Red imported fire ant

Type Description

"Worker ants: Worker ants are wingless, dark reddish brown with a black abdomen and 1.5 to 5 mm long. Workers in the genus Solenopsis are polymorphic, meaning that they physically differentiate into more than two different body forms (Holway, 2002, ISSG, 2014). The first workers of a new colony, called minim, are smaller than subsequent generations (Taber, 2000). The sting of the main worker S. invicta ants, the largest of which (in later generations) can reach lengths of up to 5 mm, can be detected under examination near the tip of the abdomen.

Developmental Stages: Eggs are spherical and creamy white in color. Larvae are legless, cream-colored and resemble the grub with a distinct head capsule. Pupae resemble worker ants and are initially creamy-white in color before adult ants emerge. Eggs, larvae and pupae are called brood.

Productive Individuals: Females are reddish brown, males are shiny and black. These ants remain in the colony until conditions are available for mating flights. The queen ants are female breeding pairs, larger than the worker ants (9 mm), and they spread their wings after a mating flight."

Habitat

"S. invicta is a social insect that forms colonies in soil or other suitable media. However, under laboratory conditions, it can be cultured without media (Banks et al., 1981). Colonies may occasionally occur in wall cavities and such enclosures.

S. invicta can live in a wide variety of habitats and can dominate modified habitats. It also thrives in the harsh conditions of South American rainforests (Trager, 1991). In disturbed and developed forest areas, S. invicta nests are abundant on roadsides and paths next to buildings. Newly mated S. invicta monarchs often move to grasslands (Taber, 2000).

Infested areas include lawns, gardens, schoolyards, parks, roadsides and golf courses. Nests are usually found in sunny open areas and are particularly common in irrigated soils.


Solenopsis invicta is native to central South America. It was first observed in the United States between 1933 and 1945. Later sightings occurred in Brazil, Alabama, and Pensacola, Florida. Currently, S. invicta covers an area of 128 million hectares in limited invasions across nine southeastern states of the United States (Alabama, Arkansas, Florida, Georgia, Louisiana, Mississippi, North Carolina, South Carolina, and Texas), as well as in Arizona, Oklahoma, Tennessee, New Mexico, and California.

Reports indicate the presence of S. invicta in the Cayman Islands, Malaysia, Singapore, Trinidad and Tobago, and the Turks and Caicos Islands (ISSG, 2014). Additionally, it has been detected in New Zealand, Australia (Brisbane), Hong Kong (Hong Kong Government Information Centre, 2005), Taiwan (Chen et al., 2005), and China (IPPC, 2014). Infestations in New Zealand have been eradicated, and efforts are underway to eliminate populations in China (ISSG, 2014).

S. invicta has spread to vulnerable island ecosystems, including some regions of Australia, North America, the Caribbean (Puerto Rico and the Virgin Islands), and the Pacific (New Zealand), and has the potential to colonize many other areas (McGlynn, 1999; Korzukhin et al., 2001; ISSG, 2010). Based on rainfall and temperature data and temperature-based predictions, Morrison et al. (2004) identified the potential global range expansion of S. invicta and concluded that large areas in Mexico, North and South America, Central America, and many Caribbean islands are at significant risk of invasion by S. invicta. Regions surrounding the Mediterranean, as well as some areas near the Black Sea and the Caspian Sea, are also reported to be at risk (Morrison et al., 2004).

In Turkey, colonies of Solenopsis invicta exist in the Çukurova region, but their epidemiological significance has not yet been investigated (Gezer and Şenel, 2012).

Local distribution is typically facilitated by the species' ability to fly. However, wind can also enhance this distribution.

"

Reproductive Information

"During mating flights, newly mated queens that survive and reach suitable nesting habitats (estimated to be around 1% due to predation and other mortality factors) shed their wings and enter the ground. They are confined to a chamber and begin laying eggs. Newly mated polygynous queens lay 20-30 eggs per day, while monogynous queens lay approximately 200 eggs per day. Mature monogynous queens can produce 800-1000 eggs per day (Taber, 2000). Larvae hatch from eggs 6 to 10 days after oviposition.

Larvae feed on energy produced from the breakdown of flight muscles, infertile (trophic) eggs, young larvae, and fat reserves. The first emerging worker ants are equally small and are called nanitics or minim workers.

Queens from polygynous colonies are not as successful as monogynous queens in establishing new colonies. Polygynous queens are smaller, produce fewer workers, and have a lower probability of insemination due to the higher prognosis of sterile males in polygynous colonies. Therefore, most new colonies in polygynous dominant areas arise through budding."

