Fire ants, primarily species like Solenopsis invicta, are well-known aggressive stinging pests recognized for their distinctive soil mounds. They are a common presence in many landscapes, often surprising people with their painful stings. Understanding their origins and preferred habitats clarifies their widespread presence.
Native Geographical Range
Fire ants are native to South America’s tropical and subtropical regions, including parts of Brazil, Argentina, Paraguay, and Uruguay. Within this native distribution, fire ants are frequently found in the Pantanal wetlands and along the floodplains of the Paraguay River.
In these South American ecosystems, fire ant populations are naturally regulated by a diverse array of predators, parasites, and competitors. This ecological balance helps to keep their numbers in check, resulting in significantly lower densities compared to areas where they have been introduced.
Global Invasion and Spread
Fire ants have expanded far beyond their native South American origins, largely due to human activities. They were first introduced into the United States, likely through the port of Mobile, Alabama, in the 1930s, and have since spread throughout the southeastern states, including Alabama, Florida, Georgia, Louisiana, Mississippi, North Carolina, and Texas. Their spread continues westward into states like California, New Mexico, and Arizona.
Beyond the Americas, fire ants have established populations in Australia, particularly in Queensland, with initial detections occurring in 2001. They have also invaded numerous regions across Asia, including China, Taiwan, Japan, the Philippines, Singapore, and Hong Kong. Various Caribbean islands have also become home to these invasive ants. In 2023, fire ants were detected in Sicily, marking their presence in Europe.
The primary mechanism for their global dispersal is human commerce, with ants inadvertently hitching rides in contaminated soil, nursery stock, hay, and other materials. Shipping ports have played a significant role in their spread, as colonies can travel long distances in cargo and even ship ballast soil. Their rapid expansion in new territories is facilitated by their remarkable adaptability and the absence of natural enemies that control their populations in their native range. These ants are considered “disturbance specialists,” thriving in human-altered environments.
Preferred Habitats and Environments
Within their geographical ranges, fire ants show a strong preference for certain types of environments. They thrive in disturbed soils and open, sunny areas. These include common landscapes such as lawns, pastures, agricultural fields, roadsides, meadows, parks, playgrounds, and golf courses.
Fire ants are also highly adaptable to urban and suburban settings. They are frequently encountered near sidewalks, foundations of buildings, and utility boxes. A consistent need for moisture means they often build their mounds near water sources, including irrigation channels, lakes, ponds, rivers, and areas prone to flooding. While they can infest various soil types, they tend to favor well-drained loamy soils, though they are observed in clay soils where prevalent. Nests are typically within the top meter of soil, though they can extend deeper in softer types.