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Holotype major worker. Costa Rica, Heredia: 6km ENE Vara Blanca, 10.18333°N 84.11667°W, ±2000m, 2000m, 6 Nov 2002 (J. Longino#4838) [INBC, unique specimen identifier CASENT0610059].
Paratypes: major and minor workers. Same data as holotype [BMNH, CAS, EAPZ, ECOSCE, FMNH, INBC, LACM, MCZ, MHNG, MIZA, MZSP, MEL, UCD, ICN, USNM].
With the morphometric profile of P. rutilana Wilson, from Brazil, and P. ulothrix Wilson, which occurs at lower elevation on the same mountain slope as the type locality. Minor worker: face with extensive carinulate etching on anterior face, extending posterior to compound eyes, versus face almost completely smooth and shining, with a few longitudinal carinulae between frontal carina and compound eye, but none extending posterior to eye (rutilana); clypeus with a somewhat produced posterior portion between frontal carinae, dropping abruptly to anterior portion, versus clypeus shallowly and evenly convex (rutilana, ulothrix); dorsal surface of hind tibia with subdecumbent setae subequal in length to maximum width of tibia versus with suberect setae longer than maximum width of tibia (ulothrix); color dark red brown versus orange (ulothrix). Major worker: undersurface of head extensively sculptured with carinulate etching and faint foveolae versus undersurface of head largely smooth and shining, with a few longitudinal carinulae laterally (rutilana, ulothrix); inner hypostomal teeth stout and located closer to midline than to outer hypostomal teeth versus inner hypostomal teeth small and located about midway between outer hypostomal teeth and midline (rutilana); clypeus smooth and shining versus with median longitudinal carina (rutilana); postpetiole in dorsal view trapezoidal versus globular (rutilana, ulothrix); tibial pilosity as in minor worker; color dark red brown versus orange (ulothrix).
Description of minor worker
Measurements (paratype): HL 0.58, HW 0.58, HLA 0.16, SL 0.57, EL 0.15, ML 0.74, PSL 0.05, PMG 0.00, SPL 0.03, PTW 0.11, PPW 0.16, CI 100, SI 98, PSLI 9, PMGI 0, SPLI 4, PPI 146.
Measurements (n=6): HL 0.58-0.65, HW 0.57-0.60, SL 0.57-0.60, CI 92-100, SI 98-100.
Mandible smooth and shining; clypeus smooth and shining, somewhat produced posteriorly between frontal carinae, dropping abruptly to anterior portion; face with fine longitudinal carinulae between frontal carina and compound eye, extending just posterior to eye, concentric around antennal insertion, and fan-like medial to frontal carina, median face between frontal carinae and posterior portion of face smooth and shining; margin of vertex rounded with small median impression; occipital carina narrow, not visible in full face view; scape with abundant suberect setae, the longest subequal in length to maximum width of scape; promesonotal groove absent; propodeal spines present; pronotum smooth and shining; anepisternum foveolate; katepisternum foveolate dorsally and posteriorly, with large medial shiny patch; dorsal face dorsal portion of lateral face of propodeum foveolate, metapleural bulla smooth and shining with three longitudinal rugae; abundant setae on promesonotal dorsum; dorsal (outer) margin of hind tibia with subdecumbent setae subequal in length to maximum width of tibia; first gastral tergum smooth and shining; gastral dorsum with abundant erect setae; color dark red brown.
Description of major worker
Measurements (holotype): HL 1.20, HW 1.16, HLA 0.24, SL 0.62, EL 0.16, ML 0.94, PSL 0.07, PMG 0.00, SPL 0.05, PTW 0.19, PPW 0.27, IHT 0.25, OHT 0.44, CI 97, SI 54, PSLI 6, PMGI 0, SPLI 4, PPI 144, HTI 56.
Measurements (n=3): HL 1.15-1.20, HW 1.12-1.18, SL 0.62-0.66, CI 97-102, SI 54-57.
Mandibles smooth and shiny; clypeus smooth and flat with straight anterior border; side of head between frontal carina and compound eye with widely-spaces longitudinal rugae, grading to reticulate rugae underlain with foveolate sculpture on scrobal area, grading to smooth and shining posteriorly, medial area with radiating fan of longitudinal rugae between frontal carinaegrading to smooth and shining with irregular small patches of foveolate sculpture; head with abundant short subdecumbent setae projecting from sides of head in face view; scape smooth and shining, terete at base, with abundant suberect setae, the longest of which longer than maximum width of scape; hypostomal margin straight; median tooth prominent, triangular; inner hypostomal teeth pointed, stout, closer to midline than to outer hypostomal teeth; undersurface of head extensively sculptured with carinulate etching and faint foveolae; promesonotal groove absent; propodeal spines present; promesonotum and katepisternum smooth and shining; ventral portion of side of propodeum smooth and shining with three coarse longitudinal rugae; dorsal portion of propodeum foveolate; dorsal (outer) margin of hind tibia with subdecumbent setae subequal in length to maximum width of tibia; pilosity abundant on mesosomal dorsum; postpetiole in dorsal view trapezoidal; first gastral tergite smooth and shining, with abundant flexuous erect setae; color dark red brown.
This species occurs in mature cloud forest. It appears to be a narrow elevational specialist, occurring only above 1900m on Volcan Barva. Minor workers have been collected in Winkler samples, Berlese samples, and sweepnet samples from Project ALAS. A complete nest series was obtained from a nest in epiphytic soil on a rotten log in an old treefall gap. The nest was in the side of the log where there was a vertical wall of humus. On excavation, small chambers were found at about 1cm depth, and the nest center was about 10cm deep. There were several hundred workers, numerous soldiers (in the deepest part of the nest), about a dozen adult males, brood, and one dealate queen. The outer chambers contained small plant seeds, thinly spread on the walls and floors.
FIGURE 18. Pheidole picobarvaHNS. Major worker: A, face view; B, lateral view; C, dorsal view; D, hypostomal margin. Minor worker: E, face view; F, lateral view; G, dorsal view; H, hind tibia. A-D, Holotype major worker; E-H, Paratype minor worker. Scale bar 0.5mm for E, 1mm for others.
The name is in reference to the restricted geographic range of this species on the peak of Volcan Barva in Costa Rica.
Found most commonly in these habitats: 32 times found in montane wet forest, 2 times found in cloud forest, 1 times found in mature wet forest.
Found most commonly in these microhabitats: 2 times nest in dead wood, 26 times Hojarasca, 2 times carril (lindero) hacia trampa M/15, 1 times tomada en la naciente cerca del refugio, 1 times Sobre Vegetacion, 1 times alrededor del Refugio,suelo suspendido en tronco inclinado, 1 times Ex sifted leaf litter, 1 times alrededor del Refugio.
Collected most commonly using these methods: 26 times Mini Winkler, 1 times search, 7 times Berlese, 1 times Sweeping.
Elevations: collected from 1950 - 2000 meters, 1999 meters average
Type specimens: Holotype Pheidole picobarva: casent0610059; Paratype: fmnhins0000050040, fmnhins0000050041; Paratype Pheidole picobarva: casent0610042, casent0610043, casent0610044, casent0610045, casent0610046, casent0610047, casent0610048, casent0610049, casent0610050, casent0610051, casent0610052, casent0610053, casent0610054, casent0610055, casent0610056, casent0610057, casent0610058, casent0610060