Polyergus

is a Holarctic genus of obligate social parasites that attack the closely-related genus Formica. They are commonly called 'Amazon ants' or 'slave-raiding ants'. Polyergus workers are apparently unable to perform the tasks involved in nest construction, foraging, and brood care. Work is instead carried out by the host Formica, who are captured as larvae and pupae during spectacular afternoon raids.