Western Harvester Ants

Within the United States, western harvester ants (Pogonomyrmex occidentalis) are primarily seen in the mountain ranges of most of the western states. Western harvester ants measure about 6.5 to 10 mm in length and are dark red in color.

Unlike some other ant species, western harvester ants prefer to dwell in areas where the soil has already been disturbed. The nests of western harvester ants measure approximately 90 cm tall and 490 to 600 cm deep. While they appear to be merely piles of dirt, the nests contain several interior chambers. Western harvester ants often remove all surrounding plants in order to prevent shade. These ants cover their mounds with charcoal, dead leaves, small rocks and other debris to keep them warm, and they remain inside the nests during the hottest parts of the day. There have been reports of damage to pavement because of the mounds of western harvester ants. The mounds were built at the edge of the pavement and caused erosion when it rained.

Western harvester ants feed on seeds and insects, but typically eat only one species at a time. Western harvester ants can travel long distances in search of food, and different species of harvester ants exhibit different foraging behaviors. Red harvester ants leave scent trails of their routes, while California harvester ants leave their nests one at a time and go in all directions without leaving trails.

Western harvester ants can be defensive of their nests when they perceive a threat and can deliver a painful sting.

This species swarms primarily during summer. Western harvester ants mate in flight, and newly fertilized queens then begin their own colonies.