The term “red ants” is a broad description applying to many species, most of which pose little threat beyond a minor bite. The real source of concern is the invasive Red Imported Fire Ant (Solenopsis invicta), a species that has spread across large parts of the southern United States. Whether red ants are problematic depends entirely on the presence of this aggressive species, as its negative effects on health and property make it a significant pest.
Identifying the Problematic Species
The Red Imported Fire Ant (RIFA) worker is easily distinguished from most other reddish-brown ants by physical traits and behavior. Workers are polymorphic, meaning they vary significantly in size within a single colony, ranging from one-sixteenth to one-fifth of an inch in length. They have a reddish-brown head and thorax, but their abdomen, or gaster, is often a darker, shiny black color.
A clear sign of this species is their distinctive nesting structure: a dome-shaped mound of loose soil. Unlike native ant species, the RIFA mound does not have a visible opening in the center. Instead, the ants enter and exit the colony through underground tunnels extending outward from the nest. These mounds can reach up to 18 inches high and 24 inches wide, particularly in undisturbed, sunny areas like lawns and pastures.
The most definitive identification marker is the aggressive behavior displayed when a nest is disturbed. When the mound is inadvertently kicked or stepped on, hundreds to thousands of ants will swarm out immediately. They rapidly climb onto the source of the disturbance and begin to sting en masse. This collective defensive action is unique to the imported fire ant and is the strongest indicator that the problematic species is present.
Health and Infrastructure Hazards
The primary danger comes from their venom, a complex substance injected through a stinger located at the tip of the abdomen. The venom is unusual for an insect, consisting of over 95% water-insoluble piperidine alkaloids, known as solenopsins. These cytotoxic solenopsin alkaloids cause the immediate burning pain and the formation of the characteristic white pustule at the sting site.
Within eight to 24 hours of the sting, a sterile pustule develops as a localized reaction to the venom. This small bump can easily rupture, leading to a risk of secondary bacterial infection if improperly treated. The trace proteins in the venom are potent allergens, posing the most severe health risk by potentially triggering a systemic allergic reaction. In sensitized individuals, this can escalate rapidly to life-threatening anaphylaxis, requiring immediate emergency medical intervention.
The ants also present a serious threat to immobile individuals and pets who are unable to move away from an active mound. Infants, elderly persons, and small domestic animals can receive hundreds of stings, leading to severe reactions or death due to the sheer volume of injected venom. Beyond biological threats, the ants are a persistent cause of infrastructure failure due to their attraction to electrical devices. They frequently infest utility boxes, air conditioning units, and traffic signal controls, seeking warmth and dry conditions.
The ants cause short circuits by bridging electrical contacts with their bodies, which leads to their electrocution. Dying ants release alarm pheromones that attract more workers, resulting in a dense accumulation of dead ants within the equipment housing. This mass of ant bodies, along with soil and debris, can cause corrosion and interfere with switching mechanisms. The movement of colonies into sheltered enclosures, such as pad-mounted transformers, can cause power outages and expensive repairs.
Controlling the Population
Controlling the Red Imported Fire Ant population requires a strategic, long-term approach, often called the two-step method. The first step involves broadcasting a slow-acting insecticidal bait over the entire infested area to target the colony systemically. Worker ants collect the bait, typically a pesticide mixed with a food source like soybean oil, and carry it back to the nest.
The slow-acting ingredient is shared with the queen and the developing brood, eventually leading to the queen’s death or sterility and the colony’s gradual decline. For optimal results, this broadcast application should occur when ants are actively foraging, typically in the late afternoon or early evening when temperatures are moderate and the ground is dry. This broad treatment can reduce the overall fire ant population by 80 to 90 percent over several weeks.
The second step is the targeted treatment of individual mounds that require immediate control, such as those near playgrounds or high-traffic areas. This involves applying a fast-acting contact insecticide, like a liquid drench or dust, directly to the mound. It is important not to disturb the mound before treating it, as this will cause the ants to swarm and scatter, making the treatment less effective.
For safety reasons, especially when ants are nesting in electrical housings, professional pest control or an electrician should be consulted. They have the specialized products and training necessary to safely eliminate colonies from energized equipment without causing further damage or personal injury. Following both steps semi-annually, in the spring and fall, provides the most comprehensive and lasting control.