Monomorium pharaonis, full face view of a worker (Lamar Co., AL) (photo by Ryan J. Whitehouse and Joe A. MacGown)

Monomorium pharaonis, lateral view of a worker (Lamar Co., AL) (photo by Ryan J. Whitehouse and Joe A. MacGown)

Monomorium pharaonis, dorsal view of a worker (Lamar Co., AL) (photo by Ryan J. Whitehouse and Joe A. MacGown)

Monomorium pharaonis, antenna of a worker (Lamar Co., AL) (photo by Ryan J. Whitehouse and Joe A. MacGown)

Monomorium pharaonis, worker in an airbag sensor of a car (photo by Joe A. MacGown)

Monomorium pharaonis, worker in an airbag sensor of a car (photo by Joe A. MacGown)

Monomorium pharaonis, full face view of a queen(Lake Co., FL) (photo courtesy of Antweb.org)

Monomorium pharaonis, lateral view of a queen (Lake Co., FL) (photo courtesy of Antweb.org)

Monomorium pharaonis, dorsal view of a queen (Lake Co., FL) (photo courtesy of Antweb.org)

Monomorium pharaonis, full face view of a male (photo courtesy of Antweb.org)

Monomorium pharaonis, lateral view of a male (photo courtesy of Antweb.org)

Monomorium pharaonis, dorsal view of a male (photo courtesy of Antweb.org)

Introduction
Monomorium Mayr, 1885 is an extremely diverse genus worldwide with most of its diversity occurring in the old world tropics with 10 species currently listed for North America. These ants occupy various types of habitats from bare lands to well developed forests. Foraging typically occurs on the ground, but some arboreal species exist.

Monomorium species can be identified by the presence of a petiole and post-petiole, 12 segmented antennae with a three segmented club, a raised medial area on the clypeus with fine longitudinal ridges and the lack of propodeal armament.

Monomorium pharaonis (Linnaaeus), the pharaoh ant, is a tiny, yellow ant thought to be native to Africa. This species is a widespread tramp that occurs in many warm regions of the world. In temperate regions, including many parts of the US where it has been recorded, populations are in heated structures. Populations of this species in Mississippi are spotty, and most records are from indoor infestations.

Taxonomic History
Formica pharaonis Linnaeus, 1758: 580 (w.) EGYPT. Palearctic. "Egypt." Mayr, 1865: 90 (m.); André, 1883: 338 (q.); Forel, 1891: 164 (w.q.m.); Wheeler & Wheeler, 1955: 121 (l.); Petralia & Vinson, 1980: 383 (l.); Imai, 1966: 119 (k.). Combination in Monomorium: Mayr, 1862: 752. Senior synonym of Monomorium antiguensis, Monomorium domestica: Roger,1862:294;of Monomorium contigua, Monomorium fragilis: Mayr,1886: 359; of Monomorium minuta: Emery, 1892: 165; Bolton, 1987: 288; of Monomorium vastator:Donisthorpe, 1932: 449. See also: Smith, 1979: 1383; Bolton, 1987: 356; Atanassov & Dlussky, 1992: 164; Heterick, 2006: 100.

Diagnosis

Identification
Worker: Minute (HL 0.56–0.64 mm, HW 0.44–0.49 mm, SL 0.47–0.52 mm, EL 0.08–0.10 mm, MeSL 0.63–0.72 mm) (n=5, MEM specimens). Overall light yellowish-brown with the posterior half of the gaster fading to brown or yellow with brown infuscation. Head longer than wide, rectangular, with fine micro reticulate punctation that does not completely obscure the shiny integument; with scattered, short, appressed to semi erect setae; clypeus raised, narrowed, with multiple, weak carinae; eyes small, located on sides of the head near the midline; ocelli lacking; mandibles with four teeth; antenna 12-segmented, with 3-segmented club, scape extending beyond posterior border of head by about the length of pedicel. Mesosoma with promesonotum smoothly curved and arched upward in lateral view, promesonotal suture weak; metanotal suture strongly impressed, propodeum distinctly separated from promesonotum and slightly depressed, propodeal dorsum about twice the height of propodeal declivity; entire mesosoma with dense, fine punctulate sculpture; promesonotum with a few long, erect setae. Waist two segmented, with a few long, erect setae, and dense, fine punctulate sculpture; petiole pedunculate, node conical in lateral view, petiole’s height about 3/4 length of petiolar segment; postpetiole somewhat circular in lateral view, elliptical in dorsal view, wider than petiole. Gaster mostly shiny, with scattered, but numerours long, erect setae present; sting present.

