforce. Solid and liquid bait insecticides, if improperly applied in a location, may be moved through waterflow in to waterways. As snow melts and rainfall moves over and through the ground, the water picks up improperly applied insecticides and deposits them in to larger bodies of water such as rivers and wetlands, or percolates in to watersheds. Researchers have also been experimenting with other methods, such as fumigation, injecting the mound, mound drenching, and surface dusting. Mound drenching entails pouring large volumes of toxic liquid into the mound. While this may affect a large portion of the mound, it is possible it may not reach the queen, thus preventing the destruction of the colony. Surface dusting is similar to mound drenching, except insecticides are applied on top of the mound and soak into the soil when wet. Mound injections use pressurising and injecting insecticides into the mound, but the queen may not be affected by this. Mounds can be eliminated effectively through fumigation. Broadcast treatment is sometimes used by spraying infected areas with agricultural equipment. Finally, spot treatment with insecticides can be used by drilling and injecting the mound with residual insecticide. Aside from chemical control, other methods that can be employed against these ants include mechanical and electrical devices. However, it is unknown whether or not these devices are effective. Ant-proofing can be effective against colonies nesting inside buildings by caulking and sealing cracks, which successfully suppresses the population outside the walls. Homeowners have used their own methods to remove mounds by pouring boiling water on them or igniting them with flammable liquids. Although these methods may be effective, they are not recommended because they can be harmful to humans and the environment. ==Notes==