Pogonomyrmex loaensis Johnson 2021, NEW SPECIES
Creators: name: Johnson, Robert A.
Publisher: name: Zenodo
Year: 2021
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Hymenoptera
Formicidae
Pogonomyrmex
Pogonomyrmex loaensis

description: Pogonomyrmex loaensis NEW SPECIES   
(Figures 48–50)  
Distribution—51A  
Holotype worker [MNNC: CASENT0922560]: CHILE, Antofagasta: El Loa Province, Rt B-223 at 4.1 km S Machuca, 13,200’ (4000 m), 22 March 2017 (R.A. Johnson #5833). Paratypes, same data as holotype: IFML (3 workers), LACM (9 workers), MACN (3 workers), MCZC (9 workers), MNNC (12 workers), RAJC (35 workers, 1 dealate queen), UCDC (3 workers), USNM (9 workers).  
 Worker diagnosis. Workers of this species are uniquely characterized by the following combination of features: (1) first gastral tergum with striae extending over anterior two-thirds or more of medial portion of segment, (2) head and mesosoma concolorous ferruginous orange to reddish-orange, (3) medial rugae on dorsum of postpetiole longitudinal anterad and usually curving laterally posterad, more lateral anterior rugae curving laterally and forming concentric arcs, (4) longitudinal rugae on mesonotum diverge toward humeral shoulders of pronotum, anterior margin of pronotum with one to several transverse rugae, and (5) rugae on medial portion of clypeus converge anterad to form up to several concentric narrowly rounded V’s (Figure 48).   
 Measurements — holotype (n = 12 paratypes). HL 1.59 (1.55–1.79); HW 1.70 (1.58–1.89); MOD 0.37 (0.36– 0.40); OMD 0.39 (0.37–0.44); SL 1.19 (1.14–1.36); PNW 1.08 (1.03–1.25); HFL 1.68 (1.62–1.87); ML 1.79 (1.82– 2.06); PW 0.44 (0.41–0.50); PPW 0.57 (0.57–0.65). Indices: SI 70.00 (68.05–77.71); CI 106.92 (97.06–112.26); OI 21.76 (20.88–23.42); HFI 98.82 (98.35–104.14).   
 Description. Head subquadrate to quadrate (CI = 97.06–112.26); posterior margin flat to weakly convex in fullface view. Longitudinal rugae on cephalic dorsum prominent; in full-face view, medial rugae weakly diverging to diverging toward posterior corners; for most workers, posterior margin with one to few transverse rugae restricted to medial area or extending along entire margin. Interrugae on cephalic dorsum moderately to strongly granulate, with a beaded appearance, dull to weakly shining; posterior corners rugose, interrugae weakly granulate, weakly shining. Anterior margin of clypeus moderately concave, rugae on medial portion of clypeus converge anterad to form up to several concentric narrowly rounded V’s. Numerous long, curved, bristle-like, cream to light yellowish macrochaetae project from anterior margin of clypeus and basolateral margin of mandibles. Mandibles with six to seven teeth; mandibular dorsum coarsely rugose. MOD ranging from 0.21–0.26× HL. In profile, eyes situated slightly anterior to middle of head, OMD = 1.02–1.16× MOD. In full-face view, eyes protruding slightly beyond lateral margins of head. Antennal scapes (SI = 70.18–80.28) failing to reach posterior corners of head by width of basal funicular segment. Antennal scapes weakly to moderately striate, interstriae weakly to moderately punctate, weakly shining to smooth and shining; basal flange well developed with carinate margin. Psammophore well developed.   
Mesosomal profile flat to weakly convex; all mesosomal surfaces with prominent widely spaced, subparallelparallel rugae. Wavy to irregular rugae on dorsum of promesonotum diverge toward humeral shoulders of pronotum then continue ventrally onto pronotal sides; anterior margin of pronotum with one to several transverse rugae that continue ventrally onto sides of pronotum. In dorsal view, humeral shoulders of pronotum enlarged, strongly angulate. Promesonotal suture absent to weakly impressed. Wavy to irregular rugae on mesopleura angle posterodorsally; transverse rugae on dorsum of propodeum traverse anteroventrally on sides. Superior propodeal spines consist of short, triangular teeth to moderately long spines; spines connected by a well defined keel. Inferior propodeal spines slightly wider than high, triangular, apex weakly rounded to subacuminate, height often similar to length of superior spines. Propodeal spiracles narrowly ovate facing posterad. Interrugae on mesosoma smooth and shining to weakly coriarious, weakly shining. Legs weakly to moderately coriarious, weakly shining to shining.  