Queen: HL 0.66–-0.68mm, HW 0.62–0.63mm, SL 0.58–0.62mm PW 0.52–0.73mm (n=2, measurements from Heterick 2006). Head, mesosoma, waist and appendages orangish yellow to orangish brown with mesoscutum and legs sometimes lighter, and dark brownish black coloration at posterior region of mesoscutellum; and gaster with orangish yellow at base of first tergite and posterior edges of tergites, with remainder dark brown to brownish black. Head slightly longer than wide, with fine reticulation posteriorally, and becoming strialate below eye level, clypeus mostly smooth and shining, numerous (but not dense) short, slightly appressed setae present; ocelli present; eyes large and at approximate midline of head in side view; scape length slightly less than head length, with appressed setae; mandibles with strong apical tooth followed by three shorter teeth of about equal size. Mesosoma with fine reticulation/punctation, and dorsum with numerous, short, semi erect setae directed posteriorly; mesoscutum rounded anteriorly then flattened propodeum rounded. Waist with semi erect, slightly flexous setae directed posteriorly (setae longer than those on mesosomal dorsum); petiole conical in side view, pedunculate, rounded dorsally; postpetiole rounded in lateral and dorsal views.

Male: Mayr described the male in 1865, but the only measurement he provided was that it was 3.0 mm long. The type was photographed by Antweb.org, and the following identification information was garnered from viewing those photos  Head, mesosoma, waist, and gaster dark brownish black; antennnae pale yellow; coxae and tibia light brown; and femora pale yellow brown. Head slightly wider than long; entire head in full face view with foveolate sculpture; scattered short, semi erect setae present; eyes large, about half the head length; ocelli present, not noticeably elevated; antenna 13-segmented (including scapes); scape about length of funicular segments 2+3; mandibles present. Mesosoma with light foveolate sculpture except for mid region of mesopleuron, which is smoother, and shiny; mesosomal dorsum with scattered, short semi erect setae. Wings transparent; veins with little pigmentation, distal segments reduced to vestigial lines; m–cu absent; cu–a absent. Waist with a few, short, setae, directed posteriorly; petiolar peduncle thickened, node triangular in lateral view, strongly pitted with small fovea; petiole rounded in lateral and dorsal views, with numerous small foveo present. Gaster mostly lacking sculpture except for light reticultion on anterior region of first tergite, otherwise, smooth and shining; with scattered short, semi erect to erect setae, especially dorsally, and with a patch of more dense, longer setae on posterior sternites.

Workers of Monomorium pharaonis can be identified by their minute size, yellowish brown color, light punctulate sculpture that does not obscure the shiny integument, 12-segmented antennae that terminates in a 3-segmented club,  raised and narrowed clypeaus with a pair of fine longitudinal carinae, lack of propodeal spines, and sting. This species can be separated from other Monomorium species In the southeastern US by its light golden yellow color with brownish infuscation on the gaster. Species of thief ants in the related genus Solenopsis have 10-segmented antennae and lack fine sculpture.

Biology and Economic Importance
Monomorium pharaonis is a widespread species that is suspected to inhabit most, if not all, commercially important cities in the United States. Colonies are polygynous, and even though some winged females are produced, they spread through budding. This species requires little space to start a colony and has been known to form colonies between layers on linen and sheets of stationary in houses.

