Strumigenys trieces

Based on the hundreds of litter samples that have recorded this species, Strumigenys trieces occurs in mature wet forest habitats. It nests in dead wood on the forest floor. Workers forage in the leaf litter. (Longino, Ants of Costa Rica)

Identification
A member of the gundlachi-complex in the Strumigenys gundlachi group.

Longino (Ants of Costa Rica) - Mandibles in full-face view linear, elongate and narrow; ventral surface of petiole without spongiform tissue; leading edge of scape with freely projecting hairs; inner margin of mandible without a tooth or distinctly enlarged denticle at or near the midlength; labral lobes short, trigger hairs at apices of lobes long; outer margins of mandibles relatively straight; mandibles short and thick, with inner margin convex; mandible with exactly 3 small preapical teeth; ground pilosity of head nearly or quite obsolete. Similar to: Strumigenys gundlachi, Strumigenys eggersi and Strumigenys subedentata.

Longino (2006) - Intensive collecting at La Selva Biological Station and the Barva Transect has revealed a complex of five closely similar but consistently separable species related to Strumigenys subedentata. Strumigenys subedentata occurs throughout the Neotropics, usually in lowland wet to somewhat seasonal sites, in both mature and second growth forests. It is often collected in samples of litter and rotten wood from the forest floor. Strumigenys trieces occurs on the Atlantic slope of Central America from Nicaragua to Panama, from sea level to 1100 m elevation. It occurs most abundantly in mature wet forest where, like S. subedentata, it inhabits leaf litter and rotten wood on the forest floor. Three species – Strumigenys oconitrilloae, Strumigenys cascanteae, and Strumigenys paniaguae – occur as a graded series of elevational specialists, with S. oconitrilloae occurring at La Selva and the 300 m site on the Barva Transect, S. cascanteae occurring at the 300 m site and at a 600 m site in the nearby Arenal National Park, and S. paniaguae occurring at the 500 m, 1100 m, and 1500 m sites on the Barva Transect. These three all show a tendency to be arboreal, nesting under bark flaps or epiphytes and rarely occurring in samples of litter and rotten wood from the forest floor. A sixth species in this complex, Strumigenys connectens (Kempf, 1958), occurs in Colombia and Ecuador.

Bolton (2000) - Closest related to Strumigenys connectens, Strumigenys decipula and Strumigenys subedentata; see under the last named for discussion.

Distribution based on Regional Taxon Lists
Neotropical Region: Costa Rica, Honduras, Nicaragua, Panama.

Nomenclature

 *  trieces. Strumigenys trieces Brown, 1960b: 50, fig. 8 (w.) COSTA RICA. Combination in Pyramica: Bolton, 1999: 1673; in Strumigenys: Baroni Urbani & De Andrade, 2007: 129. See also: Bolton, 2000: 194.

Worker
Bolton (2000) - TL 2.3-2.4, HL 0.57-0.62, HW 0.45-0.49, CI 77-82, ML 0.27-0.30, MI 46-52, SL 0.22-0.26, SI 46-53, PW 0.33-0.35, AL 0.62-0.68 (10 measured). Characters of gundlachi complex. Inner margins of mandibles strongly convex in full-face view, at full closure touching at about the midlength and diverging both proximally and distally. Apex of mandible with 3 minute intercalary denticles between apicodorsal and apicoventral teeth. Preapical denticles 3 in number, spaced out and located in the apical third of the mandible length, the proximal (basalmost) denticle usually the largest (rarely otherwise); denticles usually about equidistant but sometimes the proximal more widely separated from the other two. Scape broadening medially but not expanded into a wide lobe, SL ca 3.5 X the maximum scape width. Eye usually with 4 ommatidia in the longest row. Pronotum markedly depressed, the dorsum only weakly convex, bluntly marginate dorsolaterally. Ground-pilosity of head and alitrunk of sparse minute appressed pubescence. Apicoscrobal hair short. Cephalic dorsum with a pair of short erect hairs at highest point of vertex and another pair close to occipital margin. Pronotal humeral hair present. Mesonotal dorsum with a single pair of erect hairs. Head, alitrunk and waist segments reticulate-punctate except for katepistemum which is mostly smooth. First gastral stemite smooth, not reticulate basally.

Type Material
Holotype worker, COSTA RICA: no locality data, 18.vii.1931 (F. Nevennann) [examined].

References based on Global Ant Biodiversity Informatics

 * Bolton, B. 2000. The Ant Tribe Dacetini. Memoirs of the American Entomological Institute 65
 * Brown W. L. Jr. 1960. The neotropical species of the ant genus Strumigenys Fr. Smith: group of gundlachi (Roger). Psyche (Cambridge) 66: 37-52.
 * Brown W. L. Jr. 1962. The neotropical species of the ant genus Strumigenys Fr. Smith: synopsis and keys to the species. Psyche (Cambridge) 69: 238-267.
 * Fernández, F. and S. Sendoya. 2004. Lista de las hormigas neotropicales. Biota Colombiana Volume 5, Number 1.
 * Kempf, W.W. 1972. Catalago abreviado das formigas da regiao Neotropical (Hym. Formicidae) Studia Entomologica 15(1-4).
 * Longino J. T. L., and M. G. Branstetter. 2018. The truncated bell: an enigmatic but pervasive elevational diversity pattern in Middle American ants. Ecography 41: 1-12.
 * Longino J. T., and R. K. Colwell. 2011. Density compensation, species composition, and richness of ants on a neotropical elevational gradient. Ecosphere 2(3): 16pp.
 * Longino J. et al. ADMAC project. Accessed on March 24th 2017 at https://sites.google.com/site/admacsite/
 * Sosa-Calvo J., S. O. Shattuck, and T. R. Schultz. 2006. Dacetine ants of Panama: new records and description of a new species. Proceedings of the Entomological Society of Washington 108: 814-821.