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Subfamily MYRMICINAE
Tribe SOLENOPSIDINI

Monomorium floricola (Jerdon, 1851)

Bicolored trailing ant

Authors: Joe A. MacGown and Ryan J. Whitehouse
Uploaded 2009; last updated 25 February 2016

Monomorium floricola, full face view of a worker (Alachua Co., FL) (photo by Ryan J. Whitehouse and Joe A. MacGown)
Monomorium floricola, lateral view of a worker (Alachua Co., FL) (photo by Ryan J. Whitehouse and Joe A. MacGown)
Monomorium floricola, dorsal view of a worker (Alachua Co., FL) (photo by Ryan J. Whitehouse and Joe A. MacGown)
Monomorium floricola, full face view of a queen (Ecuador) (photo by Antweb.org)
Monomorium floricola, lateral view of a queen (Ecuador) (photo by Antweb.org)
Monomorium floricola, dorsal view of a queen (Ecuador) (photo by Antweb.org)
Monomorium floricola, full face view of a male (Mayotte) (photo by Antweb.org)
Monomorium floricola, lateral view of a male (Mayotte) (photo by Antweb.org)
Monomorium floricola, dorsal view of a male (Mayotte) (photo by Antweb.org)
Monomorium floricola, lateral view of wings of a male (Mayotte) (photo by 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. Most foraging occurs on the ground, although 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 floricola (Jerdon) (Myrmicinae), the bicolored trailing ant, is a minute, bicolored widely distributed tramp ant thought to be native to the Old World (possibly Asia). In the US, outdoor populations are only know to occur in Florida, coastal Alabama, and coastal Mississippi. Occasionally, populations are found in heated buildings such as greenhouses in temperate regions of both Europe and the US.

Taxonomic History (Bolton 2016)
Atta floricola Jerdon, 1851: 107 (w.) INDIA. Indomalaya. Forel, 1893: 388 (q.m.); Wheeler, 1905: 88 (q.m.); Donisthorpe, 1914: 136 (gynandromorph); Crawley, 1920: 217 (gynandromorph); Wheeler & Wheeler, 1955: 121 (l.). Combination in Monomorium: Mayr, 1879: 671. Senior synonym of Monomorium poecilum: Emery, 1894: 151; of Monomorium specularis: Mayr, 1879: 671; of Monomorium cinnabari: Wheeler, 1913: 486; of Monomorium floreanum: Brown, in Linsley & Usinger, 1966: 175; of Monomorium angusticlava, Monomorium impressum: Bolton, 1987: 390; of Monomorium furina, Monomorium philippinensis: Heterick, 2006: 122. See also: Solis, Fox, Kato, et al. 2010: 15

Identification
Worker: Minute (HL 0.41–0.43 mm, HW 0.31–0.34 mm, SL 0.28–0.32 mm, EL 0.06–0.07 mm, MeSL 0.42–0.47 mm) (n=5) (MEM specimens). Head dark orangish brown to brown, mesosoma and waist light orangish brown and occasionally infuscated, gaster dark brown, and antennae and legs yellowish brown to light orangish brown. Head longer than wide, rounded rectangular; lacking sculpture, smooth and shiny; with scattered semi erect to erect setae; clypeus raised, narrowed, with a pair of fine longitudinal carinae; eyes small (about 5-6 facets in longest diameter), located on side of head just in front of midline; ocelli lacking; mandibles with 3 teeth and a minute basal denticle; antenna 12-segmented, with a 3-segmented club. Mesosoma elongate, somewhat narrowed; promesonotum broadly rounded (in lateral view); metanotal groove impressed; propodeum broadly rounded, dorsum longer than declivity, lacking spines or denticles,; entire mesosoma smooth and shiny except for transverse striae at base of anepisternum, in metanotal suture, and base of propodeum; with scattered short, erect setae and a pair of long, erect setae on humeri. Waist two-segmented, smooth and shiny with with several elongate, semi erect setae present; petiole pedunculate, node about twice as long as tall, broadly conical in lateral view; postpetiole circular in lateral and dorsal views. Gaster is smooth and shiny with sparse, elongate, erect setae present; sting present.

