Pogonomyrmex araucania

Pogonomyrmex atacama workers are solitary foragers. Nests are placed in open, exposed sites with a tumulus that ranges from 15–20 cm in diameter. Sexuals have been collected on 23 March, indicating that mating flights occur during the austral summer. Partial nest excavations indicated that colonies probably contain up to 1000 workers.

Identification
Workers of this species are uniquely characterized by the following combination of features:
 * 1) well developed psammophore
 * 2) first gastral tergum lacking striae, weakly to strongly coriarious along base or extending over anterior one-half of segment or with faint, barely visible, unincised striae on anterior one-third to one-half of segment
 * 3) posterior margin and usually posterior one-third or more of first gastral tergum smooth and shining to strongly shining, rarely weakly coriarious
 * 4) transverse rugae on posterior surface of petiolar node and dorsum of postpetiole
 * 5) head and mesosoma concolorous to nearly concolorous light to dark ferruginous orange to reddish-brown
 * 6) clypeus orangish to orangish-red, concolorous with adjacent cephalic dorsum
 * 7) legs and antennal scapes usually orangish-brown, occasionally brownish to blackish
 * 8) superior propodeal spines long, length > 0.6× the distance between their bases
 * 9) in profile, most hairs on dorsum of mesosoma < 0.5× MOD and no longer than length of superior propodeal spines

Pogonomyrmex araucania is distinguished from all congeners except for Pogonomyrmex spinolae by:
 * 1) first gastral tergum lacking striae, weakly to strongly coriarious along base to over anterior one-half or more of segment or with faint, barely visible, unincised striae on anterior one-third to one-half of segment
 * 2) superior propodeal spines long, length > 0.6× the distance between their bases
 * 3) transverse rugae on posterior surface of petiolar node and dorsum of postpetiole
 * 4) head and mesosoma concolorous to nearly concolorous light to dark ferruginous orange to reddish-brown.

Length of hairs on the dorsum of the mesosoma appears to be the only character that reliably separates P. araucania and P. spinolae. In P. araucania these hairs are shorter with most hairs < 0.6–0.7× MOD; these hairs are longer in P. spinolae, with most approaching to exceeding MOD.

Pogonomyrmex atacama likely co-occurs with Pogonomyrmex loaensis and possibly other P. rastratus-group species. Pogonomyrmex atacama and P. loaensis are similar, but they can be distinguished based on the following characters. In P. atacama: (1) striae extend over the anterior one-third to one-half of the medial portion of the first gastral tergum, and (2) posterior corners of head usually smooth and shining to strongly shining. In P. loaensis: (1) striae extend over the anterior two-thirds or more of the medial portion of the first gastral tergum, and (2) the posterior corners of the head rugose. Pogonomyrmex atacama is distinguished from most other P. rastratus group species based on striae extending over the anterior one-third to one-half of the first gastral tergum.

Pogonomyrmex bolivianus is the only species with this character that is likely to be confused with P. atacama. In P. atacama: (1) the posterior corners of head smooth and shining to strongly shining for most to all workers in a series, (2) mandibles with seven teeth, (3) longitudinal rugae on dorsum of mesonotum regular; anterior margin of pronotum usually with one to few transverse rugae, (4) superior propodeal spines consist of short, triangular teeth to long spines, (5) rugae on dorsum of postpetiole mostly longitudinal, and (6) one to few rugae on medial portion of clypeus converging anterad forming a narrowly rounded V-shaped pattern. In P. bolivianus: (1) the posterior corners of head rugose, (2) longitudinal rugae on dorsum of promesonotum irregular, continuing to anterior margin of pronotum, (3) mandibles with six teeth, (4) superior propodeal spines consist of short, triangular teeth, (5) rugae on dorsum of postpetiole mostly transverse, and (6) rugae on frontal triangle subparallel-parallel, continuing onto clypeus.

Queen diagnosis. Queens of this species are diagnosed by the following combination of features:
 * 1) caste specific morphology of the mesosoma related to wing-bearing and presence of ocelli on head
 * 2) striae extend over anterior two-thirds or more of medial portion of first gastral tergum, posterolateral margins smooth and shining,
 * 3) transverse rugae cover posterior surface of petiolar node and dorsum of postpetiole
 * 4) longitudinal rugae on cephalic dorsum posterior to eyes strongly irregular, often with short lateral branches, interrugae strongly granulate, dull, with a beaded appearance
 * 5) in posterodorsal view, rugae along posterior margin of head and in profile, rugae posterior to eyes strongly irregular, with numerous short lateral branches
 * 6) in profile, rugae on pronotal sides rugoreticulate
 * 7) head, pronotum, mesoscutum, mesoscutellum, concolorous reddish-orange to reddish-brown
 * 8) part to most of anepisternum and/or katepisternum blackish to black
 * 9) in profile, hairs on dorsum of mesoscutum and mesoscutellum rarely > 0.5–0.6× MOD

Male diagnosis. Males of this species are diagnosed by the following combination of features
 * 1) first gastral tergum lacking striae
 * 2) bicolored: head and mesosoma black, gaster ferruginous orange
 * 3) erect hairs lacking on first gastral tergum
 * 4) anterior portion to all of anepisternum and katepisternum smooth and shining
 * 5) posterior surface of petiolar node mostly smooth and shining
 * 6) dorsum of postpetiole with faint regular, transverse or longitudinal rugae, interrugae mostly smooth and shining
 * 7) interrugae on mesoscutum and mesoscutellum weakly granulate, weakly shining to smooth and shining.
 * Note that no characters were found to separate males of P. araucania and Pogonomyrmex maulensis.

Distribution
Pogonomyrmex atacama inhabits sites at elevations from 3805–4095 m. This species occurs in the Central Andean dry puna ecoregion, as defined by Olson et al. (2001).

Distribution based on Regional Taxon Lists
Neotropical Region: Argentina, Chile.

Nomenclature

 * . Pogonomyrmex araucania Johnson, 2021: 39, figs. 14B, 15-17 (w.aq.m.) ARGENTINA (Neuquén).

Type Material

 * Holotype worker [MACN: CASENT0914128]: ARGENTINA, Neuquén: Departamento Aluminé, 4.8 km E Villa Pehuenia, 38o53.3’S 71o08.3’W, 3830’ (1160 m), 9 February 2011 (R.A. Johnson #4700).
 * Paratypes, same data as holotype: IFML (3 workers), LACM (3 workers), MACN (3 workers), MCZC (3 workers), MNNC (3 workers), RAJC (20 workers, 1 alate queen), UCDC (3 workers), USNM (3 workers).