Genus Formica - Wood ants, mound ants, & field ants

Anglicized - for-MY-kuh (preferred), FOR-micka (also heard)

Formica Linnaeus 1758

Formica is the Latin word for "ant", still found in various derivations in the modern languages derived from Latin, e.g., French fourmi, Spanish hormiga, Portuguese formiga, etc. It was first used by Linnaeus for all ants (i.e. equivalent to Formicidae). That Linnean genus is now divided up onto about 15 subfamilies and almost 300 genera).

~100 spp. in our area(1), close to 300 total

Workers 4‒8 mm, stretched out, from border of clypeus to tip of abdomen. Some are weakly polymorphic.

Alates -- 5‒13 mm (males and females about the same length in each species)

workers have conspicuous ocelli, double row of bristles on flexor (ventral) surface of middle and hind tibiae, mesosoma with "bumpy" (stair-stepped) profile, dorsal surface of propodeal profile as long or longer than the posterior, declivitous face.

Antennomere and palp segment counts are typical for Aculeata, antennae 12-segmented (13 in males), palp formula 6,4.

Northern Hemisphere, Subarctic to Warm Temperate zones (at high elevations south to Honduras)

Known as wood (or forest) ants, field ants or mound ants, depending on habitat preference and nesting habits of the various species. Most prefer non-flooded, open woodlands, openings in temperate forest, or grasslands. A few (mostly northern) species are more or less specialists in openings in boreal forests, fens or bogs, riparian areas, and a small number of species can (but do not always) live in the full shade of closed canopy deciduous or mixed forests. Nests are built in soil or less often in rotten wood on the ground. The nest may be elevated above the surface as a mound constructed of earth and/or plant fragments.

Active from the first warm days of spring till frost, but often with an unexplained lull in activity in August. Mating flights late June through early August.

Predatory with a sweet tooth. Attack and kill or scavenge all manner of arthropods and less often earthworms, and avidly seek honeydew and extrafloral nectar, often foraging high in trees to gather these sweets.

Mating flights peak late June through early July in the South, a little later at high elevations and latitudes. Many or possibly all species in the rufa, microgyna, exsecta & sanguinea groups have dependent colony foundation, effected by mated queens entering a colony of her own species and joining the queen numbers there, or of a fusca, neogagates, pallidefulva group species and usurping the resident queen(s). Colonies are nearly always founded by individual queens in these host groups, but some may form small groups, or re-enter a (probably related) colony of their own species

The fusca, pallidefulva & sanguinea groups have been revised, but the taxonomy is still difficult, as differences among the species are subtle, and often the diagnostic characters are not depicted in images posted at BG. The rufa/microgyna & neogagates groups are much in need of revision, so Creighton (1950) must serve for their identification.

Lasius are perhaps most similar and found in the same habitats, differing in their inconspicous or missing ocelli, lack of a pair of longitudinal rows of bristles on the flexor (ventral) surfaces of the middle and hind tibiae, and by the dorsal surface of the propodeum being shorter than the posterior declivitous face. Lasius also differ in their smaller size (2.5‒4 mm), small eyes, and reduced palp segmentation of many species.

Myrmecocystus workers are of similar size and coloring to many Formica, but may be recognized by their very elongate maxillary palp, and desert habitat. Camponotus minor workers are in the size range, but have a flat to gently curved mesosomal profile, i.e., pro-metanotal profile continuous with propodeal profile rather than "stair-stepped".