 Peduncle of petiole approximately 0.8× as long as petiolar node, anteroventral margin with a broadly rounded process. In profile, posterior surface of petiolar node weakly convex; petiolar node asymmetrical with anterior surface shorter than posterior surface, apex subangulate to angulate. In dorsal view, petiolar node longer than wide, widest immediately posterior to spatulate anterior margin. Posterior surface of petiolar node with transverse rugae, rugae often arcuate anterad or rugae longitudinal. Dorsum of postpetiole convex in profile; in dorsal view, widest near posterior margin, narrowing to anterior margin, maximum width and length similar; medial rugae on dorsum of postpetiole longitudinal anterad and usually curving laterally posterad, more lateral anterior rugae curving laterally to form concentric arcs. Rugae on dorsum of postpetiole finer, denser than those on posterior surface of petiolar node, interrugae on both surfaces weakly granulate-punctate, weakly shining to shining. Striae extend over more than anterior two-thirds of first gastral tergum, posterolateral margins smooth and shining.   
Erect, short to medium length, whitish pilosity moderately abundant on head. Moderately abundant semidecumbent to decumbent pilosity on scape; abundant decumbent hairs on funicular segments. Legs with moderately abundant, suberect to decumbent whitish setae. Rest of body with moderately dense, erect, medium length, whitish setae; longest hairs on mesosoma usually about 0.4–0.5× MOD. Head and mesosoma ferruginous orange to reddishorange; petiolar node, postpetiole orangish-black to blackish orange; gaster orangish-black to blackish; mandibles, antennae, legs blackish to black (Figure 48).  
 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 cover anterior two-thirds or more of medial portion of first gastral tergum, (3) body mostly concolorous ferruginous orange, (4) longitudinal rugae on cephalic dorsum posterior to eyes regular, lacking short lateral branches, interrugae weakly to moderately granulate, weakly shining, (5) rugae on medial portion of clypeus sometimes converge anterad to form up to several concentric narrowly rounded V’s, (6) in dorsal view, metanotum lacking longitudinal rugae, (7) superior propodeal spines moderately long, length greater than width at base, (8) inferior propodeal spines moderately well developed, triangular with height slightly less than width, and (9) transverse or longitudinal rugae cover posterior surface of petiolar node and dorsum of postpetiole (Figure 49).   
 Measurements —(n = 1 + 1 paratype). HL 1.58–1.92; HW 1.81–1.97; MOD 0.40–0.43; OMD 0.39–0.45; SL 1.22–1.34; PNW 1.31–1.37; HFL 1.81–1.95; ML 2.34–2.49; PW 0.48–0.54; PPW 0.70–0.75. Indices: SI 61.93– 74.03; CI 102.60–114.56; OI 21.83–22.10; HFI 98.98–100.00.   
 Description. With caste-specific morphology of the mesosoma related to wing-bearing and presence of small ocelli on head. In full-face view, head quadrate to slightly wider than long (CI = 102.60–114.56), broadest just posterior to eyes, posterior margin flat. Longitudinal rugae on cephalic dorsum prominent, wavy to regular; in full-face view, medial rugae diverging toward posterior corners of head; interrugae moderately to strongly granulate, weakly shining, with a beaded appearance; rugae on medial portion of clypeus converge anterad to form up to several concentric narrowly rounded V’s. Mandibles with six teeth, dorsal surface rugose. Psammophore well developed.   
