Pseudomyrmex brunneus

Identification
Ward (1985) - Similar to Pseudomyrmex ejectus.The major differences between the two species are in the shapes of the propodeum, petiole, and postpetiole (note especially the non-overlapping values of PWI and PPWI). In addition, P. brunneus tends to have a more densely sculptured (and opaque) head than P. ejectus and to exhibit less contrasting light and dark brown coloration on the mesosoma, petiole and post petiole.

Distribution based on Regional Taxon Lists
Neotropical Region: Costa Rica, Greater Antilles, Mexico.

Biology
Ward (1985) - At Cola de Caballo, near Monterrey, I collected workers and larvae of P. brunneus in dead twigs of a small tree, probably Melia azedarach, and in the dead stalk of an unidentified mint. The latter nest contained a single dealate queen, P. ejectus was also found nesting in a dead mint stalk at this locality.

This appears to be an uncommon Mexican species, which occurs sympatrically with P. ejectus.

Nomenclature

 *  brunneus. Pseudomyrma brunnea Smith, F., 1877b: 63 (w.) MEXICO. Emery, 1895c: 270 (q.); Wheeler, G.C. & Wheeler, J. 1956: 382 (l.). Combination in Leptalea: Smith, M.R. 1951a: 788; in Pseudomyrmex: Wheeler, G.C. & Wheeler, J. 1956: 382. Senior synonym of nigrita: Ward, 1985b: 231.
 * nigrita. Pseudomyrma brunnea var. nigrita Enzmann, E.V. 1944: 82, pl. 2, fig. 12 (w.) MEXICO. Combination in Pseudomyrmex: Kempf, 1972a: 216. Junior synonym of brunneus: Ward, 1985b: 231.

Worker
Ward (1985) - Measurements (n = 10): HL 0.77-0.86, HW 0.67-0.72, MFC 0.012-0.024, CI 0.83-0.90. OI 0.57-0.63, REL 0.51-0.56, REL2 0.58-0.64, OOI 0.67-1.20, VI 0.70-0.78, FCI 0.017-0.035, SI 0.43-0.50, SI2 0.69-0.80, FI 0.41-0.45, PDI 0.56-0.75, MPI 0.052-0.075, NI 0.57-0.65, PLI 0.47-0.58, PWI 0.54-0.65, PPWI 1.26-1.54.

Worker Diagnosis. —Small, brown species, with wide head and broadly rounded occiptal margin (HW 0.67-0.72, CI 0.83-0.90). Similar to p. ejectus F. Smith (q.v.) except as follows: basal face of propodeum between one half and three quarters the length of declivitous face (POI 0.56-0.75); petiole shorter and broader than that of p. ejectus (PWI 0.54-0.65); petiolar node somewhat displaced posteriorly; postpetiole short and wide (PPWI 1.26-1.54). Front of head opaque, densely coriarious-imbricate; sculpture becoming weaker towards the vertex, with scattered, fine punctures on a (usually) sublucid, coriarious background; mesosoma subopaque, coriarious to coriarious-imbricate; petiole, postpetiole, and gaster increasingly (in that order) less coriarious and more smooth and shining. Erect pilosity very sparse; appressed pubescence scattered over body; abdominal tergite IV with appressed hairs separated by about their lengths, and not obscuring the shiny integument. Body dark brown, little or no contrast in color between the head, mesosoma, petiole, postpetiole, or gaster; mandibles and apical ends of tarsi luteous.

Type Material
Ward (1985) - Holotype (unique syntype) worker. Mexico (Examined).

Pseudomyrma brunnea var. nigrita Enzmann. 1945, p, 82, Syntype workers, Mirador, Mexico (E. Skwarra) (Examined).

References based on Global Ant Biodiversity Informatics

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 * Wheeler W. M. 1942. Studies of Neotropical ant-plants and their ants. Bulletin of the Museum of Comparative Zoology 90: 1-262.