Linepithema humile

(Mayr, 1868)

Argentine ant

, the , is a highly native to northern Argentina, Uruguay, Paraguay, Bolivia and southern Brazil. It has become established in Mediterranean climate regions worldwide through human-mediated . The forms expansive supercolonies through unicolonial organization, where neighboring colonies cooperate rather than compete. This structure enables rapid growth and displacement of native species. L. humile is considered one of the most ecologically damaging ants globally.

Linepithema humile by no rights reserved, uploaded by Jesse Rorabaugh. Used under a CC0 license.Linepithema humile by no rights reserved, uploaded by Jesse Rorabaugh. Used under a CC0 license.Linepithema humile by no rights reserved, uploaded by Jesse Rorabaugh. Used under a CC0 license.

Pronunciation

How to pronounce Linepithema humile: //lɪnˌɛpɪˈθiːmə ˈhjuːmaɪl//

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Identification

are small, approximately 2–3 mm in length, with a uniform dull to shiny brown coloration. The petiole consists of a single node. have 12 segments with no club. The mesosoma lacks spines or prominent . Distinguished from similar small brown ants by the combination of single-node petiole, lack of antennal club, and smooth body surface. Odorous house ants (Tapinoma sessile) differ in having a distinct odor when crushed and different petiolar structure.

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Habitat

Occupies disturbed in Mediterranean climate zones, including urban areas, agricultural lands, and riparian corridors. Thrives in areas with moderate temperatures and adequate moisture. In California, has been observed expanding along rivers and streams near urban areas. Tolerates a wide range of abiotic conditions, facilitating establishment across diverse environments.

Distribution

Native to northern Argentina, Uruguay, Paraguay, Bolivia and southern Brazil. Introduced and established in South Africa, New Zealand, Australia, Japan, Easter Island, Hawaii, Europe, and the continental United States (particularly California and the Southeast). In Europe, present in southern Europe for over 100 years; first recorded in Corsica in 1957. Spreads principally through human-mediated jump-.

Diet

feeder with flexible dietary requirements. Tends and protects honeydew-producing hemipterans such as scale insects, establishing mutualistic relationships that can damage crops and ornamental plants. Food preferences vary seasonally; protein preference observed during December and January in some . sources including honeydew and sugary substances are regularly exploited.

Life Cycle

Colonies contain multiple queens (polygynous), enabling rapid growth and spread. Reproductive division of labor with queens producing and sterile performing colony tasks. Winged reproductive forms () disperse to found new colonies. In laboratory conditions, colonies starved for 48 hours showed increased susceptibility to toxic baits, suggesting nutritional stress affects colony dynamics.

Behavior

Forms polydomous colonies with multiple interconnected nests rather than single central locations. Nest network expansion from initial nests occurs rapidly over 5–10 days to relatively stable distributions. Expansion favors food-rich areas over water-rich areas. do not deposit or follow signature marks during exploration of novel areas, resulting in more expansive worker distribution and less clumping than trail-following . Colony-level satiation limits complete saturation, potentially leaving areas available for other species. Communicates primarily through chemical () and tactile cues; vision is not particularly acute. Lays between food sources and nests. Uses to trigger defensive responses. Cuticular chemistry enables nestmate recognition and cooperative among workers from different nests within supercolonies.

Ecological Role

form supercolonies that displace or eradicate native , altering composition. Changes ant-vertebrate interactions and ant-plant relationships in invaded . Tending of hemipterans affects plant growth and production. Colony-level satiation may leave unoccupied patches available for other species. Bacterial diversity in invasive populations includes core such as Lactobacillus and Gluconobacter, potentially contributing to invasion success. Serves as for Deformed wing virus and virus 1, with unknown effects on ant populations.

Human Relevance

Designated as a tramp ant due to exceptional ability to spread and establish in new areas. Considered a significant agricultural pest through mutualistic relationships with crop-damaging hemipterans. Causes economic damage to infrastructure. Management costs in New Zealand estimated at NZ$60 million annually. Controlled through chemical sprays, poison baits, and toxic ; bait efficacy varies with colony starvation level and season of application. extracts from pupae and cadavers show potential for targeted delivery systems. Subject of research investigating pathogenic bacteria and viruses, including virus 1 as a possible control agent.

Similar Taxa

More Details

Population Decline in New Zealand

The in New Zealand experienced an unexpected decline hypothesized to result from effects, prompting research into viral and bacterial agents as potential mechanisms.

RNAi Research Applications

L. humile has been used as a model for interference studies in ants, demonstrating that orally administered dsRNA can spread systemically and knock down tissue-specific genes including odorant receptors, affecting nestmate recognition .

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Sources and further reading