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Solenopsis invicta (Family Formicidae)

Red Imported Fire Ant



Red Imported Fire Ants have been found in Brisbane and at one site near Cooroy on Queensland's Sunshine Coast. (QLD)


Red Imported Fire Ants are small ordinary-looking ants that vary in length from 2 to 6 mm. They are a uniform red-brown colour and almost indistinguishable from many native ant species likely to be seen in the average backyard. Some features that distinguish these ants from other species are: two segments forming the petiole separating the thorax from the gaster; a sting is present, as are: an antenna with ten segments (including the two-segmented club); four mandibular teeth; a tooth on each side and one in the centre of the lower edge of the clypeus.

Their nests are distinctive and more easily recognised, and consist of dome-shaped mounds usually 40–60 cm across and 20–40 cm in height. Exit holes are absent, as fire ants enter the nest through tunnels which extend a metre or so away from the mound.

Ecology/Way of Life:

Red Imported Fire Ants prefer open and disturbed sites such as residential and industrial areas as well as open forests. They feed on a variety of food sources, including other insects, carrion, nectar from flowers, seeds; in fact almost anything edible. Colonies can be very large with up to 500,000 workers in colonies with a single queen, and in smaller (around 200,000 workers) colonies with many queens. New queens and males are produced in batches and these fly from the nest on still, warm days after rain. After mating in the air, the queens land, remove their wings, and start a new colony. It will take one or more years for a new colony to repeat this cycle.

Like many ant species, Red Imported Fire Ants communicate through the use of pheromones, or chemicals which trigger certain behaviours. Use of such pheromones enable Red Imported Fire Ants to muster extra workers when needed, such as when food sources are discovered or when help is needed to defend the nest.

Preferred Image

Interaction with Humans/Threats:

Two striking features of these ants are their aggressive nature and their painful sting. When the nest is disturbed, workers will swarm out in large numbers and sting any nearby intruder. The resulting stings produce distinctive, painful pustules that take a week or more to heal.

Stings from Red Imported Fire Ants are painful, and common in areas where the ant is found. These ants defend their nest aggressively and attack intruders in large numbers. They are also responsible for damage to electrical installations, irrigation equipment, some crops, livestock. In the USA, the total damage bill for control and the damage they cause tops one billion dollars (US) annually. Fortunately they have not spread far in Australia and a large program to eradicate them has commenced. Some people are allergic to Red Imported Fire Ant venom and for them, a sting can be life threatening.

Other Comments:

Scientific Name: Solenopsis invictasolen = channel or pipe, and opsis = appearance or face, and the species name comes from the Latin invicta = invincible or unconquered. Before 1972 the species was called Solenopsis saevissima or Solenopsis richteri.

Further Reading:

Collins, L. and Scheffrahn, R.H. (2003). Red Imported Fire Ant.

Reimer, N. and VanGelder, E. (2005). Solenopsis Invicta.

Texas A&M University. Department of Entomology. The Texas Imported Fire Ant Research and Management Project. (2005).

The Queensland DPI. (2005). Fire Ants.


Text, map and image by C. Vanderwoude, M. Elson-Harris and M. K. McNaught

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Images and Multi-media:  
Attached Image  
image/gif 50601 bytes Solenopsis invicta
Distribution Map  
image/gif 5195 bytes Distribution of Solenopsis invicta

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