Red imported fire ant
Encyclopedia
See main article Fire ant
.
The red imported fire ant (Solenopsis invicta), or simply RIFA, is one of over 280 species
in the widespread genus
Solenopsis
. Although the red imported fire ant is native to South America
, it has become a pest in the southern United States
, Australia
, Taiwan
, Philippines
, and the southern Chinese
provinces of Guangdong
, Guangxi
, Fujian
and Hong Kong
. There are also reports of ant hills in Macau
, the former Portuguese enclave that borders the province of Guangdong. RIFA are known to have a strong, painful, and persistent irritating sting that often leaves a pustule on the skin.
In the 1930s, colonies were accidentally introduced into the United States through the seaport of Mobile, Alabama
: cargo ships from Brazil
docking at Mobile unloaded goods infested with the ants. Biologist E.O. Wilson says that he reported the first colony, in the Mobile area, when he was 13. The ants then spread from Alabama to almost every state of the American South, from Texas to Maryland. Since the 1990s infestations have been reported in New Mexico in the Southwest. They have also been reported in California in the West, but probably arrived via ship or truck rather than by spreading.
In a similar way, the ants were accidentally introduced into Australia in 2001.
s released by the first ant to attack and sting in concert, often killing smaller animals by overloading their immune system
s.
RIFAs compete successfully against other ants, and have been enlarging their range.
They are a pest, not only because of the physical pain they can inflict, but also because their mound-building activity can damage plant roots, lead to loss of crops, and interfere with mechanical cultivation. It is not uncommon for several fire ant mounds to appear suddenly in a suburban yard or a farmer's field, seemingly overnight. Their stings are rarely life-threatening to humans and other large animals, causing only 80 documented deaths as of 2006. However, they often kill smaller animals, such as birds. They sometimes kill newborn calves if they do not get on their feet quickly enough. The sting of the RIFA has venom composed of a necrotizing
alkaloid
, which causes both pain and the formation of white pustules that appear one day after the sting.
Fire ants are excellent natural predators and are biological controls for pests such as the sugarcane borer, the rice stink bug, the striped earwig
, aphid
s, the boll weevil
, the soybean looper, the cotton leafworm
, the hornfly, and many other pests harmful to crops. However, they also kill beneficial pollinator
s, such as ground-nesting bee
species. Seeds, fruits, leaves, roots, bark, nectar, sap, fungi, and carrion are all fire ant prey, and they are not shy about creating their own carrion
, either. They are proficient enough at overwhelming intruders that they can virtually clear an area of invertebrates, lizards, and ground-dwelling birds.
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 will come together and form a huge ball or raft that is able to float, with the workers on the outside and the queen inside. Once the ball hits a tree or other stationary object, the ants swarm onto it and wait for the water levels to recede. To contend with drought conditions, their nest structure includes a network of underground foraging tunnels that extends down to the water table. Also, although they do not hibernate during the winter, colonies can survive temperatures as low as 16 °F (-8.9 °C).
RIFAs were the first clearcut case discovered of a green-beard gene
, by which natural selection can favor altruistic behavior.
, Arkansas
, Arizona
, California
, Florida
, Georgia
, Kentucky
, Louisiana
, Maryland
, Mississippi
, North Carolina
, New Mexico
, Oklahoma
, South Carolina
, Tennessee
, Texas
, and Virginia
. The U.S. Department of Agriculture also lists the entire island of Puerto Rico
as infested (USDA Quarantine Map).
RIFAs were still on the move in the US in the early twentyfirst 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.
Red imported fire ants have both a pedicel
and postpediole
. In other words, they belong to a group of ants that have two humps between the thorax
and abdomen. The workers have ten antennal segments terminating in a two-segmented club. It is often difficult to distinguish between the red imported fire ant Solenopsis invicta and some other species in the genus. A number of characters are used, but are not always consistent between the black imported fire ant (Solenopsis richteri) or hybrids between the two species. Positive identifications can be made using high performance liquid chromatography
(HPLC) to distinguish differences in the cuticular hydrocarbons.
The RIFA's introduction to the United States was in the late 1930s. Traveling in soil used as ballast
on cargo ships, 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 (18.1 in) in height, although in Alabama some mounds have been reported to be over 60 cm high (2 ft) 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. 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. However, it has not been found that electric or magnetic fields attract the ants. Rather, when wandering ants cause electrical shorts, they attempt to sting the wire and produce powerful semiochemical
s, including defensive and recruitment pheromone
s. 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$750 million in damage to agricultural assets, including veterinary bills and livestock loss, as well as crop loss.
has been seriously affected by the red fire ant. A few people are reported to have succumbed to venom from the ant stings. A large campaign to kill the ants has been partially effective, but it has not been able to eliminate all of them.
In China
in January 2005, a controversy arose when it became known that Guangdong
's provincial government had suppressed all information about the spread of fire ants in the province since the middle of 2004. Hong Kong
newspapers, including Appledaily, Mingpao, Hong Kong Economic Times, Singtao and Takungpao (the latter funded by the Chinese government), have also reported the ants have been found in both Shenzhen
and Wuchuan
in Guangdong province.
According to a press briefing of the Agriculture
, Fisheries and Conservation Department of Hong Kong, the city authorities have also located several ant-hills of Solenopsis invicta in an artificial wetland
in Hong Kong's northwestern section.
