Pogonomyrmex bolivianus, 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 : 54-55

Pogonomyrmex bolivianus NEW SPECIES

( Figure 23 )

Distribution—22B

Holotype worker [ CASC: CASENT0914125 ]: BOLIVIA, La Paz: 45 mi S La Paz, 25 February 1951 (E.S. Ross & A.E. Michelbacher) . Paratypes, same data as holotype: CASC (7 workers) , MCZC (2 workers) , MNHN (2 workers) , RAJC (2 workers) , USNM (2 workers) .

Worker diagnosis. Workers of this species are uniquely characterized by the following combination of features: (1) first gastral tergum with striae along base to extending over anterior one-third to one-half of medial portion of segment, rest of tergum smooth and polished, strongly shining, (2) longitudinal rugae on dorsum of promesonotum irregular, continuing to anterior margin of pronotum, (3) mesosoma dark ferruginous orange to orangish-brown, (4) posterior corners of head rugose, (5) superior propodeal spines consist of short, triangular teeth with a length less than width at base, (6) height of inferior propodeal spines greater than length of superior propodeal spines, (7) mandibles with six teeth, (8) rugae on frontal triangle subparallel-parallel, continuing onto clypeus, and (9) rugae on dorsum of postpetiole mostly transverse ( Figure 23 ).

Measurements — holotype (n = 12 paratypes). HL 1.54 (1.43–1.61); HW 1.66 (1.53–1.69); MOD 0.32 (0.31– 0.35); OMD 0.42 (0.41–0.47); SL 1.16 (1.07–1.31); PNW 1.08 (1.06–1.18); HFL 1.57 (1.42–1.65); ML 1.87 (1.65– 1.95); PW 0.40 (0.37–0.43); PPW 0.55 (0.54–0.69). Indices: SI 69.88 (66.46–77.51); CI 107.79 (100.64–110.00); OI 19.28 (18.45–22.88); HFI 94.58 (89.38–101.90).

Description. Head quadrate to wider than long (CI = 100.64–110.00); posterior margin flat in full-face view. Longitudinal rugae on cephalic dorsum prominent; in full-face view, medial rugae diverging toward posterior corners of head. Rugae on frontal triangle subparallel-parallel, continuing onto clypeus. Interrugae on cephalic dorsum weakly to moderately granulate-punctate, weakly shining to shining; posterior corners rugose, interrugae mostly smooth and 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 margin of mandibles. Mandibles with six teeth; mandibular dorsum coarsely rugose. MOD ranging from 0.19–0.25× HL. In profile, eyes situated slightly anterior to middle of head, OMD = 1.20–1.43× MOD. In fullface view, eyes protruding slightly beyond lateral margins of head. Antennal scapes (SI = 66.46–77.51) reaching posterior corners of head or failing to do so by less than length of basal funicular segment. Antennal scapes strongly striate, interstriae moderately granulate, dull to weakly shining; basal flange well developed with carinate margin. Psammophore well developed.

Mesosomal profile weakly to moderately convex; all mesosomal surfaces with prominent widely spaced, wavy to irregular rugae. In dorsal view, humeral shoulders of pronotum enlarged, dorsolateral margin weakly to moderately angulate. Promesonotal suture usually weakly to moderately impressed. Wavy to irregular, longitudinal rugae on mesonotum continue onto pronotum, medial rugae continue to anterior margin of pronotum, lateral rugae diverging to humeral shoulders of pronotum. Rugae on pronotal sides irregular, traversing ventrally or posteroventrally or weakly rugoreticulate. Irregular rugae on mesopleura angle posterodorsally; irregular transverse or oblique rugae on dorsum of propodeum traverse ventrally or anteroventrally on sides. Superior propodeal spines consist of short, triangular, acuminate teeth, spines connected by a weak to well defined keel. Inferior propodeal spines moderately well developed, wider than high, triangular, tips rounded to broadly rounded, height greater than length of superior spines. Propodeal spiracles narrowly ovate facing posterad. Interrugae on mesosoma weakly granulate-punctate, weakly shining to smooth and shining. Legs weakly coriarious, weakly shining.

Peduncle of petiole about as long as petiolar node, anteroventral margin with poorly developed rounded process. In profile, posterior surface of petiolar node weakly convex; node asymmetrical with anterior surface longer than posterior surface, apex subangulate to weakly rounded. In dorsal view, petiolar node longer than wide, sides subparallel, narrowest posterad, anterior margin spatulate to broadly rounded. Sides and posterior surface of petiolar node with regular to wavy transverse to occasionally oblique rugae. Dorsum of postpetiole convex in profile; in dorsal view, widest near posterior margin, narrowing to anterior margin, width and length similar. Transverse rugae on dorsum of postpetiole finer, denser than those on posterior surface of petiolar node, interrugae on both surfaces weakly granulate, weakly shining to smooth and strongly shining. Striae extending over anterior one-third to onehalf of medial portion of first gastral tergum, weakly shining with a silky appearance, posterior portion smooth and polished, strongly shining.

Erect, mostly short to medium length, whitish pilosity moderately abundant on head, few hairs> 0.4–0.5× MOD. Moderately abundant suberect to semidecumbent pilosity on scape; abundant decumbent hairs on funicular segments. Legs with moderately abundant suberect to decumbent whitish to pale yellow setae. Rest of body with moderately dense, erect, medium-length, whitish to pale yellow setae. Head and mesosoma dark ferruginous orange to orangish-brown, mesosoma sometimes slightly darker than head; mandibles, antennae, legs, petiolar node, postpetiole, gaster dark brownish-orange ( Figure 23 ).

Queen. Unknown.

Male. Unknown.

Additional material examined. None.

Etymology. The specific epithet, bolivianus , is derived from Ross & Michelbacher collecting the syntype series in Bolivia.

Discussion. Pogonomyrmex bolivianus is not known to co-occur with any congeners, but note that very few series of Pogonomyrmex have been collected from the Bolivian altiplano. Regardless, P. bolivianus is easily diagnosed by longitudinal striae that cover only the anterior one-third to one-half of the first gastral tergum with the rest of the tergum smooth and polished, strongly shining. Pogonomyrmex atacama is the only species with this character that is likely to be confused with P. bolivianus . 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) rugae on dorsum of postpetiole mostly transverse, and (5) rugae on frontal triangle subparallel-parallel, continuing onto clypeus. 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) rugae on dorsum of postpetiole mostly longitudinal, and (5) one to few rugae on frontal triangle converging anterad forming a narrowly rounded V-shaped pattern. Pogonomyrmex cusquena is another congener from high elevation habitats, but P. cusquena lacks striae on the first gastral tergum.

Biology. Nothing is known about the biology of P. bolivianus . The collection locale for the syntype series was given only as 45 mi south of La Paz, which is within the Bolivian altiplano at an elevation that likely ranges from 3940–4240 m. It seems likely that P. bolivianus is restricted to altiplano habitats of Bolivia and probably nearby areas of Peru. Pogonomyrmex bolivianus is only known from the type locality, which appears to be in the Central Andean dry puna ecoregion, as defined by Olson et al. (2001) ( Figure 22B ).

Figures

FIGURE 22. Geographic distribution of: (A) Pogonomyrmex atratus, (B) P. bolivianus, and (C) P. carbonarius. The large black circle in each panel denotes the type locality. See text regarding the type locality for P. atratus.

FIGURE 23. Photographs of Pogonomyrmex bolivianus holotype worker: (A) frontal view of head, (B) lateral view of body, and (C) dorsal view of body (CASENT0914125). Photographs by Michele Esposito from www.AntWeb.org.