Pogonomyrmex eremicus, Johnson, 2025

Pogonomyrmex eremicus NEW SPECIES

( Figures 1–5 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5 , 7 View FIGURE 7 , 8 View FIGURE 8 )

Distribution— Figure 6 View FIGURE 6

Holotype worker [ MACN: CASENT0235268 View Materials ]: ARGENTINA, Mendoza: Departamento Las Heras, Ruta 39 at 4.1 km S boundary of Parque Nacional El Leoncito , 32º06.7’S, 69º21.8’W, 7250 feet ( 2195 m), 31 December 2005 ( R.A. Johnson #3727) GoogleMaps . Paratypes, same data as holotype: MACN (10w), MCZC (3w), MZSP (6w), RAJC (8w, 6 intercastes), USNM (3w). Additional paratype series GoogleMaps , same data as holotype—RAJ#3728: CASC (3w), MACN (12w), RAJC (8w, 5 intercastes), UCDC (3w), USNM (6w); same locale as holotype, but on 8 February, 2010 — RAJ#4419: RAJC (1eq-CASENT0249055) GoogleMaps .

Worker. Diagnosis. Within the P. brevibarbis group, workers of this species are uniquely characterized by the following character combination: (1) small size ( HW < 1.50 mm), (2) bicolored body—mandibles, mesosoma, petiole, postpetiole amber orange to dark reddish-orange; head orangish-brown to brown; first gastral tergum dark brown, (3) eyes large ( MOD = 0.32–0.48 mm; OI = 23.81–33.62), and (4) in profile, petiolar node angulate, anterior margin usually with a crest elevated above posterior margin ( Figures 1 View FIGURE 1 , 2A–B View FIGURE 2 ).

Measurements — holotype ( n = 60 paratypes). HL 1.20 (1.10–1.37); HW 1.11 (0.98–1.31); MOD 0.35 (0.32– 0.48); OMD 0.35 (0.31–0.44); SL 1.04 (0.94–1.39); PNW 0.79 (0.70–0.86); HFL 1.10 (1.03–1.62); ML 1.48 (1.30– 1.64); PW 0.30 (0.27–0.39); PPW 0.39 (0.36–0.46). Indices: CI 92.50 (88.00–98.01); OI 31.53 (23.81–33.62); SI 93.69 (83.67–96.46); HFI 99.10 (100.00–115.52).

Description. In full-face view, head elongate to subquadrate (CI = 88.00–98.01), posterior margin flat, rounding evenly into subparallel lateral margins, head not narrowing anterior to eyes; anterior margin of clypeus flat to weakly emarginate; mandibles with six teeth; antennal scapes reaching to surpassing posterior corners by up to length of first funicular segment (SI = 83.67–96.46); basal flange of scape flattened, moderately well-developed with carinate margin.

In profile, eyes large (OI = 23.81–33.62), situated near middle of head. Promesonotal profile weakly convex, mesopropodeal suture weakly to moderately impressed, propodeum flat to weakly convex; superior propodeal spines long, strongly tapered, acuminate, length less than width between their bases, about one-third to one-half the length of posterior face of propodeum; inferior propodeal spines well-developed, triangular with broad base, acuminate, length approximately 0.5–1.0× that of superior spines; inferior and superior spines usually connected by a translucent lamellar-like process; propodeal spiracles circular, facing posterad. Peduncle of petiole about 0.8× as long as petiolar node, anteroventral margin usually with triangular tooth-like process; petiolar node asymmetrical with anterior surface shorter than posterior surface; apex weakly angulate to angulate, anterior margin usually with a small but distinct crest elevated above flattened posterior surface.

In dorsal view, mesosoma very narrowed at posterior margin near propodeal spines; petiolar node longer than wide, widest near middle, narrowing to a rounded to bluntly angulate anterior margin; postpetiole widest near posterior margin, narrowing to anterior margin; maximal width usually less than maximal length.