There have also been reports of colonies in metro Manila
and the Province of Cavite
in the Philippines since July 2005; however, since early 2007, they have spread now as far as the Bicol Region
.
An outbreak of the RIFA in Queensland
, Australia
, was discovered on 22 February 2001. The ants were believed to be present in shipping containers arriving at the Port of Brisbane from the United States. Anecdotal evidence suggests fire ants may have been present in Australia for six to eight years prior to formal identification. While the outbreak is restricted to a small (800 km2) region of southeast Queensland in and around Brisbane, the potential social, economic, and ecological damage prompted the Australian government to respond rapidly. The initial emergency response was followed by the formation of the Fire Ant Control Centre in September 2001. Joint state and federal funding of A$
175 million was granted for a six-year eradication program involving the employment of more than 600 staff and the broad-scale baiting of approximately 678.9 km2 between 8 and 12 times, followed by two years of surveillance. Following the completion of the fourth year of the eradication program, the Fire Ant Control Centre estimated eradication rates of greater than 99% from previously infested properties. The latest (May 8) Federal budget confirmed the Program will receive extended Commonwealth funding of approximately A$10 million for at least another two years, until June 2009, to treat the residual infestations found most recently, and to fund validation of the overall treatment and surveillance program. (see:) As in previous years, the States have agreed in principle to match the Federal funding. That decision is set to be ratified in June 2007.
use. From the 1950s into the 1970s, Mirex
was extensively used in an attempt to eradicate the species. However, the pesticide inadvertently aided the fire ants' spread by killing numerous native ant species that compete successfully with them. Mirex also caused even broader ecological harm that was often attributed to the fire ants. For example, it was first thought that the ants were linked to the decline of overwintering birds (e.g. the Loggerhead Shrike
), but a later study showed that the pesticides were largely to blame. RIFAs have virtually no natural biological control agents
native to, or naturalized in, the United States
, China
, Philippines
, or Australia
. Current research is focused on introducing biological control agents from the RIFA's native range.
n Thelohania solenopsae and the fungus
Beauveria bassiana
are promising pathogen
s. Solenopsis daguerrei
, a parasitic ant, invades RIFA colonies to replace the queen in hopes of gaining control of the colony. For this reason, its use as a biological control agent is also being explored.
Pseudacteon tricuspis and Pseudacteon curvatus are parasitoid phorid flies
from South America
which parasitize the ants. The female flies each lay an egg at the junction of head and thorax
of their victims, prompting a jerky dance manoeuvre by the ants. The larva
then slowly consumes the contents of the head, decapitating
the ant in the process, and uses the exoskeleton
as a pupal case.
Phorid flies have been introduced in many places in southeastern United States, and are slowly reproducing and spreading to cover the entire RIFA range. The amount of actual damage done to the ants by phorid flies is minimal, but the ants appear to be aware of the hovering flies, losing their social organization and ceasing foraging
. In addition, phorid flies are very species-specific, and should in theory leave native ant species (the fire ants' prime competitor) unmolested.
Scientists at the US Agricultural Research Service
also have been able to infect phorid flies with Kneallhazia solenopsae, a spore-producing insect pathogen, to control the population of red imported fire ants. The flies are unharmed by the pathogen and serve as vectors in transmitting the disease to the ants. The pathogen is able to reduce red imported fire ant colonies from 53-100%, and may serve as an effective biological control for the ants.
A virus, SINV-1, has been found in about 20 percent 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.
In some cases, hastily adopted biological control agents can do more harm than good (such as the mosquitofish
in Australia), and it remains to be seen how much success biological control of the red imported fire ant will have.
or pressurized steam into RIFA nests. Besides using hot steam, pouring boiling water into ant mounds has been found effective in exterminating their nests. Folk remedies have often sought a rapid increase in temperature by soaking the nest in gasoline
or kerosene
and lighting it on fire, though this is potentially dangerous. Further, the burning of the nest is ineffective due the tendency of queens to be several feet underground. This confusion stems from the observation that fuel vapor has a near instantaneous lethal effect on the ants.
In Brisbane, Australia, colonies are being eradicated or effectively controlled by ground baiting with food laced with contraceptives that render the colony's queen infertile, and toxicant
s. Mass baiting was undertaken following detection of the ants around the port of Brisbane and in southwestern Brisbane in 2001. Widespread public reporting of suspect colonies (by sending in samples of ants for identification) allowed mapping of the ant's locations. This was combined with satellite imagery
to determine the vegetated habitats most likely to be infiltrated by the ants, and the baits were targeted in these areas. Known infested areas were declared high-risk (Restricted Areas), and any material being moved from these areas which could harbour ants (soil, mulch, potted plants, potting mix, hay bales, construction machinery, etc.) had to be inspected prior to disposal or movement, and bulk waste sent to transfer stations for examination, treatment and disposal. The infestation was initially thought to cover 270 km2, with a density of up to 600,000 colonies/km2 on highly infested sites. As program activity refined data on the infested area, overall size grew to around 80,000 ha by 2006/7. At mid-2007 in the on-going nationally-funded eradication campaign, fewer than 100 active colonies were located in the entire South-East Queensland area during the six months between September 2006 and February 2007. The focus of delivering eradication has now switched largely to surveillance, while control and validation measures are expected to continue until 2009. The six year eradication campaign has cost A$175 million to date, and has just secured funding in principle for a minimum of two more years.
