Pogonomyrmex strioligaster, Johnson, 2021

Johnson, Robert A., 2021, A taxonomic revision of South American species of the seed-harvester ant genus Pogonomyrmex (Hymenoptera: Formicidae). Part II, Zootaxa 5033 (1), pp. 1-230 : 190-195

Pogonomyrmex strioligaster NEW SPECIES

( Figures 94–96 )

Distribution—90C

Holotype worker [ MACN: CASENT0922162 ]: ARGENTINA, Neuquén: Departamento Catán Lil , 54 km NE Rahue, 39º21.6’S 70º40.2’W, 3400’ (1030 m), 8 December 2003 (R.A. Johnson #3315) . Paratypes, same data as holotype: IFML (3 workers) , MACN (6 workers) , LACM (6 workers) , MCZC (5 workers) , RAJC (2 workers, 2 alate queens), UCDC (3 workers) , USNM (3 workers) .

Worker diagnosis. Workers of this species are uniquely characterized by the following combination of features: (1) striae extend over anterior one-half or more of first gastral tergum, posterolateral margins smooth and shining, (2) superior propodeal spines long, length> 0.7× the distance between their bases, (3) bicolored: head and gaster dark ferruginous orange to reddish-orange; mesosoma black or with pronotum and sometimes dorsum of mesonotum dark reddish-orange, (4) rugae on dorsum of promesonotum irregular to rugoreticulate, and (5) promesonotal suture usually present ( Figure 94 ).

Measurements — holotype (n = 6 + 6 paratypes). HL 1.62 (1.36–1.65); HW 1.63 (1.38–1.75); MOD 0.35 (0.29– 0.37); OMD 0.37 (0.30–0.41); SL 1.35 (1.16–1.39); PNW 1.05 (0.94–1.19); HFL 1.77 (1.42–1.86); ML 1.88 (1.39– 2.04); PW 0.44 (0.40–0.46); PPW 0.61 (0.47–0.63). Indices: SI 83.07 (75.30–84.62); CI 100.62 (99.31–108.33); OI 21.47 (19.19–22.56); HFI 108.59 (93.59–113.79).

Description. Head quadrate to wider than long (CI = 99.31–108.33), widest just posterior to eyes; posterior margin flat in full-face view. Longitudinal cephalic rugae prominent, wavy to irregular. In full-face view, medial rugae diverging toward posterior corners of head. Interrugae on cephalic dorsum strongly granulate, dull, with a beaded appearance; posterior corners rugose, interrugae smooth and shining to weakly coriarious, weakly shining. Anterior margin of clypeus concave, dorsum with subparallel, longitudinal rugae. Numerous long, curved, bristle-like, yellowish macrochaetae project from anterior margin of clypeus and basolateral margins of mandibles. Mandibles with six teeth; mandibular dorsum coarsely rugose. MOD ranging from 0.20–0.23× HL. In profile, eyes situated slightly anterior to middle of head, OMD = 0.92–1.21× MOD. In full-face view, eyes protruding slightly beyond lateral margins of head. Antennal scapes (SI = 75.30–84.62) ranging from failing to reach or surpassing posterior corners of head by less than width of basal funiculus; scapes with moderately strong, longitudinal striae, interstriae weakly coriarious, weakly shining to smooth and shining. Basal flange of scapes well developed with carinate margin. Psammophore well developed.

Mesosomal profile weakly convex. In dorsal view, humeral shoulders of pronotum enlarged, dorsolateral margins angulate. All mesosomal surfaces with prominent, coarse rugae; strongly irregular, longitudinal rugae to rugoreticulate on mesonotum, rugae diverging anterad toward humeral shoulders of pronotum, medial rugae sometimes continuing to anterior margin of pronotum or pronotum rugoreticulate; pronotal sides with strongly irregular rugae traversing ventrally or posteroventrally, with numerous lateral branches to rugoreticulate. Promesonotal suture usually present. Rugae on mesopleura angle posterodorsally; irregular transverse to oblique rugae on dorsum of propodeum traverse ventrally or anteroventrally on sides. Superior propodeal spines long, length about 0.7× the distance between their bases, spines connected by well developed keel. Inferior propodeal spines wider than high, apex broadly rounded to subacuminate. Propodeal spiracles narrowly ovate facing posterad. Interrugae on mesosoma weakly to strongly granulate, weakly shining to dull. Legs smooth and shining to moderately coriarious, weakly shining.

