Perissomyrmex

It seems the genus Perissomyrmex has an ancient origin before the separation of American and Asian old lands. During the long evolutionary history, the genus changes slightly in morphology. At present time, the genus is limited in species number, rare in individual amount, living mainly in the high altitude mountainous habitats, and distributed in the Oriental and Neotropical Regions. (Xu and Zhang 2012)

Identification
Xu and Zhang (2012) - The genus Perissomyrmex is most similar to Pristomyrmex in the tribe Myrmecinini, but mandibles rectangular, with two basal teeth on the masticatory margin; clypeus without longitudinal central carina; antennae nine-segmented; antennal scrobes absent; pronotum without teeth; anteroventral corner of mesopleuron not extruding; propodeal lobes short and obtuse at apices; sting usually not extruding; head and mesosoma striate.

Ogata and Okido (2007) - Individuals of Perissomyrmex are morphological variable. In particular, projected structures, such as teeth on the mandibles, propodeal spines, lateral projections on the petiolar peduncle, are varying due to wearing down or polymorphism.

Biology
Polymorphic workers, with minors and soldiers. Somewhat sparse evidence suggests soldiers make up a small proportion of the workers of a colony.

Nomenclature

 *  PERISSOMYRMEX [Myrmicinae: Myrmecinini]
 * Perissomyrmex Smith, M.R. 1947i: 281. Type-species: Perissomyrmex snyderi, by original designation.

Taxonomic Notes
Zhou & Huang (2006) - The ant genus Perissomyrmex was described by M. R. Smith in 1947 based on the type species Perissomyrmex snyderi. The genus originally contained a single species described from two minor workers collected at the Hoboken plant quarantine station of New Jersey, U.SA. The specimens were found in the tuberous root of a Begonia plant shipped from Guatemala, but there is no evidence that Guatemala, or Mesoamerica, is the center of origin for this species. Bolton (1981) suspected that the species were brought to the USA via Guatemala through human commerce from somewhere in the Oriental or the Indo-Australian region. De Andrade (in Baroni Urbani and de Andrade, 1993) described the second species of the genus, Perissomyrmex monticola, based on two minor workers and a dealated queen from Bhutan. In their paper, Baroni Urbani and de Andrade supported Bolton{s opinion and suggested that the genus Perissomyrmex has Old World origins and proposed that P. snyderi had been introduced into Guatemala. However, in the following year, P. snyderi was found in Mexico (Longino and Hartley, 1994) and the queen was first described. Longino and Hartley showed in their paper that P. snyderi is a polymorphic species and postulated that Perissomyrmex has a disjunct distribution. They also predicted that additional populations (or species) of this genus would be found in isolated and specialized habitats. Two more Old World species of Perissomyrmex have been described recently, Perissomyrmex nepalensis, from Nepal and India and Perissomyrmex fissus, from China. The description of these two species, as well as two new species, supports the disjunct distribution and the Old World origin hypotheses for Perissomyrmex.

Worker
Xu and Zhang (2012) - Weakly dimorphic terrestrial myrmicine ants with the following combination of characters.
 * 1) Head nearly square, slightly divergent forward.
 * 2) Mandibles elongate and roughly rectangular; inner margin long, with distinct triangular tooth; masticatory margin short, with apical tooth, subapical tooth, diastema, and basal tooth.
 * 3) Palp formula 4, 2.
 * 4) Anterior clypeal margin protruding, with developed teeth or lobes, and significantly notched or depressed between teeth or lobes; posterior extension between antennal sockets roughly triangular.
 * 5) Frontal lobes absent; frontal carinae poorly developed.
 * 6) Antennal sockets exposed.
 * 7) Antennae nine-segmented, scapes reach to or surpass occipital corners; antennal clubs three-segmented.
 * 8) Antennal scrobes absent.
 * 9) Eyes developed and convex, situated at about midpoints of lateral sides of head, or slightly behind midpoints.
 * 10) Promesonotal profile is a convexity distinctly higher than propodeum.
 * 11) Promesonotal suture present and weakly impressed.
 * 12) Metanotal groove deeply depressed.
 * 13) Propodeal spines developed, long and acute.
 * 14) Propodeal spiracles circular, situated in middle of lateral surfaces of propodeum.
 * 15) Propodeal lobes short and obtuse at apices.
 * 16) Petiole pedunculate anteriorly, the petiolar spiracles situated at about midlength of peduncle; petiolar node roughly triangular or trapezoidal, with distinct anterodorsal corner, posterodorsal corner usually indistinct and rounded. Subpetiolar process usually reduced, sometimes weakly toothed.
 * 17) Postpetiolar node roughly triangular and strongly inclined backward, anteroventral corner of postpetiole toothed.
 * 18) Head and mesosoma usually strongly striate.
 * 19) Pilosity abundant.