Australia
United States
Fire ant
Fire ants are a variety of stinging ants with over 285 species worldwide. They have several common names, including ginger ants, tropical fire ants and red ants.- Appearance :...
.
The red imported fire ant (Solenopsis invicta), or simply RIFA, is one of over 280 species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
in the widespread genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
Solenopsis
Fire ant
Fire ants are a variety of stinging ants with over 285 species worldwide. They have several common names, including ginger ants, tropical fire ants and red ants.- Appearance :...
. Although the red imported fire ant is native to South America
South America
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...
, it has become a pest in the southern United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
, Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
, Taiwan
Taiwan
Taiwan , also known, especially in the past, as Formosa , is the largest island of the same-named island group of East Asia in the western Pacific Ocean and located off the southeastern coast of mainland China. The island forms over 99% of the current territory of the Republic of China following...
, Philippines
Philippines
The Philippines , officially known as the Republic of the Philippines , is a country in Southeast Asia in the western Pacific Ocean. To its north across the Luzon Strait lies Taiwan. West across the South China Sea sits Vietnam...
, and the southern Chinese
People's Republic of China
China , officially the People's Republic of China , is the most populous country in the world, with over 1.3 billion citizens. Located in East Asia, the country covers approximately 9.6 million square kilometres...
provinces of Guangdong
Guangdong
Guangdong is a province on the South China Sea coast of the People's Republic of China. The province was previously often written with the alternative English name Kwangtung Province...
, Guangxi
Guangxi
Guangxi, formerly romanized Kwangsi, is a province of southern China along its border with Vietnam. In 1958, it became the Guangxi Zhuang Autonomous Region of the People's Republic of China, a region with special privileges created specifically for the Zhuang people.Guangxi's location, in...
, Fujian
Fujian
' , formerly romanised as Fukien or Huguing or Foukien, is a province on the southeast coast of mainland China. Fujian is bordered by Zhejiang to the north, Jiangxi to the west, and Guangdong to the south. Taiwan lies to the east, across the Taiwan Strait...
and Hong Kong
Hong Kong
Hong Kong is one of two Special Administrative Regions of the People's Republic of China , the other being Macau. A city-state situated on China's south coast and enclosed by the Pearl River Delta and South China Sea, it is renowned for its expansive skyline and deep natural harbour...
. There are also reports of ant hills in Macau
Macau
Macau , also spelled Macao , is, along with Hong Kong, one of the two special administrative regions of the People's Republic of China...
, the former Portuguese enclave that borders the province of Guangdong. RIFA are known to have a strong, painful, and persistent irritating sting that often leaves a pustule on the skin.
In the 1930s, colonies were accidentally introduced into the United States through the seaport of Mobile, Alabama
Mobile, Alabama
Mobile is the third most populous city in the Southern US state of Alabama and is the county seat of Mobile County. It is located on the Mobile River and the central Gulf Coast of the United States. The population within the city limits was 195,111 during the 2010 census. It is the largest...
: cargo ships from Brazil
Brazil
Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...
docking at Mobile unloaded goods infested with the ants. Biologist E.O. Wilson says that he reported the first colony, in the Mobile area, when he was 13. The ants then spread from Alabama to almost every state of the American South, from Texas to Maryland. Since the 1990s infestations have been reported in New Mexico in the Southwest. They have also been reported in California in the West, but probably arrived via ship or truck rather than by spreading.
In a similar way, the ants were accidentally introduced into Australia in 2001.
Overview
RIFAs are more aggressive than most native ant species, and have a painful sting. An animal, including humans, typically encounters them by inadvertently stepping into one of their mounds, which causes the ants to swarm up the legs, attacking en masse. The ants respond to pheromonePheromone
A pheromone is a secreted or excreted chemical factor that triggers a social response in members of the same species. Pheromones are chemicals capable of acting outside the body of the secreting individual to impact the behavior of the receiving individual...
s released by the first ant to attack and sting in concert, often killing smaller animals by overloading their immune system
Immune system
An immune system is a system of biological structures and processes within an organism that protects against disease by identifying and killing pathogens and tumor cells. It detects a wide variety of agents, from viruses to parasitic worms, and needs to distinguish them from the organism's own...
s.
RIFAs compete successfully against other ants, and have been enlarging their range.
They are a pest, not only because of the physical pain they can inflict, but also because their mound-building activity can damage plant roots, lead to loss of crops, and interfere with mechanical cultivation. It is not uncommon for several fire ant mounds to appear suddenly in a suburban yard or a farmer's field, seemingly overnight. Their stings are rarely life-threatening to humans and other large animals, causing only 80 documented deaths as of 2006. However, they often kill smaller animals, such as birds. They sometimes kill newborn calves if they do not get on their feet quickly enough. The sting of the RIFA has venom composed of a necrotizing
Necrosis
Necrosis is the premature death of cells in living tissue. Necrosis is caused by factors external to the cell or tissue, such as infection, toxins, or trauma. This is in contrast to apoptosis, which is a naturally occurring cause of cellular death...
alkaloid
Alkaloid
Alkaloids are a group of naturally occurring chemical compounds that contain mostly basic nitrogen atoms. This group also includes some related compounds with neutral and even weakly acidic properties. Also some synthetic compounds of similar structure are attributed to alkaloids...
, which causes both pain and the formation of white pustules that appear one day after the sting.
