Brachymyrmex obscurior

Nomenclature

Species:Brachymyrmex obscurior Forel, 1893

Usage: valid

General description

Brachymyrmex obscurior is a small, dull brown, non-descript and soft-bodied ant. Wilson and Taylor (1967) raised B. obscurior to species status, qualifying their decision as a, “purely provisional measure, contingent upon a fuller revision of the large and difficult genus it which it belongs.” The species is known to nest in the ground (Tschinkel and Hess, 1999), is especially well adapted to extreme, marginal environments (Morrison, 2006), and can be a common visitor to extrafloral nectaries (Koptur et al., 2010; Piovia-Scott, 2011). Brachymyrmex obscurior is considered a minor urban pest in Florida (Klotz et al., 1995), where it is rare but widespread (Deyrup, 2003).

Biology

Brachymyrmex obscurior is native to the Neotropics, and is ubiquitous across the Caribbean. The species is so common among those islands, that it is often the only single ant species to occur on the smallest cays (Morrison, 2006). However, the absence of B. obscurior from larger islands with more diverse ant faunas suggests that the species may be a poor competitor against most other ants (Morrison, 2006). The introduced range of B. obscurior includes Hawaii (Krushelnycky et al., 2005), Samoa (Wilson and Taylor, 1967), and the Solomon Islands (pers. observation) in the Pacific, the southern United States (Dash et al., 2005; Deyrup, 2003; Ipser et al., 2005), and the Netherlands (Boer and Vierbergen, 2008). Records from Antweb also indicate the species occurs in greenhouses and butterfly houses in the state of Washington.

External links

AntWeb | AntWiki | EOL | BOLD

Risk statement

Brachymyrmex obscurior is considered a minor urban pest in Florida.

Diagnostic description

Diagnosis of worker among Antkey species

Antenna 9-segmented. Antennal club indistinct. Antennal scapes surpassing the posterior margin of head by more than 1/5th their length. Eyes of moderate size (greater than 6 facets). Eye length less than malar distance. Head with or without distinct ocelli. Antennal sockets and posterior clypeal margin separated by a distance less than the minimum width of antennal scape. Dorsum of mesosoma lacking a deep and broad concavity. Metanotal groove present. Pronotum and mesonotum with pairs of erect hairs. Propodeum and petiolar node both lacking a pair of short teeth. Propodeum lacking posteriorly projecting protrusion. Metapleuron with a distinct gland orifice. Waist 1-segmented (may be hidden by gaster). Petiolar node appearing flattened. Gaster armed with acidopore. Gaster (especially first segment) with dense pilosity, giving it a dull appearance. Color dull brown.

Brachymyrmex obscurior can be distinguished from most other introduced members of the genus by the following combination of characters: (1) dense 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 distinctly less than malar length, and (5) dull brown in color. MacGown (2012)offers that the species, “is most similar to B. patagonicus, but can be differentiated by the much denser pubescence, especially on the gaster. Males of B. obscurior are concolorous dark brown; whereas males of B. patagonicus are bicolored with the head and gaster dark brown and the rest of the body, including the appendages, being pale yellowish-brown.” Additional characters cited by MacGown (2007) to separate the two include the smaller eye of B. obscurior which is shorter than the malar space, compared to the larger eye of B. patagonicus which is approximately equal to the malar length. 

Look alikes

Brachymyrmex patagonicus

Distribution

Native range. Neotropics, including Caribbean.

Introduced range. USA: Florida, Hawaii, Mississippi, Missouri, Washington. Netherlands. Samoa. Solomon Islands. 

Click here for updated occurrence data and map on antmaps.org
Click here for updated occurrence data and map on GBIF.org

Videos of live ants

Brachymyrmex obscurior at sugar bait, Hawaii, 03-28-2011

Brachymyrmex obscurior foraging on tree, Hawaii, 04-02-2011