Pogonomyrmex naegelii

A wide ranging, common South American Pogonomyrmex species.

Identification
Johnson (2015) - Worker Within the P. naegelii-group, the combination of: (1) approximately 8–10 coarse, longitudinal rugae between frontal lobes, (2) small lobe projecting dorsally from anterior margin of antennal fossa, (3) peduncle of petiole and anterior surface of petiolar node meet at an obtuse angle, (4) in dorsal view, posterior surface of petiolar node narrow, width similar to or slightly greater than distance between tips of superior propodeal spines, and (5) longest hairs on mesosoma rarely >0.7–0.8x MOD uniquely characterize this species.

Alate Queen This caste is diagnosed by: (1) caste-specific morphology of the mesosoma related to wing-bearing and presence of ocelli on head, (2) small size (HW < 1.35 mm), (3) petiolar node and postpetiole relatively narrow (petiolar node < 0.45 mm, postpetiole < 0.60 mm), (4) posterior surface of petiolar node rugoreticulate to vermiculate, and (5) mesoscutum and mesoscutellum rugoreticulate-vermiculate.

Ergatoid Queen This caste is diagnosed by: (1) ergatoid, with small ocelli on head, (2) small species (HW < 1.30 mm), (3) mesoscutum, mesoscutellum, and posterior surface of petiolar node rugoreticulate, (4) in profile, mesosomal outline discontinuous with a break between mesoscutellum and metanotum and between metanotum and propodeum.

Male This caste is diagnosed by: (1) first gastral tergum lacking striae, (2) small (HW < 1.10 mm; ML < 2.00 mm), (3) in dorsal view, posterior surface of petiolar node rugoreticulate, (4) in profile, petiolar node rounded, (5) pronotal sides rugoreticulate, (6) in profile, inferior propodeal spines moderately well-developed, broadly rounded, and (7) notauli present. Note that males are unknown for Pogonomyrmex abdominalis and Pogonomyrmex tenuipubens.

Pogonomyrmex naegelii co-occurs with the other two P. naegelii-group species. Pogonomyrmex naegelii can be distinguished from P. tenuipubens by: (1) the approximately 8–10 coarse longitudinal rugae between the frontal lobes, (2) a small lobe that project dorsally from the anterior margin of the antennal fossa, and (3) the longest hairs on the psammophore and mesosoma are coarse, their length >0.5x MOD. In P. tenuipubens: (1) there are 16–20 fine, weak, longitudinal rugae between the frontal lobes, (2) the anterior margin of the antenna fossa lacks a lobe-like projection, and (3) the psammophore and abundant hairs on the mesosoma are very short, delicate, length <0.2x MOD, except for one to few long, coarse hairs that are sometimes present on the posterior margin of head and pronotum. Pogonomyrmex naegelii can be distinguished from P. abdominalis by: (1) usually smaller (HW = 1.05–1.23 mm), (2) a small lobe that projects dorsally from anterior margin of antennal fossa, (3) peduncle of petiole and anterior surface of petiolar node meet at an obtuse angle, and (4) width of posterior surface of petiolar node is similar to or slightly greater than distance between tips of superior propodeal spines. In P. abdominalis: (1) the body is usually larger (HW = 1.14–1.33 mm; (2) no small lobe projects dorsally from anterior margin of antennal fossa, (3) the peduncle of petiole and anterior surface of petiolar node meet at or near a right angle, and (4) the posterior surface of petiolar node is distinctly wider than distance between tips of superior propodeal spines.

Distribution based on Regional Taxon Lists
Neotropical Region: Argentina, Bolivia, Brazil, Colombia, Guyana, Paraguay, Peru, Uruguay, Venezuela.

Habitat
Pogonomyrmex naegelii inhabits sites at elevations from 0–1115 m, and it is the most widespread and commonly collected Pogonomyrmex in South America. It is known from all countries except Chile, Ecuador, Suriname, and French Guiana. Pogonomyrmex naegelii occurs in numerous ecoregions, but appears to be absent from deserts, rainforests, and high-elevation areas. (Johnson 2015)

Biology
Johnson (2015) - Pogonomyrmex naegelii is a solitary forager that has a generalist and season-dependent diet that consists of grass seeds, and to a lesser extent nongrass species, various plant parts, and insects; ants and termites are the primary animal prey. The diet is primarily granivorous during the dry/cold season, whereas arthropods are collected to a greater extent during the warm/wet season (Belchior, Del-Claro, & Oliveira, 2012). Nests range from a cryptic entrance to a 10 cm tumulus, and they sometimes have a secondary entrance. Nests in the cerrado savanna of Brazil are relatively shallow, reaching about 70 cm below the soil surface and have 5–10 chambers (Belchior et al., 2012). Colonies are relatively small, ranging from 166–580 workers (n = 3 nests) (Belchior et al., 2012). Nests had one queen (n = 3) (Belchior et al., 2012), and the author has found multiple dealate queens in several nests. In the latter case, it is unknown if these queens were reproductive, especially given that colonies of the related North American species P. pima sometimes have numerous unmated dealate queens that forage (see Johnson et al., 2007).