Fire ants are excellent natural predators and are biological controls for pests such as the sugarcane borer, the rice stink bug, the striped earwig
Labiduridae
Labiduridae, whose members are known commonly as striped earwigs, is a relatively large family of earwigs in the suborder Forficulina.Labiduridae, whose members are known commonly as striped earwigs, is a relatively large family of earwigs in the suborder Forficulina.Labiduridae, whose members are...
, aphid
Aphid
Aphids, also known as plant lice and in Britain and the Commonwealth as greenflies, blackflies or whiteflies, are small sap sucking insects, and members of the superfamily Aphidoidea. Aphids are among the most destructive insect pests on cultivated plants in temperate regions...
s, the boll weevil
Boll weevil
The boll weevil is a beetle measuring an average length of six millimeters, which feeds on cotton buds and flowers. Thought to be native to Central America, it migrated into the United States from Mexico in the late 19th century and had infested all U.S. cotton-growing areas by the 1920s,...
, the soybean looper, the cotton leafworm
Alabama argillacea
The Cotton leafworm is a moth of the Noctuidae family. It is endemic to South and Central America as far south as northern Argentina, but migrates as far north as Canada, where it can be found in Ontario, Quebec, New Brunswick, Nova Scotia and Manitoba.The wingspan is 30-35 mm.The larva is...
, the hornfly, and many other pests harmful to crops. However, they also kill beneficial pollinator
Pollinator
A pollinator is the biotic agent that moves pollen from the male anthers of a flower to the female stigma of a flower to accomplish fertilization or syngamy of the female gamete in the ovule of the flower by the male gamete from the pollen grain...
s, such as ground-nesting bee
Bee
Bees are flying insects closely related to wasps and ants, and are known for their role in pollination and for producing honey and beeswax. Bees are a monophyletic lineage within the superfamily Apoidea, presently classified by the unranked taxon name Anthophila...
species. Seeds, fruits, leaves, roots, bark, nectar, sap, fungi, and carrion are all fire ant prey, and they are not shy about creating their own carrion
Carrion
Carrion refers to the carcass of a dead animal. Carrion is an important food source for large carnivores and omnivores in most ecosystems. Examples of carrion-eaters include vultures, hawks, eagles, hyenas, Virginia Opossum, Tasmanian Devils, coyotes, Komodo dragons, and burying beetles...
, either. They are proficient enough at overwhelming intruders that they can virtually clear an area of invertebrates, lizards, and ground-dwelling birds.
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 will come together and form a huge ball or raft that is able to float, with the workers on the outside and the queen inside. Once the ball hits a tree or other stationary object, the ants swarm onto it and wait for the water levels to recede. To contend with drought conditions, their nest structure includes a network of underground foraging tunnels that extends down to the water table. Also, although they do not hibernate during the winter, colonies can survive temperatures as low as 16 °F (-8.9 °C).
RIFAs were the first clearcut case discovered of a green-beard gene
Green-beard effect
The gene-centered view of evolution postulates that natural selection will increase the frequency of those genes whose phenotypic effects ensure their successful replication...
, by which natural selection can favor altruistic behavior.
United States
In the United States RIFAs have gradually spread north and west despite intense efforts to stop or eliminate them. in the United States they were found in most of the southern states: AlabamaAlabama
Alabama is a state located in the southeastern region of the United States. It is bordered by Tennessee to the north, Georgia to the east, Florida and the Gulf of Mexico to the south, and Mississippi to the west. Alabama ranks 30th in total land area and ranks second in the size of its inland...
, Arkansas
Arkansas
Arkansas is a state located in the southern region of the United States. Its name is an Algonquian name of the Quapaw Indians. Arkansas shares borders with six states , and its eastern border is largely defined by the Mississippi River...
, Arizona
Arizona
Arizona ; is a state located in the southwestern region of the United States. It is also part of the western United States and the mountain west. The capital and largest city is Phoenix...
, California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
, Florida
Florida
Florida is a state in the southeastern United States, located on the nation's Atlantic and Gulf coasts. It is bordered to the west by the Gulf of Mexico, to the north by Alabama and Georgia and to the east by the Atlantic Ocean. With a population of 18,801,310 as measured by the 2010 census, it...
, Georgia
Georgia (U.S. state)
Georgia is a state located in the southeastern United States. It was established in 1732, the last of the original Thirteen Colonies. The state is named after King George II of Great Britain. Georgia was the fourth state to ratify the United States Constitution, on January 2, 1788...
, Kentucky
Kentucky
The Commonwealth of Kentucky is a state located in the East Central United States of America. As classified by the United States Census Bureau, Kentucky is a Southern state, more specifically in the East South Central region. Kentucky is one of four U.S. states constituted as a commonwealth...
, Louisiana
Louisiana
Louisiana is a state located in the southern region of the United States of America. Its capital is Baton Rouge and largest city is New Orleans. Louisiana is the only state in the U.S. with political subdivisions termed parishes, which are local governments equivalent to counties...
, Maryland
Maryland
Maryland is a U.S. state located in the Mid Atlantic region of the United States, bordering Virginia, West Virginia, and the District of Columbia to its south and west; Pennsylvania to its north; and Delaware to its east...
, Mississippi
Mississippi
Mississippi is a U.S. state located in the Southern United States. Jackson is the state capital and largest city. The name of the state derives from the Mississippi River, which flows along its western boundary, whose name comes from the Ojibwe word misi-ziibi...