The pharoah ant is considered to be a serious house infesting ant species in the United States. Being omnivorous, any available food will sustain a colony, though they appear to prefer greasy, fatty foods and meats. This species may be found inhabiting houses, buildings and hospitals where they are often detected from their intricate foraging trails. They are especially considered a nuisance in hospitals where they are suspected to transmit pathogens.

Workers of M. pharaonis may be attracted to electricity (as is apparently the case with numerous other ant species) and may cause electrical disruption by shorting out circuits. This species has been associated with airbag sensor failure, although it was not certain that that ants caused the failure.However, ants were found within damaged circuits (see pictures above).

Pest Status

Distribution
The pharaoh ant is widespread throughout many regions of the world. In temperate regions, populations are in heated structures. The species is thought to be native to Africa.

Native Range: Thought to be Africa.

Australian: Australia, Federated States of Micronesia, Fiji, French Polynesia, Guam, Hawaii, Indonesia, Kiribati, Marshall Islands, New Caledonia, New Guinea, New Zealand, Northern Mariana Islands, Samoa, Solomon Islands, Tokelau, Vanuatu (AntWeb.org).
Ethiopian: Angola, Central African Republic, Eritrea, Gabon, Ghana, Guinea, Kenya, Liberia, Madagascar, Mali, Mozambique, Nigeria, Republic of Cameroon, Republic of Senegal, Reunion, Seychelles, South Africa, Sudan, United Arab Emirates, United Republic of Tanzania, Zimbabwe (AntWeb.org).
Nearctic: Baja California, Canada, United States (AntWeb.org and MEM).
Neotropical: Argentina, Bahamas, Bolivia, Brazil, Chile, Colombia, Costa Rica, Cuba, Dominican Republic, Ecuador, French Guiana, Galapagos Islands, Greater Antilles, Guyana, Mexico, Panama, Paraguay, Peru, Puerto Rico, Suriname, Trinidad and Tobago, Uruguay (AntWeb.org and AntWiki.org).
Oriental: Bangladesh, Borneo, Cambodia, India, Malaysia, Philippines, Singapore, Sri Lanka, Thailand, Vietnam (AntWeb.org).
Palearctic: Albania, Armenia, Austria, Balearic Islands, Belarus, Belgium, Bulgaria, Canary Islands, China, Crete, Croatia, Czech Republic, Denmark, Egypt, Estonia, Faroe Islands, Finland, France, Georgia, Germany, Greece, Hungary, Iran, Iraq, Israel, Italy, Japan, Jersey, Kyrgyzstan, Latvia, Lebanon, Lithuania, Luxembourg, Macaronesia, Montenegro, Netherlands, North Korea, Norway, Poland, Portugal, Republic of Moldova, Romania, Russian Federation, Saudi Arabia, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkmenistan, Ukraine, United Kingdom od Great Britain and Northern Ireland (AntWeb.org and AntWiki.org).

U.S. Distribution: AL, AR, AZ, CA, FL, GA, HI, IL, LA, MO, MS, NC, NM, OH, PA, SC, TN, TX, WA (AntWeb.org and MEM).
Southeastern U.S. Distribution: AL, AR, FL, GA, LA, MS, NC, SC, TN (MEM).

Acknowledgments
Thanks to AntWeb.org for use of photographs. Funding for the ant work being done by the MEM in Alabama and Mississippi is from several sources including the National Institute of Food and Agriculture, United States Department of Agriculture, under Project No. MIS-012040, the Mississippi Agricultural and Forestry Experiment Station at Mississippi State University, with support from State Project MIS-311080, NSF Grants BSR-9024810 and DFB-9200856, the Tombigbee National Forest (U.S. Forest Service), the Noxubee Wildlife Refuge, Mississippi Natural Heritage Program Research Grant, USDA Forest Service Agreement No. 08-99-07-CCS-010, the William H. Cross Expedition Fund, and primarily by the USDA-ARS Areawide Management of Imported Fire Ant Project (2001-2014) and USDA-ARS Areawide Management Invasive Ants Project. Additionally, special cooperation has been provided by State Parks, National Forests, National Wildlife Refuges, the Natchez Trace Parkway, and from various private landowners in both Alabama and Mississippi.

