Pseudomyrmex particeps

Appears to be associated exclusively with Acacia allenii, a forest species.

Identification
Ward (1993) - P. particeps is obviously a very close relative of the allopatric Pseudomyrmex nigrocinctus, but there are consistent differences between the two in eye size and color which exceed the limits of variation seen throughout the much wider range of P. nigrocinctus. Workers in the type series of P. particeps also have more elongate heads than those of P. nigrocinctus but this distinction is not seen in other samples. Differences between queens of the two species are more striking with the two known queens of P. particeps having more elongate heads (CI 0.61, compared with 0.67-0.72 in a sample of 13 P. nigrocinctus queens) and longer metatibiae relative to head width (LHT/HW 1.12 versus 0.97-1.07 in P. nigrocinctus). Additional alates of P. particeps are needed to confirm these differences and the apparent distinctions in male genitalia (see male key).

Distribution
A rare species known only from the Osa Peninsula and one adjacent locality, in Costa Rica.

Distribution based on Regional Taxon Lists
Neotropical Region: Costa Rica.

Nomenclature

 *  particeps. Pseudomyrmex particeps Ward, 1993: 146, figs. 14, 23, 54, 57, 72 (w.q.m.) COSTA RICA.

Worker
measurements (n=12). —HL 0.93-1.10, HW 0.77-0.83, MFC 0.037-0.050, CI 0.75-0.84, REL 0.44-0.48, REL2 0.55-0.60, OOI 1.47-1.96, VI 0.65-0.75, FCI 0.048-0.062, SI 0.45-0.49, SI2 0.78-0.83, NI 0.53-0.62, PLI 0.58-0.66, PWI 0.55-0.60, PPWI 1.03-1.26.

Very similar to Pseudomyrmex nigrocinctus (q.v.) except as follows. Eyes longer(REL2 0.55-0.60, EL/LHT 0.59-0.64). Front of head more strongly shining. Medium to dark brown; gaster uniformly dark brown or black; mandibles, fronto-clypeal complex, and appendages lighter brown.

Type Material
Holotype worker. —COST A RICA, Puntarenas: Rincon, Peninsula Osa, 3.iii.1965, D.H. Janzen #III. HW 0.83, HL 1.10, EL 0.50, PL 0.50, PH 0.31.

Paratypes. —Same data as holotype: series of 82 workers, 14 males, one queen (,, , , , , LACM, , , , , ).

References based on Global Ant Biodiversity Informatics

 * Fernández, F. and S. Sendoya. 2004. Lista de las hormigas neotropicales. Biota Colombiana Volume 5, Number 1.
 * Longino J. et al. ADMAC project. Accessed on March 24th 2017 at https://sites.google.com/site/admacsite/
 * Ward, P.S. 1993. Systematic studies on Pseudomyrmex acacia-ants (Hymenoptera: Formicidae) Journal of Hymenoptera Research 2(1):117-168