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.

[2] 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 sting.

Common symptoms include dizziness, chest pain, nausea, severe sweating, low blood pressure, loss of breath, and slurred speech.

[24] Buren collected a holotype worker from Cuiabá in Mato Grosso, Brazil, and provided the first official description of the ant in a journal article published by the Georgia Entomological Society.

[19] Since the first description of S. invicta, over 1,800 scientific papers using the name were published discussing a wide range of topics about its ecological behaviour, genetics, chemical communication, economic impacts, methods of control, population, and physiology.

Light-coloured areas of the head in small to medium-sized workers is restricted to only the frontal region, with a dark mark resembling an arrow or rocket being present.

The head is yellowish or yellowish-brown around the central regions, the occiput and mandibles are a similar colour to the thorax, and the wing veins range from colourless to pale brown.

[50] Fourth-instar larvae of males and queens can be differentiated based on their relative shape and body coloration,[50] and also internal gonopodal imaginal discs can differ.

[56] Like other insects, the red imported fire ant breathes through a system of gas-filled tubes called tracheae connected to the external environment through spiracles.

[59][71] Hypoxia and hypercapnia can result from red imported fire ant colonies living in poorly ventilated thermoregulatory mounds and underground nests.

The high rate of metabolic activity associated with warmer temperatures is a limiting factor on colony growth because the need for food consumption is also increased.

The red imported fire ant and S. saevissima are parapatric in Brazil, with contact zones known in Mato Grosso do Sul, Paraná state and São Paulo.

[89] In areas where water is present, they are commonly found around: irrigation channels, lakes, ponds, reservoirs, rivers, streams, riverbanks, and mangrove swamps.

[92] 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.

In August 2023, the Invasive Species Council said that without additional funding, fire ants would probably spread into northern New South Wales and west, potentially into the Murray Darling Basin.

[163] Tunnels are designed to allow effective body, limb and antennae interactions with walls, and a worker can also move exceptionally fast inside them (more than nine bodylengths per second).

These communication methods are used in a variety of activities, such as nestmate recruitment, foraging, attraction, and defence; for example, a worker may secrete trail pheromones if a food source it discovered is too large to carry.

The pressure of attacks initiated by C. insana increase over time, causing queens to exhibit different reactions, including escaping, concealment, or defence.

Pathogens include Myrmecomyces annellisae, Mattesia spp., Steinernema spp.,[209] a mermithid nematode,[210] Vairimorpha invictae, which can be transmitted via live larvae and pupae and dead adults[211][212] and Tetradonema solenopsis, which can be fatal to a large portion of a colony.

[226][227] Nuptial flight in red imported fire ants begins during the warmer seasons of the year (spring and summer), usually two days after rain.

[281] These colonies might increase their reproductive output as a result of having many queens and the possibility of exploiting greater territories by means of cooperative recruitment and interconnected mounds.

[294] It is believed that red imported fire ants have a strong impact on many herpetofauna species; scientists have noted population declines in the Florida kingsnake (Lampropeltis getula floridana), and eggs and adults of the eastern fence lizard (Sceloporus undulatus) and six-lined racerunner (Aspidoscelis sexlineata) are a source of food.

[330] This is clearly evident as scientists observed that cotton aphid (Aphis gossypii) populations, and the predation of sentinel bollworm eggs, increased in areas with red imported fire ant presence.

In the United States, the Food and Drug Administration estimates more than $5 billion is spent annually on medical treatment, damage, and control in infested areas.

[346][349] Nests can be built under pavements or even roads, as well as under driveways, foundations, lawns, edges of sidewalks, under patio slabs, in electrical boxes or near power lines.

A colony can excavate huge quantities of soil, resulting in structural problems in driveways, pavings and walls, and can also cause the formation of potholes in roads.

[3][94] Not only do they thrive in urban areas, red imported fire ants can damage equipment and infrastructure and impact business, land, and property values.

[346][357] Colonies aggregate near electrical fields and are capable of causing short circuits or interfering with switches and equipment such as air conditioners, computers, and water pumps.

[377] However, some scientists have suggested that the beneficial status of the red imported fire ant is hard to predict when geography, plant size, season, soil moisture and the use of insecticides are not considered.

Phorid flies have also been viewed as potential biological agents, as they can reduce foraging activity in red imported fire ants and affect population levels.