Literature Cited
André, Ern. 1883. Les fourmis. [part]. Pp. 281-344 in: André, Edm. 1883. 1881-1886. Species des Hyménoptères d'Europe et d'Algérie. Tome Deuxième. Beaune: Edmond André, 919 + 48 pp.

Atanassov, N.; Dlussky, G. M. 1992. Fauna of Bulgaria. Hymenoptera, Formicidae. [In Bulgarian.]. Fauna na Bûlgariya 22:1-310.

Bolton, B. 1987. A review of the Solenopsis genus-group and revision of Afrotropical Monomorium Mayr (Hymenoptera: Formicidae). Bulletin of the British Museum (Natural History). Entomology 54:263-452.

Donisthorpe, H. 1932. On the identity of Smith's types of Formicidae (Hymenoptera) collected by Alfred Russell Wallace in the Malay Archipelago, with descriptions of two new species. Annals and Magazine of Natural History (10)10:441-476.

Emery, C. 1892 ("1891"). Note sinonimiche sulle formiche. Bullettino della Società Entomologica Italiana 23:159-167.

Forel, A. 1891. Les Formicides. [part]. In: Grandidier, A. 1891. Histoire physique, naturelle, et politique de Madagascar. Volume XX. Histoire naturelle des Hyménoptères. Deuxième partie (28e fascicule). Paris: Hachette et Cie, v + 237 pp.

Heterick, B. 2006. A revision of the Malagasy ants belonging to genus Monomorium Mayr, 1855 (Hymenoptera: Formicidae). Proceedings of the California Academy of Sciences (4)57:69-202.

Imai, H. T. 1966. The chromosome observation techniques of ants and the chromosomes of Formicinae and Myrmicinae. Acta Hymenopterologica 2:119-131.

Linnaeus, C. 1758. Systema naturae per regna tria naturae, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio decima, reformata. Holmiae [= Stockholm]: L. Salvii, 824 pp.

Mayr, G. 1862. Myrmecologische Studien. Verhandlungen der Kaiserlich-Königlichen Zoologisch-Botanischen Gesellschaft in Wien 12:649-776.

Mayr, G. 1886. Notizen über die Formiciden-Sammlung des British Museum in London. Verhandlungen der Kaiserlich-Königlichen Zoologisch-Botanischen Gesellschaft in Wien 36:353-368.

Mayr, G. 1865. Formicidae. In: Novara Expedition 1865. Reise der Österreichischen Fregatte "Novara" um die Erde in den Jahren 1857, 1858, 1859. Zoologischer Theil. Bd. II. Abt. 1. Wien: K. Gerold's Sohn, 119 pp. 

Petralia, R. S.; Vinson, S. B. 1980 ("1979"). Comparative anatomy of the ventral region of ant larvae, and its relation to feeding behavior. Psyche (Cambridge) 86:375-394.

Roger, J. 1862. Synonymische Bemerkungen. 1. Ueber Formiciden. Berliner Entomologische Zeitschrift 6:283-297.

Smith, D. R. 1979. Superfamily Formicoidea. Pp. 1323-1467 in: Krombein, K. V.; Hurd, P. D.; Smith, D. R.; Burks, B. D. (eds.) 1979. Catalog of Hymenoptera in America north of Mexico. Volume 2. Apocrita (Aculeata). Washington, D.C.: Smithsonian Institution Press, pp. i-xvi, 1199-2209.

Smith, M. R. 1965. House-infesting ants of the Eastern United States, their recognition, biology, and economic importance. United States Department of Agriculture, Technical Bulletin No. 1326: i-105.

Wheeler, G. C.; Wheeler, J. 1955. The ant larvae of the myrmicine tribe Solenopsidini. American Midland Naturalist 54:119-141.

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