Sculpture: dorsum of clypeus with numerous subparallel longitudinal rugae. In full-face view, subparallel longitudinal rugae cover entire cephalic dorsum; medial rugae not diverging to posterior corners but rather continuing to posterior margin; in profile, rugae posterior to eyes not converging to weakly converging on posterior margin, often with weaker secondary rugae, interrugae coriarious to areolate, weakly shining; dorsum of mandibles coarsely rugose; antennal scapes weakly to moderately striate, weakly shining. Dorsum of promesonotum with weak to coarse, irregular, longitudinal trending rugae to coarsely rugoreticulate; anterior margin of pronotum usually carinate; pronotal sides moderately to strongly granulate, dull to weakly shining or with irregular rugae to coarsely rugoreticulate; mesopleura with wavy to strongly irregular rugae traversing posterodorsally; posterior surface of propodeum with transverse irregular rugae, coarsely rugoreticulate, or with longitudinal rugae that traverse anteroventrally on sides; interrugae on mesosoma moderately coriarious, weakly shining to smooth, strongly shining. Dorsum of petiolar node coriarious, weakly shining; anterior surface smooth, shining; in profile, sides smooth, shining to moderately coriarious. Posterior surface of postpetiole weakly coriarious, weakly shining; in profile, sides smooth, shining to weakly coriarious. First gastral tergum smooth, shining. Proxocae and profemorae coriarious, weakly shining.

Setae: antennal scapes with moderate number of nearly appressed to decumbent hairs, longest hairs about 0.75× scape width. In full-face view, sides of head with few short hairs near posterior margin and up to several hairs on malar area; posterior margin with medium-long hairs directed anterad; in profile, dorsal surface of head with moderate number of short to medium-long erect hairs and several long, curved, bristle-like, yellow-brown to brownish hairs that project from anterior margin of clypeus; psammophore poorly-developed, consisting of numerous short to long hairs scattered across ventral surface of head. Dorsum of mesosoma, petiolar node, postpetiole, and gastral terga with moderate number of erect, medium-long to long hairs, longest hairs usually on pronotum with a length of about 0.50× MOD. Procoxae with short to mostly long hairs mostly on anterior surface; profemorae with decumbent to subdecumbent hairs. Nearly all hairs on body (except for legs) brownish to black.

Color: bicolored body—mandibles, mesosoma, petiolar node, postpetiole amber orange to dark reddish-orange; head orangish-brown to dark brown; antennal scapes, first gastral tergum dark brown, often with an orangish hue, more posterior gastral terga sometimes with lighter transverse bands; legs dark brown ( Figures 1 View FIGURE 1 , 2A–B View FIGURE 2 ).

Ergatoid queen. Diagnosis.

This caste is diagnosed by: (1) three ocelli on head and mesosoma lacking morphological structures related to wings, (2) in dorsal view, pronotum large, well-developed, (3) mesoscutum poorly-developed, anterior margin barely surpassing humeral shoulders of pronotum, (4) mesoscutum and mesoscutellum separated by a distinct suture, axilla and tegula fused with adjacent segments, (5) mesoscutellum and metanotum separated by a distinct suture, (6) in profile, petiolar node angulate, anterior margin with a crest elevated above posterior surface, and (6) head and mesosoma dark orangish-brown; gaster blackish ( Figures 2C–F View FIGURE 2 , 3 View FIGURE 3 ).

Measurements —( n = 1 paratype + 3). HL 1.55–1.77; HW 1.49–1.55; MOD 0.43–0.44; OMD 0.37–0.43; SL 1.22–1.35; PNW 1.01–1.04; HFL 1.43–1.59; ML 1.87–1.97; PW 0.40–0.43; PPW 0.47–0.53. Indices: CI 88.14– 96.13; OI 27.92–29.53; SI 79.22–87.25; HFI 94.08–106.71.

Description. Similar to worker except for larger size with ocelli on head, conformation of the mesosoma, and generally darker color.

In full-face view, head elongate to subquadrate (CI = 88.14–96.13) with ocelli, posterior margin flat, rounding evenly into subparallel lateral margins, head not narrowing anterior to eyes; anterior margin of clypeus flat; mandibles with six teeth; antennal scapes not reaching to barely reaching posterior corners (SI = 79.22–87.25); basal flange of scape flattened, moderately well-developed with carinate margin.

