Pheidole erratilis

This species occurs in wet forest habitats, from sea level to 1400m elevation. Nests are in rotten wood or dead sticks on or near the forest floor. Workers are occasionally collected in Winkler or Berlese samples, but have not been collected at baits. In the Osa region, a colony was found in necrotic cavities beneath the bracts of a live Costus inflorescence. (Longino 1997, Longino 2009).

Identification
See the description in the nomenclature section.

Distribution
Widespread in wet forest to 800 m in Peñas Blancas and 2000 m in Braulio Carrillo (Longino 1997).

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

Worker
Minor

Nomenclature

 *  erratilis. Pheidole erratilis Wilson, 2003: 414, figs. (s.w.) COSTA RICA. Senior synonym of petersoni: Longino, 2009: 31.
 * petersoni. Pheidole petersoni Wilson, 2003: 486, figs. (s.w.) COSTA RICA. Junior synonym of erratilis: Longino, 2009: 31.

Description
A relatively large, brown member of the flavens group distinguished by a combination of exceptionally long pilosity and prominent, “sharkfin” shape of the humerus in major and minor, and narrow occiput surmounted by a collar in the minor.

Similar to Pheidole petersoni of Costa Rica but with longer pilosity and absence of rugoreticulum on the mesosoma in both castes, and more extensive cephalic carinulae in the major (but less extensive in the minor).

See also these less similar species: Pheidole angulifera, Pheidole ecuadorana, Pheidole pariana, Pheidole polita (in the tristis group), Pheidole tennantae, Pheidole schmalzi and Pheidole styrax.

MEASUREMENTS (mm) Holotype major: HW 1.06, HL 1.12, SL 0.62, EL 0.12, PW 0.48. Paratype minor: HW 0.56, HL 0.62, SL 0.60, EL 0.14, PW 0.34.

COLOR Major: gaster medium brown, tarsi dark yellow, rest of body and appendages light reddish brown.

Minor: body dark, almost blackish brown, appendages light reddish brown.



'''Figure. Upper: holotype, major. Lower: paratype, minor. Scale bars = 1 mm.'''

Type Material
Longino (2009):

Holotype major worker and associated paratype minor worker: Costa Rica, Prov. Alajuela, 3km S Volcan Arenal, 10°26'N 84°42'W, 700m, 17 Feb 1994 (J. Longino) [] (examined).

Pheidole petersoni Holotype major worker and associated paratype minor worker: Costa Rica, Prov. Alajuela, Peñas Blancas, 10.300° N 84.751°W, 940m, 24 Jul 1984 (J. Longino) [] (examined).

Etymology
L erratilis, wanderer, alluding to the wide range of habitats occupied in Costa Rica.

References based on Global Ant Biodiversity Informatics

 * Fernández, F. and S. Sendoya. 2004. Lista de las hormigas neotropicales. Biota Colombiana Volume 5, Number 1.
 * 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/