Peduncle of petiole about 0.8× as long as petiolar node, anteroventral margin with a well developed, rounded process that often continues posterad subparallel-parallel to dorsal margin of peduncle. In profile, posterior surface of petiolar node weakly convex; petiolar node asymmetrical with anterior surface shorter than posterior surface, apex weakly rounded to angulate. In dorsal view, petiolar node longer than wide, widest near spatulate anterior margin, gradually tapering posterad. Posterior surface of petiolar node with regular, wavy, or irregular transverse rugae. In profile, dorsum of postpetiole convex; in dorsal view, widest at or near posterior margin, tapering anterad, maximum width and length about equal. Wavy to irregular transverse to arcuate rugae on dorsum of postpetiole finer, denser than those on posterior surface of petiolar node; interrugae on posterior surface of petiolar node and dorsum of postpetiole smooth and shining to weakly coriarious, weakly shining. Striae extend over anterior one-half or more of first gastral tergum; posterolateral margins smooth and shining.

Erect, mostly short to medium-length, yellowish pilosity moderately abundant on head, one to several longer hairs along posterior margin approximately 0.8× MOD. Moderately abundant semidecumbent pilosity on scape; abundant decumbent hairs on funicular segments. Legs with moderately abundant suberect to semidecumbent yellowish setae. Mesosoma, petiolar node, postpetiole, and gastral terga with erect, moderately dense, medium-length, creamy to yellowish setae, mostly similar in length, longest approximately 0.8× MOD. Head and gaster dark ferruginous orange to reddish-orange, darker transverse band often present along posterior margin of terga; mesosoma black or with pronotum and sometimes dorsum of mesonotum dark reddish-orange; petiolar node and postpetiole blackish to black; antennal scapes and legs blackish-orange to blackish ( Figure 94 ).

Queen diagnosis. Queens of this species are diagnosed by the following combination of features: (1) striae extend over anterior one-third to one-half of medial portion of first gastral tergum, in occasional individuals striae and/or coriarious sculpture extending over slightly more than anterior one-half of tergum, rest of tergum smooth and shining, (2) head, mesoscutum, mesoscutellum, gaster ferruginous orange to orangish-black; mesopleura, propodeum blackish to black, (3) posterior corners rugose, interrugae weakly shining to dull, (4) in dorsal view, interrugae on mesoscutum moderately to strongly granulate, weakly shining to dull, and (5) transverse rugae cover posterior surface of petiolar node and dorsum of postpetiole ( Figure 95 ).

Measurements —(n = 1 + 2 paratypes). HL 1.61–1.69; HW 1.65–1.73; MOD 0.36–0.38; OMD 0.34–0.41; SL 1.24–1.31; PNW 1.34–1.44; HFL 1.67–1.79; ML 2.33–2.40; PW 0.47–0.52; PPW 0.70–0.79. Indices: SI 71.68– 79.39; CI 100.59–105.49; OI 21.18–21.97; HFI 98.27–105.29.

Description. With caste-specific morphology of the mesosoma related to wing-bearing and presence of ocelli on head. In full-face view, head quadrate to subquadrate (CI = 100.59–105.49), widest just posterior to eyes, posterior margin flat to weakly convex. Longitudinal rugae on cephalic dorsum prominent, wavy; in full-face view, medial rugae diverging toward posterior corners of head; interrugae on cephalic dorsum weakly to moderately granulate-punctate, with a beaded appearance, weakly shining to shining; posterior corners rugose, interrugae weakly granulate, weakly shining to dull. Mandibles with six teeth, dorsal surface coarsely rugose. Psammophore well developed.

