Red imported fire ants (Solenopsis invicta) are a well-known invasive species, often associated with painful stings and unsightly mounds. Only specific reproductive individuals within a colony are winged and can fly. This aerial capability is a key factor in their spread and the establishment of new colonies.
The Fire Ant’s Aerial Stage
Within a fire ant colony, only reproductive males and females, known as alates or swarmers, possess wings and can fly. Worker ants are wingless. Alates are larger than worker ants and have two pairs of translucent wings roughly the same length as their bodies. Male alates are typically smaller than female alates, with a glossier black body and a smaller head.
These winged ants emerge for flight under specific environmental conditions, usually during warm, humid periods after rainfall. Nuptial flights occur in the morning, one or two days after moderate to heavy rainfall, when temperatures are between 70°F and 95°F and wind is light. While alates are most abundant in late spring and early summer, they can be observed at any time of the year if conditions are suitable.
Purpose of Mating Flights
Fire ants fly for reproduction and to establish new colonies, a process called a “nuptial flight.” During these flights, winged males leave the nest first, forming aerial swarms. Female alates then emerge and fly into these swarms to mate in the air. After mating, the male ant dies.
The newly fertilized female, now a queen, sheds her wings and seeks a suitable location to initiate a new colony. She excavates a small chamber, often just a few centimeters below the surface, and seals the entrance before laying her first batch of eggs. This dispersal allows queens to fly up to a quarter of a mile from their parent colony, though they can be carried much farther by wind, potentially traveling for miles. While a majority of queens may land within a two-kilometer radius, some can disperse as far as 10 kilometers.
How Fire Ants Spread Beyond Flight
Beyond aerial dispersal, fire ants employ other strategies to spread and establish new territories. One method is “budding,” where a subset of the existing colony, including a queen and workers, relocates to form a satellite colony. This expands the colony’s footprint without a nuptial flight. Colonies with multiple queens can also split into distinct colonies.
Human activities also contribute to their spread, often called human-assisted dispersal. Fire ants hitchhike on infested soil, potted plants, landscaping materials, hay, or in vehicles. Quarantine measures regulate the movement of these commodities to prevent artificial spread. Additionally, fire ants survive floods by forming living rafts. These rafts, composed of thousands of ants clinging together, float on floodwaters for extended periods, even containing queens and brood, until they reach dry ground to establish a new colony.