Queen: (Description from Heterick 2006 and Antweb.org photos). Small, larger than workers. (HL 0.54–0.55 mm, HW 0.44–0.46 mm, SL 0.39–0.40 mm, PW 0.31–0.33 mm) (n=19) (measurements from Heterick 2006). Head and gaster brown; mesosoma yellowish brown or with pronotum, mesopleura, and propodeum brown; antennae orangish brown; and legs light yellowish brown. Head rectangular; mostly shiny and lacking sculpture except piligerous setal pits; with regularly placed, slightly flexuous setae; eye elliptical, large, at about midpoint of head; three small ocelli present; mandible with four teeth; antenna 12-segmented, with 3-segmented club; scape not quite reaching posterior  edge of head. Mesosoma flattened dorsally; pronotum rectangular; mesoscutum rounded anteriorly, propodeum rounded posteriorly, lacking spines or denticles; entire mesosoma shiny, with occasional light striolae on anterior region of anepisternum; mesosomal dorsum with numerous, semi erect to erect, setae present. Winged specimens not known. Waist two-segmented, smooth, shining, with numerous erect setae present; petiole pedunculate, node broadly rounded; postpetiolar node rounded, slightly wider than petiole in dorsal view. Gaster shiny, with numerous erect and semi erect setae with intersetal spaces about as long as setal length; sting present.

Male: (Description from Heterick 2006 and Antweb.org photos). Small, about the size of worker (HL 0.46 mm, HW 0.50 mm,  SL 0.16mm, PW 0.44 mm) (n=1) (measurements from Heterick 2006). Head, mesosoma, waist, and gaster dark brown; antennae, coxae, and femora brown; tibiae and tarsi pale yellowish brown. Head slightly wider than long; smooth and shiny posteriorly, then with longitudinal striae beginning at near the posterior-most point of eye; scattered, somewhat stout, whitish setae present. eyes large, about half the head length; ocelli prominent, slightly raised; antenna 13-segmented (including scapes); scape about length of funicular segments 2+3; mandibles falcate, with three small teeth apically. Mesosoma: mesoscutum rounded, broadly convex; pronotum trapezoidal; propodeal dorsum angle about 45°, declivity about 90°, unarmed; pronotum, mesoscutum, mesoscutellum, and mesopleuron shiny (except pitted sculpture on anterior portion of katepisternum and near wing bases); propodeal dorsum lacking sculpture, but with pitted sculpture laterally; mesosomal dorsum with short semi erect to erect setae directed posteriorly (not densely concentrated). Wings transparent; veins with little pigmentation, distal segments reduced to vestigial lines; m–cu absent; cu–a absent. Waist two-segmented, with curved setae, directed posteriorly (longer than setae on mesosoma); petiole rounded triangular in lateral view, rounded dorsally; with light sculpture anteriorolaterally and mostly smooth elsewhere; postpetiole rounded laterally and dorsally, with pitted sculpture except on dorsum. Gaster lacking sculpture, 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; genitalia visible externally, not greatly enlarged, parameres acutely triangular.

Workers of M. floricola can be easily recognized by the minute size; smooth, shiny, bicolored appearance; 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. Other ants in the genus in our region are either all black or all yellow. Species of thief ants in the related genus Solenopsis have 10-segmented antennae and are not typically bicolored.

Biology and Economic Importance
Monomorium floricola is an extremely successful tramp ant that is typically found in tropical and subtropical regions, including Florida, and occasionally in greenhouses in temperate locations. Colonies are polygynous, with queens all wingless. As a result, colonies rely on budding for dispersal instead of mating swarms (Snelling 2005). This species often has arboreal nest, and can form colonies in small crevices and cracks in trees and bark. Colonies are easily transported by humans and may also spread by rafting across water on hollow logs, twigs or plant debris. In natural conditions, workers feed on dead and living insects, tend honeydew producing insects, and feed at extrafloral plant nectaries. 