All mesosomal surfaces except pronotal sides with subparallel, regular to wavy rugae, rugae irregular to rugoreticulate on pronotal sides; interrugae on mesoscutum moderately to strongly granulate, weakly shining to dull, interrugae on other parts of mesosoma weakly granulate-punctate, weakly shining; superior propodeal spines moderately long, bluntly tipped; inferior propodeal spines wider than tall, apex weakly rounded to subangulate. Peduncle of petiole long, anteroventral margin with a well developed, broadly rounded process that narrows, then continues posterad parallel to dorsal surface of peduncle. In profile, petiolar node asymmetrical with anterior surface shorter than posterior surface, apex angulate. Posterior surface of petiolar node with wavy to irregular, transverse rugae, weakly shining. In dorsal view, postpetiole wider than long; dorsum with wavy to irregular, transverse rugae that are finer, denser than those on posterior surface of petiolar node, interrugae on both surfaces weakly granulate-punctate, weakly shining. Striae extend over anterior one-third to one-half of medial portion of first gastral tergum, in occasional individuals striae and/or coriarious sculpture extending over slightly more than anterior one-half of tergum, rest of tergum smooth and shining. Most body surfaces with moderately abundant suberect to erect, medium-length, whitish setae. Head, mesoscutum, mesoscutellum, gaster ferruginous orange to orangish-black, blackish transverse band often present along posterior margin of terga; pronotum blackish-orange; mesopleura, propodeum, antennae blackish to black ( Figure 95 ).

Male diagnosis. Males of this species are diagnosed by the following combination of features: (1) first gastral tergum lacking striae, (2) head and mesosoma black, gaster ferruginous orange, (3) erect hairs lacking on first gastral tergum, (4) anterior portion of anepisternum and katepisternum smooth and shining, (5) posterior surface of petiolar node with weak irregular rugae, (6) dorsum of postpetiole with weak irregular rugae, interrugae weakly shining to dull ( Figure 96 ).

Measurements —(n = 1). HL 1.23; HW 1.24; MOD 0.45; OMD 0.18; SL 0.42; HFL 1.71; ML 2.24; PW 0.52; PPW 0.70. Indices: SI 33.87; CI 100.81; OI 36.29; HFI 137.90.

Additional material examined. ARGENTINA: Neuquén: 1.0 km W entrance to Parque Nacional Lanin , 3160’, Feb 2, 2011 ( MCZC; RAJC) ; Aluminé , Jan 19–20, 1949 ( IFML; LACM; MZSP) ; Caviahue , Jan 18, 2010 ( RAJC) ; Loncopue-Caviahue , Jan 18, 2010 ( RGPC) ; 6 km S Laguna Blanca , 4600’, Dec 7, 2003 ( MCZC; RAJC) ; Las Lajas-Pino Hachado , no date ( MACN) ( Figure 90C ).

Etymology. The specific epithet strioligaster (Latin, strioli = very fine striae, plus gaster = gaster) is derived from the fine striae that extend over the anterior one-half or more of the first gastral tergum.

Discussion. Pogonomyrmex strioligaster is distinguished from all congeners by: (1) striae extending over anterior one-half or more of first gastral tergum, posterolateral margins smooth and shining, (2) head and gaster ferruginous orange, mesosoma black or with pronotum and sometimes dorsum of mesonotum dark reddish-orange, (3) superior propodeal spines long, length> 0.7x the distance between their bases, and (4) dorsum of pronotum rugoreticulate.

Biology. Little is known about the biology of P. strioligaster . The few nests that have been observed were under a stone or in a clump of grass; one colony had three entrances at the edge of a large stone. Sexuals have been collected from 8 December (callow queens) through 18 January, suggesting that mating flights occur during the austral summer. Partial nest excavations indicated that colonies contain up to 2000 or more workers.

Pogonomyrmex strioligaster inhabits sites at elevations from 955–1030 m. This species occurs in the Valdivian temperate forests and Patagonian steppe ecoregions, as defined by Olson et al. (2001) ( Figure 90C ).

Figures

FIGURE 90. Geographic distribution of: (A) Pogonomyrmex semistriata, (B) P. spinolae, and (C) P. strioligaster. The large black circle in each panel denotes the type locality.

FIGURE 94. Photographs of Pogonomyrmex strioligaster holotype worker: (A) frontal view of head, (B) lateral view of body, and (C) dorsal view of body (CASENT0922162). Photographs by Michele Esposito from www.AntWeb.org.

FIGURE 95. Photographs of Pogonomyrmex strioligaster alate queen: (A) frontal view of head, (B) lateral view of body, and (C) dorsal view of body (CASENT0922163). Photographs by Michele Esposito from www.AntWeb.org.

FIGURE 96. Photographs of Pogonomyrmex strioligaster male: (A) frontal view of head, (B) lateral view of body, and (C) dorsal view of body (CASENT0922164). Photographs by Michele Esposito from www.AntWeb.org.