This revelation means that any records before 1972 for imported fire ant are for the old designation, S. saevissima richteri, not for either of the now recognized species. All such old collections are considered to be for S. invicta in all States except AL and MS, the only states where both species are known to occur. There, the record could have been for either or both species, but no distinction can made as to which it might have been at the time of collection. The ants nest in the soil of open areas, pastures and agronomic fields, but are found occasionally in wooded areas. Mounds are generally dome-shaped in contrast to those of other fire ant species, and the sting, characterized by an intense burning sensation, is more severe.
Sensitive individuals can swell up as a result of stings and occasionally die.
The ants have a serious impact on agriculture since the hardened mounds interfere with the mechanical cultivation of fields and the ants' painful stings interfere with livestock grazing and the harvesting of crops by farm workers. A colony is usually started by a single queen, but some beginning colonies are known to contain up to 5 queens. Mature multi-queen colonies are generally the case. Reproductive forms are produced in 5-12 months. A colony may contain 240,000 workers after 3 years.