Formica rufa, also known as the red wood ant, southern wood ant, or horse ant, is a boreal member of the Formica rufa group of ants, and is the type species for that group. It is native to Europe and Anatolia[2] but is also found in North America,[3] in both coniferous and broad-leaf broken woodland and parkland.[3] Workers are bicolored red and brownish-black, with a dorsal dark patch on the head and promensonotum,[3] and are polymorphic, measuring 4.5–9 mm in length.[3] They have large mandibles and like many other ant species they are able to spray formic acid from their abdomens as a defence.[3] Formic acid was first extracted in 1671 by the English naturalist John Ray by distilling a large number of crushed ants of this species.