, North Carolina
North Carolina
North Carolina is a state located in the southeastern United States. The state borders South Carolina and Georgia to the south, Tennessee to the west and Virginia to the north. North Carolina contains 100 counties. Its capital is Raleigh, and its largest city is Charlotte...
, New Mexico
New Mexico
New Mexico is a state located in the southwest and western regions of the United States. New Mexico is also usually considered one of the Mountain States. With a population density of 16 per square mile, New Mexico is the sixth-most sparsely inhabited U.S...
, Oklahoma
Oklahoma
Oklahoma is a state located in the South Central region of the United States of America. With an estimated 3,751,351 residents as of the 2010 census and a land area of 68,667 square miles , Oklahoma is the 28th most populous and 20th-largest state...
, South Carolina
South Carolina
South Carolina is a state in the Deep South of the United States that borders Georgia to the south, North Carolina to the north, and the Atlantic Ocean to the east. Originally part of the Province of Carolina, the Province of South Carolina was one of the 13 colonies that declared independence...
, Tennessee
Tennessee
Tennessee is a U.S. state located in the Southeastern United States. It has a population of 6,346,105, making it the nation's 17th-largest state by population, and covers , making it the 36th-largest by total land area...
, Texas
Texas
Texas is the second largest U.S. state by both area and population, and the largest state by area in the contiguous United States.The name, based on the Caddo word "Tejas" meaning "friends" or "allies", was applied by the Spanish to the Caddo themselves and to the region of their settlement in...
, and Virginia
Virginia
The Commonwealth of Virginia , is a U.S. state on the Atlantic Coast of the Southern United States. Virginia is nicknamed the "Old Dominion" and sometimes the "Mother of Presidents" after the eight U.S. presidents born there...
. The U.S. Department of Agriculture also lists the entire island of Puerto Rico
Puerto Rico
Puerto Rico , officially the Commonwealth of Puerto Rico , is an unincorporated territory of the United States, located in the northeastern Caribbean, east of the Dominican Republic and west of both the United States Virgin Islands and the British Virgin Islands.Puerto Rico comprises an...
as infested (USDA Quarantine Map).
RIFAs were still on the move in the US in the early twentyfirst 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.
Morphology
See also general ant morphologyPetiole (insect)
In entomology, the term petiole is most commonly used to refer to the constricted first metasomal segment of members of the Hymenopteran suborder Apocrita; it may be used to refer to other insects with similar body shapes, where the metasomal base is constricted...
and postpediole
Petiole (insect)
In entomology, the term petiole is most commonly used to refer to the constricted first metasomal segment of members of the Hymenopteran suborder Apocrita; it may be used to refer to other insects with similar body shapes, where the metasomal base is constricted...
. In other words, they belong to a group of ants that have two humps between the thorax
Thorax
The thorax is a division of an animal's body that lies between the head and the abdomen.-In tetrapods:...
and abdomen. The workers have ten antennal segments terminating in a two-segmented club. It is often difficult to distinguish between the red imported fire ant Solenopsis invicta and some other species in the genus. A number of characters are used, but are not always consistent between the black imported fire ant (Solenopsis richteri) or hybrids between the two species. Positive identifications can be made using high performance liquid chromatography
High performance liquid chromatography
High-performance liquid chromatography , HPLC, is a chromatographic technique that can separate a mixture of compounds and is used in biochemistry and analytical chemistry to identify, quantify and purify the individual components of the mixture.HPLC typically utilizes different types of stationary...
(HPLC) to distinguish differences in the cuticular hydrocarbons.
United States
Sailing ballast
Ballast is used in sailboats to provide moment to resist the lateral forces on the sail. Insufficiently ballasted boats will tend to tip, or heel, excessively in high winds. Too much heel may result in the boat capsizing. If a sailing vessel should need to voyage without cargo then ballast of...
on cargo ships, 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 (18.1 in) in height, although in Alabama some mounds have been reported to be over 60 cm high (2 ft) 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
Electrical wiring
Electrical wiring in general refers to insulated conductors used to carry electricity, and associated devices. This article describes general aspects of electrical wiring as used to provide power in buildings and structures, commonly referred to as building wiring. This article is intended to...
of stop lights, shorting them out. This is the leading cause of traffic light shorts in Texas
Texas
Texas is the second largest U.S. state by both area and population, and the largest state by area in the contiguous United States.The name, based on the Caddo word "Tejas" meaning "friends" or "allies", was applied by the Spanish to the Caddo themselves and to the region of their settlement in...
, where the ants cause more than US$140 million in damage each year. 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. However, it has not been found that electric or magnetic fields attract the ants. Rather, when wandering ants cause electrical shorts, they attempt to sting the wire and produce powerful semiochemical
Semiochemical
A semiochemical is a generic term used for a chemical substance or mixture that carries a message. These chemicals acts as messengers within or between species...
s, including defensive and recruitment pheromone
Pheromone
A pheromone is a secreted or excreted chemical factor that triggers a social response in members of the same species. Pheromones are chemicals capable of acting outside the body of the secreting individual to impact the behavior of the receiving individual...
s. 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.
