The red imported fire ant (Solenopsis invicta), or simply RIFA, is one of over 280 species in the widespread genus Solenopsis . It is native to South America but it has become both a pest and a health hazard in the southern United States as well as a number of other countries.
In the 1930s, colonies were accidentally introduced into the United States through the seaport of Mobile, Alabama. Despite earlier views that cargo ships from Brazil docking at Mobile unloaded goods infested with the ants, [1] recent DNA research confirmed that the likely source population for all invasive S. invicta in the United States occurred at or near Formosa, Argentina, and virtually every analysis ruled out all sampled Brazilian populations as a potential source. [2] Biologist E.O. Wilson says that he reported the first colony, in the Mobile area, when he was 13. [3] The ants then spread from Alabama to almost every state of the American South, from Texas to Maryland and a few other Mid-Atlantic states. Since the 1990s infestations have been reported in New Mexico and parts of Arizona in the Southwest. They have also been reported in California in the West, but probably arrived via ship or truck rather than by spreading. [4] In a similar way, the ants were accidentally introduced into Australia in 2001. [5]
In the United States, RIFAs have gradually spread north and west despite intense efforts to stop or eliminate them. As of 2011 [update] in the United States they were found in most of the southern states: Alabama, Arkansas, Arizona, California, Delaware, Florida, Georgia, Kentucky, Louisiana, Mississippi, North Carolina, New Mexico, Oklahoma, South Carolina, Tennessee, Texas, and Virginia. Likely due to absence of South American competitors - and lower numbers of native competitors - S. invicta dominates more extrafloral nectaries and hemipteran honeydew sources in the southern U.S. than in its home range, probably contributing to its higher population densities in its invasive range. [6] The U.S. Department of Agriculture also lists the entire island of Puerto Rico as infested. [7]
RIFAs were still on the move in the U.S. in the early 21st century, often traveling from one area to another in turf, root balls of nursery plants, and other agricultural products. They could be controlled, but not eradicated. A number of products are available, which can be used on a mound-by-mound basis to destroy ant colonies when they appear. With all such efforts, it is important to reach and kill the queens, which may be as far as six feet (2 m) underground; otherwise, some queens may simply move a short distance away and quickly re-establish the colony. However, during the past few years, even this technique resulted in failure to control colony growth. Scientists then discovered that an adaptation in RIFAs had resulted in many populations having multiple queens in mounds over a large area. [4]
In areas where Solenopsis invicta (red imported fire ants) founded colonies, larger colonies of Tetramorium caespitum (pavement ants) have destroyed them, leading entomologists to conclude that this conflict between the two species would decelerate the northward spread of Solenopsis invicta. [8] [9]
The RIFA's introduction to the United States was in the late 1930s. Traveling in soil used as ballast on cargo ships, [10] they came in through the seaport of Mobile, Alabama. They build mounds, usually no larger than 46 cm (18 in) in diameter and 46 cm (18 in) in height, although in Alabama some mounds have been reported to be over 60 cm (24 in) high and larger, especially in fields where cattle graze. They build on soil close to homes and other buildings, and sometimes forage indoors for food and moisture. They are a nuisance, and can threaten sleeping or bedridden individuals and pets. Occasionally, they feed on vegetable plants in home gardens. The worst damage usually occurs during hot, dry weather, when they invade flower beds while seeking warmth and moisture. If disturbed, fire ants bite and sting the intruder.
They are apparently attracted to electrical equipment, and crawl into air conditioning units and the electrical wiring of stop lights, shorting them out. This is the leading cause of traffic light shorts in Texas, where the ants cause more than US$140 million in damage each year[ citation needed ]. Several ant species, including fire ants, have been shown to contain ferromagnetic nanoparticles that may contribute information about the geomagnetic field for orientation during foraging or migration. [11] However, it has not been found that electric or magnetic fields attract the ants. [12] Rather, when wandering ants cause electrical shorts, they attempt to sting the wire and produce powerful semiochemicals, including defensive and recruitment pheromones. [13] The chemical signals draw additional ants to the short. The only effective protection is to bar ants from the equipment physically or with insecticides.
The FDA estimates more than US$5 billion is spent annually on medical treatment, damage, and control in RIFA-infested areas. Further, the ants cause approximately US$750 million in damage to agricultural assets, including veterinary bills and livestock loss, as well as crop loss. [14] It has been proposed that modern insecticides are not effective in large-scale control of fire ants; therefore, a number of new strategies are proposed. [15] These include the use of entomopathogenic fungi [16] [17] and even specific viruses. [18]
Most ants are capable of biting, stinging, and spraying irritant chemicals. However, only relatively few species can harm humans; among which some can cause significant injury or, in rare cases, death. Like wasps, individual ants are capable of stinging multiple times as they do not lose their stingers.
