The Red Imported Fire Ant (Solenopsis invicta) does not have established, self-sustaining colonies in Iowa. While the ant has not colonized the area, the threat of accidental introduction remains a concern for state agricultural and entomological authorities. Public vigilance is an important part of the strategy to prevent the establishment of this pest.
The Established Range of Fire Ants
The Red Imported Fire Ant (Solenopsis invicta) is native to South America. It was accidentally introduced into the United States in the 1930s through Mobile, Alabama, and spread rapidly across the Southeast. Its established range covers a significant portion of the southern US, extending from Florida and North Carolina west through Texas and into parts of Oklahoma and Arkansas.
This distribution is limited by environmental factors, particularly cold temperatures to the north. However, the ants can travel long distances via human commerce, posing a risk to non-infested states like Iowa. They are often transported inadvertently in soil, potted plants, nursery stock, sod, or cargo containers from infested regions.
Climatic Constraints Preventing Establishment
The cold winter climate prevents the Red Imported Fire Ant from establishing permanent colonies in Iowa. The survival and reproduction of S. invicta colonies depend on soil temperatures. Extended periods of freezing temperatures increase the rate of “winter kill,” where a large portion of the worker population dies off.
Scientific models show the ant is unlikely to successfully colonize areas where minimum winter temperatures consistently fall below a certain threshold. The deep, prolonged cold in Iowa soil prevents queens from producing the reproductive offspring needed to sustain colony growth over multiple seasons. Even if a colony survives a mild winter, a subsequent harsh season eliminates the population, preventing long-term establishment.
Ants in Iowa Commonly Mistaken for Fire Ants
Many native Iowa ants are mistaken for the Red Imported Fire Ant due to reddish coloration or aggressive behavior when nests are disturbed. Field Ants (Formica species) are common misidentifications, as some varieties are reddish-brown and deliver a painful bite. Unlike fire ants, which sting and inject venom, field ants bite and spray formic acid into the wound, causing a burning sensation.
Another mistaken species is the Pavement Ant (Tetramorium immigrans), which is yellowish-red to dark brown and builds small soil mounds near sidewalks or driveways. True S. invicta workers measure 1/8 to 1/4 inch long. Their colonies feature a distinctive mound of loose, dome-shaped soil that lacks a single central entrance hole. If a disturbed mound has a visible hole in the center, it is generally a native species.
Reporting and Monitoring Potential Sightings
Public vigilance is essential for invasive species management, as early detection aids eradication efforts. If a suspicious ant or mound is found, citizens should contact a state authority immediately to confirm the species. Appropriate contacts include the Iowa State University Extension and Outreach or the Iowa Department of Agriculture and Land Stewardship.
Secure photographs of the ants and the mound, as visual evidence aids identification. Do not attempt to treat or destroy the colony until official identification is made. Disturbing the nest can cause the ants to scatter and spread the problem. Reporting non-native pests helps the state monitor for accidental introductions that could threaten Iowa’s environment and agriculture.