Pogonomyrmex spinolae (Emery, 1906) 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 : 184-189

Pogonomyrmex spinolae NEW STATUS

( Figures 2G–H , 91–93 )

Distribution—90B

Pogonomyrmex bispinosus var. spinolae Emery, 1906: 158 (queen, male). Syntypes examined: 1 queen, 1 male [MSNG].

CHILE, Bíobío: Tucapel (Claude Gay leg.). MSNG queen here designated LECTOTYPE [ CASENT0280987 ]. Pogonomyrmex vermiculatus Emery : Snelling & Hunt, 1976: 75, incorrect synonymy.

Worker diagnosis. Workers of this species are uniquely characterized by the following combination of features: (1) well developed psammophore, (2) first gastral tergum lacking striae, weakly to strongly coriarious along base or extending over anterior one-half of segment or with faint, barely visible, unincised striae on anterior one-third to one-half of segment, (3) posterior margin and usually posterior one-third or more of first gastral tergum smooth and shining to strongly shining, rarely weakly coriarious, (4) transverse rugae on posterior surface of petiolar node and dorsum of postpetiole, (5) head and mesosoma concolorous to nearly concolorous light to dark ferruginous orange to reddish-brown, (6) clypeus ferruginous orange to reddish-brown, concolorous with adjacent cephalic dorsum, (7) legs and antennal scapes usually orangish-brown, occasionally brownish to blackish, and (8) superior propodeal spines long, length> 0.6× the distance between their bases, (8) legs and antennal scapes usually orangish-brown, occasionally brownish to blackish, and (9) for most to all workers in a series, at least several hairs on dorsum of mesosoma> 0.7–0.8× MOD and greater than length of superior propodeal spines ( Figure 91 ).

Measurements —(n = 25). HL 1.33–1.72; HW 1.47–1.84; MOD 0.28–0.36; OMD 0.31–0.45; SL 1.06–1.39; PNW 0.96–1.21; HFL 1.44–1.92; ML 1.68–2.10; PW 0.33–0.47; PPW 0.52–0.65. Indices: SI 67.03–79.41; CI 101.20–111.97; OI 17.83–21.43; HFI 85.29–109.09.

Redescription. Head subquadrate to wider than long (CI = 101.20–111.97), broadest just posterior to eyes; posterior margin flat in full-face view. Longitudinal rugae on cephalic dorsum prominent, sometimes becoming more irregular to weakly rugoreticulate posterior to eyes; in full-face view, medial rugae usually diverging toward posterior corners of head. Posterior corners rugose, interrugae weakly to moderately granulate, weakly shining to dull, occasionally smooth and shining. Cephalic interrugae strongly granulate, dull, with a beaded appearance. Anterior margin of clypeus concave, dorsum with numerous subparallel, longitudinal rugae. Numerous long, curved, bristle-like, yellowish macrochaetae project from anterior margin of clypeus and ventral side of mandibles. Mandibles with six teeth; mandibular dorsum coarsely rugose. MOD ranging from 0.18–0.23× HL. In profile, eyes situated slightly anterior to middle of head, OMD = 0.94–1.41× MOD. In full-face view, eyes protruding slightly beyond lateral margins of head. Antennal scapes (SI = 67.03–79.41) failing to reach posterior corners of head by less than length of basal funicular segment. Antennal scapes smooth and shining to moderately coriarious, weakly shining, often with weak longitudinal striae, basal flange moderately well developed, flattened, with carinate margin. Psammophore well developed.

Mesosomal profile weakly to moderately convex. All mesosomal surfaces with prominent subparallel, irregular rugae to rugoreticulate. In dorsal view, humeral shoulders of pronotum enlarged, anterolateral margins angulate. Dorsum of mesonotum with strongly irregular, longitudinal rugae that diverge toward humeral shoulders of pronotum, anteromedial portion of pronotum rugoreticulate or anterad portion to all of pronotum and sometimes anterad portion of mesonotum rugoreticulate. Pronotal sides rugoreticulate. Irregular rugae on mesopleura angle posterodorsally, secondary rugae sometimes present; irregular transverse to oblique rugae on dorsum of propodeum traverse anteroventrally onto mesopleura. Promesonotal suture usually absent. Superior propodeal spines long, length> 0.6× the distance between their bases, spines connected by well defined keel; inferior propodeal spines broader than high, apex weakly rounded to acuminate. Propodeal spiracles narrowly ovate facing posterad. Interrugae on mesosoma weakly to moderately granulate-punctate, weakly shining. Legs weakly to moderately coriarious, weakly shining.

