Eurhopalothrix semicapillum

This species inhabits mature wet forest in mid-montane to lower cloud forest habitats. It is known from 500–1500 m elevation but is most common around 1100 m. All specimens are from Winkler samples of sifted litter and rotten wood from the forest floor. In the Cordillera de Tilarán and C. de Guanacaste it occurs in upper montane forest but not in the cool, wet ridge-crest cloud forest. On the Barva transect it was rare at 500 m (<1% of miniWinkler samples), common at 1100 m (40% of samples), and absent at 1500 m and 2000 m. (Longino 2013)

Identification
Mandible with single tooth row; face with 14–18 specialized spatulate setae (anterior row 8, middle row 4 (2), posterior row 6 (4); ground pilosity of face spatulate, decumbent, weakly differentiated from specialized projecting setae, in discrete patches on posterolateral face, leaving median strip bare, anterior border of ground pilosity gradual, extending a short distance beyond anterior row of specialized projecting setae; posteromedian vertex with shallow depression; pronotum with 1 pair spatulate setae, lacking on mesonotum; pair of spatulate setae on posterior border of petiolar node; first gastral tergite with at most 3 pairs spatulate setae in two longitudinal rows, posterior pair sometimes flanked by outer pair. Similar to Eurhopalothrix circumcapillum, Eurhopalothrix machaquila, Eurhopalothrix megalops, Eurhopalothrix ortizae, Eurhopalothrix oscillum, Eurhopalothrix schmidti. (Longino 2013)

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

Nomenclature

 *  semicapillum. Eurhopalothrix semicapillum Longino, 2013: 139, figs. 2B, 6B, 14D, 30, 36 (w.) COSTA RICA.

Worker
HW 0.61–0.71, HL 0.61–0.68, SL 0.34–0.40, SLL 0.03–0.05, CI 100–104, SLI 7–14 (n=7). Labrum anterolateral gibbosities of basal portion developed as sharply right-angled, ventrally-directed teeth, apical portion elongate, flexed dorsally, relatively narrow, with a minute notch at apex; apex with a fringe of short, non-capitate translucent setae; mandible triangular, dorsal surface convex, smooth and shining apically, grading to punctate basally, rounding into ventral surface; interior surface concave, smooth and shining; masticatory margin a single row of 11 flattened acute triangular teeth; scape with moderately developed basal lobe; scrobe deep, sharply delimited dorsally and ventrally, abutting deep antennal socket; surface of scrobe shallowly foveolate; eye small, about 5 ommatidia across greatest diameter; clypeus approximately planar, uniformly covered with small puncta; sides of head above eyes moderately angulate; surface of face with longitudinal median impression; entire surface of face punctate, puncta larger posteromedially but still nearly confluent (more widely spaced on E. circumcapillum); occipital carina indistinct; undersurface of head uniformly punctate; postgenal suture a well-developed longitudinal trough, darker than surrounding cuticle.

Promesonotal profile convex, somewhat flat-topped, meeting flat dorsal face of propodeum at obtuse angle; metanotal groove a narrow impressed groove; dorsal and posterior faces of propodeum distinct, meeting at obtuse angle, dorsal face shorter than posterior face; propodeal spine laminar, translucent, triangular, acute, ventral margin rounding into narrow infradental lamella that extends down posterior face to propodeal lobe; propodeal spiracle small, directed posteriorly in small concavity between base of propodeal spine and dorsum of metapleural gland bulla; all of mesosoma except posterior face of propodeum uniformly punctate with smooth interspaces; posterior face of propodeum smooth to very faintly sculptured; no transverse carinae between bases of propodeal spines; puncta on promesonotum larger than those on katepisternum and side of propodeum; interspaces sublucid on promesonotum, more matte on katepisternum and side of propodeum.

Petiolar peduncle joins anterior face of petiolar node at rounded obtuse angle; anterior face of node meets sloping flat dorsal face at rounded right angle; posterior face of node very short; ventral margin of petiole with short, acute, anteroventral tooth; postpetiole low and broad, with a broad longitudinal sulcus dorsally; first gastral sternite lacking anterior sagittal keel; petiole, postpetiole, and gaster densely punctate, puncta on anterior portions of first gastral tergite and sternite similar to those on posterior portion, separated by smooth interspaces that are less than or equal to width of puncta.

