Linepithema humile

Nomenclature

Species: Linepithema humile (Mayr, 1868)

Usage: valid
Vernacular name: Argentine Ant

General description

The Argentine ant, Linepithema humile, is among the world’s most notorious, successful and well-studied invasive ant species. Linepithema humile is a nondescript, soft-bodied, small (2.2–2.6 mm), dull light to dark brown ant with large inset eyes. The species is native to the Paraná River drainage in South America, which stretches across northern Argentina, Uruguay, Paraguay, and southern Brazil (Wild, 2004). Linepithema humile thrives in Mediterranean climates, and over the past century it has spread to across the globe by human-mediated transport to Chile, western and southern North America, Hawaii, New Zealand, Easter Island, Australia, Japan, Africa, and southern Europe (Suarez et al., 2001; Wetterer et al., 2009). Argentine ants are significant pests, and are documented to cause substantial harm to native arthropod communities (Cole et al., 1992; Rowles & O'Dowd, 2009a), vertebrate communities (Suarez & Case, 2002; Suarez et al., 2005), plant communities (Christian, 2001; Ives et al., 2011; Lach, 2005; Rowles & O'Dowd, 2009b). Argentine ants are also significant agricultural pests (Vega & Rust, 2001)and urban/residential pests (Klotz et al., 2008a; Klotz et al., 2008b).

External links

Antweb | Antwiki | EOL | BOLD

Risk statement

Argentine ants are significant ecological, agricultural, and urban/residential pests.

Diagnostic description

Diagnosis of worker among Antkey species

Antenna 12-segmented. Antennal scape length less than 1.5x head length. Eyes medium to large (greater than 6 facets); do not break outline of head; placed distinctly below midline of face. Antennal sockets and posterior clypeal margin separated by a distance less than the minimum width of antennal scape. Anterior clypeal margin variously produced, but never with one median and two lateral rounded projections. Mandible lacking distinct basal angle. Profile of mesosomal dorsum with two distinct convexities. Dorsum of mesosoma lacking a deep and broad concavity; lacking erect hairs. Promesonotum separated from propodeum by metanotal groove. Propodeum with dorsal surface not distinctly shorter than posterior face; angular, with flat to weakly convex dorsal and posterior faces. Propodeum and petiolar node both lacking a pair of short teeth. Mesopleura and metapleural bulla covered with dense pubescence. Propodeal spiracle bordering posterior margin of propodeal profile. Waist 1-segmented. Petiole upright and not appearing flattened. Gaster armed with ventral slit. Erect hairs lacking from cephalic dorsum (above eye level), pronotum, and gastral tergites 1 and 2. Dull, not shining, and color uniformly light to dark brown. Measurements: head length (HL) 0.56–0.93 mm, head width (HW) 0.53–0.71 mm.

Among the species treated here, Linepithema humile is most easily confused with the Argentine Ant, L. iniquum. It can be separated from that species by the following characters: (1) the mesopleura and metapleural bulla are covered in pubescence and have a dull (versus glabrous) surface; (2) erect hairs are lacking (versus present) on cephalic dorsum (above eye level), gastral tergites 1 and 2, and often present on pronotum; (3) the profile of mesosomal dorsum has two (versus three) distinct convexities; (4) the propodeum is angular (versus globular) and is flat or weakly convex with dorsal and posterior faces (versus strongly and uniformly convex); and (5) the propodeal spiracle is bordering (versus distinctly anterior to) the posterior margin of propodeal profile.

Look alikes

Linepithema iniquum, Iridomyrmex anceps

Distribution

Native range. Paraná River drainage in South America.

Introduced range. Chile, western and southern North America, Hawaii, New Zealand, Easter Island, Australia, Japan, Africa, and southern Europe.

Click here for updated occurrence data and map on antmaps.org
Click here for updated occurrence data and map on GBIF.org

Adult worker and queen in the species' native range. Photo by ©Alexander L. Wild, alexanderwild.com	Adult worker. Photo by ©Alexander L. Wild, alexanderwild.com
Adult tending a citrus scale insect for honeydew. Photo by ©Alexander L. Wild, alexanderwild.com	A feisty little Argentine ant (Linepithema humile) attacks a much larger fire ant (Solenopsis invicta). Both species co-exist naturally in subtropical South America, but in the southern United States where both have been accidentally introduced, the fire ant has displaced the Argentine ant Photo by ©Alexander L. Wild, alexanderwild.com
A trail of Argentine ants. Photo by ©Alexander L. Wild, alexanderwild.com	Lateral view of body, entire, adult worker. Head and body approximately uniform in color.
Lateral view of body, surface characters, adult worker. Erect hairs lacking from cephalic dorsum (above eye level), pronotum, and gastral tergites 1 and 2.	Lateral view of body, surface characters, adult worker. Erect hairs are absent on cephalic dorsum (above eye level), gastral tergites 1 and 2, and are often also present on the pronotum. Used in Antkey to separate Linepithema humile from Linepithema iniquum.
Anterior view of head, adult worker. Head and body approximately uniform in color.	Close-up view of antenna, adult worker. Antennal club indistinct.
Anterior view of eye / ocellus, adult worker. Eyes situated distinctly below midline of face.	Anterior dorsal view of mandibles, adult worker. Mandible lacking distinct basal angle.
Lateral view of thorax / mesosoma, adult worker. Profile of mesosomal dorsum with two distinct convexities.	Lateral view of thorax / mesosoma, adult worker. The profile of mesosomal dorsum with only two distinct convexities (promesonotum and propodeum). The metanotum is not distinctly raised. Used in Antkey to separate Linepithema humile from Linepithema iniquum.
Lateral view of thorax / mesosoma, adult . Metanotal impression (arrow). Note also the mesosoma dorsum lacking erect hairs.	Lateral view of propodeum, adult worker. Propodeum shape.
Lateral view of propodeum, adult worker. The propodeum is angular, with flat to weakly convex dorsal and posterior faces. Used in Antkey to separate Linepithema humile from Linepithema iniquum.	Lateral view of propodeum, adult worker. Propodeum with dorsal surface not distinctly shorter than posterior face.
Lateral view of thorax / mesosoma, adult worker. Dense pubescence covering mesopleura.	Lateral view of body, surface characters, adult worker. The mesopleura and metapleural bulla covered with dense pubescence giving the surface a dull appearance. Used in Antkey to separate Linepithema humile from Linepithema iniquum.
Lateral view of propodeum, adult worker. Propodeum angular, with flat to weakly convex dorsal and posterior faces.	Lateral view of spiracle, adult worker. Propodeal spiracle on posterior border of propodeum.
Lateral view of propodeum, adult worker. The propodeal spiracle is bordering posterior margin of the propodeum. Used in Antkey to separate Linepithema humile from Linepithema iniquum.	Lateral view of waist, adult worker. Waist only one-segmented.
Lateral view of thorax / mesosoma, adult worker. Mesosoma lacking erect hairs.