Peduncle of petiole about 0.8× long as petiolar node, anteroventral margin with moderately to well developed rounded process that narrows posterad, then continues subparallel-parallel to near posteroventral margin of petiolar node. In profile, posterior surface of petiolar node weakly convex, node asymmetrical with posterior surface longer than anterior surface, apex weakly rounded to subangulate. In dorsal view, petiolar node longer than broad, widest near spatulate anterior margin, gradually tapering posterad. Posterior surface of petiolar node with regular to irregular, wavy or arcuate, transverse rugae. Dorsum of postpetiole convex in profile; in dorsal view, widest at or near posterior margin, tapering to anterior margin, maximum width and length about equal. Wavy to irregular, transverse rugae on dorsum of postpetiole finer, denser than those on posterior surface of petiolar node; interrugae on both surfaces weakly to moderately coriarious, weakly shining. First gastral tergum weakly to strongly coriarious along base to extending over anterior one-half of segment, sculpturing sometimes appearing as faint, barely visible, unincised striae on anterior one-third to one-half of segment; posterior margin and usually posterior one-third or more of first gastral tergum smooth and shining to strongly shining, rarely weakly coriarious.

Erect, medium-length, white to cream colored pilosity moderately abundant on head, most hairs approximately 0.3–0.4× MOD. Moderately abundant suberect to semidecumbent pilosity on scape; abundant decumbent hairs on funicular segments. Legs with moderately abundant suberect to decumbent white to yellowish setae. Mesosoma, petiolar node, postpetiole, and gastral terga with erect, moderately dense, medium-length to long, white setae, longest hairs on mesosoma and posterior surface of petiolar node. For most to all workers in a series, at least several hairs on dorsum of mesosoma> 0.7–0.8× MOD and greater than length of superior propodeal spines. Body concolorous dark reddish-brown or with mesosoma and gaster slightly darker reddish-brown to reddish-black ( Figure 91 ).

Queen diagnosis. Queens of this species are diagnosed by the following combination of features: (1) castespecific morphology of the mesosoma related to wing-bearing and presence of ocelli on head, (2) striae and coriaceous sculpture cover more than anterior two-thirds of medial portion of first gastral tergum, posterolateral margins smooth and shining or first gastral tergum smooth and shining, (3) transverse rugae cover posterior surface of petiolar node and dorsum of postpetiole, (4) longitudinal rugae on cephalic dorsum posterior to eyes strongly irregular, often with short lateral branches; interrugae strongly granulate, dull, with a beaded appearance, (5) head, pronotum, mesoscutum, mesoscutellum, anepisternum, katepisternum nearly concolorous to concolorous ferruginous orange, reddish-brown to brownish-red, or reddish-black, and (6) in profile, most hairs on dorsum of mesoscutum and mesocutellum approach to exceed MOD ( Figures 2G–H & 92 ).

Measurements — lectotype (n = 12). HL 1.71 (1.37–1.56); HW 1.80 (1.43–1.61); MOD 0.40 (0.31–0.37); OMD 0.44 (0.31–0.43); SL 1.20 (1.01–1.13); PNW 1.34 (1.13–1.28); HFL 1.79 (1.30–1.60); ML 2.45 (2.03–2.36); PW 0.53 (0.38–0.45); PPW 0.73 (0.59–0.71). Indices: SI 66.67 (64.38–73.82); CI 105.26 (99.72–111.11); OI 22.22 (20.13–25.17); HFI 99.44 (89.66–103.40).

