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Brachymyrmex patagonicus (the Dark Rover Ant) is the type species of the genus, and is a small, shiny, light brown to dark brown species with reduced pilosity. The original type material used by Mayr (1868) to describe the B. patagonicus cannot be located, prompting the species to be redescribed based on Chilean material also examined and determined by Mayr (Quiran et al., 2004). The redescription was part of a larger effort to clear up the confusion surrounding Brachymyrmex taxonomy ( Quirán 2005; 2007), but several errors concerning the erroneously small size of the workers and queens of B. patagonicus were also published (MacGown et al., 2007). Brachymyrmex patagonicus is native to at least the South America region of the Neotropics (Quiran et al., 2004), and is introduced to the southeastern United States (MacGown et al., 2007), and at least the Netherlands in Europe (Boer & Vierbergen, 2008). A review of B. patagonicus as an emerging pest species in the Gulf Coast region of the United States provides a thorough account of the taxonomy, invasion history and biology (MacGown et al., 2007). The authors suggest that B. patagonicus shows considerable potential as a nuisance species, perhaps comparable to the effects Tapinoma melanocephalum has in tropical and subtropical regions.
Native Range (Quiran et al., 2004): Argentina, Paraguay, Bolivia, Brasil (RS, SP, RJ, AM), Guianas, Venezuela.
Introduced Range. Netherlands. USA: Arizona, Alabama, Georgia, Florida, Louisiana, Mississippi, Missouri, Texas.
In Paraguay: Amambay, Boquern, Canindey, Central, Concepcin, Cordillera, Itapa, Misiones, eembuc, Paraguar, Pte. Hayes
The first record B. patagonicus in the United states, from Louisiana in 1978, was misidentified as B. musculus (Wheeler & Wheeler, 1978). The species continued to be referred to under that name in publications, including subsequent faunal lists for Florida (Deyrup, 2003; Deyrup et al., 2000), until MacGown et al. (2007) determined that all records of B. musculus in the region in fact referred to B. patagonicus.
The species nests in a variety of both natural and disturbed habitats. Natural habitats reported from MacGown et al. (2007) include pine forests (with nests often in loose bark at the bases of the tree trunks), beaches (with nests at the bases of plants), mixed forests (nests in soil, dead wood, and litter), and prairie remnants (nests in soil, accumulations of organic litter, and grass thatch). In disturbed areas, nests of B. patagonicus are especially frequent in landscaping mulch, a habitat that is increasing exponentially throughout the Southeast, and which positions colonies to make forays into buildings. In disturbed areas it also nests in soil under objects on the ground (stones, bricks, railroad ties, lumbers, or a variety of other objects), under grass at edges of lawns and parking lots, in leaf litter, at the bases of trees, in rotting wood, in piles of dead wood, and in accumulations of trash.
The diet of B. patagonicus is thought to consist largely of honeydew harvested from a diversity of insects, especially subterranean hemipterans (Dash et al., 2005), and are attracted to sweet baits such as honey or cookies (MacGown et al., 2007).
Colonies of B. patagonicus may contain many hundreds of workers packed into a small sheltered area, and colonies are often abundant and may be found within a few centimeters from one another (MacGown et al., 2007). The social structure of B. patagonicus has not been studied, but apparently separate colonies show considerable mutual tolerance (MacGown et al., 2007). Although it has been reported that B. patagonicus may be found in higher numbers subsequent to the suppression of Solenopsis invicta (Dash, 2004), the species is also known to coexist with both S. invicta and S. invicta x S. richteri (MacGown et al., 2007).
Brachymyrmex patagonicus is considered a nuisance pest, primarily because altaes and foraging workers may enter houses, hospitals, schools and other man-made structures to forage and/or nest (MacGown et al., 2007). The species can occur in very high numbers, especially in metropolitan areas, and pest control operators have expressed difficulty controlling it. However, there are no reports thus far of B. patagonicus causing structural damage, bites or stings, transmitting disease, nor invading food stores.
