Functional groups are mutually exclusive; a species may be classified into only one group. Groups restricted to single taxa, the DOMINANT DOLICHODERINES, SUBORDINATE CAMPONOTINI, and GENERALIZED MYRMICINES, do not include all members of that taxon. For instance, a myrmicine may be classified as a CRYPTIC species, and a dolichoderine may be an OPPORTUNISTOPPORTUNISTS are weedy species that inhabit areas with high stress or disturbance; OPPORTUNISTS compete poorly with other ants. GENERALIZED MYRMICINES are generalized in food and nesting requirements, and defend food resources when they are close to their nest. SPECIALIST PREDATORS consume other arthropods, and interact little with other ants. CRYPTIC ants primarily nest and forage in soil and leaf litter. Bestelmeyer & Weins (1996) consider ARMY ANTS, nomadic group-raiders, as a separate functional group. Because both Old World and New World ARMY ANTS have a unique convergent life history, they are regarded separately.