Introduction
Brachymyrmex is a New World genus whose members are minute, soft-bodied, have a small petiolar scale, and a nine segmented antenna without a club. Workers have well developed eyes. Color ranges from pale light-yellow to dark brown. Species is this genus usually nest in soil or rotting wood.

A word of caution, this group is in drastic need of revision and the names are subject to change. This particular species, although distinctive from any others so far discovered in Mississippi, has been going by a couple of names, B. musculus Forel and B. patagonicus, for the last 30 years since it was first discovered to occcur in the United States in 1978 (Wheeler and Wheeler 1978). Brachymyrmex patagonicus, which is the type species, was recently redescribed (Quiran et al, 2004). A recent publication by MacGown et al (2007) and a poster by MacGown and Hlll (2007) presented the known distrubution of this species (which appears to be rapidly expanding) in the U.S., figures of all castes, biological and pest status, and brief dignoses of all castes.

Identification
Brachymyrmex patagonicus is a small dark reddish-brown species with pale tarsi and mandibles and brownish-yellow antennae. The promesonotum usually has at least four erect hairs. The gaster has sparse, but rather long pubescense. The head is slightly wider than long. The eyes are relatively large; about as long as the length of the malar space. Minute ocelli are present. The scape obviously surpasses the occipital border.

Brachymyrmex patagonicus is most similar to B. obscurior, another exotic species. It differs in the size of the eye, which is much larger in B. patagonicus than in B. obscurior. Additionally, the males of these two species are quite different in color. Males of B. patagonicus are bicolored with the head and gaster dark brown and the rest of the body (see photo above), including the appendages, being pale yellowish-brown. Males of B. obscurior are concolorous dark brown. Brachymyrmex sp.-01, recorded from Florida, is also dark brown in color, but lacks erect hairs on the body. Another similar species, not yet reported from the U.S., but possible, is B. heeri. This brownish colored species differs in that the workers lack ocelli. An undescribed brown species known only from two queens collected from Arkansas (Lloyd Davis, pers. comm.) is unusual in that the queens are tiny, about the size of typical workers. All other known species present in this region are yellowish in color.

Biology and Economic Importance
We have found this species nesting in rotting wood and in the soil. I have seen this species nesting in a variety of habitats ranging from sand at the bases of plants on a beach, in soil in rich mixed forests, to hardwood mulch in subburban settings. This species is considered a nuisance pest and is increasingly being found in houses and other man-made structures. Alates have been collected from late April through early August. I have had calls from pest control operators (PCOs)in central Mississippi and Florida who have expressed great difficulty in controlling this species even with repeating applications as many as 15 times! PCOs have stated that although this species has been been found in various food sources, it seems to be especially attracted to sweet liquids.

Distribution
Brachymyrmex patagonicus is an exotic species native to Argentina. This species appears to be very common in northern FL, the southern portions of GA, AL, MS, and most of LA, and has been found in SC, AR, TX, AZ, and NV as well (NV record from Wild, 2008). This exotic species is spreading at an alarming rate and will likely be found in TN before long, if it is not already there.

Literature Cited

MacGown, J. A., J.G. Hill, and M. A. Deyrup. 2007. Brachymyrmex patagonicus (Hymenoptera: Formicidae), an emerging pest species in the southeastern United States. Florida Entomologist 90: 457-464. [pdf]

MacGown, J. A. and J. G. Hill.  2007.  Brachymyrmex patagonicus (Hymenoptera:  Formicidae), an emerging pest species introduced into the southeastern United States. Mississippi Entomological Society 24-26 Oct. 2007. [power point poster]

Quiran, E. M., J. J. Martinez, and A. O. Bachmann. 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 Zoologica Mexicana 20: 273-285.

Wheeler, G. C. and J. Wheeler. 1978.  Brachymyrmex musculus, a new ant in the United States.  Entomological News 89: 189-190. 

Wild, A. 2008. Myrmecos Blog: Rover Ants (Brachymyrmex patagonicus), an emerging pest species. http://myrmecos.wordpress.com/2008/05/27/rover-ants-brachymyrmex-patagonicus-an-emerging-pest-species/ (accessed 5 June 2008).

Links and Fact Sheets

AntWeb Images

Discover Life Images

Layton, B. and J. A. MacGown. 2008. Rover Ants: Mississippi Extension Pest Control Sheet. [pdf]

Myrmecos Blog: Rover Ants (Brachymyrmex patagonicus), an emerging pest species. http://myrmecos.wordpress.com/2008/05/27/rover-ants-brachymyrmex-patagonicus-an-emerging-pest-species/