Monomorium pharaonis

Arguable the most ubiquitous house ant in the world.

Identification
Wetterer (2010) - Monomorium pharaonis workers vary in color, even within a colony, from uniform yellow to yellow with a dark brown rear of the gaster. Several other Monomorium species are also known as tramp ants, transported worldwide through human commerce, including Monomorium destructor (JERDON, 1851), Monomorium floricola (JERDON, 1851), Monomorium monomorium BOLTON, 1987, Monomorium sechellense EMERY, 1894, and Monomorium subopacum (SMITH, 1858). Of these tramp species, M. pharaonis resembles only M. destructor in color, but has a much narrower range of worker size (M. pharaonis: 2.2 - 2.4 mm length; M. destructor: 1.8 - 3.5 mm length; BOLTON 1987). Monomorium pharaonis also can be easily distinguished from M. destructor because the head, alitrunk, petiole, and postpetiole of the workers are matte (not shiny) in M. pharaonis, but are almost entirely smooth and shiny in M. destructor.

Distribution
Found throughout the world.

This taxon was described from Egypt.

It is also found in Mozambique, Australia, Philippines, Ecuador, Brazil, New Guinea, Bolivia, Uruguay, Chile, Colombia, Argentina, Suriname, Paraguay, French Guiana, Guyana, Mexico, Panama, Costa Rica, Canada, United States, Dominican Republic, Puerto Rico, Bahamas, Israel, Eritrea, Kenya, Tanzania, India, Zimbabwe, Seychelles, Réunion, Angola, Cameroon, Egypt, Sudan, Ghana, Mali, Nigeria, Kyrgyzstan, Turkmenistan, Japan, Iran (Islamic Republic of), Bangladesh, Viet Nam, Thailand, and United Kingdom of Great Britain and Northern Ireland.

Biology
Collingwood (1979) Colonies are very large, polygynous and polycalic often with several millions of individuals. Workers and queens forage in long trails and live by scavenging on food materials, dead animals and insects. Nests are often sited deep in foundations and are very difficult to eradicate by fumigation or insecticides.

Associations with Humans
Wetterer (2010) Monomorium pharaonis is particularly notorious as a pest in hospitals, where it is known as a vector for disease. In tropical areas, M. pharaonis occurs both indoors and out, but in temperate areas, it is found almost exclusively indoors. It is by far the most common tropical ant found in heated buildings of Europe and North America.

Nomenclature

 *  pharaonis. Formica pharaonis Linnaeus, 1758: 580 (w.) EGYPT. Mayr, 1865: 90 (m.); André, 1883a: 338 (q.); Forel, 1891b: 164 (w.q.m.); Wheeler, G.C. & Wheeler, J. 1955c: 121 (l.); Petralia & Vinson, 1980: 383 (l.); Imai, 1966: 119 (k.). Combination in Monomorium: Mayr, 1862: 752. Senior synonym of antiguensis, domestica: Roger, 1862c: 294; of contigua, fragilis: Mayr, 1886c: 359; of minuta: Emery, 1892b: 165; Bolton, 1987: 288; of vastator: Donisthorpe, 1932c: 449. See also: Smith, D.R. 1979: 1383; Bolton, 1987: 356; Atanassov & Dlussky, 1992: 164; Heterick, 2006: 100.
 * antiguensis. Formica antiguensis Fabricius, 1793: 357 (w.) WEST INDIES. Junior synonym of pharaonis: Roger, 1862c: 294.
 * domestica. Myrmica domestica Shuckard, 1838: 627 (w.q.) GREAT BRITAIN. Smith, F. 1851: 119 (m.). Junior synonym of pharaonis: Roger, 1862c: 294. See also: Curtis, 1854: 217; Bolton, 1987: 356.
 * minuta. Atta minuta Jerdon, 1851: 105 (w.q.) INDIA. Junior synonym of pharaonis: Emery, 1892b: 165; Bolton, 1987: 288, 356.
 * vastator. Myrmica vastator Smith, F. 1857a: 71 (w.) SINGAPORE. Combination in Monomorium: Mayr, 1886c: 359. Junior synonym of destructor: Dalla Torre, 1893: 66; of pharaonis: Donisthorpe, 1932c: 449.
 * contigua. Myrmica contigua Smith, F. 1858b: 125 (q.) SRI LANKA. Junior synonym of pharaonis: Mayr, 1886c: 359.
 * fragilis. Myrmica fragilis Smith, F. 1858b: 124 (w.) SINGAPORE. Junior synonym of pharaonis: Mayr, 1886c: 359.