Australasia
Since September 2004, TaiwanTaiwan
Taiwan , also known, especially in the past, as Formosa , is the largest island of the same-named island group of East Asia in the western Pacific Ocean and located off the southeastern coast of mainland China. The island forms over 99% of the current territory of the Republic of China following...
has been seriously affected by the red fire ant. A few people are reported to have succumbed to venom from the ant stings. A large campaign to kill the ants has been partially effective, but it has not been able to eliminate all of them.
In China
People's Republic of China
China , officially the People's Republic of China , is the most populous country in the world, with over 1.3 billion citizens. Located in East Asia, the country covers approximately 9.6 million square kilometres...
in January 2005, a controversy arose when it became known that Guangdong
Guangdong
Guangdong is a province on the South China Sea coast of the People's Republic of China. The province was previously often written with the alternative English name Kwangtung Province...
's provincial government had suppressed all information about the spread of fire ants in the province since the middle of 2004. Hong Kong
Hong Kong
Hong Kong is one of two Special Administrative Regions of the People's Republic of China , the other being Macau. A city-state situated on China's south coast and enclosed by the Pearl River Delta and South China Sea, it is renowned for its expansive skyline and deep natural harbour...
newspapers, including Appledaily, Mingpao, Hong Kong Economic Times, Singtao and Takungpao (the latter funded by the Chinese government), have also reported the ants have been found in both Shenzhen
Shenzhen
Shenzhen is a major city in the south of Southern China's Guangdong Province, situated immediately north of Hong Kong. The area became China's first—and one of the most successful—Special Economic Zones...
and Wuchuan
Wuchuan City
Wuchuan City is a city district of Guangdong Province, China. It is under the administration of Zhanjiang city....
in Guangdong province.
According to a press briefing of the Agriculture
Agriculture
Agriculture is the cultivation of animals, plants, fungi and other life forms for food, fiber, and other products used to sustain life. Agriculture was the key implement in the rise of sedentary human civilization, whereby farming of domesticated species created food surpluses that nurtured the...
, Fisheries and Conservation Department of Hong Kong, the city authorities have also located several ant-hills of Solenopsis invicta in an artificial wetland
Wetland
A wetland is an area of land whose soil is saturated with water either permanently or seasonally. Wetlands are categorised by their characteristic vegetation, which is adapted to these unique soil conditions....
in Hong Kong's northwestern section.
There have also been reports of colonies in metro Manila
Metro Manila
Metropolitan Manila , the National Capital Region , or simply Metro Manila, is the metropolitan region encompassing the City of Manila and its surrounding areas in the Philippines...
and the Province of Cavite
Cavite
Cavite is a province of the Philippines located on the southern shores of Manila Bay in the CALABARZON region in Luzon, just 30 kilometers south of Manila. Cavite is surrounded by Laguna to the east, Metro Manila to the northeast, and Batangas to the south...
in the Philippines since July 2005; however, since early 2007, they have spread now as far as the Bicol Region
Bicol Region
The Bicol Region or Bicolandia is one of the 17 regions of the Philippines. Its regional center is Legazpi City...
.
An outbreak of the RIFA in Queensland
Queensland
Queensland is a state of Australia, occupying the north-eastern section of the mainland continent. It is bordered by the Northern Territory, South Australia and New South Wales to the west, south-west and south respectively. To the east, Queensland is bordered by the Coral Sea and Pacific Ocean...
, Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
, was discovered on 22 February 2001. The ants were believed to be present in shipping containers arriving at the Port of Brisbane from the United States. Anecdotal evidence suggests fire ants may have been present in Australia for six to eight years prior to formal identification. While the outbreak is restricted to a small (800 km2) region of southeast Queensland in and around Brisbane, the potential social, economic, and ecological damage prompted the Australian government to respond rapidly. The initial emergency response was followed by the formation of the Fire Ant Control Centre in September 2001. Joint state and federal funding of A$
Australian dollar
The Australian dollar is the currency of the Commonwealth of Australia, including Christmas Island, Cocos Islands, and Norfolk Island, as well as the independent Pacific Island states of Kiribati, Nauru and Tuvalu...
175 million was granted for a six-year eradication program involving the employment of more than 600 staff and the broad-scale baiting of approximately 678.9 km2 between 8 and 12 times, followed by two years of surveillance. Following the completion of the fourth year of the eradication program, the Fire Ant Control Centre estimated eradication rates of greater than 99% from previously infested properties. The latest (May 8) Federal budget confirmed the Program will receive extended Commonwealth funding of approximately A$10 million for at least another two years, until June 2009, to treat the residual infestations found most recently, and to fund validation of the overall treatment and surveillance program. (see:) As in previous years, the States have agreed in principle to match the Federal funding. That decision is set to be ratified in June 2007.
Countermeasures
Many scientists and agencies are attempting to develop methods to stop the spread of the RIFA. Traditionally, control has been achieved through pesticidePesticide
Pesticides are substances or mixture of substances intended for preventing, destroying, repelling or mitigating any pest.A pesticide may be a chemical unicycle, biological agent , antimicrobial, disinfectant or device used against any pest...
use. From the 1950s into the 1970s, Mirex
Mirex
Mirex is a chlorinated hydrocarbon that was commercialized as an insecticide and later banned because of its impact on the environment. This white crystalline odorless solid is a derivative of cyclopentadiene. It was popularized to control fire ants but by virtue of its chemical robustness and...
was extensively used in an attempt to eradicate the species. However, the pesticide inadvertently aided the fire ants' spread by killing numerous native ant species that compete successfully with them. Mirex also caused even broader ecological harm that was often attributed to the fire ants. For example, it was first thought that the ants were linked to the decline of overwintering birds (e.g. the Loggerhead Shrike
Loggerhead Shrike
The Loggerhead Shrike is a passerine bird. It is the only member of the shrike family endemic to North America; the related Northern Shrike occurs north of its range but also in the Palearctic....
