Argentine ant

Definition

A small, dark-colored invasive ant species, Linepithema humile, native to the floodplains of northern Argentina, Uruguay, Paraguay, Bolivia, and southern Brazil. Distinguished by its unicolonial social structure—where geographically separate colonies recognize each other as kin and do not fight—allowing formation of vast supercolonies spanning hundreds of kilometers. A globally significant pest in Mediterranean-climate regions, where it disrupts native ant communities through competitive displacement, tends honeydew-producing hemipterans that damage crops, and indirectly affects plants and vertebrates by altering arthropod assemblages.

Etymology

From Argentina + ant, referring to the species' native range in the Río de la Plata basin.

Example

In California's coastal scrub, Argentine ant supercolonies have displaced over half of native ant species, including seed-dispersing harvester ants (Pogonomyrmex), triggering cascading declines in horned lizard populations that specialize on native ants as prey.

Synonyms

• Linepithema humile

Related Terms

• Invasive species
• unicoloniality
• supercolony
• competitive exclusion
• tramp ant
• honeydew-tending
• biological invasion
• Formicidae
• Linepithema

Usage Notes

Often contrasted with multicolonial ant species where colonies defend territory against all conspecifics. The term 'Argentine ant' refers specifically to L. humile; do not apply to other South American ants. In invasion biology literature, 'Argentine ant' and 'Linepithema humile' are used interchangeably, though the scientific name is preferred in taxonomic contexts. The unicolonial trait varies geographically—native-range populations show more typical colony boundaries, while introduced populations often display extreme unicoloniality.