Polyergus is a small genus of ants with 14 described species. They are also referred to by the names "slave-raiding ants" and "Amazon ants". They are characterized by their habit of raiding nests (of Formica) for workers.
Polyergus workers are incapable of caring for brood, for the most part due to their dagger-like, piercing mandibles. As such, they have evolved to rely on certain species of ants in the genus Formica. They have lost the instinct for carrying out even rudimentary brood care, and even for feeding themselves (which they are unable to do). Polyergus 'workers' exist more as a force of improvised soldiers, acting in essence solely to raid the Formica nests. The captured ants are generally referred to as "slaves" in scientific and popular literature, though recent attempts have been made to apply other human cultural models. Some of these describe the Polyergus as "raiders", "pirates", or "kidnappers". They also describe the Formica workers as "helper-ants" or "domesticated animals".[citation needed]
As far as is known, all established Polyergus colonies have only one queen. However, many contain ergatoids, large, worker-like members with large gasters. These may be substitute reproductive individuals after the queen's death, but this has not been proven. To found a new colony, a lone Polyergus queen invades a nest of the host species, or encounters and moves in with a colony-founding queen of the host species and her first few workers. In the latter case, the host queen is allowed to survive until her little colony has reared a sufficient number of host workers to support the parasite queen, something the Polyergus queen cannot do herself. The young Polyergus queen then kills the existing Formica queen (immediately if sufficient workers are present, later if these are not yet reared) and becomes accepted by the Formica workers. These proceed to rear the first and all subsequent Polyergus brood. Clearly, this complicated and lengthy process often fails, as Polyergus colonies are relatively rare, though each mature colony produces dozens or hundreds of new potential queens each year. To counteract the natural mortality of the Formica worker population, Polyergus workers must conduct regular raids over a 6-8 week period, every summer over the 10- to 15-year lifespan of their colony.[3]
Polyergus lucidus returning from raid on Formica incerta: Three of the Formica ants already incorporated into the mixed colony are visible to the right of the nest entrance.
Species
The genus Polyergus is split up into three groups, or "complexes". There is the lucidus group, the rufescens group, and the samurai group.
lucidus group
Polyergus lucidusMayr, 1870 – eastern United States, southern Ontario
Polyergus montivagusWheeler, 1915 – New England states to northern Florida in eastern United States, southern Ontario, Canada and west to Wisconsin and northern New Mexico, United States
Polyergus sanwaldiTrager, 2013 – United States, New England west to North Dakota
rufescens group
Polyergus rufescens(Latreille, 1798) – all of Europe, to western China and Kazakhstan
Polyergus brevicepsEmery, 1893 – north-central United States, west to Colorado, northern Arizona
Polyergus bicolorWasmann, 1901 – Wisconsin and Michigan, United States, west to North Dakota and south-central Canada
Polyergus mexicanusForel, 1899 – Dakotas and Arkansas, to western United States and Canada, and south at high altitude in mountains of Durango, Mexico.
Polyergus topoffiTrager, 2013 – high desert to mid-elevation mountains from Hidalgo, Mexico to southern Arizona, United States
Polyergus vinosusTrager, 2013 – southern California to northern Baja California, Mexico
samurai group
Polyergus nigerrimusMarikovsky, 1963 – Mongolia, Tuvan Republic, southern Russia
Polyergus samuraiYano, 1911 – Japan, Korea, eastern China, southeastern Russia
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