This species commonly infests households where it feeds on various sugary and protein rich foods (Smith 1965), and is therefore considered a minor nuisance pest. Although it has a stinger, M. floricola is not considered to be a serious stinging pest.

Distribution
Native Range: Probably Tropical Asia, but already had a widespread range by the time ant surveys began.

Australian: Australia, Cook Islands, Federated States of Micronesia, Fiji, French Polynesia, Guam, Hawaii, Indonesia, Kiribati, Marshall Islands, New Caledonia, New Guinea, Norfolk Island, Northern Mariana Islands, Palau, Samoa, Solomon Islands, Tokelau, Tonga, Vanuatu, Wallis and Fortuna Islands (AntWiki.org).
Ethiopian: Comoros, Ghana, Mauritius, Mayotte, Nigeria, Republic of Cameroon, Reunion, Seychelles, Togo, United Republic of Tanzania (AntWiki.org).
Nearctic: United States (AntWiki.org and MEM).
Neotropical: Anguilla, Bahamas, Barbados, Brazil, Cayman Islands, Chile, Colombia, Costa Rica, Cuba, Dominican Republic, Ecuador, El Salvador, French Guiana, Galapagos Islands, Greater Antilles, Guatemala, Guyana, Haiti, Lesser Antilles, Mexico, Paraguay, Puerto Rico, Suriname, Trinidad and Tobago (AntWiki.org).
Oriental: Borneo, India, Krakatau Islands, Malaysia, Nicobar Island, Philippines, Sri Lanka, Vietnam (AntWiki.org).
Palearctic: China, Japan, Republic of Korea, United Kingdom of Great Britain and Northern Ireland (AntWiki.org).

U.S. Distribution: AL, FL, HI, MS (MEM).
Southeastern U.S. Distribution: Al, FL, MS (MEM).

Acknowledgments
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
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.

Bolton, B. 2016.  Bolton World Catalog Ants. Available online: http://www.antweb.org/world.jsp. Accessed 9 March 2016.

Crawley, W. C. 1920. A gynandromorph of Monomorium floricola, Jerd. Entomologist's Record and Journal of Variation 32:217-218.

Donisthorpe, H. 1914. Myrmecophilous notes for 1913. Entomologist's Record and Journal of Variation 26:37-45.

Emery, C. 1894. Studi sulle formiche della fauna neotropica. VI-XVI. Bullettino della Società Entomologica Italiana 26:137-241.

Forel, A. 1893. Formicides de l'Antille St. Vincent, récoltées par Mons. H. H. Smith. Transactions of the Entomological Society of London 1893:333-418.

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.

Linsley, E. G.; Usinger, R. L. 1966. Insects of the Galápagos Islands. Proceedings of the California Academy of Sciences (4)33:113-196.

Mayr, G. 1879. Beiträge zur Ameisen-Fauna Asiens. Verhandlungen der Kaiserlich-Königlichen Zoologisch-Botanischen Gesellschaft in Wien 28:645-686.

Smith, M.R. 1965. House-infesting ants of the Eastern United States, Their Recognition, Biology, and Economic Importance. Agricultural Research Service, United States Department of Agriculture Technical Bulletin No. 1326.

Snelling, R. R. 2005: Wasps, ants, and bees: aculeate Hymenoptera. In: Lazell, J. (Ed.): Island: fact and theory in nature. University of California Press, Berkeley, CA, pp. 283-296.

Wetterer, J.K. 2010. Worldwide spread if the flower ant, Monomorium floricola (Hymenoptera: Formicidae). Myrmecological News 13, 19-27.

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

Wheeler, W. M. 1905. The ants of the Bahamas, with a list of the known West Indian species. Bulletin of the American Museum of Natural History 21:79-135.

Wheeler, W. M. 1913. The ants of Cuba. Bulletin of the Museum of Comparative Zoology 54:477-505.

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