Argentine ant (Linepithema humile) is an insect pest. It is a native of Brazil and was first detected in Louisiana in the 1890's.
These ants are one of the world's most invasive species. In its introduced range, the Argentine ant often displaces most or all native ants. This can, in turn, imperil other species in the ecosystem, such as native plants that depend on native ants for seed dispersal, or lizards that depend on native ants for food. Argentine ants sometimes tend aphid colonies, and their protection of this plant pest can cause problems in agricultural areas by protecting plant pests from predators and parasitoids.