Collection dates for sexuals range from 3–25 December. Mating flights have not been observed, but they likely occur during austral summer based on dates on which sexuals have been collected. Pogonomyrmex naegelii has both alate and ergatoid queens. From collections to date, the author has not seen any series in which both queen phenotypes were collected in the same colony, similar to observations for Pogonomyrmex pima (Johnson et al., 2007). One alate queen had eight ovarioles (unpub. data).

Nomenclature

 *  naegelii. Pogonomyrmex naegelii Forel, in Emery, 1878a: x (w.) BRAZIL. Mayr, 1887: 612 (q.m.); Wheeler, G.C. & Wheeler, J. 1972b: 237 (l.). Combination in P. (Ephebomyrmex): Wheeler, W.M. 1902c: 390; in Ephebomyrmex: Kempf, 1972a: 106; in Pogonomyrmex: Bolton, 1995b: 341. Senior synonym of rupununi, venezuelensis: Kempf, 1960f: 428. See also: Forel, 1886b: xli; Gallardo, 1932b: 109.
 * rupununi. Pogonomyrmex (Ephebomyrmex) venezuelensis var. rupununi Weber, 1943b: 71 (w.) GUYANA. Junior synonym of naegelii: Kempf, 1960f: 428.
 * venezuelensis. Pogonomyrmex (Ephebomyrmex) venezuelensis Weber, 1943b: 69, fig. 2 [fig. is incorrectly captioned as Leptothorax anduzei] (w.) VENEZUELA. Junior synonym of naegelii: Kempf, 1960f: 428.

Johnson (2015):

Worker
Johnson (2015) - Lectotype (n = 31 + 1 paralectotype). HL 1.15 (1.05–1.23); HW 1.15 (1.06–1.20); MOD 0.24 (0.22–0.28); OMD 0.28 (0.21–0.31); SL 0.84 (0.80–0.94); PNW 0.78 (0.69–0.84); HFL 1.15 (0.95–1.20); ML 1.34 (1.20–1.46); PW 0.30 (0.28–0.36); PPW 0.45 (0.40–0.49). Indices: SI 73.04 (68.97–85.45); CI 100.00 (91.53–106.25); OI 20.87 (20.17–24.30); HFI 100.00 (84.82–103.64).

Head subquadrate to quadrate (CI = 91.53–106.25), widest just posterior to eye; posterior margin flat to weakly concave. Longitudinal rugae on cephalic dorsum prominent, usually moderately to coarsely rugoreticulate especially medial to eyes and near posterior margin; approximately 8–10 coarse longitudinal rugae between frontal lobes; in full-face view, medial rugae not diverging toward posterior corners of head. In profile, area posterior to eyes moderately to strongly rugoreticulate. Cephalic interrugae moderately to strongly granulate, dull to weakly shining; vertex rugose to rugoreticulate. Anterior margin of clypeus flat to weakly concave, dorsal surface with numerous subparallel, longitudinal rugae; small lobe projects dorsally from anterior margin of antennal fossa. Mandible with six teeth; mandibular dorsum coarsely rugose. Up to several moderately long, curved, bristle-like, yellow-brown to brownish hairs project from anterior margin of clypeus and basolateral margin of mandibles. MOD ranging from 0.19–0.25x HL. In profile, eyes situated anterior to middle of head, OMD = 0.84–1.25x MOD. Antennal scapes moderately long (SI = 70.83–85.45), failing to reach vertex by 1.0–1.5x length of basal funicular segment; entire scape with strong longitudinal striae, dull to weakly shining. Basal flange of scape flattened, well-developed with carinate margin. Psammophore poorly-developed, consisting of short to medium-length hairs scattered across ventral side of head.

Mesosomal profile convex; all mesosomal surfaces rugoreticulate to vermiculate. Mesoepinotal sulcus sometimes weakly to moderately impressed. Dorsum of promesonotum and sides of pronotum rugoreticulate to vermiculate. Mesopleura with highly irregular rugae angling posterodorsally to rugoreticulate-vermiculate. Dorsum and sides of propodeum with irregular to very irregular, transverse rugae to occasionally rugoreticulate-vermiculate. Superior propodeal spines moderately long, acuminate, connected by well-defined keel; spine length approximately 0.7–0.8x distance between their bases. Inferior propodeal spines well-developed, acuminate, length approximately 0.5–1.0x that of superior spines, base wider than length of superior spines; inferior and superior spines connected by crest that defines the propodeal declivity. Propodeal spiracles ovoid to circular facing posterad. Interrugae on mesosoma weakly to strongly granulate, dull to weakly shining to smooth and strongly shining. Legs moderately coriarious, weakly shining.

