Field Ant


Actual Size: 4 to 8 mm

Characteristics: Large; black, brown, or yellowish to bicolored red and black


  • Sometimes referred to as thatching or mound ants.
  • Herd and maintain aphid colonies on shrubs and trees
  • Can be confused with carpenter ants


There are more than 100 species of field ants distributed throughout the U.S. The Allegheny mound ant is found in the east and a common species in the west is the western thatching ant. They are called field ants because they prefer nesting in the open, but many of the northern species nest in woodlands. Field ants build mounds in open areas like lawns and meadows, and their mounds reach sizes of three to four feet wide and up to two feet tall. These ants are rarely found indoors, but are common around homes and other buildings.

Field Ant Habitat

Field ant colonies can survive for ten years or more and each colony contains a queen that lays all the eggs. These ants nest in soil or decayed logs, and are sometimes referred to as “thatching” or “mound” ants because some species construct their nests from small twigs, grass stems, leaves, and pine or fir needles. Field ants usually nest near rocks, trees, sidewalks, fences and foundations of structures. Unlike many ant pests species, these ants do not come indoors for food. They feed exclusively on outdoor food resources, such as live and dead insects and the honeydew produced by aphids.

Field Ant Behaviors, Threats or Dangers

Field ants do not sting, but they do bite if disturbed. If nests are disturbed or stood upon, ants may aggressively swarm out of the nest and bite the intruder. Their bite can pierce the skin, and they can spray formic acid, which may make a wound sting. The irritating formic acid can sometimes be smelled when dispensed by enough ants. In the northeastern United States, the Allegheny mound ant builds mounds similar in size to the red imported fire ant, causing “fire ant scares” in that part of the country.

Field Ant Prevention

Since field ants often avoid entering houses, low-level populations do not need to be treated. However, there are a few measures homeowners can take to prevent field ants from nesting. Store firewood above ground and at least 15 feet away from homes and buildings. Cut back tree limbs and branches that serve as a bridge to structures. Seal cracks and openings around the foundation, especially where utility pipes and wires enter from the outside.