Fire ants represent an invasive species that has established a significant presence across various regions of the United States. These insects, originally from South America, have spread considerably, impacting both natural environments and human activities. Their presence is a concern due to their painful stings and the ecological and economic disruptions they cause.
What Are Fire Ants?
Fire ants are commonly known as red imported fire ants, scientifically identified as Solenopsis invicta. These ants originated in South America, specifically from areas within Argentina and Brazil. They were first introduced into the United States accidentally, arriving through the seaport of Mobile, Alabama, between 1933 and 1945, likely via cargo ships.
Fire ant appearance varies within a colony. Worker ants are typically reddish-brown to black and range in size from about 1/8 to 1/4 inch (2.4 to 6 mm) in length. Queens are larger, measuring around 6 to 8 mm. Fire ant colonies exhibit a complex social structure, consisting of a queen or multiple queens responsible for egg-laying, along with numerous worker ants that perform tasks such as foraging, caring for the young, and defending the colony. A mature colony can house hundreds of thousands of workers, with some multiple-queen colonies containing up to 40 million ants.
Where Fire Ants Are Found
Fire ants are primarily established across the southeastern United States. Their current range includes all or parts of Alabama, Arkansas, California, Florida, Georgia, Louisiana, Mississippi, North Carolina, Oklahoma, South Carolina, Tennessee, Texas, and Virginia. Infestations have also been sporadically reported in states such as Arizona, Delaware, Kentucky, Maryland, and New Mexico, as well as in Puerto Rico.
Their expansion is influenced by both natural processes and human activities. Mating flights allow winged queens to fly for miles and establish new colonies. During flood events, these ants can form large floating rafts of their bodies, enabling colonies to survive and disperse to new areas. Human movement of infested materials significantly contributes to their spread, including transporting infested soil, nursery stock, potted plants, agricultural commodities, or inadvertently carrying colonies on dirty machinery.
Recognizing and Understanding the Threat
Fire ant mounds are a primary indicator of their presence. These mounds are typically dome-shaped, appearing as loose piles of soil, and notably lack a central opening. Undisturbed mounds often measure about 18 inches across and 8 to 12 inches tall, growing larger in open pastures. In areas with sandy soils, mounds may be less pronounced, and during hot or dry conditions, colonies may move deeper underground, making mounds less visible.
Fire ant stings are painful, causing a burning sensation, swelling, and redness. Within hours, small pustules or blisters may form at the sting sites, which can be itchy and may take up to 10 days to heal. While most reactions are localized, some individuals can experience severe allergic reactions, including anaphylaxis, characterized by difficulty breathing, rapid heartbeat, and swelling of the throat or tongue.
Beyond human health, fire ants pose threats to agriculture, wildlife, and infrastructure.
Agriculture
In agriculture, they can damage over 50 types of crops by feeding on seeds and seedlings, and their mounds can interfere with and damage farm equipment during cultivation and harvesting. Livestock, particularly young animals, are vulnerable to stings around sensitive areas like the eyes, mouth, and nose, which can lead to blindness or suffocation.
Wildlife
For wildlife, fire ants prey on ground-nesting birds, small mammals, reptiles, and amphibians, disrupting ecosystems and displacing native ant species. They can also reduce food sources for other animals.
Infrastructure
Fire ants are known to nest inside electrical equipment, such as traffic signal boxes and air conditioners, causing short circuits and costly equipment failures. They can also undermine roads and other structures, leading to damage.