Pogonomyrmex forelii, 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 : 82-85

Pogonomyrmex forelii NEW SPECIES

( Figure 37 )

Distribution—36B

Holotype worker [ MACN: CASENT0922168 ]: ARGENTINA, Chubut: Departamento Mártires, Rt 25 at 11.4 km E Las Plumas, 43º39.3’S, 67º14.4’W, 1280 feet (390 m), 21 February 2014 (R.A. Johnson #5223) . Paratypes, same data as holotype: IFML (3 workers) , MACN (6 workers) , MCZC (6 workers) , LACM (6 workers) , RAJC (21 workers) , UCDC (3 workers), USNM (3 workers) .

Worker diagnosis. Workers of this species are uniquely characterized by the following combination of features: (1) striae cover more than anterior one-half of first gastral tergum, posterolateral margins smooth and shining, (2) head and mesosoma blackish to black, gaster dark ferruginous orange to orangish-black, (3) superior propodeal spines moderately long to long, length> 0.6× the distance between their bases, and (4) most workers in a series with one to several transverse, wavy to irregular rugae on anterodorsal margin of pronotum ( Figure 37 ).

Measurements — holotype (n = 13 paratypes). HL 1.70 (1.46–1.72); HW 1.78 (1.68–1.79); MOD 0.39 (0.33– 0.38); OMD 0.42 (0.38–0.46); SL 1.38 (1.21–1.40); PNW 1.18 (1.07–1.19); HFL 1.73 (1.61–1.84); ML 1.95 (1.80– 2.04); PW 0.47 (0.40–0.47); PPW 0.66 (0.60–0.67). Indices: SI 77.53 (69.32–79.55); CI 104.71 (103.70–116.22); OI 21.91 (19.54–21.84); HFI 97.19 (91.48–102.79).

Description. Head subquadrate to wider than long (CI = 103.70–116.22); posterior margin flat in full-face view. Longitudinal cephalic rugae prominent; in full-face view, medial rugae usually diverging toward posterior corners of head. Interrugae on cephalic dorsum strongly granulate-punctate, dull to weakly shining, with a beaded appearance; posterior corners rugose, interrugae smooth and shining to moderately coriarious, weakly shining. Anterior margin of clypeus moderately concave, dorsum with numerous, subparallel, longitudinal rugae. Numerous long, curved, bristle-like, yellowish macrochaetae project from anterior margin of clypeus and basolateral margins of mandibles. Mandibles with six or rarely seven teeth; mandibular dorsum rugose. MOD ranging from 0.20–0.25× HL. In profile, eyes situated slightly anterior to middle of head, OMD = 1.05–1.33× MOD. In full-face view, eyes protruding slightly beyond lateral margins of head. Antennal scapes (SI = 69.32–79.55) failing to reach posterior corners of head by less than width of basal funicular segment to reaching posterior corners of head. Antennal scapes with or without weak longitudinal striae, interstriae weakly to moderately granulate, weakly shining; basal flange well developed with carinate margin. Psammophore well developed.

Mesosomal profile flat to weakly convex; all mesosomal surfaces with prominent subparallel-parallel, wavy to irregular rugae. In dorsal view, humeral shoulders of pronotum enlarged, dorsolateral margins angulate. Dorsum of mesonotum with irregular longitudinal rugae (rarely rugoreticulate) that diverge toward humeral shoulders of pronotum; most workers with one to several transverse (sometimes very irregular) rugae on anterodorsal margin of pronotum that continue ventrally on pronotal sides or pronotal sides rugoreticulate; rugae on mesopleura angle posterodorsally. Superior propodeal spines moderately long to long, length> 0.6× the distance between their bases, spines connected by a well developed keel; irregular transverse rugae on dorsum of propodeum traverse anteroventrally on sides. Inferior propodeal spines moderately developed, wider than high, tips blunt to subacuminate. Propodeal spiracles narrowly ovate facing posterad. Interrugae on mesosoma densely granulate, dull to weakly shining. Legs moderately coriarious, weakly shining.

