Pseudomyrmex subtilissimus

Identification
A moderately elongate head (broader than Pseudomyrmex tenuissimus, more elongate than Pseudomyrmex spiculus and Pseudomyrmex villosus), short petiole, and light brown color (with banded gaster) characterize P. subtilissimus (Ward 1989).

Distinguishable from all other acacia-associated Pseudomyrmex by its small size (HW < 0.60), elongate head (CI < 0.66), apedunculate petiole, and scarcity of standing pilosity (Ward 1993).

Distribution
Costa Rica and Nicaragua.

Distribution based on Regional Taxon Lists
Neotropical Region: Colombia, Costa Rica, Mexico, Nicaragua.

Biology
Ward (1989) - This species has been collected only in, or on, swollen-thorn acacias, in association with Pseudomyrmex flavicornis (F. Smith). The collection records suggest that it is an obligate, non-aggressive acacia ant which somehow manages to coexist with P. flavicornis.

Nomenclature

 *  subtilissimus. Pseudomyrma subtilissima Emery, 1890b: 65, pl. 6, fig. 7 (w.q.) COSTA RICA. [Also described as new by Emery, 1894k: 53.] Combination in Pseudomyrmex: Kempf, 1972a: 224. See also: Ward, 1989: 432; Ward, 1993: 161.

Worker
measurements (n=17, except for FI where n=16). - HL 0.86-0.95, HW 0.55-0.59, MFC 0.020-0.032, CI 0.60-0.65, OI 0.52-0.59, REL 0.49-0.54, REL2 0.80-0.87, OOI 0.38-0.89, VI 0.79-0.88, FCI 0.035-0.055, SI 0.41-0.47, SI2 0.50-0.57, FI 0.44-0.53, POI 1.60-1.88, MPI 0.015-0.039, NI 0.52-0.66, PLI 0.65-0.75, PWI 0.56-0.68, PPWI 1.18-1.35.

diagnosis. - Similar to Pseudomyrmex spiculus (q.v.) except as follows: smaller, head more elongate (HW 0.55-0.59, CI 0.60-0.65), eyes shorter, not reaching the level of the median ocellus (REL 0.49-0.54); basal face of propodeum flatter, meeting the decIivitous face at a more distinct angle; petiole shorter, higher (PLI 0.65-0.75). Most of body uniformly light brown; gaster dark brown, with contrasting light brown band on anterior half of abdominal tergite IV.

Type Material
Syntype workers, one dealate queen, Alajuela, Costa Rica (Alfaro) [Examined]. One syntype worker here designated as LECTOTYPE.

References based on Global Ant Biodiversity Informatics

 * Branstetter M. G. and L. Sáenz. 2012. Las hormigas (Hymenoptera: Formicidae) de Guatemala. Pp. 221-268 in: Cano E. B. and J. C. Schuster. (eds.) 2012. Biodiversidad de Guatemala. Volumen 2. Guatemala: Universidad del Valle de Guatemala, iv + 328 pp
 * Castano-Meneses, G., M. Vasquez-Bolanos, J. L. Navarrete-Heredia, G. A. Quiroz-Rocha, and I. Alcala-Martinez. 2015. Avances de Formicidae de Mexico. Universidad Nacional Autonoma de Mexico.
 * Emery C. 1890. Studii sulle formiche della fauna neotropica. Bull. Soc. Entomol. Ital. 22: 38-8
 * Enzmann E. V. 1944. Systematic notes on the genus Pseudomyrma. Psyche (Camb.) 51: 59-103.
 * Fernández, F. and S. Sendoya. 2004. Lista de las hormigas neotropicales. Biota Colombiana Volume 5, Number 1.
 * Harada A. Y., and S. M. Ketelhut. 2009. Formigas da reserva florestal Adolpho Ducke: um grupo ainda pouco estudado? In: Fonseca C. R. V., C. Magalhaes, J. A. Rafael, and E. Franklin. Fauna de artropodes da reserva Florestal Ducke: estado actual do conhecimento taxonomico e biologico p 231-247.
 * Kempf W. W. 1978. A preliminary zoogeographical analysis of a regional ant fauna in Latin America. 114. Studia Entomologica 20: 43-62.
 * Kempf, W.W. 1972. Catalago abreviado das formigas da regiao Neotropical (Hym. Formicidae) Studia Entomologica 15(1-4).
 * Maes, J.-M. and W.P. MacKay. 1993. Catalogo de las hormigas (Hymenoptera: Formicidae) de Nicaragua. Revista Nicaraguense de Entomologia 23.
 * Vasquez-Bolanos M. 2011. Checklist of the ants (Hymenoptera: Formicidae) from Mexico. Dugesiana 18(1): 95-133.
 * Vásquez-Bolaños M. 2011. Lista de especies de hormigas (Hymenoptera: Formicidae) para México. Dugesiana 18: 95-133
 * 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
 * Wheeler W. M. 1942. Studies of Neotropical ant-plants and their ants. Bulletin of the Museum of Comparative Zoology 90: 1-262.
 * Wheeler W.M. 1935. Check list of the ants of Oceania. Occasional Papers of the Bernice Pauahi Bishop Museum 11(11):1-56.
 * Wheeler, William Morton. 1934. Ants From The Islands Off The West Coast Of Lower California and Mexico. The Pan-Pacific Entomologist. 10(3):131-144.