Pseudomyrmex pisinnus

Identification
Ward (1989) - This small, slender species is easily recognized by the combination of small size, elongate head, long basal face of propodeum, and low petiole. The short scapes (relative to head length), sublucid appearance, and light orange-brown color are also distinctive.

Distribution based on Regional Taxon Lists
Neotropical Region: Brazil, Peru.

Biology
The type series was collected in a dry stem of Eupatorium sp. The Peruvian specimens are from primary rain forest. (Ward 1989)

Nomenclature

 *  pisinnus. Pseudomyrmex pisinnus Ward, 1989: 425, fig. 11 (w.) BRAZIL.

Worker
measurements (n=8). —HL 0.75-0.78, HW 0.47-0.51, MFC 0.009-0.016, CI 0.61-0.68, OI 0.49-0.55, REL 0.52-0.54, REL2 0.78-0.86, OOI 0.73-1.58, VI 0.76-0.87, FCI 0.018-0.033, SI 0.41-0.45, SI2 0.50-0.54, FI 0.46-0.52, POI 1.46-1.69, MPI 0.029-0.047, NI 0.59-0.64, PU 0.67-0.77, PWI 0.54-0.65, PPWI 1.07-1.20.

diagnosis. —Very small species (HW 0.47-0.51) with elongate head (CI 0.61-0.68), and short scapes relative to eye length (S12 0.50-0.54); sides of head subparallel; occipital margin flat to slightly concave, in frontal view; funicular segments II and III notably broader than long (FU 1.16-1.48, n=4). Fore femur broad; metanotal groove rather weakly impressed; basal face of Propodeum rounding into the much shorter declivitous face. Petiolar node rather long and low, the dorsum broadly rounded in lateral profile (PU 0.67-0.77); postpetiole about as broad as long.

Head sublucid, covered with numerous piligerous punctures; punctures relatively coarse but appearing somewhat effaced, and separated (at least on the upper half of the head) by shiny interspaces of one or more diameters' distance, especially in the region immediately posterior to the compound eye. Mesosoma weakly punctate to coriarious-imbricate, sublucid dorsally. Petiole, postpetiole, and gaster subopaque to sublucid, covered with numerous, fine piligerous punctures. Erect pilosity and appressed pubescence present on most of the body; erect hairs present on the pronotum, mesonotum and propodeum, but relatively short, sparse, and inconspicuous, except for one pair on the pronotal shoulders and a second pair above the juncture of the basal and declivitous faces of the propodeum. Body light orange-brown to yellow-brown, with darker infuscation on the anterior third of the first gastric (fourth abdominal) tergite, on the succeeding gastric tergites, and on part of the hind femur; mandibles paler luteous.

Type Material
Holotype worker. —BRAZIL, SP: Monte Aprazivel, Faz. Bacuri [20°45'S, 49°42'W], 19.vii.1974, in Eupatorium stem, M. Dimiz, no. 644. HW 0.51, HL 0.78, EL 0.41, PL 0.30, PH 0.22.

Paratypes. —Same data as holotype, four workers (,, MZSP, ).

References based on Global Ant Biodiversity Informatics

 * Brandao C. R. F., F. A. Esteves, and L. P. Prado. 2010. A catalogue of the Pseudomyrmecinae ant type specimens (Hymenoptera, Formicidae) deposited in the Museu de Zoologia da Universidade de Sao paulo, Brazil. Papeis Avulsos de Zoologia 50(45): 693-699.
 * Fernández, F. and S. Sendoya. 2004. Lista de las hormigas neotropicales. Biota Colombiana Volume 5, Number 1.
 * Ribas C. R., J. H. Schoereder, M. Pic, and S. M. Soares. 2003. Tree heterogeneity, resource availability, and larger scale processes regulating arboreal ant species richness. Austral Ecology 28(3): 305-314.
 * Ribas C. R., and J. H. Shoereder. 2007. Ant communities, environmental characteristics and their implications for conservation in the Brazilian Pantanal. Biodivers. Conserv. 16: 1511-1520.
 * Schoereder J. H., T. G. Sobrinho, M. S. Madureira, C. R. Ribas, and P. S. Oliveira. 2010. The arboreal ant community visiting extrafloral nectaries in the Neotropical cerrado savanna. Terrestrial Arthropod Reviews 3: 3-27.
 * Ulyssea M. A., and C. R. F. Brandao. 2013. Ant species (Hymenoptera, Formicidae) from the seasonally dry tropical forest of northeastern Brazil: a compilation from field surveys in Bahia and literature records. Revista Brasileira de Entomologia 57(2): 217224.
 * Ulysséa M. A., C. R. F. Brandão. 2013. Ant species (Hymenoptera, Formicidae) from the seasonally dry tropical forest of northeastern Brazil: a compilation from field surveys in Bahia and literature records. Revista Brasileira de Entomologia 57(2): 217-224.
 * Vasconcelos, H.L., J.M.S. Vilhena, W.E. Magnusson and A.L.K.M. Albernaz. 2006. Long-term effects of forest fragmentation on Amazonian ant communities. Journal of Biogeography 33:1348-1356
 * Ward, P. S. 1989. Systematic Studies on Pseudomyrmecine Ants: Revision of the Pseudomyrmex Oculatus and P. Subtilissimus Species Groups with Taxonomic Comments on Other Species. Questiones Entomologicae 25: 393-468