The yellow crazy ant, also known as the long-legged ant or Maldive ant, is a species of ant, thought to be native to West Africa or Asia. They have been accidentally introduced to numerous places in the world's tropics.
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.
The red imported fire ant, also known as the fire ant or RIFA, is a species of ant native to South America. A member of the genus Solenopsis in the subfamily Myrmicinae, it was described by Swiss entomologist Felix Santschi as a variant of S. saevissima in 1916. Its current specific name invicta was given to the ant in 1972 as a separate species. However, the variant and species were the same ant, and the name was preserved due to its wide use. Though South American in origin, the red imported fire ant has been accidentally introduced in Australia, New Zealand, several Asian and Caribbean countries, Europe and the United States. The red imported fire ant is polymorphic, as workers appear in different shapes and sizes. The ant's colours are red and somewhat yellowish with a brown or black gaster, but males are completely black. Red imported fire ants are dominant in altered areas and live in a wide variety of habitats. They can be found in rain forests, disturbed areas, deserts, grasslands, alongside roads and buildings, and in electrical equipment. Colonies form large mounds constructed from soil with no visible entrances because foraging tunnels are built and workers emerge far away from the nest.
The black imported fire ant, or simply BIFA, is a species of ant in the genus Solenopsis. It was long thought to either be a subspecies or a color variation of Solenopsis invicta, but is now recognized as its own species with a demonstratively different range and living habits. BIFA seem to be more tolerant of cold and a less dominant species than RIFA. Due to the BIFA higher body content of water than the RIFA conclusions demonstrate the certain factor plays a role in their differences of living regions.
Metarhizium robertsii – formerly known as M. anisopliae, and even earlier as Entomophthora anisopliae (basionym) – is a fungus that grows naturally in soils throughout the world and causes disease in various insects by acting as a parasitoid. Ilya I. Mechnikov named it after the insect species from which it was originally isolated – the beetle Anisoplia austriaca. It is a mitosporic fungus with asexual reproduction, which was formerly classified in the form class Hyphomycetes of the phylum Deuteromycota.
Tetramorium immigrans—also known as the immigrant pavement ant, pavement ant, and the sugar ant in parts of North America—is an ant native to Europe, which also occurs as an introduced pest in North America. Its common name comes from the fact that colonies in North America usually make their nests under pavement. This is one of the most commonly seen ants in North America, being well adapted to urban and suburban habitats. It is distinguished by one pair of spines on the back, two nodes on the petiole, and grooves on the head and thorax.
Solenopsis daguerrei is a species of parasitic ants native to Argentina and Uruguay . The young queens of the species invade the nests of other species, such as the red imported fire ant (RIFA). This is made possible by the fact that the S. daguerrei queen produces pheromones which are very similar to those produced by the queens of the host species. The young queen finds a queen of the host species and latches onto it, eating the food intended for the host queen and slowly killing it. The S. daguerrei queen then begins laying eggs. These are taken care of by the host ants, sometimes preferentially to their own brood. S. daguerrei only produce winged virgin queens and males. No workers are needed, since these are provided by the host species. The winged ants fly off to mate and invade new colonies.
Solenopsis geminata or tropical fire ant is a species of fire ants, described by Fabricius in 1804, in the tribe Solenopsidini; it was originally placed in the Atta genus. This species has a pan-tropical distribution.
The tawny crazy ant or Rasberry crazy ant, Nylanderia fulva, is an ant originating in South America. Like the longhorn crazy ant, this species is called "crazy ant" because of its quick, unpredictable movements. It is sometimes called the "Rasberry crazy ant" in Texas after the exterminator Tom Rasberry, who noticed that the ants were increasing in numbers in 2002. Scientists have reorganised the genera taxonomy within this clade of ants, and now it is identified as Nylanderia fulva.
The Brackenridge Field Laboratory (BFL) is an urban research station owned by the University of Texas at Austin. Established officially in 1967, it contains 82 acres of land and research infrastructure. It is dedicated to studies in biology. The extensive historical data kept about its diverse habitats has been important to the study of biodiversity, ecological succession and ecology. Some of the key studies into the red imported fire ant and potential biocontrol agents such as phorid flies have originated at the field station. It also contains the second largest insect collection in Texas. Since 1973 the Brackenridge Field Laboratory has been a subject of controversy due to the high value of the land.
Solenopsis saevissima, commonly known in Brazil as formiga de fogo, formiga-vermelha, or formiga-lava-pes, is one of more than 185 species in the genus Solenopsis. It, along with 13 other species, is also a member of the Solenopsis saevissima species group which are popularly known as fire ants.
Kneallhazia solenopsae is a unique pathogenic intracellular microsporidium, that infects two of the fire ant species: the red Solenopsis invicta and the black Solenopsis richteri in North and South America.
