Field Ant: Facts, Identification & Control

Field ants are a large group of ant species. These ants make their nests in the ground in lawns, gardens, fields, and parks. Depending on the species, the size of the workers ranges from 1/8 to ΒΌ. The color of field ants may be red, black, or a combination of red and black.

Field ants usually nest near trees, rocks, sidewalks, fences, or foundations of buildings. Many species of field ants make a mound with the soil that they excavate under the ground. Sometimes people mistake these mounds for fire ant activity. Field ants do not sting. They bite when they are disturbed. Some field ants can spray formic acid while they bite, so their bites can be painful.

Some species of field ants, like the red-and-black thatching ant, Formica obscuripes (Forel), make mounds of leaves, grass, twigs, or even pine needles. Others, like the California red-and-black field ant, Formica occidua (Wheeler) and the brown field ant, Formica cinerea (Mayr), make their nests in cracks of sidewalks or beside trees or foundation walls.

Field ants eat honeydew. This is a sweet substance that they get from insects like mealybugs and aphids. They find the aphids on trees and shrubs. Some species of field ants, like the silky ants, Formica fusca (L.), keep herds of aphids so there is always a supply of honeydew. Field ants also eat other insects. Some field ants are attracted to meats. Many species of field ants are scavengers.

Field ants do not usually invade homes. The workers will often hunt for food on decks, porches, and patios. Sometimes people see black field ants on the wood deck and assume they are carpenter ants.

Preventing field ant problems begins with a careful inspection. Look for things that the ants might use as nesting sites. Place firewood on racks off of the ground and store it away from the house. Move mulch away from the foundation to discourage ants from nesting. Make sure exterior doors close tightly. Replace weather-stripping where it is missing.

Liquid insecticide may be effective against individual field ant mounds. A liquid insecticide barrier applied to the outside foundation can help prevent workers from wandering into the home. If the ant nest is hard to find, ant bait may be the best choice for control.

Incomplete treatment can make the problem worse. If the treatment does not eliminate the entire colony, the ant population can rebound. When the surviving workers resume foraging and feeding, the problem will return. It is advisable to contact the local pest control professionals. They will have the products and the equipment to control field ants effectively.