Costa Rica: This is a common species of synanthropic habitats in Costa Rica. It can be found in small parks in the middle of San José, in hotel landscaping, along road edges, in scrubby second growth vegetation, and in pastures. It occurs in almost any bioclimatic region: dry Guanacaste lowlands, wet Atlantic slope lowlands, Central Valley urban areas, and roads and pastures near Monteverde cloud forest. Nests are often under stones on the ground but also occur in cavities in low vegetation. Colonies are polygynous, with multiple dealate queens often occurring together in nests. Workers are omnivorous and opportunistic foragers. (Prior to Jan 2019, Longino identified most Costa Rican material of this species as heeri.)
Brachymyrmex patagonicus can be distinguished from most other introduced members of the genus by the following combination of characters: (1) sparse pubescence on the first gastral tergite, (2) antennal scapes exceeding posterior margin of head by at least 1/5 their length, (3) erect hairs on the pronotum and mesonotum, (4) eye length approximately equal to malar length, and (5) shiny brown in color. In North America, the species is most readily confused with B. obscurior, but can be separated by the sparser pilosity on the gaster and the larger eyes.
Redescription from MacGown et al. 2007
Diagnosis of Male. Size minute, mesosomal length 0.43-0.51 mm ( n = 10). Head and mesosoma medium brown to blackish-brown, gaster usually blackish-brown, often darker than head and mesosoma, tarsi and mandibles pale, and antennae brownish-yellow. Head slightly longer than wide, covered with fine pubescence, and with a few longer erect hairs; antennal scapes surpassing occipital border of head by 1/5 their total length; eyes relatively large, about as long as length of malar space and placed at approximately the middle third of side of head; 3 tiny, barely visible ocelli present. Promesonotum with 3-9 (usually 4-6) stout, erect hairs present dorsally, with fine pubescence that does not obscure the shiny sheen of integument. Gaster with scattered, long, erect hairs, especially along the edges of the tergites, and with sparse, decumbent hairs, separated by about 1/3 to 2/3 their length.
Diagnosis of Female. Mesosomal length 1.24-1.42 mm ( n = 10). Concolorous light brown. Head wider than long, with abundant, fine pubescence, and with long erect hairs present; large compound eyes located at middle of side of head; 3 large ocelli present; frontal lobes well developed; scapes surpassing occipital border by 1/4 their length. Mesosoma with moderately dense, fine pubescence, and 30-40 long erect hairs (about 3-4 times length of fine pubescence); anepisternum and katepisternum separated by a distinct suture, with erect hairs present. Forewing with pterostigma; hind wing with 7 hammuli. Gaster with moderately dense, fine pubescence, and erect hairs along apical edges of sternites and tergites.
Diagnosis of Male. Mesosomal length 0.8 mm ( n = 2). Head dark brown to blackish-brown, rest of body, including appendages, very light brown. Head wider than long, with fine, sparse pubescence, lacking erect hairs except on mouthparts, and with smooth, shiny integument; frontal lobes reduced; scapes surpassing occipital border by more than 1/5 their length, first segment of funiculus enlarged, almost globular, wider than succeeding segments; eyes large, about 1/2 length of head, and located on lower half of head; 3 large, prominent, raised ocelli present. Mesosoma with sparse pubescence Figs. 4-6. Full-face views of Brachymyrmex patagonicus: (4) worker, (5) male, and (6) female. Scale bar equals 0.5 mm. and shiny integument, lacking erect hairs. Hind wing with 5 or 6 hammuli. Gaster shiny, lacking pubescence, with scattered erect hairs on last few sternites and tergites.
Boer, P. & Vierbergen, B. (2008) Exotic ants in The Netherlands (Hymenoptera: Formicidae). Entomol. Ber. (Amsterdam), 68, 121-129.
Dash, S.T. (2004) Species diversity and biogeography of ants (Hymenoptera: Formicidae) in Louisianna, with notes on their ecology. M.S. thesis, Louisiana State University. v + 290 p.
