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".