Dorymyrmex bureni, also known as the pyramid ant, is a species of ant in the genus Dorymyrmex. Described by Trager in 1988, the species is endemic to the United States and Mexico. Pyramid ants are medium-sized ants, ranging from 2–4 mm. They are light orange in color and fast moving. Unlike other ants in the area like red imported fire ants, this species is not aggressive towards humans. The workers have a foul smelling coconut odor when crushed. Dorymyrmex bureni hunt living insects, even other winged ants. They also search for sap-sucking insects from which they collect honeydew. On the head of these ants are curved hairs, used for transporting beads of damp sand. Colonies are small. Nests usually have a single entrance with a mound of sand shaped like a crater. Dorymyrmex bureni prefer sandy soil. This species of ant is not an indoor pest, and pesticides should not be used. They are found throughout Florida.
The red imported fire ant is an invasive species in Australia originating from South America but imported to Australia, New Zealand, the United States of America and several Asian and Caribbean countries. Fire ants are listed by the International Union for Conservation of Nature (IUCN) as one of the world's most invasive species.
The toxicology of fire ant venom is relatively well studied. The venom plays a central role in the biology of Red imported fire ants, such as in capturing prey, and in defending itself from competitors, assailants, and diseases. Some 14 million people are stung annually in the United States, suffering reactions that vary from mild discomfort, to pustule formation, swelling, and in rare cases, systemic reactions followed by anaphylactic shock. Fire ant venoms are mainly composed (>95%) of a complex mixture of insoluble alkaloids added to a watery solution of toxic proteins. For the Red imported fire ant Solenopsis invicta Buren there are currently 46 described proteins, of which four are well-characterised as potent allergens.
Brachymyrmex patagonicus is a species of ant in the family Formicidae. B. patagonicus, commonly known as the dark rover ant, is native to Argentina and Paraguay. They were first reported in St. Tammany Parish, Louisiana in 1978 from a single colony collected in 1976. It is believed that the species was introduced through New Orleans, which is a common entry point for many tropical species, but other locations such as Mobile, Alabama, or Pensacola, Florida, are also likely. For many years B. patagonicus, B. musculus, and B. obscurior were misidentified as being separate species but after a comparison of specimens from the Louisiana State University Arthropod Collection (LSUC), it was found that all three were the same species. B. patagonicus is considered a nuisance pest due to their tendency to infest man made structures but they have received a lack of attention because they do not bite, sting, or carry disease.
Pseudacteon tricuspis is a parasitic phorid fly that decapitates its host, the imported Solenopsis invicta fire ant. There are over 70 described species within the Pseudacteon genus, which parasitize a variety of ant species. However, P. tricuspis is very specific to its host ant and will not attack other native ant species, making it a good biological control against the fire ant. P. tricuspis was also introduced into the United States for this purpose. Aside from the United States, P. tricuspis has also been found in South America, Europe, and Asia. Female P. tricuspis deposit their eggs directly into the fire ant host. Deposition into the ant host determines the sex of the egg, which grows within the host until adulthood, killing and decapitating the host in the process. Interestingly, P. tricuspis has a male-biased sex ratio, where the males are smaller than the females.
In ecology, a tramp species is an organism that has been spread globally by human activities. The term was coined by William Morton Wheeler in the bulletin of the American museum of natural history in 1906, used to describe ants that “have made their way as well known tramps or stow-aways[sic] to many islands The term has since widened to include non-ant organisms, but remains most popular in myrmecology. Tramp species have been noted in multiple phyla spanning both animal and plant kingdoms, including but not limited to arthropods, mollusca, bryophytes, and pteridophytes. The term "tramp species" was popularized and given a more set definition by Luc Passera in his chapter of David F William's 1994 book Exotic Ants: Biology, Impact, And Control Of Introduced Species.
An ant supercolony is an exceptionally large ant colony, consisting of a high number of spatially separated but socially connected nests of a single ant species, spread over a large area without territorial borders. Supercolonies are typically polygynous, containing many egg-laying females. Workers and queens from different nests within the same supercolony can freely move among the nests, and all workers cooperate indiscriminately with each other in collecting food and care of the brood, and show no apparent mutual aggressive behavior.
Although Tetramorium caespitum is an introduced species, it may be beneficial in some scenarios. One example would be the potential for this ant to keep out more damaging ant invaders. In laboratory experiments, workers from colonies of Tetramorium caespitum destroyed recently founded colonies of the red imported fire ant, Solenopsis invicta (King and Phillips 1992). Such conflict in nature may help impede the northern expansion of fire ants.
The interactions between a colony of Tetramorium caespitum and subcolonies of Solenopsis invicta introduced within 20 cm of the mature T. caespitum nest were studied in the laboratory. The subcolonies of S. invicta were destroyed by workers of T. caespitum. The ranges of these species are contiguous in North Carolina and it is predicted that if S. invicta moves northward, interactions between them may intensify.