Dash, S.T., Hooper-Bui, L.M. & Seymour, M.A. (2005) The pest ants of Louisiana. A guide to their identification, biology, and control. Louisiana State University, Louisiana Agricultural Experiment Station, Louisiana Cooperative Extension Service, Pub. 2915
Deyrup, M. (2003) An updated list of Florida ants (Hymenoptera: Formicidae). Florida Entomol., 86, 43-48.
Deyrup, M., Davis, L. & Cover, S. (2000) Exotic ants in Florida. Trans. Am. Entomol. Soc., 126, 293-326.
MacGown, J.A., Hill, J.G. & Deyrup, M.A. (2007) Brachymyrmex patagonicus (Hymenoptera: Formicidae), an emerging pest species in the southeastern United States. Florida Entomol., 90, 457-464.
Mayr, G. (1868) Formicidae novae Americanae collectae a Prof. P. de Strobel. Annu. Soc. Nat. Mat. Modena, 3, 161-178.
Quiran, E. (2005) El genero Neotropical Brachymyrmex Mayr (Hymenoptera: Formicidae) en la Argentina. II. Redescripcion de las especies B. admotus Mayr, de B. brevicornis Emery y B. gaucho Santschi. Neotrop. Entomol., 34, 761-768.
Quiran, E. (2007) El Genero Neotropical Brachymyrmex Mayr (Hymenoptera: Formicidae) en la Argentina. III. Redescripcion de las especies: B. aphidicola Forel, de B. australis Forel y B. constrictus Santschi. Neotrop. Entomol., 36, 699-706.
Quiran, E.M., Martinez, J.J. & Bachmann, A.O. (2004) The Neotropical genus Brachymyrmex Mayr 1868 (Hymenoptera: Formicidae) in Argentina. Redescription of the type species, B. patagonicus Mayr 1868; B. bruchi Forel, 1912 and B. oculatus Santschi, 1919. Acta Zool. Mex. (N.S.), 20, 273-285.
Wheeler, G.C. & Wheeler, J. (1978) Brachymyrmex musculus, a new ant in the United States. Entomol. News, 89, 189-190.
Amambay, Boquerón, Canindeyú, Central, Concepción, Cordillera, Itapúa, Misiones, Ñeembucú, Paraguarí, Pte. Hayes (ALWC, IFML, INBP, LACM, MHNG, NHMW). Literature records: Cordillera(Forel 1906, Forel 1909).
Found most commonly in these habitats: 0 times found in on ground at edge of parking lot and grassy area, 0 times found in on ground at edge of parking lot and mowed grassy area, 0 times found in deciduous forest, 0 times found in on ground at roadside, 0 times found in in gas station parking lot, 0 times found in in house, 0 times found in along transect in grassy area by highway, 0 times found in Black Belt Prairie, 0 times found in mixed pine/hardwood forest, 2 times found in roadside, ...
Found most commonly in these microhabitats: 4 times nest under stone, 3 times ex sifted leaf litter, 1 times nesting in cracks at base of tree, 1 times inside NPS quarters temp housing on table, 4 times at bait, 1 times ground forager(s), 1 times under bark of dead Populus, 1 times mercury vapor lamp, 0 times litter, 1 times ground nest, 1 times ground foragers, ...
Collected most commonly using these methods: 0 times Lindgren Funnel baited with Typosan and alpha-pinene, 28 times direct collection, 1 times Lindgren funnel, 0 times Malaise trap, 0 times bait, 0 times cookie bait, 0 times Lindgren funnel baited with Typosan and alpha pinene, 0 times Lindgren Funnel baited with Typosan, 9 times search, 0 times sweeping, 5 times hand collecting, ...
Elevations: collected from 4 - 2270 meters, 383 meters average
Collect Date Range: collected between 1950-11-28 00:00:00.0 and 2022-05-18 00:00:00.0