In profile, eyes large (OI = 27.92–29.53), situated near middle of head. Axilla and tegula fused with adjacent segments and lacking morphological structures related to wings; mesosomal profile weakly convex with distinct scutoscutellar suture (between mesoscutum and mesoscutellum), mesometanotal suture (between mesoscutellum and metanotum), and metapropodeal suture (between metanotum and propodeum) ( Figures 2C–F View FIGURE 2 ); superior propodeal spines long, length greater than width at base, bluntly tipped, about two-thirds to three-quarters the length of posterior face of propodeum; inferior propodeal spines well-developed, triangular with broad base, acuminate, length approximately one-half that of superior spines; inferior and superior propodeal spines connected by translucent lamellar-like process; propodeal spiracles circular, facing posterad. Peduncle of petiole about 0.8× as long as petiolar node, anteroventral margin usually with triangular tooth-like process; petiolar node asymmetrical with anterior surface shorter than posterior surface; apex weakly angulate to angulate, anterior margin usually with a small but distinct crest elevated above flattened posterior surface.

In dorsal view, pronotum large, well-developed, lateral margins narrowing posterad, rounding evenly to anterior margin; anterior margin of pronotum visible, extending anterad of mesoscutum; mesoscutum poorly-developed, shaped like a parabolic arc with angulate anterior margin; scutoscutellar suture (between mesoscutum and mesoscutellum), mesometanotal suture (between mesoscutellum and metanotum), and metapropodeal suture (between metanotum and propodeum) present and distinct. The scutoscutellar suture is the most variable across queens, ranging from weakly impressed and not crossing the entire segment to well impressed and crossing the entire segment. Petiolar node longer than wide, widest near middle, narrowing to an angulate to spatulate anterior margin; postpetiole widest posterad, narrowing anterad, maximal width and length similar.

Sculpture: dorsum of clypeus with numerous subparallel longitudinal rugae, interrugae smooth, shining to weakly coriarious, weakly shining. In full-face view, subparallel longitudinal rugae cover entire cephalic dorsum; medial rugae not diverging to posterior corners but rather continuing to posterior margin; in profile, longitudinal rugae on malar area, ventrad to eyes, and posterior to eyes with secondary branching posterior to eyes, rugae weakly converging to posterior corners; posterior corners rugose; dorsum of mandibles coarsely rugose; antennal scapes weakly to moderately striate, weakly shining. Dorsum and sides of pronotum coarsely rugoreticulate; dorsum of mesoscutum coarsely rugoreticulate with longitudinal trending rugae; mesoscutellum with coarse longitudinal rugae; anepisternum with few transverse to oblique trending rugae; katepisternum with irregular rugae that traverse posterodorsad; propodeal sides with rugae that become transverse on dorsal surface; propodeal declivity smooth, shining; interrugae on mesosoma coriarious to areolate. In profile, petiolar peduncle weakly sculptured to smooth and shining, petiolar node and postpetiole coriarious to areolate; in dorsal view, petiolar node weakly sculptured, postpetiole coriarious to weakly areolate. First gastral tergum smooth, shining. Procoxae strongly coriarious; profemorae moderately coriarious.

Setae: antennal scapes with moderate number of nearly appressed to decumbent hairs, longest hairs about 0.50× scape width. In full-face view, sides of head with few short hairs near posterior margin and up to several hairs on malar area; posterior margin with medium-long hairs directed anterad; in profile, cephalic dorsum with moderate number of short to medium-long erect hairs and several long, curved, bristle-like, yellow-brown to brownish hairs that project from anterior margin of clypeus; psammophore poorly-developed, consisting of numerous short to long hairs scattered across ventral side of head. Dorsum of mesosoma, petiolar node, postpetiole, and gastral terga with moderate number of erect, medium-long to long hairs, longest hairs on pronotum <0.50× MOD. Procoxae with short to mostly long hairs mostly on anterior surface; profemorae with decumbent to subdecumbent hairs. Nearly all hairs on body (except for legs) brownish to black.

Color: bicoloration less distinct, generally darker in color than workers and intercastes; mandibles, mesosoma, petiolar node, postpetiole dark reddish-orange; head, legs, first gastral tergum orangish-brown to dark blackishorange, anterior margin of first gastral tergum usually more orangish ( Figures 2C–F View FIGURE 2 , 3 View FIGURE 3 ).

Intercaste. Diagnosis.

