Pogonomyrmex occidentalis

Mature colonies consist of up to 20,000 workers and one queen. A queen can live up to 30 years, and many colonies survive for 20 years. A colony inhabits a nest that is up to deep. The queen stays at the bottom of the nest, and workers usually relocate themselves and brood within the nest, capturing safe levels of heat. A colony's nest is topped by an irregularly conical nest mound Individual queens found colonies on their own, without workers or other queens. Survivorship of colonies in the first year is negatively correlated with increasing density of foundresses. Factors independent of colony density are responsible for >90% of foundress mortality. Queens in some populations found colonies claustrally and in others, semi-claustrally. Many of the eggs laid in the first batch die or are unembryonated. During colony founding, larvae may eat eggs. The first workers produced, known as nanitics, are stunted. They measure 2 mm long (33% shorter than typical workers of established colonies). 2/188 founding queens survived from July to March. ==Workers==

Workers' bodies are usually dark red and those in a mature colony are on average 6 mm long. In the field, workers are active when the temperature at the surface of the colony's mound is . ==Nutrition==

Workers harvest seeds and pollen directly from plants and gather fallen seeds. Some seeds are sometimes stored in chambers within the nest and are depleted during winter. Workers also gather newly dead insects. Workers generally forage April–September. Workers generally forage throughout the day during cooler months and only 5–11 am and 3–9 pm during the summer. Given a choice, workers select a diversity of seeds or seeds that are new to the colony. Workers defend foraging territories against neighboring colonies. Different plant environments support different densities of colonies. Foragers produce more period mRNA during darkness, the timing of which varies seasonally. == Association with Myrmecocystus mexicanus ==

Cole et al. surveyed the distribution of Myrmecocystus mexicanus nests, (a species of North American honey ant) relative to the distribution of P. occidentalis nests at a site in western Colorado and found that there was a definite spatial association between the two species. They also observed that M. mexicanus feeds on dead or close-to-death P. occidentalis workers, and believed that P. occidentalis provides the main source of food for the M. mexicanus colonies at that site. Thus, the M. mexicanus situates nests nearby P. occidentalis colonies to collect this source of nutrition. There was no substantial evidence that M. mexicanus actively predates healthy P. occidentalis workers. ==Biomass and brood production==

Different developmental stages of ants within a colony process different kinds of food; larvae ingest solids, while adults ingest liquids, including larval excretions. Immature individuals cannot pass from one larval stage to another or to adulthood without the help of adults; adults help immature individuals remove their old larval and/or pupal skins during ecdysis (molting). As larvae are relatively immobile, they only interact with nutrients as adults bring the nutrients to the larvae or the larvae to the nutrients. Bigger colonies do not necessarily produce a greater total reproductive biomass. Colonies stop producing brood before they overwinter. ==Mating==

Colonies release alates synchronously. in swarms. Major mating swarms are about apart, Gynes mate with 2–11 (an average of 6.3) genetically distinct males. The colonies of queens that mate with more males grow faster. Males sometimes mate multiple times. Larger males are more successful at mating (i.e. they are overrepresented among collected maters), but small males can still mate. Certain shape characteristics improve male chances of mating success. New colonies are founded in a clumped pattern, around the mating sites. Smaller colonies have closer nearest neighbors. Smaller nests are more likely to die. The further a colony is from its nearest neighbor (especially for small colonies), the higher the colony's survival probability. Colony age and size are correlated, especially in young colonies. ==References==