Wetterer (2010): Monomorium pharaonis appears to have originated in tropical Asia, where widespread outdoor records have been reported. Also, Monomorium longi FOREL, 1902 and Monomorium wroughtoni FOREL, 1902, the two species thought to be most closely related to M. pharaonis, are endemic to tropical Asia. Although M. pharaonis was first described from Egypt, I found no evidence supporting the popular, but apparently mistaken, idea that M. pharaonis is native to Africa.

Worker
Heterick 2006 - HEAD: Head oval; vertex weakly convex; frons shining and finely striolate and microreticulate; pilosity of frons consisting of a few short, thick, erect setae interspersed with short, appressed setulae. Eye moderate, eye width 1–1.5× greatest width of antennal scape; (in full-face view) eyes set above midpoint of head capsule; (viewed in profile) eyes set posteriad of midline of head capsule; eye elliptical, curvature of inner eye margin may be more pronounced than that of its outer margin. Antennal segments 12; antennal club three-segmented. Clypeal carinae indicated by multiple weak ridges; anteromedian clypeal margin broadly convex; paraclypeal setae moderately long and fine, curved; posteromedian clypeal margin approximately level with antennal fossae. Anterior tentorial pits situated nearer antennal fossae than mandibular insertions. Frontal lobes straight, parallel. Psammophore absent. Palp formula 2,2. Mandibular teeth four; mandibles with sub-parallel inner and outer margins, striate; masticatory margin of mandibles approximately vertical or weakly oblique; basal tooth approximately same size as t3 (four teeth present).

MESOSOMA: Promesonotum shining and microreticulate throughout; (viewed in profile) promesonotum broadly convex; promesonotal setae two to six; standing promesonotal setae consisting of very short, incurved decumbent setae only; appressed promesonotal setulae well-spaced over entire promesonotum. Metanotal groove strongly impressed, with distinct transverse costulae. Propodeum shining and microreticulate; propodeal dorsum flat throughout most of its length; propodeum smoothly rounded or with indistinct angle; standing propodeal setae consisting of one prominent pair anteriad, with other shorter setae very sparse or absent; appressed propodeal setulae well-spaced and sparse; propodeal spiracle equidistant from metanotal groove and declivitous face of propodeum. Vestibule of propodeal spiracle absent or not visible. Propodeal lobes present as blunt-angled flanges.

PETIOLE AND POSTPETIOLE: Petiolar spiracle lateral and situated within anterior sector of petiolar node; node (viewed in profile) conical, vertex tapered; appearance of node shining and distinctly microreticulate; ratio of greatest node breadth (viewed from front) to greatest node width (viewed in profile) about 1:1; anteroventral petiolar process present as a thin flange tapering posteriad; ventral petiolar lobe present; height ratio of petiole to postpetiole between 4:3 and 1:1; height–length ratio of postpetiole about 1:1; postpetiole shining and microreticulate; postpetiolar sternite not depressed at midpoint, its anterior end an inconspicuous lip or small carina.

GASTER: Pilosity of first gastral tergite consisting of well-spaced, erect and semi-erect setae interspersed with a few appressed setulae.

GENERAL CHARACTERS: Color yellowish, gastral tergites with brown infuscation in basal sector. Worker caste monomorphic.

LECTOTYPE MEASUREMENTS (M. vastator): The physical condition and alignment of the worker does not permit ready measurements.

LECTOTYPE MEASUREMENTS (M. fragile): HML 1.52 HL 0.56 HW 0.42 CeI 75 SL 0.48 SI 114 PW 0.23.

OTHER WORKER MEASUREMENTS: HML 1.39–1.48 HL 0.53–0.56 HW 0.42–0.45 CeI 78–81 SL 0.45–0.49 SI 105–111 PW 0.22–0.28 (n=8).