All mesosomal surfaces with regular to wavy, subparallel rugae, interrugae weakly to moderately granulatepunctate, weakly shining; in dorsal view, metanotum lacking longitudinal rugae; superior propodeal spines moderately long, length greater than width at base; inferior propodeal spines moderately well developed, triangular with height slightly less than width. Peduncle of petiole long, anteroventral margin with a broadly rounded process. In profile, petiolar node asymmetrical with anterior surface shorter than posterior surface, apex of node angulate. Posterior surface of petiolar node with strongly arcuate to strongly oblique to longitudinal, wavy rugae, interrugae weakly granulate-punctate, weakly shining. In dorsal view, postpetiole about as long as wide, dorsum with transverse to weakly arcuate, wavy rugae posterad, anterad rugae strongly arcuate or traversing medially from lateral margin then curving anterad to become longitudinal; anterolateral rugae concentric, curving from lateral to anterior margin; rugae on dorsum of postpetiole finer, denser than those on posterior surface of petiolar node; interrugae weakly granulate-punctate, weakly shining to smooth and shining. Striae cover anterior two-thirds or more of medial portion first gastral tergum, posterolateral margins smooth and shining. Most body surfaces with moderately abundant suberect to erect, short, whitish to cream-colored setae. Legs and antennae black; parts of gaster (especially sternites) orangish-black to blackish-orange; rest of body concolorous ferruginous orange (Figure 49).  
 Male diagnosis. Males of this species are diagnosed by the following combination of features: (1) striae extend over more than anterior one-half of first gastral tergum, (2) area posterior to eyes with weakly irregular to irregular longitudinal rugae that continue to posterior margin, (3) notauli present, (4) scape lacking erect or semi-erect hairs, (5) in profile, petiolar node broadly rounded, and (6) body mostly a concolorous ferruginous orange except for blackish borders on mesosomal segments (Figure 50).   
 Measurements —(n = 1). HL 1.26; HW 1.30; MOD 0.46; OMD 0.20; SL 0.36; HFL 1.58; ML 2.06; PW 0.48; PPW 0.65. Indices: SI 27.69; CI 103.17; OI 35.38; HFI 121.54.   
 Additional material examined.  CHILE. Antofagasta:  32.0 km E Jct Rts 23 & 27 (E side of San Pedro de Atacama), 13,110’, Apr 2 2017 (RAJC); 2 km N Socaire, 3400 m, Dec 21, 2001 (RAJC); Rt 23 at 2.0 km SW Socaire, 10,490’, Mar 23, 2017 (RAJC); Rt B-155 at 3.8 km E Turi, 10,380’, Mar 21, 2017 (RAJC) (Figure 51A).   
 Etymology. The specific epithet, loaensis, is geographical in origin, and it is derived from the type series being collected in El Loa Province, Chile.   
 Discussion. Pogonomyrmex loaensis likely co-occurs with P. atacama and possibly other P. rastratus -group species. Pogonomyrmex loaensis and P. atacama are similar, but they can be distinguished based on the following characters. In P. loaensis: (1) striae extend over anterior two-thirds or more of medial portion of first gastral tergum, and (2) posterior corners of head rugose. In P. atacama: (1) striae extend over anterior one-third to one-half of medial portion of first gastral tergum, and (2) posterior corners of head usually smooth and shining to strongly shining. Pogonomyrmex loaensis is separated from other congeners by the combination of: (1) striae extending over anterior two-thirds or more of medial portion of first gastral tergum, (2) head and mesosoma concolorous ferruginous orange to reddish-orange, (3) medial rugae on dorsum of postpetiole longitudinal anterad and usually curving laterally posterad, more lateral anterior rugae curving laterally and forming concentric arcs, (4) longitudinal rugae on mesonotum diverge toward humeral shoulders of pronotum, anterior margin of pronotum with one to several transverse rugae, and (5) one to few rugae on medial portion of clypeus converge anterad to form up to several concentric, narrowly rounded V’s.   
 Biology. Pogonomyrmex loaensis workers are solitary foragers. Nests of P. loaensis are placed under a stone in open, exposed sites. The nest entrance consisted of a tumulus up to 15 cm in diameter. One male was collected on Mar 21, indicating that that mating flights occur during the austral summer. Partial nest excavations indicated that colonies contain up to 1000 workers.   
 Pogonomyrmex loaensis inhabits sites at elevations from 3175–4040 m in the Central Andean dry puna ecoregion, as defined by Olson et al. (2001) (Figure 51A).
description: Published as part of Johnson, Robert A., 2021, A taxonomic revision of South American species of the seed-harvester ant genus Pogonomyrmex (Hymenoptera: Formicidae). Part II, pp. 1-230 in Zootaxa 5033 (1) on pages 104-110, DOI: 10.11646/zootaxa.5033.1.1, http://zenodo.org/record/5499124