Multicolonial
Guides
Brachymyrmex
Rover Ants
Brachymyrmex is a genus of minute ants in the subfamily Formicinae, commonly known as rover ants. Workers are distinguished by having only nine antennal segments—fewer than most ants—and by the petiole being concealed by the gaster in dorsal view. The genus contains 44 species and 17 subspecies, though species-level identification is challenging due to minimal morphological variation, small size, and soft-bodied workers. Brachymyrmex patagonicus, the dark rover ant, has become a significant invasive pest in the southern United States and other regions worldwide.
Brachymyrmex patagonicus
Dark Rover Ant, Black Rover Ant
Brachymyrmex patagonicus is a small invasive ant native to South America that has established populations across the southern United States, Europe, Asia, and the Caribbean. Workers are diminutive (1.0–2.0 mm), brown to black, with nine-segmented antennae and relatively large eyes compared to congeners. The species exhibits an unusual multicolonial social structure for an invasive ant, with most colonies consisting of a single nest headed by one queen, maintaining aggression toward non-nestmates rather than forming supercolonies. It is a significant nuisance pest of buildings but does not bite, sting, or vector disease.