Male diagnosis. Males of this species are diagnosed by the following combination of features: (1) first gastral tergum lacking striae, (2) first gastral tergum with several to numerous suberect to erect hairs, (3) mesoscutum mostly smooth and shining, and (4) notauli absent ( Figure 93 ).

Measurements — paralectotype (n = 12). HL 1.42 (1.12–1.25); HW 1.35 (1.15–1.32); MOD 0.47 (0.41–0.49); OMD 0.16 (0.13–0.25); SL 0.41 (0.31–0.51); HFL 1.81 (1.41–1.74); ML 2.37 (1.87–2.29); PW 0.48 (0.40–0.50); PPW * (0.62–0.72). Indices: SI 30.37 (26.50–41.80); CI 95.07 (96.69–106.45); OI 34.81 (33.33–41.18); HFI 134.07 (118.49–151.30). * = missing.

Additional material examined. CHILE: Bíobío: Rt N-31 at 5.8 km E San Fabián de Alico , 1580’, Mar 2, 2014 ( MNNC; RAJC) ; Rt Q-45 at 9.2 km E Antuco , 2310’, Feb 28, 2014 ( IFML; LACM; MACN; MCZC; MNNC; RAJC; UCDC; USNM) ; Rt Q-59 at 5.8 km S Tucapel , 1050’, Mar 1, 2014 ( RAJC) ; Penco, Mar 14, 1945 ( USNM) . Maule: Rt 115 at Paso Nevado (pueblo), 1500’, Mar 3, 2014 ( RAJC) ; Hwy 115 at 5.0 km E Lago Colbún, 1520’, Sep 11, 2014 ( RAJC) ; 115 at 51.4 km W Paso Pehuenche , 3550’, Mar 3, 2014 ( RAJC) . Metropolitan: Camino Embalse El Yeso at 9.5 km ENE turnoff from Camino Al Volcán, 5700’, Feb 8, 2019 ( RAJC) ( Figure 90B ).

Etymology. Emery did not give information regarding the naming of this taxon in his description, but it is apparent that the name honored Spinola, who first described the queen and male as Atta bispinosus .

Discussion. Pogonomyrmex spinolae is distinguished from congeners by: (1) first gastral tergum lacking striae, weakly to strongly coriarious along base or extending over anterior one-half of segment or with faint, barely visible, unincised striae on anterior one-third to one-half of segment, (2) superior propodeal spines long, length> 0.6× the distance between their bases, (3) transverse rugae on posterior surface of petiolar node and dorsum of postpetiole, and (4) head and mesosoma concolorous to nearly concolorous light to dark ferruginous orange to reddish-brown. Pogonomyrmex araucania is the only congener that also fits this diagnosis. Length of hairs on the dorsum of the mesosoma separates P. spinolae and P. araucania . In P. spinolae these hairs are longer, with most hairs approaching to exceeding the MOD, while in P. araucania these hairs are shorter with most hairs <0.6–0.7× MOD. Note that hair length varies among individuals such that determinations should be made after examining several or more workers.

Pogonomyrmex bispinosus var. spinolae was described from queens and males that Gay collected at a mating aggregation near Tucapel, Chile. These were among the syntypes of Spinola’s P. bispinosus , but Emery separated them from the bispinosus worker syntype, which was from Santa Rosa, a site approximately 500 km north of Tucapel (see also Johnson, 2015). In his discussion, Emery (1906) noted that syntype queens from the Spinola collection had a streaked (= striate) basal segment (= first gastral tergum) and that this character did not coincide with the description for the syntype worker. Therefore, Emery reidentified the sexuals as the new variety P. bispinosus var. spinolae . That Emery separated the queen from P. bispinosus was correct given that P. bispinosus queens are ergatoid (Johnson, 2015). Consequently, determining the identity of P. bispinosus var. spinolae necessitated examining series that contained workers and sexuals from the type locality.

