Linepithema humile

Definition

A small, light-to-medium brown dolichoderine ant native to the Paraná River drainage of South America and now among the most widespread invasive insects globally. Colonies are unicolonial, forming expansive supercolonies with minimal intraspecific aggression across introduced ranges, which facilitates ecological dominance and displacement of native ant fauna. The species has become a model organism for studying invasion genetics, chemical ecology, and community-level impacts of biological invasions.

Etymology

Linepithema from Greek linein (to smear, referring to the anal gland secretion used for trail marking) + pithēma (a thing poured or an offering); humile Latin for lowly or humble, likely alluding to the species' small size and inconspicuous appearance.

Example

In California's coastal scrub, Linepithema humile supercolonies extend for hundreds of kilometers with no detectable genetic differentiation, allowing workers from San Diego to integrate seamlessly with those from San Francisco—an extreme case of the unicolonial syndrome that underlies its invasive success.

Synonyms

• Argentine ant

Related Terms

• unicoloniality
• supercolony
• Invasive species
• Formicidae
• Dolichoderinae
• tramp ant
• ecological dominance
• invasion meltdown

Usage Notes

The common name 'Argentine ant' is widely used in applied contexts, though the species' native range spans multiple countries (Argentina, Uruguay, Paraguay, Bolivia, southern Brazil). In invasion biology literature, L. humile serves as the archetypal unicolonial ant, though recent work has questioned whether unicoloniality is a fixed trait or context-dependent. The species is frequently contrasted with multicolonial native ants in studies of colony structure and aggression. Several subspecies names exist (e.g., L. h. platense, L. h. gallardoi) but are rarely applied in contemporary taxonomy; most populations are treated as nominate L. humile.