Dorsal surface of scape covered with uniform short, decumbent, spatulate setae; leading edge of scape with projecting clavate setae, short near apex of scape, gradually lengthening to longest setae on basal lobe; ground pilosity on clypeus obsolete; conspicuous ground pilosity of face composed of large setae, similar in shape and slightly larger than those on scape, decumbent, distributed in two patches, gradually fading in front of anterior row of projecting specialized setae (about 2 rows of decumbent ground setae in front of projecting setae), patch delimited medially to leave bare median furrow, patch extending laterally to posterolateral margins of head; projecting specialized setae spatulate, about twice as long as wide, curved, about twice as large as ground pilosity (and thus not highly differentiated from it), full complement typically 18, with curved anterior row of 8 (occasionally 6), transverse median row of 4 (occasionally 2), and posterior row of 6 on vertex margin, outermost pair smaller than inner 2 pairs and occasionally missing; ground pilosity obsolete on dorsal mesosoma and metasoma; 1 pair of projecting spatulate setae on pronotum, similar to those on face; legs with ground pilosity similar to that on face, dense on apices of femora, dorsal and anterior faces of mid and hind tibia, weaker on dorsal and posterior face of fore and midtibia, sparser to absent elsewhere; apex of foretibia with 1 larger spatulate seta, apices of mid and hind tibia with 2; basitarsus with 3–5 pairs suberect clavate setae, remaining tarsomeres each with pair of suberect clavate setae, tarsal setae smaller on foretarsus than on mid and hind tarsus; hind margin of dorsal face of petiolar node with 1 pair prominent spatulate setae; row of 4 spatulate setae on hind margin of postpetiole, median pair smaller than lateral pair; first gastral tergite with erect clavate setae, full complement 3 pairs in two longitudinal rows, population in Cordillera de Tilarán with additional pair flanking posterior pair (4 setae along posterior border of tergite), Cordillera Volcánica Central population lacking flanking pair.

Color dark brown.

Queen
HW 0.67, HL 0.66–0.68, SL 0.37–0.39, SLL 0.04, CI 101, SLI 10–11 (n=2). Similar to worker in most respects; ocelli present; compound eye much larger than worker eye; anepisternum separated from katepisternum by U-shaped groove; metapleuron separated from propodeum by broad U-shaped groove; puncta fading on anterodorsal katepisternum, leaving small smooth patch; pronotum with 1 pair spatulate setae; mesoscutum with 6 straight, erect, narrowly clavate setae; axilla with clavate seta; scutellum with 1 pair spatulate setae; petiolar node with pair of spatulate setae; posterior margin of postpetiole with lateral pair spatulate setae and smaller median pair; first gastral tergite with number and arrangement of erect setae similar to worker, but setae straight, longer, more narrowly clavate.

Type Material
Holotype worker: Costa Rica, Heredia: 16km SSE La Virgen, 10.26667 -84.08333, ± 2 km, 1100 m, 21 Apr 2001, montane wet forest, Berlese sample (ALAS 11/B/all), CASENT0639343. Paratype workers, queens: same data as holotype, CASENT0639342; same data but 14 Mar 2001, ex sifted leaf litter (ALAS 11/WF/02) , CASENT0639374 (dealate queen), CASENT0639377; , CASENT0639381; , CASENT0639376 (dealate queen), CASENT0639379; , CASENT0639380; , CASENT0639375 (dealate queen), CASENT0639378.

Etymology
The name is in reference to the partially delimited patches of ground pilosity on the face. It is a noun in apposition and thus invariant.

References based on Global Ant Biodiversity Informatics

 * Longino J. T. 2013. A review of the Central American and Caribbean species of the ant genus Eurhopalothrix Brown and Kempf, 1961 (Hymenoptera, Formicidae), with a key to New World species. Zootaxa 3693(2): 101-151.
 * 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. et al. ADMAC project. Accessed on March 24th 2017 at https://sites.google.com/site/admacsite/