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Red imported fire ant
Fire ants 01.jpg
A group of fire ant workers
Scientific classification
Genus:
Solenopsis (ant)
Species:
invicta
Synonyms
  • Solenopsis saevissima wagneri Santschi, 1916

The red imported fire ant (Solenopsis invicta), 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.

Etymology and common names

The specific epithet 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" or "face" from Ancient Greek. 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: the "fire ant", "red ant" or "tramp ant". In Brazil, locals call the ant toicinhera, which derives from the Portuguese word toicinho (pork fat).

Description

Solenopsis invicta - fire ant worker
Closeup face view of a worker

The ant's colours are red and somewhat yellowish with a brown or black gaster, but males are completely black.

Polymorphism

Anatomical differences of S. invicta workers
Anatomical differences of red imported fire ant workers: The scale bar is 1 mm.

The red imported fire ant is polymorphic, as workers appear in different shapes and sizes.

Habitat

Solenopsis invicta distribution
The native range of S. invicta

Red imported fire ants are dominant in altered areas and live in a wide variety of habitats. They can be found in rainforests, 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.

S. invicta mounds found alongside road
Mounds found alongside a road in the United States

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.

Behaviour

These ants exhibit a wide variety of behaviours, such as building rafts when they sense that water levels are rising. They also show necrophoric behaviour, where nestmates discard scraps or dead ants on refuse piles outside the nest.

Mating

Nuptial flight occurs during the warm seasons, and the alates may mate for as long as 30 minutes.

Communication

Workers communicate by a series of semiochemicals and pheromones, which are used for recruitment, foraging, and defence.

Social structure

Colony founding can be done by a single queen or a group of queens, which later contest for dominance once the first workers emerge. Workers can live for several months, while queens can live for years; colony numbers can vary from 100,000 to 250,000 individuals. Two forms of society in the red imported fire ant exist: polygynous colonies (nests with multiple queens) and monogynous colonies (nests with one queen).

Diet

Dead hatching alligators due to solenopsis invicta
Hatching alligators are especially vulnerable to attacks by red imported fire ants.

Foraging takes place on warm or hot days, although they may remain outside at night. They are omnivores and eat dead mammals, arthropods, insects, seeds, and sweet substances such as honeydew from hemipteran insects with which they have developed relationships.

Predators

Predators include arachnids, birds, and many insects including other ants, dragonflies, earwigs, and beetles.

Parasites

The ant is a host to parasites and to a number of pathogens, nematodes, and viruses, which have been viewed as potential biological control agents.

Relationship with humans

Venom

Venom plays an important role in the ant's life, as it is used to capture prey or for defence. About 95% of the venom consists of water-insoluble piperidine alkaloids known as solenopsins, with the rest comprising a mixture of toxic proteins that can be particularly potent in sensitive humans; the name fire ant is derived from the burning sensation caused by their bite. More than 14 million people are stung by them in the United States annually, where many are expected to develop allergies to the venom. Most victims experience intense burning and swelling, followed by the formation of sterile pustules, which may remain for several days. However 0.6% to 6.0% of people may suffer from anaphylaxis, which can be fatal if left untreated. Common symptoms include dizziness, chest pain, nausea, severe sweating, low blood pressure, loss of breath, and slurred speech. More than 80 deaths have been recorded from red imported fire ant attacks. Treatment depends on the symptoms; those who only experience pain and pustule formation require no medical attention, but those who suffer from anaphylaxis are given epinephrines. Whole body extract immunotherapy is used to treat victims and is regarded as highly effective.

As pest

Fire ant mound (16371103174)
Mound marked for future research

The ant is viewed as a notorious pest, causing billions of dollars in damage annually and impacting wildlife. The ants thrive in urban areas, so their presence may deter outdoor activities. Nests can be built under structures such as pavements and foundations, which may cause structural problems, or cause them to collapse. Not only can they damage or destroy structures, but red imported fire ants also can damage equipment and infrastructure and impact business, land, and property values. In agriculture, they can damage crops and machinery, and threaten pastures. They are known to invade a wide variety of crops, and mounds built on farmland may prevent harvesting.

They also pose a threat to animals and livestock, capable of inflicting serious injury or killing them, especially young, weak, or sick animals. Despite this, they may be beneficial because they consume common pest insects on crops. Common methods of controlling these ants include baiting and fumigation; other methods may be ineffective or dangerous. Due to its notoriety and importance, the ant has become one of the most studied insects on the planet, even rivalling the western honey bee (Apis mellifera).

Images for kids

See also

Kids robot.svg In Spanish: Solenopsis invicta para niños

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