Peduncle of petiole about as long as petiolar node, anteroventral margin with weakly to strongly-developed triangular process. In profile, petiolar node asymmetrical with anterior surface shorter than posterior surface; apex weakly rounded to subangulate; anterior surface meeting peduncle of petiole at an obtuse angle. In dorsal view, petiolar node longer than wide, widest near middle, narrowing to spatulate to subangulate anterior margin; maximal width of posterior surface similar to slightly greater than distance between tips of superior propodeal spines; posterior surface and sides strongly rugoreticulate-vermiculate, interrugae weakly to moderately granulate, weakly shining. Dorsum of postpetiole convex in profile; in dorsal view, postpetiole widest at or near posterior margin, narrowing near middle to convex anterolateral margin; maximal width about equal to length; dorsum and sides moderately to coarsely rugoreticulate or with several irregular, longitudinal to oblique rugae, interrugae moderately to strongly granulate, dull to weakly shining. Ventral process of postpetiole large, bulbous, height similar to dorsal portion of postpetiole. First gastral tergum moderately to strongly coriarious, weakly shining, to smooth and strongly shining; anterior margin to anterior one-half often with weak to moderately strong longitudinal striae.

Erect yellow-brown to brownish pilosity moderately abundant on head, similar in length, mostly short, often with one or more longer hairs that approximate MOD. Moderately abundant suberect to semidecumbent pilosity on scape, abundant decumbent hairs on funicular segments. Legs with moderately abundant semidecumbent, brownish setae. Mesosoma, petiolar node, postpetiole, gastral terga with moderately dense, erect setae, mostly similar in length, longest approximately 0.7–0.8x MOD; hairs on propodeum less dense. Concolorous tan to tannish-brown with darker to blackish gaster.

Queen
Alate (n = 11). HL 1.15–1.29; HW 1.15–1.26; MOD 0.24–0.32; OMD 0.23–0.30; SL 0.85–0.98; PNW 0.87–1.01; HFL 1.09–1.30; ML 1.56–1.75; PW 0.34–0.44; PPW 0.50–0.60. Indices: SI 73.91–78.86; CI 95.93–107.83; OI 20.69–25.40; HFI 87.90–108.47. Ergatoid (n = 6). HL 1.12–1.27; HW 1.17–1.27; MOD 0.23–0.29; OMD 0.23–0.28; SL 0.83–0.94; PNW 0.89–0.99; HFL 1.09–1.22; ML 1.45–1.60; PW 0.39–0.41; PPW 0.56–0.63. Indices: SI 65.35–77.78; CI 94.49–110.71; OI 18.55–23.93; HFI 89.76–99.19.

Ergatoid; small species (HW = 1.17–1.27 mm), head subquadrate to wider than long (CI = 94.49–110.71), posterior margin flat to weakly concave. Longitudinal rugae on cephalic dorsum prominent medially, becoming rugoreticulate laterally; interrugae weakly to moderately coriarious, weakly shining. Mandible with six teeth, dorsal surface coarsely rugose. Psammophore poorly-developed, consisting of numerous short hairs scattered across ventral side of head.

All mesosomal surfaces rugoreticulate. In profile, mesoscutum and mesoscutellum flattened, mesoscutellum angled upward posterad; metanotum discontinuously connected to mesoscutellum and propodeum. Superior and inferior propodeal spines moderately well-developed, similar in length. Peduncle of petiole long, anteroventral margin with small to moderately well-developed acuminate triangular process. In profile, petiolar node asymmetrical with anterior surface notably shorter than posterior surface, apex angulate. Postpetiole slightly wider than long. Posterior surface of petiolar node coarsely rugoreticulate, dorsum of postpetiole finely rugoreticulate; interrugae weakly to moderately punctate, weakly shining. First gastral tergum weakly to strongly coriarious, dull to weakly shining with faint to moderately strong longitudinal striae near base that sometimes extend over anterior one-half of tergum. Most body surfaces with abundant suberect to erect, brownish hairs that are similar in length, longest approximately 0.5–0.7x MOD. Body concolorous tannish-brown to orangish-brown, posterior gastral terga often darker.

Male
(n = 12). HL 0.89–1.10; HW 0.84–1.08; MOD 0.32–0.42; OMD 0.06–0.18; SL 0.14–0.23; HFL 1.03–1.40; ML 1.51–1.95; PW 0.33–0.43; PPW 0.44–0.58. Indices: SI 14.00–22.12; CI 94.38–109.18; OI 33.98–42.00; HFI 106.80–136.00.

Type Material
Syntypes examined: 1 worker, 2 workers , 1 worker , BRAZIL, Rio de Janeiro (Carlos Naegeli leg.); MSNG worker here designated LECTOTYPE [CASENT0280989].

Etymology
The specific epithet, naegelii (Latinization of Naegeli), is derived from Carlos Naegeli, who collected the syntype workers.