), but a later study showed that the pesticides were largely to blame. RIFAs have virtually no natural biological control agents
Biological pest control
Biological control of pests in agriculture is a method of controlling pests that relies on predation, parasitism, herbivory, or other natural mechanisms...
native to, or naturalized in, the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
, China
People's Republic of China
China , officially the People's Republic of China , is the most populous country in the world, with over 1.3 billion citizens. Located in East Asia, the country covers approximately 9.6 million square kilometres...
, Philippines
Philippines
The Philippines , officially known as the Republic of the Philippines , is a country in Southeast Asia in the western Pacific Ocean. To its north across the Luzon Strait lies Taiwan. West across the South China Sea sits Vietnam...
, or Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
. Current research is focused on introducing biological control agents from the RIFA's native range.
Biological methods
The microsporidian protozoaProtozoa
Protozoa are a diverse group of single-cells eukaryotic organisms, many of which are motile. Throughout history, protozoa have been defined as single-cell protists with animal-like behavior, e.g., movement...
n Thelohania solenopsae and the fungus
Fungus
A fungus is a member of a large group of eukaryotic organisms that includes microorganisms such as yeasts and molds , as well as the more familiar mushrooms. These organisms are classified as a kingdom, Fungi, which is separate from plants, animals, and bacteria...
Beauveria bassiana
Beauveria bassiana
Beauveria bassiana is a fungus that grows naturally in soils throughout the world and acts as a parasite on various arthropod species, causing white muscardine disease; it thus belongs to the entomopathogenic fungi. It is being used as a biological insecticide to control a number of pests such as...
are promising pathogen
Pathogen
A pathogen gignomai "I give birth to") or infectious agent — colloquially, a germ — is a microbe or microorganism such as a virus, bacterium, prion, or fungus that causes disease in its animal or plant host...
s. Solenopsis daguerrei
Solenopsis daguerrei
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 . This is made possible by the fact that the S. daguerrei queen produces pheromones which are very similar...
, a parasitic ant, invades RIFA colonies to replace the queen in hopes of gaining control of the colony. For this reason, its use as a biological control agent is also being explored.
Pseudacteon tricuspis and Pseudacteon curvatus are parasitoid phorid flies
Phorid fly
Phoridae is a family of small, hump-backed flies resembling fruit flies. Phorid flies can often be identified by their escape habit of running rapidly across a surface rather than taking to the wing. This behaviour is a source of one of their alternate names: scuttle fly. They are a diverse and...
from South America
South America
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...
which parasitize the ants. The female flies each lay an egg at the junction of head and thorax
Thorax
The thorax is a division of an animal's body that lies between the head and the abdomen.-In tetrapods:...
of their victims, prompting a jerky dance manoeuvre by the ants. The larva
Larva
A larva is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle...
then slowly consumes the contents of the head, decapitating
Decapitation
Decapitation is the separation of the head from the body. Beheading typically refers to the act of intentional decapitation, e.g., as a means of murder or execution; it may be accomplished, for example, with an axe, sword, knife, wire, or by other more sophisticated means such as a guillotine...
the ant in the process, and uses the exoskeleton
Exoskeleton
An exoskeleton is the external skeleton that supports and protects an animal's body, in contrast to the internal skeleton of, for example, a human. In popular usage, some of the larger kinds of exoskeletons are known as "shells". Examples of exoskeleton animals include insects such as grasshoppers...
as a pupal case.
Phorid flies have been introduced in many places in southeastern United States, and are slowly reproducing and spreading to cover the entire RIFA range. The amount of actual damage done to the ants by phorid flies is minimal, but the ants appear to be aware of the hovering flies, losing their social organization and ceasing foraging
Foraging
- Definitions and significance of foraging behavior :Foraging is the act of searching for and exploiting food resources. It affects an animal's fitness because it plays an important role in an animal's ability to survive and reproduce...
. In addition, phorid flies are very species-specific, and should in theory leave native ant species (the fire ants' prime competitor) unmolested.
Scientists at the US Agricultural Research Service
Agricultural Research Service
The Agricultural Research Service is the principal in-house research agency of the United States Department of Agriculture . ARS is one of four agencies in USDA's Research, Education and Economics mission area...
also have been able to infect phorid flies with Kneallhazia solenopsae, a spore-producing insect pathogen, to control the population of red imported fire ants. The flies are unharmed by the pathogen and serve as vectors in transmitting the disease to the ants. The pathogen is able to reduce red imported fire ant colonies from 53-100%, and may serve as an effective biological control for the ants.
A virus, SINV-1, has been found in about 20 percent 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
Biopesticide
Biopesticides include "naturally occurring substances that control pests , microorganisms that control pests , and pesticidal substances produced by plants containing added genetic material or PIPs."Biopesticides are biochemical pesticides that are naturally occurring substances that control pests...
to control fire ants.
