Fire ants are a common sight across Texas, with their distinctive mounds dotting landscapes from urban parks to agricultural fields. Most Texans recognize these ants as an invasive species, known for their aggressive behavior and painful stings. While they are now an established part of the state’s environment, these ants were not always present in North America. Their widespread presence today is the result of a journey that began far from Texas.
Journey to North America
The red imported fire ant, Solenopsis invicta, is native to South America. These ants are believed to have first arrived in the United States accidentally through the port of Mobile, Alabama. This initial introduction likely occurred in the 1930s, with some sources suggesting an earlier arrival around 1918 for the black imported fire ant, Solenopsis richteri.
The most probable method of their arrival was through cargo ships, where they were likely stowed away in soil used as ballast. From Mobile, Alabama, the ants began to spread across the southeastern United States, aided by both natural means and human activities.
Establishing a Foothold in Texas
Fire ants reached Texas in the mid-20th century, around 1956 or 1957. Their entry into the state was a continuation of their natural expansion from neighboring states. However, human-assisted transport also played a significant role in their rapid colonization across Texas.
Their swift spread was aided by the movement of nursery stock, hay, agricultural commodities, soil, and equipment. The ants can also travel long distances when newly mated queens land on vehicles like cars, trucks, or trains. Once established, fire ant colonies can spread quickly through mating flights of winged reproductive ants and by forming rafts to float on floodwaters.
The red imported fire ant spread across Texas at a rate of approximately 20-30 miles per year between 1957 and 1982. This rapid expansion allowed them to infest over a third of Texas by 1985. Today, they are found throughout much of the state, including the eastern two-thirds, adapting well to diverse environments, though their spread has slowed in the drier parts of West Texas.
Consequences of Their Presence
Fire ants have significant ecological, agricultural, and human health impacts. In ecosystems, fire ants can displace native ant species, outcompeting them for resources and sometimes directly preying on them. This disruption can lead to a reduction in the population numbers of indigenous ants. Ground-nesting birds, such as the Bobwhite Quail, are particularly vulnerable, as fire ants are known to attack and consume newly hatched chicks or destroy unhatched eggs.
In agriculture, fire ants cause economic losses by damaging crops like sorghum, corn, and citrus seedlings. They can also girdle young trees and interfere with farm machinery due to their large mounds. For livestock, fire ant stings can affect young and newborn animals, making them especially susceptible to the venomous stings.
Fire ants also pose a direct threat to human health. Their stings are painful, causing blisters or pustules. For sensitive individuals, stings can trigger allergic reactions. These ants can also forage indoors, and can pose a threat to bedridden individuals or small children.