Harvester ants make their nests in the ground in open, sunny areas. Some species make only one opening to the nest. The workers clear away the vegetation around the nest. The clear space can be more than 30 feet in diameter.
Some species of harvester ants place stones, sticks, and pieces of dead grass on the soil in the area that they have cleared. Scientists suspect that the debris absorbs heat and helps to heat the nest that is underground. During the year, as the angle of the sun changes, the workers may move the nest if the area becomes shady.
The workers excavate galleries and tunnels under the ground. Scientists found one nest that extended more than ten feet into the soil. The workers take the soil out of the nest as they dig the tunnels. Some species build a mound with the excavated soil. Other species carry the soil away from the nest opening.
Harvester ant workers collect seeds. In the dry environment of the southwestern United States, harvester ants are probably the major seed predator. The ants are able to compete successfully with mammals, like mice, for seeds.
This seed gathering is the reason these ants were given their common name of “harvester”. The workers bring most of the seeds back to the nest. However when they find the seeds of some plants, they remove part of the seed for food and discard the rest. Harvester ants can cause crop damage by taking the seeds of wheat and oats. They also take seeds from alfalfa, Johnson grass, mesquite, and Bermuda grass.
If a harvester ant worker finds some seeds, she first tries to pick one up. If the worker can pick up one of the seeds, she starts back toward the nest. Along the way, she leaves a trail of a chemical called a pheromone. The scent of the pheromone will mark the way back to the seeds. When she reaches the nest, she recruits other workers to return to get the rest of the seeds.
If a harvester ant worker finds seeds that are too large for her to carry alone, she “calls for help” by releasing a pheromone into the air. Other harvester ant workers respond to the smell of the pheromone and come to help.
Harvester ant workers also collect insects when they are available. In their book, “Ants”, Wilson and H