This caste is diagnosed by: (1) three ocelli on head and mesosoma lacking morphological structures related to wings, (2) head width similar to that of worker (HW = 0.98–1.31 mm vs. HW = 1.11–1.27 mm for intercaste), but smaller than that of ergatoid queens (HW = 1.11–1.27 mm for intercastes vs. HW = 1.49–1.55 mm for ergatoid queens), (3) in dorsal view, pronotum large, well-developed, extending well beyond anterior margin of mesoscutum, (3) mesoscutum poorly-developed, anterior margin barely surpassing humeral shoulders of pronotum, (4) mesoscutum and mesoscutellum fused, separated only by a faint line; axilla and tegula fused with adjacent segments, (5) mesoscutellum and metanotum separated by a distinct suture, (6) in profile, petiolar node angulate, anterior margin with a crest elevated above posterior surface, and (6) head and mesosoma dark orangish-brown; gaster blackish ( Figures 2 View FIGURE 2 G-J, 4).

Measurements —( n = 11 paratypes). HL 1.13–1.34; HW 1.11–1.27; MOD 0.36–0.42; OMD 0.30–0.36; SL 0.86–1.07; PNW 0.78–0.86; HFL 1.21–1.35; ML 1.44–1.62; PW 0.29–0.36; PPW 0.38–0.43. Indices: CI 89.76– 96.03; OI 30.51–36.28; SI 78.18–90.60; HFI 106.03–112.50.

Description. Similar to ergatoid queen except for smaller size, conformation of the mesosoma, and lighter color.

In full-face view, head elongate to subquadrate (CI = 89.76–96.03) with ocelli, posterior margin flat, rounding evenly into subparallel lateral margins, head not narrowing anterior to eyes; anterior margin of clypeus flat; mandibles with six teeth; antennal scapes not reaching to barely reaching posterior corners (SI = 78.18–90.60); basal flange of scape flattened, moderately well-developed with carinate margin.

In profile, eyes large (OI = 30.51–36.28), situated near middle of head. Mesosomal segments mostly lacking sutures and lacking morphological structures related to wings, i.e., axilla and tegula; mesosomal profile weakly convex with mesoscutum and mesoscutellum fused with a faint impression separating the two; metanotum visible as an upturned tongue-like process directed posterad; superior propodeal spines long, length greater than width at base, bluntly tipped, about two-thirds to three-quarters the length of posterior face of propodeum; inferior propodeal spines well-developed, triangular with broad base, acuminate, length approximately one-half that of superior spines; inferior and propodeal spines connected by a translucent lamellar-like process; propodeal spiracles circular, facing posterad. Petiolar peduncle about 0.8× as long as petiolar node, anteroventral margin usually with triangular tooth-like process; petiolar node asymmetrical with anterior surface shorter than posterior surface; apex weakly angulate to angulate, anterior margin usually with a small but distinct crest elevated above flattened posterior surface.

In dorsal view, pronotum large, well-developed, lateral margins narrowing posterad and rounding evenly to anterior margin that extends well beyond anterior margin of mesoscutum; mesoscutum shaped like a parabolic arc with angulate anterior margin; axilla and tegula fused to adjacent segments ( Figures 2G–J View FIGURE 2 ); mesoscutum, mesoscutellum, and metanotum fused: scutoscutellar suture (between mesoscutum and mesoscutellum) absent to a faint line, mesometanotal suture (between mesoscutellum and metanotum) absent to faintly impressed; metanotum shaped like an upturned tongue-like process directed posterad, about 2–3× wider than high; metapropodeal suture (between metanotum and propodeum) deeply impressed; propodeum with an upturned carinate anterior margin. Petiolar node longer than wide, widest near middle, narrowing to an angulate to spatulate anterior margin; postpetiole widest posterad, narrowing anterad, maximal width and length similar.

Sculpture: dorsum of clypeus with numerous subparallel longitudinal rugae, interrugae smooth,shining to weakly coriarious, weakly shining. In full-face view, subparallel longitudinal rugae cover entire cephalic dorsum; medial rugae not diverging to posterior corners but rather continuing to posterior margin; in profile, rugae posterior to eyes not converging to weakly converging on posterior margin, often with weaker secondary rugae, interrugae coriarious to areolate, weakly shining; posterior corners rugose; dorsum of mandibles coarsely rugose; antennal scapes weakly to moderately striate, weakly shining. Dorsum and sides of pronotum coarsely rugose to rugoreticulate; dorsum of mesoscutum coarsely rugoreticulate with longitudinal trending rugae; mesoscutellum with coarse longitudinal rugae; mesopleura with few irregular longitudinal to oblique rugae that traverse posterodorsad; propodeal sides with irregular rugae that traverse posterodorsad becoming mostly transverse on dorsum of propodeum; propodeal declivity smooth, shining; interrugae on mesosoma coriarious to areolate, mostly shining. In profile, petiolar peduncle weakly sculptured to smooth and shining, petiolar node and postpetiole coriarious; in dorsal view, petiolar node coriarious, weakly shining; postpetiole faintly coriarious, shining. First gastral tergum smooth, shining. Procoxae strongly coriarious; profemorae moderately coriarious.

