Myrmicinae

Myrmicinae is distinguished from other ant subfamilies by the combination of: (1) petiole with two nodes, (2) distinct postpetiole with abdominal segment III markedly smaller than segment IV and set off by a constriction, (3) well-developed clypeus positioning antennal sockets away from the anterior head margin, and (4) pronotum inflexibly fused to the mesosoma. These features separate myrmicines from Formicinae (single petiole node, acidopore present), Dolichoderinae (single node, often with distinct odor), and Pseudomyrmecinae (elongate wasp-like form, single node, large eyes). The presence of a functional sting in many species further aids identification.

Nests are permanent and constructed in diverse substrates: soil, rotting wood, under stones, in trees, and in arboreal vegetation. Some species nest in specialized microhabitats including clay banks, leaf litter, and epiphytes. The subfamily includes both ground-dwelling and arboreal foragers, with some species occupying forest canopies.

Cosmopolitan distribution across all major biogeographic regions. The subfamily appears in the fossil record from the Middle Eocene of North America (approximately 47–52 million years ago), with Myrmecites rotundiceps from the Green River Formation representing one of the oldest known members. Myrmicine ants first appear in Eurasian deposits in Late Eocene Baltic amber (40 million years ago).

Activity patterns vary by species and climate. Some temperate species exhibit winter activity (e.g., Prenolepis imparis forages on warm winter days). Tropical and subtropical species generally maintain year-round activity, with reproductive flights timed to seasonal moisture availability. In seasonally wet environments such as northern Argentina, peak activity typically occurs September through January.

Highly variable across the subfamily. Many species are generalist omnivores, feeding on seeds, arthropod prey, and liquid resources including honeydew and extrafloral nectar. The Attini (leafcutter ants and relatives) are obligate fungus-farmers, cultivating basidiomycete fungi on harvested plant material. Some species are specialized seed predators (harvester ants). Adult ants typically consume liquid food carried in the crop, including pre-digested food regurgitated by larvae or glandular secretions.

Colony foundation varies: some species are monogynous (single queen), others polygynous. Queens may be winged (alates) or ergatoid (wingless). In Ocymyrmex foreli, colonies contain 16–1586 adults with continuous queen production year-round. Monomorium triviale reproduces through obligatory thelytokous parthenogenesis, with virgin queens producing workers and new queens without mating. Development includes egg, larva, pupa (without cocoon), and adult stages. Some species exhibit complex caste systems with distinct worker subcastes.

Social organization ranges from small cryptic colonies to large, complex societies. Many species exhibit trail-based foraging and resource recruitment. Attini engage in sophisticated fungus-farming behavior, including substrate preparation, fungal cultivation, and antibiotic application to control garden parasites. Some Stenamma species use clay 'door-pebbles' to block nest entrances when encountering aggressive ants such as army ants. Slave-making behavior occurs in some lineages, with workers raiding nests of related species to capture brood. Mating behavior in Myrmecina graminicola involves females depositing sex pheromone from the poison gland onto the substrate ('sexual calling'), with copulation lasting 40–60 seconds.

Myrmicine ants are significant ecosystem engineers and keystone species in many communities. Leafcutter ants (Attini) are dominant herbivores in Neotropical forests, processing substantial quantities of plant biomass and influencing vegetation structure. Harvester ants affect plant community composition through seed predation and dispersal. As predators and scavengers, myrmicines regulate arthropod populations. Their nests modify soil structure and nutrient distribution. The subfamily supports diverse associated fauna including myrmecophilous beetles, mites, and other invertebrates that inhabit ant colonies.

Several myrmicine species are economically important pests. Solenopsis invicta (red imported fire ant) is a major invasive species causing agricultural damage, ecological disruption, and medical issues through stings. Atta and Acromyrmex species are significant agricultural pests in Latin America, defoliating crops and harvesting plant material for fungal gardens. Some species serve as biological control targets, with research programs investigating entomopathogens and parasitoids (e.g., Pseudacteon phorid flies) for fire ant management. Conversely, myrmicines contribute to ecosystem services including soil aeration and nutrient cycling.

• FormicinaeLack the two-noded petiole and distinct postpetiole; possess a single petiole node and an acidopore (opening for defensive acid secretion) at the gaster tip.
• DolichoderinaeHave a single petiole node and often produce distinctive chemical odors; lack the well-developed postpetiole constriction characteristic of Myrmicinae.
• PseudomyrmecinaeExhibit elongate, wasp-like body form with large eyes and single petiole node; often arboreal with aggressive stinging behavior, differing from typical myrmicine morphology.

• BugGuide
• Wikipedia
• GBIF taxonomy match
• iNaturalist taxon
• NCBI Taxonomy
• Catalogue of Life
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• Social organization and reproduction inOcymyrmex foreli (Formicidae: Myrmicinae) Soziale Organisation und Fortflanzung bei Ocymyrmex foreliFormicidae-Myrmicinae)
• Mating behavior in the ant, Myrmecina graminicola (Myrmicinae)
• Ecology, behavior and microbiology of fungus-farming ants (Formicidae, Myrmicinae, Attini, Attina) in Atlantic rainforest
• The Crematogaster (Hymenoptera, Formicidae, Myrmicinae) of Costa Rica
• Comprehensive analysis of male-free reproduction in Monomorium triviale (Formicidae: Myrmicinae)
• Morphological and Behavioral Characters of the Two Species Groups of the Ant Genus Myrmicaria (Insecta: Hymenoptera: Formicidae: Myrmicinae) from Southeast Asia
• Taxonomy of the ant genus Carebara Westwood (Formicidae, Myrmicinae) in the Malagasy Region
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• Cytogenetic analysis of some species of Cyphomyrmex Mayr, 1862 and Apterostigma Mayr, 1865 (Formicidae, Myrmicinae) from the Guiana Shield.