In some cases, hastily adopted biological control agents can do more harm than good (such as the mosquitofish
Mosquitofish
The mosquitofish is a species of freshwater fish, also commonly, if ambiguously, known by its generic name, gambusia. It is sometimes called the western mosquitofish, to distinguish it from the eastern mosquitofish . It is a member of the family Poeciliidae of order Cyprinodontiformes...
in Australia), and it remains to be seen how much success biological control of the red imported fire ant will have.
Physical methods
Researchers have also been experimenting with extreme temperature change to exterminate RIFAs, such as injecting liquid nitrogenLiquid nitrogen
Liquid nitrogen is nitrogen in a liquid state at a very low temperature. It is produced industrially by fractional distillation of liquid air. Liquid nitrogen is a colourless clear liquid with density of 0.807 g/mL at its boiling point and a dielectric constant of 1.4...
or pressurized steam into RIFA nests. Besides using hot steam, pouring boiling water into ant mounds has been found effective in exterminating their nests. Folk remedies have often sought a rapid increase in temperature by soaking the nest in gasoline
Gasoline
Gasoline , or petrol , is a toxic, translucent, petroleum-derived liquid that is primarily used as a fuel in internal combustion engines. It consists mostly of organic compounds obtained by the fractional distillation of petroleum, enhanced with a variety of additives. Some gasolines also contain...
or kerosene
Kerosene
Kerosene, sometimes spelled kerosine in scientific and industrial usage, also known as paraffin or paraffin oil in the United Kingdom, Hong Kong, Ireland and South Africa, is a combustible hydrocarbon liquid. The name is derived from Greek keros...
and lighting it on fire, though this is potentially dangerous. Further, the burning of the nest is ineffective due the tendency of queens to be several feet underground. This confusion stems from the observation that fuel vapor has a near instantaneous lethal effect on the ants.
In Brisbane, Australia, colonies are being eradicated or effectively controlled by ground baiting with food laced with contraceptives that render the colony's queen infertile, and toxicant
Toxicant
A toxicant is a chemical compound that has an effect on organisms.A distinction can be drawn between "toxic" and toxin, with the latter being a subcategory of the former....
s. Mass baiting was undertaken following detection of the ants around the port of Brisbane and in southwestern Brisbane in 2001. Widespread public reporting of suspect colonies (by sending in samples of ants for identification) allowed mapping of the ant's locations. This was combined with satellite imagery
Satellite imagery
Satellite imagery consists of photographs of Earth or other planets made by means of artificial satellites.- History :The first images from space were taken on sub-orbital flights. The U.S-launched V-2 flight on October 24, 1946 took one image every 1.5 seconds...
to determine the vegetated habitats most likely to be infiltrated by the ants, and the baits were targeted in these areas. Known infested areas were declared high-risk (Restricted Areas), and any material being moved from these areas which could harbour ants (soil, mulch, potted plants, potting mix, hay bales, construction machinery, etc.) had to be inspected prior to disposal or movement, and bulk waste sent to transfer stations for examination, treatment and disposal. The infestation was initially thought to cover 270 km2, with a density of up to 600,000 colonies/km2 on highly infested sites. As program activity refined data on the infested area, overall size grew to around 80,000 ha by 2006/7. At mid-2007 in the on-going nationally-funded eradication campaign, fewer than 100 active colonies were located in the entire South-East Queensland area during the six months between September 2006 and February 2007. The focus of delivering eradication has now switched largely to surveillance, while control and validation measures are expected to continue until 2009. The six year eradication campaign has cost A$175 million to date, and has just secured funding in principle for a minimum of two more years.
Genomics
The fire ant genome was sequenced in 2010. This creates new opportunities for research on fire ant behavior, and offers new opportunities for directed control measures that minimize environmental impact. The sequence can be searched and downloaded at antgenomes.org.External links
- The Incredible Floating Fire Ant
- National Pest Management Association's fact sheet on fire ant control, infestations and prevention
- Imported Fire Ants: Biology, Control, and Management at eXtension
- Database of fire ant genes
Australia
- Department of Primary Industries & Fisheries, Queensland - Fire ants page
United States
- Species Profile- Red Imported Fire Ant (Solenopsis invicta Buren), National Invasive Species Information Center, United States National Agricultural LibraryUnited States National Agricultural LibraryThe United States National Agricultural Library is one of the world's largest agricultural research libraries, and serves as a National Library of the United States and as the library of the United States Department of Agriculture...
. Lists general information and resources for Red Imported Fire Ant. - The Alabama Fire Ant Management Program
- Clemson University Sandhill Research and Education Center RIFA Page
- Texas Imported Fire Ant Research and Management Project
- History, Biology, Control of Imported Fire Ants
- USDA Imported Fire And Household Insects research unit
- Behavioral and Community Interaction of Phorid Flies and Fire Ants (UT Austin, Dr. Gilbert)
- The imported fire ant: how to control it. hosted by the UNT Government Documents Department
- red imported fire ant on the UFUniversity of FloridaThe University of Florida is an American public land-grant, sea-grant, and space-grant research university located on a campus in Gainesville, Florida. The university traces its historical origins to 1853, and has operated continuously on its present Gainesville campus since September 1906...
/ IFASInstitute of Food and Agricultural SciencesThe University of Florida’s Institute of Food and Agricultural Sciences is a federal-state-county partnership dedicated to developing knowledge in agriculture, human and natural resources, and the life sciences, and enhancing and sustaining the quality of human life by making that information...
Featured Creatures Web site - Red Imported Fire Ant Center for Invasive Species Research