[1] These large (5– to 7-mm) ants prefer arid chaparral habitats and are native to the Southwestern United States.

Red harvester ant nests are characterized by a lack of plant growth and small pebbles surrounding the entrance to the tunnel, which usually descends at a pronounced angle.

[3] The main food source for red harvester ants usually consists of seeds, which they hoard in great numbers.

Foragers still in the nest interpret this to mean food searches will be profitable: low energy input with a high chance of a seed reward.

[6] The ability for a colony to quickly regulate its foraging behavior is quite important since their food source is variable and scattered.

This regulatory ability is variable in itself, influenced by food availability, current need to eat, and colony health.

[2] Overall, the red harvester ant demonstrates a remarkable ability in social cognition, cost-benefit analysis, and behavioral economics.

[11] Interspecies competition exists between harvester ant populations, presenting challenges to successful foraging.

One example of this is the competition for access to seed resources between the Novomessor cockerelli and Pogonomyrmex barbatus species of harvester ants.

Novomessor cockerelli ants engage in interference competition against Pogonomyrmex barbatus colonies by "plugging" entrances to the nest with sand and small rocks.

This delays activity of P. barbatus for one to three hours, shifting the onset of foraging until later in the day when the temperature is substantially higher.

Research indicated that the affected P. barbatus populations did not take efforts to compensate for the interference in their activities, such as by inducing higher rates of foraging.

[12] Red harvester ants are eusocial insects, characterized by a high level of cooperation and an organized division of labor.

After copulation, the male usually dies, while the now-fertilized queen returns to the ground to search for a suitable nesting site.

Some individuals are specialized for reproductive function, while other ants are responsible for nonreproductive roles such as defense, caring for the brood, and foraging for food.

The system of division of labor naturally arises in conjunction with the formation of the group, rather than as a secondary adaptation; otherwise solitary queen harvest ants placed in forced association had division of labor arise in groups that lack an evolutionary history of such social arrangements.

[13] Within nonreproductive P. barbatus worker ants, five major tasks are performed: foraging, maintenance of the nest, defense, midden work, and convening.

Over the course of the following six to eight weeks, the primary brood of nonreproductive worker ants emerges and begins to forage and build the colony.

This occurs as a result of sexually stimulating pheromones secreted from the poison glands of reproductive P. barbatus females.

These pheromones are perfectly detected by males of the species upon physical contact, resulting in the stimulation of sexual behavior.

Consequently, the communal mating displays heavily favor reproduction with larger or more persistent males which are able to overpower the females and successfully copulate.

Harvester ants defend their colonies vigorously against real or perceived attacks, whether by large or small animals.

The effect spreads through the lymphatic system, sometimes causing dangerous reactions, especially in animals sensitive or allergic to their venom.

Their decline has affected many native species, especially those for which the red harvester ant is a chief source of food, such as the Texas horned lizard.