Setae: antennal scapes with moderate number of nearly appressed to decumbent hairs, longest hairs with a length of about 0.75× scape width. In full-face view, sides of head with few short hairs near posterior margin and up to several hairs on malar area; posterior margin with medium-long hairs directed anterad; in profile, cephalic dorsum with moderate number of short to medium-long erect hairs and several long, curved, bristle-like, yellow-brown to brownish hairs that project from anterior margin of clypeus; psammophore poorly-developed, consisting of numerous short to long hairs scattered across ventral side of head. Dorsum of mesosoma, petiolar node, postpetiole, and gastral terga with moderate number of erect, medium-long to long hairs, longest hairs usually on pronotum about 0.50× MOD. Procoxae with short to mostly long hairs mostly on anterior surface; profemorae with decumbent to subdecumbent hairs. Nearly all hairs on body (except for legs) brownish to black.

Color: bicolored body—mandibles, mesosoma, petiolar node, postpetiole amber orange to dark reddish-orange; head orangish-brown to dark brown; antennal scapes, first gastral tergum dark brown, often with an orangish hue, more posterior gastral terga sometimes with lighter transverse bands; legs dark brown ( Figures 2G–J View FIGURE 2 , 4 View FIGURE 4 ).

Male. Diagnosis. This caste is diagnosed by: (1) small size (HW < 0.95 mm; ML < 1.90 mm), (2) light to dark brown body, (3) peduncle of petiole and petiolar node meet at a discernible angle, (4) in profile, petiolar node broadly rounded, and (5) pronotal sides strongly granulate ( Figure 5 View FIGURE 5 ).

Measurements —( n = 11). HL 0.91–1.07; HW 0.79–0.91; MOD 0.38–0.43; OMD 0.13–0.21; SL 0.32–0.61; HFL 0.93–1.45; ML 1.55–1.86; PW 0.27–0.35; PPW 0.36–0.41. Indices: CI 78.50–96.74; OI 42.22–54.54; SI 38.10–67.78; HFI 108.14–174.70.

Additional material examined. ARGENTINA: Mendoza: Depto. Las Heras: 7.0 km E Rt 39 on road to Los Berros, 7160’, Jan 19, 2008 ( RAJC); 18.2 km E Rt 39 on road to Los Berros, 7200’, Jan 19, 2008 ( MCZC; RAJC); Rt 39 at 5.1 km S Parque Nacional El Leoncito, 7050’, Jan 18, 2008 ( MCZC; RAJC) ( Figure 6 View FIGURE 6 ) .

Etymology. The specific epithet, eremicus (from Latin, eremic = of the desert, lonely), is a geographical adjective derived from this species being endemic to the Uspallata-Calingasta Valley, which is an isolated mid-elevation valley in the Monte Desert that lies between the Precordillera on the east and the Andean Cordillera on the west. This valley also has been referred to as the Eremean District, Argentina ( Roig et al. 2009).

Morphometrics. Intercastes were found in only two colonies, and the first analysis compared body size between intercastes in those two colonies and separately between workers from those same two colonies. Intercastes from both colonies were similar in size as were workers based on a MANOVA (intercastes: Wilks' λ = 0.418, F 5, 5 = 1.39, P = 0.363; workers: Wilks' λ = 0.925, F 5, 55 = 0.890, P = 0.495; Box’s M test 15, 13711 df = 32.829, P = 0.013). Workers, intercastes, and ergatoid queens were then all compared using a MANOVA, finding that body size differed significantly across the three castes (Wilks' λ = 0.095, F 10, 138 = 30.86, P << 0.001; Box’s M test 15, 1225 df = 25.083, P = 0.166). Univariate F tests of between-subjects effects within MANOVA showed that all five morphological characters (HW, HL, ML PNW, eye size) differed significantly across the three castes ( F 2, 73 > 65.1, P < 0.001). A post-hoc Duncan’s multiple range test showed that ergatoid queens were significantly larger than workers and intercastes for all five morphological measures ( P <0.05), whereas intercastes were significantly larger than workers for ML, PNW, and eye size, but not for HW and HL ( Table 1).

