Polyergus mexicanus is a species of slave-making ant in the subfamily Formicinae. It is the most widely distributed species of Polyergus in North America. It is an obligatory social parasite, unable to feed itself or look after the colony and reliant on ants of another species, Formica, to undertake these tasks. The parasitic ants are known as "dulotics" (from the Greek "dulos" meaning a slave) and the ants they parasitise are the "hosts". In a revision of the genus Polyergus in 2013, Trager reinstated five species previously thought to be synonymous with Polyergus breviceps. P. mexicanus was one of these, a widely distributed species found in western North American and originally described by the Swiss myrmecologist Auguste Forel in 1899, the type locality being Mexico. It is likely that most species mentioned in scientific journals as P. breviceps are in fact P. mexicanus. Order: Hymenoptera, Family: Formicidae.