Queen
Heterick 2006 - HEAD: Head square; vertex always planar; frons matt and uniformly reticulate-punctate; frons a mixture of well-spaced, distinctly longer erect and semi-erect setae interspersed with shorter setae or setulae, which are decumbent or appressed, longer setae thickest on vertex. Eye elliptical, curvature of inner eye margin may be more pronounced than that of its outer margin; eyes (in full-face view) set at about midpoint of head capsule; eyes (viewed in profile) set around midline of head capsule.

MESOSOMA: Anterior mesoscutum smoothly rounded, thereafter more-or-less flattened; pronotum, mesoscutum and mesopleuron uniformly reticulate-punctate, punctations tending to form fine striolae on dorsum of mesoscutum; length-width ratio of mesoscutum and scutellum combined between 7:3 and 2:1. Axillae narrowly separated (i.e., less than width of one axilla). Standing pronotal/mesoscutal setae consisting of well-spaced, incurved, erect and semi-erect setae only; appressed pronotal, mescoscutal and mesopleural setulae well-spaced over entire surface. Propodeum uniformly reticulate-punctate; always smoothly rounded; propodeal dorsum convex; standing propodeal setae consisting of two or more pairs of prominent setae anteriad, with a few decumbent setae around declivitous face; appressed propodeal setulae well-spaced and sparse; propodeal spiracle equidistant from metanotal groove and declivitous face of propodeum; propodeal lobes present as bluntly angled flanges.

WING: Wing not seen (queen dealated).

PETIOLE AND POSTPETIOLE: Petiolar spiracle lateral and situated within anterior sector of petiolar node; node (viewed in profile) conical, vertex tapered; appearance of node matt and reticulate-punctate; ratio of greatest node breadth (viewed from front) to greatest node width (viewed in profile) about 1:1. Anteroventral petiolar process absent or vestigial; height ratio of petiole to postpetiole about 1:1; height–length ratio of postpetiole about 4:3; postpetiole matt and reticulate-punctate; postpetiolar sternite forming a narrow wedge-shaped projection through strong convergence of its anterior and posterior ends.

GASTER: Pilosity of first gastral tergite consisting of well-spaced, erect and semi-erect setae interspersed with a few appressed setulae.

GENERAL CHARACTERS: Color orange-yellow, gaster brown, with large, yellow sector at apex of first tergite. Brachypterous alates not seen. Ergatoid or worker-female intercastes not seen.

HOLOTYPE MEASUREMENTS (M. contiguum): HML 2.43 HL 0.68 HW 0.63 CeI 93 SL 0.62 SI 98 PW 0.73.

OTHER QUEEN MEASUREMENTS: HML 2.37 HL 0.66 HW 0.62 CeI 94 SL 0.58 SI 94 PW 0.52 (n=1).

Type Material
Heterick 2006:

Formica pharaonis L. 1758:580. Syntype ☿'s, EGYPT [whereabouts of type material unknown]

Formica antiguensis Fabricius 1793:357. Syntype ☿, WEST INDIES: Antigua [whereabouts of type material unknown]. Syn. under M. pharaonis (L.): Roger 1862b: 294.

Myrmica domestica Shuckard 1838:627. Syntype ☿'s, GREAT BRITAIN: London [no types known to exist]. Syn. under M. pharaonis (L.): Roger 1862b:294.

Atta minuta Jerdon 1851:105. Syntype ☿'s, INDIA [no types known to exist]. Syn. under M. pharaonis (L.): Emery1892:165.

Myrmica vastator Smith 1857:71. Syntype ☿'s (lectotype here designated), SINGAPORE [examined].

Myrmica fragilis Smith 1858:124. Syntype ☿'s (lectotype here designated), SINGAPORE [examined]. Syn. under M. pharaonis (L.): Mayr 1886:359.

Myrmica contigua Smith 1858:125. Holotype, SRI LANKA [examined]. Syn. under M. pharaonis (L.): Mayr 1886:359.

Additional References

 * Heterick, B. E. 2006. A revision of the Malagasy ants belonging to genus Monomorium Mayr, 1855 (Hymenoptera: Formicidae). Proceedings of the California Academy of Sciences. 57:69-202.