Peduncle of petiole about 0.8× as long as petiolar node, anteroventral margin with a weakly rounded process that usually continues posterad subparallel-parallel to dorsal surface 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, narrowing posterad. Sides and posterior surface of petiolar node with wavy to irregular transverse, arcuate or occasionally nearly longitudinal rugae. In profile, dorsum of postpetiole convex; in dorsal view, widest near posterior margin, narrowing anterad, width and length similar to slightly wider than long. Dorsum of postpetiole with wavy to irregular transverse rugae, occasionally with rugae on anterior one-half of postpetiole curving toward anterior margin; rugae on dorsum of postpetiole finer, denser than those on posterior surface of petiolar node; interrugae on both surfaces smooth and shining to moderately coriarious, weakly shining. First gastral tergum with striae over more than anterior one-half of segment, striae often extending to posterior margin of segment or with posterior margin strongly coriarious, dull; posterolateral margins usually smooth and shining.

Erect, mostly short to medium-length, whitish pilosity moderately abundant on head. Moderately abundant suberect to semidecumbent pilosity on scape; abundant decumbent hairs on funicular segments. Legs with moderately abundant suberect to decumbent whitish to light yellowish setae. Rest of body with moderately dense, erect, medium-length, whitish setae. Head, mesosoma, petiolar node black, anterior portion of pronotum occasionally with a weak orangish infusion; postpetiole orangish-black; gaster dark ferruginous orange with darker bands along posterior margins of terga ( Figure 37 ).

Queen. Unknown.

Male. Unknown.

Additional material examined. None.

Etymology. This species is named to honor Auguste Forel, who described nine South American species/subspecies of Pogonomyrmex .

Discussion. Pogonomyrmex forelii likely to co-occurs with several P. rastratus -group species, but its coloration (black head and mesosoma and light to dark ferruginous orange gaster) and striae that cover anterior one-half or more of the first gastral tergum distinguish it from all congeners except P. catanlilensis , P. granulatus , and P. varicolor . Pogonomyrmex forelii is distinguished from P. catanlilensis by: (1) superior propodeal spines moderately long to long, length> 0.6× the distance between their bases, and (2) most workers in a series with one to several transverse (sometimes very irregular) rugae on anterodorsal margin of pronotum. In P. catanlilensis , (1) superior propodeal spines variable, consisting of tubercles, denticles, and short teeth to long spines, and (2) rugae on anterodorsal margin of pronotum longitudinal, oblique, or rugoreticulate for most workers in a series. Pogonomyrmex forelii is distinguished from P. granulatus by their moderately long to long superior propodeal spines with a length> 0.6× the distance between their bases. In P. granulatus , the superior propodeal spines consist of tubercles, denticles, or short teeth with their length always less than 0.2× the distance between their bases. Pogonomyrmex forelii is distinguished from P. varicolor by: (1) superior propodeal spines moderately long to long, length> 0.6× the distance between their bases, (2) most workers in a series with one to several transverse (sometimes very irregular) rugae along the anterodorsal margin of pronotum, and (3) for all workers in a series, head black; gaster dark ferruginous orange. In P. varicolor , (1) superior propodeal spines consist of tubercles, denticles, or short teeth for at least some workers in a series, (2) for most workers in a series, anterodorsal margin of pronotum with longitudinal or oblique rugae or rugoreticulate, and (3) for at least some workers in a series, head usually other than black and/or gaster other than light to dark ferruginous orange.

Biology. Nothing is known regarding the biology of P. forelii except that the type colony had a 15 cm tumulus in an open, exposed site in a disturbed roadside, with vegetation consisting of Stipa sp. (Poaceae) , Larrea sp. (Zygophyllaceae) , Atriplex sp. (Amaranthaceae) , and other shrubs. The type colony was at an elevation of 385 m in the extreme southern part of the Low Monte ecoregion, as defined by Olson et al. (2001) ( Figure 36B ).

Figures

FIGURE 36. Geographic distribution of: (A) Pogonomyrmex excelsior, (B) P. forelii, and (C) P. granulatus. The large black circle in each panel denotes the type locality.

FIGURE 37. Photographs of Pogonomyrmex forelii holotype worker: (A) frontal view of head, (B) lateral view of body, and (C) dorsal view of body (CASENT0922168). Photographs by Michele Esposito from www.AntWeb.org.