Riso Patron (1924) indicated that there are two Tucapels in the Bíobío Region of Chile, one near the coastal town of Concepción and one in Bíobío Province. Baeza (2012) gave an account of travels by Gay saying that he visited Tucapel, which was near Antuco in Bíobío Province; this Tucapel is presumed to be the type locality. Queens and males collected from colonies near Tucapel and Antuco matched the lectotype queen and male that I examined with the exception that the lectotype queen is larger and lighter in color than the other more recently collected queens (see queen measurements above). These collections also associated workers with queens and males. Santschi (1925) described putative workers of P. brevispinosus var. spinolae , but examination of these workers revealed that they were P. semistriata and not P. spinolae (see discussion under P. semistriata ).

It is also notable that queens of P. spinolae displays colony level variation in regard to striae on the first gastral tergum. In two colonies, all queens had striae that extended over most of their first gastral tergum, while all queens in a third colony lacked striae on their first gastral tergum.

The seven workers from Penco, Concepción Province, Chile ( USNM, examined) were identified as P. spinolae , but their ferruginous orange coloration was very light compared to the dark red to reddish-black workers collected by the author. It seems likely that color of these workers faded in the 60+ years since they were collected by Chapin (see CASENT0103404 at http://www.antweb.org/), as also apparently occurred in the lectotype queen. Regardless, workers should be recollected from this area to verify their identity .

Biology. Pogonomyrmex spinolae workers are solitary foragers, but workers have also been observed to forage in loose columns of scattered foragers. Nests are placed in open, exposed sites or in a grass clump or under a stone. Nests have one or two entrances that are typically surrounded by a tumulus up to 25 cm in diameter; most nests also have an external chaff midden up to 20 cm in diameter. Sexuals have been collected from February 28–March 3 indicating that mating flights occur during the austral summer. The syntype series of sexuals was collected by Gay, who said only that he observed numerous winged queens and males during a mating flight ( Spinola, 1851), but he did not indicate a date. Partial nest excavations indicated that colonies probably contain up to 1000 workers.

Pogonomyrmex spinolae inhabits sites at elevations from 320–1690 m. This species occurs in the Valdivian temperate forests and Chilean matorral ecoregions, as defined by Olson et al. (2001) ( Figure 90B ).

Figures

FIGURE 2. Closeup photographs of the mesosoma in dorsal view and in profile that distinguish between brachypterous and fully alate queens of Pogonomyrmex: (A–B) dealate brachypterous queen of P. tinogasta (CASENT0235287), (C–D) brachypterous queen of P. atacama (CASENT0922568), (E–F) dealate queen of fully winged P. mapuche (CASENT0280985), and (G–H) fully winged queen of P. spinolae (CASENT0869792). Red arrows (A, B, E, F) show remaining wing scars after the wings have been lost in a brachypterous (A–B) and fully alate queens (E–F). Blue, green, and yellow arrows show morphological differences between brachypterous and fully alate queens. Blue arrows show the much enlarged pronotum in brachypterous queens (A & C) compared to the pronotum of fully alate queens (E & G). Green arrows show differences in the profile of the pronotum, with brachypterous queens having either a sloping (B) or vertical pronotum (D), whereas fully alate queens always have a vertical pronotum (F & H). Yellow arrows show brachypterous queens with the mesoscutum meeting the pronotum on a horizontal plane (A) or the mesoscutum slopes at 45o from the juncture of the pronotum to the dorsum of the mesoscutum (D), whereas the mesoscutum continues vertically from the pronotum in fully alate queens (F & H). Photographs by Michele Esposito and Robert Johnson from www.AntWeb.org.

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 91. Photographs of Pogonomyrmex spinolae worker: (A) frontal view of head, (B) lateral view of body, and (C) dorsal view of body (CASENT0914359). Photographs by Michele Esposito from www.AntWeb.org.

FIGURE 92. Photographs of Pogonomyrmex spinolae alate queen: (A) frontal view of head, (B) lateral view of body, and (C) dorsal view of body (CASENT0914360). Photographs by Michele Esposito from www.AntWeb.org.

FIGURE 93. Photographs of Pogonomyrmex spinolae male: (A) frontal view of head, (B) lateral view of body, and (C) dorsal view of body (CASENT0914361). Photographs by Michele Esposito from www.AntWeb.org.