Pseudomyrmex particeps Ward, 1993
Worker diagnosis. Relatively small, HW 0.77-0.83, with elongate head (CI 0.75-0.84) and moderately elongate eyes (REL 0.44-0.48, EL/LHT 0.59-0.64); median clypeal lobe laterally rounded; petiole narrow (PWI 0.55-0.60); head densely punctulate and subopaque, becoming sublucid posteriorly; body medium to dark brown.
Similar species. P. nigrocinctus.
Distribution. Costa Rica.
Biology. P. particeps is a rare species of obligate acacia-ant, known only from the Osa Peninsula and one adjacent locality, in Costa Rica. It appears to be associated exclusively with Acacia allenii, a forest species.