Lifecycle

"After hatching, larvae undergo four stages (instars) of development over a period of 12 to 15 days before pupating for 9 to 16 days. Development takes approximately 22 to 37 days depending on temperature. Most worker ants live for 60 to 150 days, with larger ants living longer, but workers can survive for 8 months or longer in colder weather. Newly established colonies develop winged reproductive ants approximately 6 to 8 months later and can produce 4000 to 6000 alates per year. Queen ants live for about 7 years and lay eggs.

Worker ants build and maintain the colony, care for the queen and brood, defend the colony, and forage for food. Their roles within the colony are determined by the size and needs of the colony and the age of the worker ants. Young workers serve as nurse ants, tending to the queen and brood by feeding and moving them. Older workers serve as reserves to defend the colony, construct and maintain the mound, and provide care. The oldest worker ants become foraging specialists. The tendency of larger workers to increase with the age of the colony facilitates the continual increase in labor efficiency (Tschinkel, 1988)."

Nutrition Information

"Fire ants are omnivores that consume sugars (carbohydrates), certain amino acids, ions in solution, and some fats containing polyunsaturated fatty acids. While they primarily feed on other arthropods and their exudates, particularly those produced by some sucking insects (Homoptera), they also consume dead plant and animal tissues such as seeds and fruits for developing or ripening.

Sugars are mainly utilized by workers, while amino acids are preferably consumed by queens and larvae. Plant oils are consumed equally between workers and larvae (Taber, 2000).

Worker ants use their mouthparts for biting and sipping. They store food in their crop and postpharyngeal gland (for oils only) before feeding it to other workers, and eventually larvae and the queen through a process called trophallaxis. Young larval stages (larvae) are fed only with liquid food. However, the final (fourth) larval stage can digest solid food particles. Worker ants place solid food particles in a small area just in front of and below the larva's mouth (an area called the presternum), where they externally digest proteins by secreting enzymes and chewing and ingesting smaller particles (Taber, 2000)."

General Impact Information

"Solenopsis invicta is a species of ant native to South America. It is an aggressive ant that thrives in high densities, thus able to dominate many potential food sources. It reproduces and spreads rapidly. Additionally, if disturbed, it can quickly relocate to ensure the survival of the colony. Due to its high reproductive capacity, large colony size, ability to exploit human disturbances, wide range of food sources, and ability to inflict painful stings, S. invicta is highly damaging. Its ability to sting allows it to suppress prey and even drive away larger vertebrate competitors from resources (ISSG, 2014). After being observed in the 1930s, S. invicta has become widespread in the southern United States and the Caribbean (Morrison et al., 2004). Its presence has also been reported in some areas of Australia and New Zealand. S. invicta is one of the most notorious invasive ants and has been nominated for the list of 100 Worst Invasive Species compiled by the Invasive Species Specialist Group (ISSG, 2014).

While considered beneficial as they feed on other insects in agricultural areas, red imported fire ants can cause damage by feeding on newly planted sorghum seeds. This pest sometimes damages the first leaves and roots of germinated seeds. Worker ants chew the thin seed coat, killing the embryo. They can also rarely damage the endosperm of dry seeds. By feeding on the embryo and endosperm, they create a rough and pitted hole, separating them from the seed. This damage leads to losses in germinating seeds and reductions in emerging sorghum plants (Şahbaz et al., 2012).

S. invicta creates tunnels through roots and tubers, feeds on plants, fruits, and seeds, and can infest young citrus trees (Stewart and Vinson, 1991). In addition to directly damaging plants, S. invicta exacerbates populations of other insect pests such as Homoptera (e.g., aphids, scale insects, and mealybugs). The ants consume the sugary sap produced by these pests and protect them from natural enemies."

General Management Information

Production practices aimed at reducing wireworm damage also prove effective in reducing damage caused by red imported fire ants. Additionally, besides seed treatment, proper preparation of the seedbed is necessary for better seedling emergence. Particularly under dry conditions, soil around the seed should be compacted well to hinder ant access to the seed (Şahbaz et al., 2012).

General Pathway Information

"The spread of S. invicta has been facilitated through the transportation of infested individuals or materials such as soil, pots, grass, and hay bales. Objects contaminated with soil pose a high risk due to the natural intertwining of soil with S. invicta.

It has been reported that outdoor electrical equipment or equipment in contact with the ground is often invaded by S. invicta. Electrical equipment provides colonies with warmth and shelter, making them attractive for infestation. Examples of invaded equipment include air conditioning units, power company transformers, traffic signal control cabinets, electric pumps, and automotive electrical systems.

It is believed that S. invicta was introduced to the port of Mobile, Alabama in the United States from northern Argentina or southern Brazil between 1930 and 1945 (Taber, 2000). Subsequently, S. invicta spread westward at a rate of 198 km per year."

Notes

The species has no reported uses.

References