(Figures 7A, 33)

Distribution—32B

Holotype worker [MUSM: CASENT0923342]: PERU, Caylloma Province: Yanque, 15 o 38.9’S 71 o 39.6’W, 3425 m, 2 April 2015 (M. Prebus #4524). Paratypes, same data as holotype: MCZC (1 worker), MMPC (1 worker), MUSM (1 worker), RAJC (4 workers), USNM (1 worker).

Worker diagnosis. Workers of this species are uniquely characterized by the following combination of features: (1) first gastral tergum smooth and strongly shining, (2) superior propodeal spines consist of acuminate denticles to short teeth, length usually similar to or less than height of inferior propodeal spines, (3) in profile, lateral portion of head from posterior margin of eyes to posterior corners faintly rugose to mostly smooth and shining, rugae weakening posterad, posterior corners smooth and shining to strongly shining, (4) longitudinal rugae on promesonotum strongly irregular with numerous lateral branches to rugoreticulate, (5) promesonotal suture not impressed, and (6) rugae present on posterior surface of postpetiole (Figures 7A, 33).

Measurements — holotype (n = 7 paratypes). HL 1.53 (1.34–1.52); HW 1.58 (1.42–1.56); MOD 0.32 (0.32– 0.35); OMD 0.41 (0.32–0.40); SL 1.11 (1.00–1.10); PNW 1.03 (0.99–1.07); HFL 1.41 (1.39–1.53); ML 1.67 (1.62– 1.71); PW 0.43 (0.35–0.40); PPW 0.59 (0.50–0.56). Indices: SI 70.25 (65.36–76.92); CI 103.27 (100.00–109.15); OI 20.25 (21.57–23.45); HFI 89.24 (92.90–02.11).

Description. Head quadrate to wider than long (CI = 100.00–109.15); posterior margin flat in full-face view. Longitudinal rugae on cephalic dorsum prominent, regular to wavy; in full-face view, medial rugae continuing to posterior margin. Interrugae on cephalic dorsum weakly granulate, weakly shining to shining; in profile, lateral portion of head from posterior margin of eyes to posterior corners faintly rugose to mostly smooth and shining, rugae weakening posterad, posterior corners smooth and shining to strongly shining. Anterior margin of clypeus moderately concave, dorsum with numerous subparallel, longitudinal rugae; interrugae smooth and shining. Numerous long, curved, bristle-like, yellowish macrochaetae project from anterior margin of clypeus and basolateral margin of mandibles. Mandibles with six teeth; mandibular dorsum coarsely rugose, rugae sometimes absent distad. MOD ranging from 0.20–0.25× HL. In profile, eyes situated slightly anterior to middle of head, OMD = 0.91–1.29× MOD. In full-face view, eyes protruding slightly beyond lateral margins of head. Antennal scapes (SI = 65.36–76.92) just failing to reach to reaching posterior corners, scapes smooth and shining to weakly striate, interstriae weakly shining to smooth and shining. Basal flange well developed with carinate margin. Psammophore well developed.

Mesosomal profile weakly to moderately convex; all mesosomal surfaces with prominent, irregular, subparallel-parallel rugae to rugoreticulate. Longitudinal rugae on promesonotum strongly irregular with numerous lateral branches to rugoreticulate. Rugae on pronotal sides angling posteroventrally or posterad, usually with short lateral branches to sometimes rugoreticulate. In dorsal view, humeral shoulders of pronotum enlarged, dorsolateral margin rounded. Promesonotal suture not impressed. Weakly irregular to irregular rugae on mesopleura angle posterodorsally or posterad, rugae sometimes with short lateral branches; irregular transverse, oblique, or longitudinal rugae on dorsum of propodeum. Superior propodeal spines consist of acuminate denticles to short teeth, length usually less than width at base, well defined keel connecting spines usually lacking. Inferior propodeal spines slightly wider than high, broadly triangular, apex bluntly rounded to subangulate, height similar to or greater than length of superior propodeal spines. Propodeal spiracles narrowly ovate facing posterad. Interrugae on mesosoma moderately granulate-punctate, weakly shining; pronotal sides and mesopleura usually more strongly granulate-punctate than dorsal surface. Legs smooth and shining to weakly coriarious, weakly shining.

Peduncle of petiole slightly shorter than petiolar node, anteroventral margin with a poorly developed, broadly rounded process. In profile, posterior surface of petiolar node weakly convex; petiolar node asymmetrical with anterior surface notably shorter than posterior surface, apex subangulate to angulate. In dorsal view, petiolar node longer than wide, sides subparallel anterad, widest near spatulate anterior margin, narrowing posterad. Sides and posterior surface of petiolar node with regular to irregular transverse rugae, occasionally with very regular rugae traversing in all directions or strongly coriarious with faint rugae. Dorsum of postpetiole convex in profile; in dorsal view, widest near posterior margin, narrowing anterad, maximum width and length about equal; transverse to arcuate, regular to wavy rugae posterad, anterad rugae concentric and traversing medially from lateral margin then curving anterad to become longitudinal; rugae on dorsum of postpetiole finer, denser than those on posterior surface of petiolar node; interrugae on both surfaces smooth and shining. First gastral tergum smooth and strongly shining.

Erect, mostly short to medium length, whitish pilosity moderately abundant on head, most hairs <0.2–0.3× MOD. Moderately abundant suberect to semidecumbent pilosity on scape; abundant decumbent hairs on funicular segments. Legs with moderately abundant suberect to decumbent, white setae. Rest of body with moderately dense, erect, medium-length, whitish to yellowish hairs, longest hairs on dorsum of mesosoma approximately 0.3–0.4× MOD. Head ferruginous orange to reddish-orange; mesosoma, antennae slightly darker reddish-orange; petiole, postpetiole, gaster, legs brownish-orange (Figures 7A, 33).

Queen. Unknown.

Male. Unknown.

Additional material examined. None.

Etymology. The specific epithet, colca, is derived from the type workers being collected adjacent to Colca Canyon in Peru, which is the second deepest canyon in the world.

Discussion. Pogonomyrmex colca is distinguished from all congeners except for P. cusquena by the combination of: (1) first gastral tergum smooth and strongly shining, (2) superior propodeal spines consist of acuminate denticles to short teeth, length usually similar to or less than height of inferior propodeal spines, (3) in profile, lateral portion of head from posterior margin of eyes to posterior corners faintly rugose to mostly smooth and shining, rugae weakening posterad, posterior corners smooth and shining to strongly shining, (4) longitudinal rugae on promesonotum strongly irregular with numerous lateral branches to rugoreticulate, and (5) promesonotal suture not impressed. Pogonomyrmex colca is most similar to P. cusquena, from which it is separated by: (1) longitudinal rugae on promesonotum strongly irregular with numerous lateral branches to rugoreticulate, and (2) promesonotal suture not impressed. In P. cusquena: (1) longitudinal rugae on promesonotum regular to moderately irregular with few lateral branches, and (2) promesonotal suture usually weakly to moderately impressed.

Biology. Nothing is known about the biology of P. colca. Pogonomyrmex colca is only known from the type locality at an elevation of approximately 3425 m in the Peruvian Yungas ecoregion, as defined by Olson et al. (2001) (Figure 32B).