Harvester ants, a non-generic name, are any of the species or genera of ants that collect seeds (called seed predation), or mushrooms as in the case of Euprenolepis procera, which are stored in the nest in communal chambers called granaries. Seed harvesting by some desert ants is an adaptation to the lack of typical ant resources such as prey or honeydew from homopterans. Harvester ants increase seed dispersal, protection, and provide nutrients that increase seedling survivorship of the desert plants. In addition, ants provide soil aeration through the creation of galleries and chambers, mix deep and upper layers of soil, and incorporate organic refuse into the soil.
Ants may play an important role in the dynamics of plant communities by acting either as seed dispersal agents or as seed predators, or both. There are two main mechanisms through which ants disperse seeds. One is myrmecochory, or seed dispersal mediated by the elaiosome, i.e., a lipid-rich seed appendage that mainly attracts non-granivorous ants and provides rewards for seed dispersal. The other one is diszoochory, or seed dispersal performed by seed-harvesting ants that is not mediated by any particular seed structure. While the former has traditionally been recognized mainly as a mutualism, the latter is usually perceived as an antagonism.
Harvester ants foraging in hot, dry conditions lose water, but obtain water from metabolizing fats in the seeds that they eat. Positive feedback on foraging activity, from returning foragers with food, allows the colony to regulate its foraging activity according to the current costs of desiccation and the benefits based on current food availability.
In many harvester ant species, foraging behavior is influenced by the weather. For example, in the ant Messor andrei, recruitment to food bait is higher in more humid conditions. Both humidity and food availability are affected by day to day changes in weather conditions. Food is distributed by wind and flooding and rain uncovers seeds in the top layer of the soil. In Pogonomyrmex barbatus, daily changes in conditions such as humidity and food availability produce strong daily trends in the foraging activity of all colonies.
Colonies may vary in the relation between humidity and foraging activity. Colonies differ consistently from year to year in how often they forage at all and most colonies forage on days with high humidity and high food availability, such as those just after a rain when flooding has exposed a layer of seeds in the soil. Few colonies forage on very dry days. Colonies also differ in how likely they are to adjust the rate of outgoing foragers to the rate of forager return. While all colonies tend to adjust outgoing foraging rate closely when conditions are good, only some colonies do so in poor conditions.
Species and genera
- Aphaenogaster cockerelli, seed-harvesters
- Euprenolepis procera, nomadic mushroom-harvesters, a previously unknown lifestyle among ants
- Pogonomyrmex maricopa, a venomous species found in Arizona, USA
- Pogonomyrmex occidentalis, seed-harvesters
- Messor, seed-harvesters
- Pheidole, seed-harvesters 
- Pogonomyrmex, seed-harvesters
- Pogonomyrmex barbatus
- Uppstrom & Klompen 2011, p. 1
- Arnan et al. 2012, p. 2
- Gordon, Dektar & Pinter-Wollman 2013, p. 1
- Gordon, Dektar & Pinter-Wollman 2013, pp. 1–2
- Gordon, Dektar & Pinter-Wollman 2013, p. 2
- Whitford & Steinberger 2009, p. 551
- LaPolla 2009, p. 1
- "Pogonomyrmex occidentalis (Cresson, 1865)". Integrated Taxonomic Information System.
- Steinberger, Leschner & Shmida 1991, p. 241
- "Species: Pheidole militicida". antweb.org. AntWeb. Retrieved 19 October 2013.
- Johnson 2000, p. 89
- Gordon & Hölldobler 1987, p. 341
- Arnan, X.; Molowny-Horas, R.; Rodrigo, A.; Retana, J. (2012), "Uncoupling the Effects of Seed Predation and Seed Dispersal by Granivorous Ants on Plant Population Dynamics", in Adler, Frederick R, PLoS ONE 7 (8): 1–11, doi:10.1371/journal.pone.0042869, PMC 3413678, PMID 22880125
- Gordon, D. M.; Dektar, K. N.; Pinter-Wollman, N. (2013), "Harvester Ant Colony Variation in Foraging Activity and Response to Humidity", in Moreau, Corrie S, PLoS ONE 8 (5): 1–6, doi:10.1371/journal.pone.0063363, PMC 3662670, PMID 23717415
- Gordon, D. M.; Hölldobler, B. (1987), "Worker Longevity in Harvester Ants (Pogonomyrmex)", Psyche: A Journal of Entomology 94 (3–4): 341–346, doi:10.1155/1987/63930
- Johnson, R. A. (2000), "Seed-harvester ants (Hymenoptera: Formicidae) of North America: an overview of ecology and biogeography.", Sociobiology 36 (1): 89–122
- LaPolla, John S. (2009), "Taxonomic Revision of the Southeast Asian Ant Genus Euprenolepis.", Zootaxa 2046: 1–25
- Steinberger, Y.; Leschner, H.; Shmida, A. (1991), "Chaff piles of harvester ant (Messor spp.) nests in a desert ecosystem", Insectes Sociaux 38 (3): 241–250, doi:10.1007/BF01314910
- Uppstrom, K. A.; Klompen, H. (2011), "Mites (Acari) Associated with the Desert Seed Harvester Ant, Messor pergandei (Mayr)", Psyche: A Journal of Entomology 2011: 1–7, doi:10.1155/2011/974646
- Whitford, Walter G.; Steinberger, Yosef (2009), "Harvester Ants (Hymenoptera: Formicidae) Discriminate Among Artificial Seeds with Different Protein Contents.", Sociobiology 53 (2B): 549–558