The western harvester ant, Pogonomyrmex occidentalis (Cresson), is a large ant. The workers are about ¼” long. In colonies of western harvester ants, all of the workers are the same size. These ants are usually a vivid red in color.
The western harvester ant is found across most of the western United States. The range extends from California to Kansas. From Montana and North Dakota the western harvester ant is found southward to the Texas Panhandle.
Western harvester ant workers build a cone-shaped mound. The mound can be very large and many mounds are visible from far away. The mound contains tunnels and chambers. The workers move the queen and the immature ants up into the mound for the temperature.
There are usually entrance holes on the sides of the mound. The workers cover the mound with pebbles and gravel. Scientists suspect that the pebbles absorb heat and transfer it to the nest inside the mound.
Western harvester ant workers gather seeds to feed the colony. They store the seeds in special chambers inside the mound. Scientists think that the dry environment inside the mound prevents the seeds from germinating. Scientists have found that the ants seem to try to make their nest near the plants that produce the seeds.
During the summer, colonies of western harvester ants produce ants with wings. Scientists call these winged ants alates. Since the winged ants fly out of their nests in large numbers, many people call them swarmers.
Scientists have found that the mating flights of western harvester ants usually happen within a day or two of a rainfall. If everything works perfectly, the male and female alates from many colonies will fly out of their nests at the same time.
The inseminated females fly away after mating. These will be the founding queens of new colonies. The males die soon after mating.