Formica rufa species group

The Formica rufa group is a subgeneric group within the genus Formica, first proposed by William Morton Wheeler. This group contains the mound-building species of Formica commonly termed "wood ants" or "thatch-mound ants", which build prominent nests consisting of a mound of grass, litter, or conifer needles. The species Formica rufa or the red wood ant is the type species of this subgroup.

This particular group can inhabit open deciduous woodlands, dense pine forests, and even moorland. Workers vary in size, the largest reaching about 10 mm long. They can produce formic acid in their abdomens and eject it 12 cm in the air when threatened. The only function of males is to mate in flight with queens. Species previously attributed to the Microgyna group were transferred to the  F. rufa group by the Wheelers in 1986.

Colonies
The genetic relationships in F. rufa group colonies can be complex. Colonies can be polygynous (having multiple queens) and these are often polydomous (having multiple nests per colony). Queens may be singly or multiply mated, and in polygynous colonies, may or may not be related. Colonies are rarely, if ever, independently formed. They either bud off from existing colonies, or are formed by temporary social parasitism of colonies of F. fusca or other closely related species. A wood ant queen ousts the existing queen, lays eggs, and the F. fusca workers raise her offspring until the nest is taken over. Some species in the F. rufa group sometimes form enormous "supercolonies" consisting of hundreds or thousands of nests. The largest documented example is an F. yessensis colony in Japan covering 2.7 km2 containing an estimated 306 million workers and 1 million queens.

Member species
European species include:
 * Formica aquilonia Yarrow, 1955
 * Formica lugubris Zetterstedt, 1838
 * Formica paralugubris Seifert, 1996
 * Formica polyctena Förster, 1850
 * Formica pratensis Retzius, 1783
 * Formica rufa Linnaeus, 1761

North American species include:
 * Formica ciliata Mayr, 1886
 * Formica coloradensis Creighton, 1940
 * Formica comata Wheeler, 1909
 * Formica criniventris Wheeler, 1912
 * Formica dakotensis Emery, 1893
 * Formica fossaceps Buren, 1942
 * Formica integra Nylander, 1856
 * Formica integroides Emery, 1913
 * Formica laeviceps Creighton, 1940
 * Formica microgyna Wheeler, 1903
 * Formica mucescens Wheeler, 1913
 * Formica obscuripes Forel, 1886
 * Formica obscuriventris Mayr, 1970
 * Formica oreas Wheeler, 1903
 * Formica planipilis Creighton, 1940
 * Formica propinqua Creighton, 1940
 * Formica ravida Creighton, 1940
 * Formica reflexa Buren, 1942
 * Formica subnitens Creighton, 1940

Asian species
 * Formica yessensis