Harvester ants are a group of ants known for collecting seeds, which they transport to their nests for storage and consumption. This seed-gathering activity, known as seed predation, along with their nest-building habits, contributes to their ecological role, influencing plant communities and soil properties. They play a role in the ecosystems they inhabit, affecting nutrient cycling and soil aeration.
Global Distribution
Harvester ants are primarily found across the arid and semi-arid regions of North, Central, and South America. The genus Pogonomyrmex, a prominent genus, is found across these continents, with some species also present on Caribbean islands like Haiti. While they are abundant in the Western United States, their distribution spans various latitudes where suitable dry conditions exist.
Different species within the harvester ant group exhibit distinct, yet sometimes overlapping, geographical ranges. For example, the red harvester ant (Pogonomyrmex barbatus) is found from Kansas and Oklahoma, extending through western Texas into Mexico, and south through New Mexico and Arizona. The Florida harvester ant (Pogonomyrmex badius) is the only Pogonomyrmex species on the East Coast of the United States, typically inhabiting Florida scrub and similar Atlantic coastal plain environments. These ants are generally prevalent in regions characterized by open land, including grasslands and deserts.
Environmental Preferences
Harvester ants prefer specific environmental conditions for foraging and nesting. They thrive in warm, dry climates, particularly arid and semi-arid regions like deserts, grasslands, and open woodlands, where temperatures are often high. Activity levels of harvester ants are influenced by weather, with some species showing increased foraging during more humid conditions, while others are active at high temperatures, even near 50°C.
Soil type is an important factor; harvester ants typically prefer well-drained, sandy soils for nest construction. They are often found in exposed areas where vegetation is sparse, as they clear plants around their nests to regulate temperature and maintain dry conditions. Soil moisture is particularly important for colony establishment and the development of larvae and pupae. The availability of seeds, which form the primary component of their diet, is a major determinant of their presence in a given area.
Underground Dwellings
Harvester ants construct subterranean nests that serve multiple purposes, including protection, brood rearing, and food storage. These nests consist of a network of descending shafts and horizontal chambers. The shafts can descend at varying angles, becoming steeper at greater depths, while chambers are used for different functions, such as nurseries and granaries for storing seeds. A single nest can reach considerable depths, with some reported to extend up to 2.5 meters (15 feet) deep with hundreds of chambers.
The nest entrance is typically surrounded by a cleared area of bare soil, which can range from 3 to 35 feet in diameter. Some species may also incorporate small pebbles, gravel, or other debris around the entrance, forming a distinct mound. This cleared disk helps regulate the nest’s internal temperature by allowing direct sunlight exposure. Harvester ant nests can have a single entry hole or multiple entrances, and distinct foraging trails often radiate outwards, used to collect and transport seeds.