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.)
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
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. 2007Diagnosis 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.
Taxonomic history
Emery, 1906c PDF: 179 (q.).Senior synonym of Brachymyrmex patagonicus atratula: Quirán et al., 2004 PDF: 275.Senior synonym of Brachymyrmex laevis: Ortiz-Sepúlveda et al., 2019 10.1007/s13127-019-00406-2 PDF: 75.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).
Brachymyrmex patagonicus is a species of ant in the family Formicidae.[1][2][3][4][5][6][7] B. patagonicus, commonly known as the dark rover ant, is native to Argentina and Paraguay.[8][9] They were first reported in St. Tammany Parish, Louisiana in 1978 from a single colony collected in 1976.[10] It is believed that the species was introduced through New Orleans, which is a common entry point for many tropical species, but other locations such as Mobile, Alabama, or Pensacola, Florida, are also likely.[8] For many years B. patagonicus, B. musculus, and B. obscurior were misidentified as being separate species but after a comparison of specimens from the Louisiana State University Arthropod Collection (LSUC), it was found that all three were the same species.[8] B. patagonicus is considered a nuisance pest due to their tendency to infest man made structures but they have received a lack of attention because they do not bite, sting, or carry disease.[8]
Dark rover ants are small brown ants that are typically less than 2.5 millimeters in length.[9] Worker ants in this species range from 1.0mm to 2.0mm, whereas queens are around 3.0mm.[11] Males are around 1.0mm in length.[11] The antennae of the worker ants contain nine segments which is common among all species of Brachymyrmex.[12][11] B. patagonicus have long hairs along the mesosoma and relatively large eyes compared to the other species in the Brachymyrmex genus.[12] On the dorsal surface of the gaster, the distribution of appressed hairs is sparse.[12]
These three subspecies belong to the species Brachymyrmex patagonicus:
Data sources: i = ITIS,[1] c = Catalogue of Life,[2] g = GBIF,[3] b = Bugguide.net[4]
Few studies have been conducted on the diet of B. patagonicus but it has been observed in nature that this species visits extrafloral nectaries for nectar.[13] Another theory suggests that a major part of their diet is honeydew from hemipterans.[8] In Laboratory settings, an artificial diet containing 30% honey solution, liquid tuna mixture, and caterpillar pieces was observed to support B. patagonicus.[14]
Most invasive ant species display polygyne tendencies, dispersal by budding, and development of supercolonies that contain hundreds of reproductive queens each.[9] The colony structure of Brachymyrmex patagonicus differs from most invasive ant species in that they are multicolonial and monodomous.[9] This means that each colony consists of a single nest that is genetically different from others around it.[9] In 80% of nests, a single queen heads the colony.[9] In the remaining 20%, there is no queen present.[9] In about 50% of nests headed by a single queen, the queen is only mated by one male.[9]
B. patagonicus is native to South America, and more specifically Argentina and Paraguay. It has been introduced in multiple parts of the world including the United states, Asia, and parts of Europe.[15] In less than 50 years after the introduction of the species into the United States, members of B. patagonicus are now commonly found in 14 states ranging from North Carolina to California.[8][16][17]
B. patagonicus commonly form their colonies in the soil, at bases of trees, in leaf litter, piles of wood, and trash piles.[11] In southern areas of the United states, colonies are found in both natural and disturbed areas but are more prevalent in areas near human activity.[11] In landscaped areas, they are commonly found in mulch and man made structures.[8] Laboratory studies have shown B. patagonicus have a preference for moist environments[18]
B. patagonicus are found to coexist with many native and introduced species including those typically intolerant to other ant species such as Solenopsis invicta and Solenopsis xyloni.[8] It is hypothesized that B. patagonicus may play an important role in the regulation of the populations of the invasive cactus moth (Cactoblastic cactorum).[13] This theory is currently under investigation.[13]
Brachymyrmex patagonicus is a species of ant in the family Formicidae. B. patagonicus, commonly known as the dark rover ant, is native to Argentina and Paraguay. They were first reported in St. Tammany Parish, Louisiana in 1978 from a single colony collected in 1976. It is believed that the species was introduced through New Orleans, which is a common entry point for many tropical species, but other locations such as Mobile, Alabama, or Pensacola, Florida, are also likely. For many years B. patagonicus, B. musculus, and B. obscurior were misidentified as being separate species but after a comparison of specimens from the Louisiana State University Arthropod Collection (LSUC), it was found that all three were the same species. B. patagonicus is considered a nuisance pest due to their tendency to infest man made structures but they have received a lack of attention because they do not bite, sting, or carry disease.
