Fire ants are a group of stinging ants within the genus Solenopsis, encompassing over 200 species. These insects typically have a copper-brown head and thorax with a darker abdomen, and worker ants range from 2 to 6 millimeters. Fire ants secure themselves with a bite before delivering a sting that injects a toxic alkaloid venom. This venom produces a burning sensation, which is the origin of their name. They are known for their aggressive nature, painful stings that can cause significant reactions in some individuals, and their capacity to harm plants, animals, and human infrastructure.
Their Original Home
Fire ants are native to South America, primarily originating from the continent’s tropical and subtropical regions. The red imported fire ant (Solenopsis invicta), a well-known species, comes from the Pantanal region of Brazil, Paraguay, and northern Argentina. This habitat features warm climates and areas prone to flooding.
These ants thrive in environments with fluctuating water levels, notably surviving floods by forming living rafts. Their native ecosystems provided specific environmental conditions that shaped their biology and behavior. This natural resilience contributed to their success when introduced to new territories globally.
Where They Are Found Now
Fire ants have expanded their geographical footprint beyond South America, due to human activity. The red imported fire ant, for example, was accidentally introduced into the United States around 1918, likely via cargo ships docking in Mobile, Alabama. They have since spread across much of the southeastern United States, establishing populations in states like Mississippi, Florida, Georgia, and Texas. Their northern migration in North America is generally limited by cold winter temperatures that can freeze soil deeply enough to affect overwintering colonies.
Beyond North America, these invasive ants have established populations globally. They were detected in Australia in Brisbane in 2001, likely arriving on cargo. Japan has also reported infestations, often linked to international trade. Countries in Asia, such as China and Taiwan, have experienced incursions, with fire ants threatening agriculture and public health.
Human transportation largely facilitates the global spread of fire ants, as they “hitchhike” on goods, vehicles, and plants. Their ability to adapt to diverse environments and form large, aggressive colonies allows them to outcompete native species and quickly establish themselves. Suitable climates, often mirroring their native subtropical conditions, are an important factor in their successful colonization of new areas.
Specific Nest Locations
Fire ants construct characteristic mounds, especially in open, sunny areas like pastures, lawns, and cultivated fields. These mounds are typically made of loose soil and lack a central opening, unlike many other ant species. While visible mounds are common, particularly in disturbed soils, their extensive tunnel systems can extend several feet underground and laterally.
In urban and suburban settings, fire ants build nests in locations such as gardens, park edges, and even around structures. They can infest electrical boxes, air conditioning units, and irrigation systems, causing property damage. In agricultural areas, their mounds can make plowing and cultivation difficult and damage crops.
Fire ant colonies are adaptable to environmental conditions. During hot, dry weather, they maintain colonies deeper underground for cooler, moister conditions. Conversely, during cold or wet periods, they move colonies higher above ground to avoid waterlogged soil and benefit from solar heating.