Morphology also was a significant predictor of caste in the discriminant analysis (Wilks' λ = 0.095 for functions 1 through 2, Chi-square 10 df = 166.8, P <0.001; Wilks’ λ = 0.640 for function 2, Chi-square 4 df = 31.7, P <0.001), correctly classifying 74 of 76 (97.4%) individuals ( Table 2, Figure 7 View FIGURE 7 ). Discriminant function 1 accounted for 91.0% of the variance, while discriminant function 2 accounted for the remaining 9.0% of the variance. The leave-one-out classification method showed that the discriminant model was robust as all individuals were classified the same as in the regular discriminant analysis. The standardized canonical function coefficients indicated that HW and PNW were more important than HL, ML, and eye size for both discriminant functions ( Table 3).

I further investigated morphological measures related to size of the head and mesosoma for workers and intercastes by examining the range of sizes and size-frequency distribution for the four morphological measures. Interestingly, HW, HL, and ML for intercastes had a smaller range of sizes (both minimum and maximum) than for workers (workers: HW = 0.98–1.31; HL = 1.10–1.37; ML = 1.30–1.64; intercastes: HW = 1.11–1.27; HL = 1.13–1.34; ML = 1.44–1.62), whereas PNW for intercastes had a larger minimum size but the maximum size was the same (workers: PNW = 0.70–0.86 mm; intercastes: PNW = 0.78–0.86 mm). That the mean HW and HL did not differ between workers and intercastes was indicated by the similar percent size-frequency distribution exhibited by both castes, whereas the significantly larger mean ML and PNW for intercastes was indicated by their percent size-frequency distribution being shifted to larger sizes ( Figure 8 View FIGURE 8 ). Alternatively, eye area overlapped to a large degree for workers and intercastes (workers = 0.056 –0.087 mm 2; intercastes = 0.078 –0.090 mm 2). Interestingly, workers from one non-type colony had at least some workers that were much larger than those in the two type colonies, but smaller than ergatoid queens except for a barely overlapping HW (workers [ n = 4]: HW = 1.38–1.49 mm; HL = 1.43–1.54 mm; ML = 1.66–1.85 mm; PNW = 0.92–0.96 mm; ergatoid queens ( HW = 1.49–1.55 mm; HL = 1.55–1.77 mm; ML = 1.87–1.97; PNW = 1.01–1.04 mm). GoogleMaps

Biology. Live ergatoid queens were dissected in the laboratory under a dissecting microscope and found to contain an average of 8.3 ± 2.2 ovarioles ( n = 3), a full spermatheca, and yellow bodies which indicate active oogenesis (C. Peeters, pers. comm.). No intercastes were dissected. One nest contained two mated ergatoid queens, while two other colonies contained one ergatoid queen. Overall, intercastes were found in two colonies and ergatoid queens were found in three colonies, but intercastes and ergatoid queens were not found in the same colony. At this point, there is no evidence as to whether intercastes and ergatoid queens occur in the same colony.

Nests consist of small craters ranging from 10–15 cm in diameter, but they sometimes lacked an external tumulus; cryptic nests were located by baiting workers with cookie crumbs, then following them back to the nest. Colonies appear to consist of around 500– 700 workers. A total of 14 males were collected from one colony in January 2008, indicating that mating flights occur during the austral summer.

Pogonomyrmex eremicus appears to be a narrow endemic with a geographic distribution that is restricted to a small portion of the Uspallata-Calingasta Valley along the northern border of Mendoza Province, Argentina ( Figure 6 View FIGURE 6 ). The Uspallata-Calingasta Valley is an isolated, mid-elevation desert valley that lies between the Precordillera on the east and the Andean Cordillera on the west. This valley forms a distinct natural area within the Monte Desert that contains numerous endemic beetle species ( Roig-Juñent et al. 2001). Pogonomyrmex eremicus is known only from silty-clayey soils, relatively hard clayey, saline soils, and deep sandy soils; associated vegetation consisted of Larrea sp. , Atriplex sp. , Lycium sp. , and grasses. Pogonomyrmex eremicus is known from elevations that range from 2135–2200 m, and it occurs in the Southern Andean Steppe ecoregion, as defined by Olson et al. (2001).