Patagonomyrmex laevigatus, Johnson, Robert A. & Moreau, Corrie S., 2016

Johnson, Robert A. & Moreau, Corrie S., 2016, A new ant genus from southern Argentina and southern Chile, Patagonomyrmex (Hymenoptera: Formicidae), Zootaxa 4139 (1), pp. 1-31 : 17-22

Patagonomyrmex laevigatus NEW COMBINATION

( Figures 6–8 )

Pogonomyrmex (Ephebomyrmex) laevigatus Santschi, 1921: 97 (worker). Syntypes examined: 5 workers [MACN], 2 workers [ZSM], #1077, CHILE, Llanqihue Province: Cayutué (Dr. Wolffhügel leg.); Kusnezov, 1949: 301 (male, in key). MACN worker here designated LECTOTYPE [CASENT0217258].

Ephebomyrmex laevigatus (Santschi) ; Kusnezov, 1960: 354, first combination in Ephebomyrmex .

Pogonomyrmex laevigatus Santschi ; Snelling & Hunt, 1976: 75, revived combination in Pogonomyrmex .

Worker. Diagnosis. This species is uniquely characterized by the following combination of features: (1) longitudinal rugae on cephalic dorsum rarely continue to posterior margin, (2) interrugae on cephalic dorsum and dorsum of promesonotum mostly smooth and shining, (3) posterior surface of petiolar node smooth and shining, (4) inferior propodeal spines triangular, height and width similar, notably shorter than superior spines, and (5) body mostly concolorous dark brownish-black to black ( Figure 6 ).

Measurements. Lectotype (n = 12). HL 1.18 (1.11–1.24); HW 1.06 (0.97–1.13); MOD 0.28 (0.24–0.30); OMD 0.23 (0.20–0.25); SL 0.96 (0.84–0.95); PNW 0.73 (0.66–0.76); HFL 1.10 (0.99–1.16); ML 1.57 (1.32–1.53); PW 0.28 (0.25–0.31); PPW 0.42 (0.41–0.49). Indices: SI 90.57 (84.07–97.94); CI 89.83 (78.86–92.79); OI 26.42 (23.76–27.84); HFI 103.77 (97.27–113.40).

Redescription. Longitudinal rugae on cephalic dorsum prominent, weakly wavy, widely-spaced, beginning on frontal lobes but rarely extending to posterior margin; posterior margin flat in full-face view. Wavy to irregular, often discontinuous rugae arc from mandibular margins to frontal lobes and traverse longitudinally above and below eyes, usually terminating before vertex; lateral rugae weaker than those on cephalic dorsum. Interrugae on cephalic dorsum smooth and shining; vertex and posterior margin of head weakly granulate-punctate, weakly shining to smooth and shining. Dorsum of clypeus with several moderately strong, subparallel, longitudinal rugae. Mandible with six teeth; mandibular dorsum strongly rugose. MOD ranging from 0.20–0.25x HL. In profile, eyes situated anterior to middle of head, OMD = 0.76–0.93x MOD. In full-face view, eyes protruding slightly beyond lateral margins of head. Antennal scapes long (SI = 84.07–97.94), surpassing vertex by less than length of second funicular segment; scapes weakly to moderately granulate-punctate, often with faint striae, weakly shining; basal flange moderately well-developed with carinate margin.

Mesosomal profile strongly convex; dorsum of promesonotum smooth and shining; longitudinal rugae on mesospleura and metapleura wavy to irregular, interrugae weakly to moderately granulate-punctate, weakly shining. Promesonotal suture absent to weakly impressed on occasional individuals. Superior propodeal spines long, narrowing to blunt tip, length rarely>0.7–0.8x the distance between their bases; inferior propodeal spines moderately well-developed, triangular, acuminate, length and width similar, distinctly shorter than superior spines. Propodeal spiracles weakly ovate to circular facing posterad. Legs weakly granulate, weakly shining to smooth and shining.

Peduncle of petiole about as long as petiolar node, anteroventral margin of peduncle of petiole with a small, acuminate spine. In profile, posterior surface of petiolar node weakly convex; petiolar node asymmetrical with anterior surface shorter than posterior surface, apex bluntly angulate to rounded. In dorsal view, petiolar node longer than wide, sides subparallel, narrowing to rounded to bluntly angulate anterior margin. Dorsum of postpetiole convex in profile; in dorsal view, widest near posterior margin, narrowing to anterior margin, maximum width and length similar; posterior surface and sides of petiolar node and dorsum and sides of postpetiole smooth and shining; first gastral tergum smooth and shining.

Erect, short to long, copperish-brown hairs abundant on head, one to few approaching to slightly exceeding MOD. Moderately abundant subdecumbent to decumbent hairs on antennal scapes; abundant decumbent to appressed hairs on funicular segments. Legs with moderately abundant subdecumbent to decumbent setae. Mesosoma with moderately dense, medium to long, erect setae, longest approaching MOD; petiolar node, postpetiole, gastral terga with moderately dense, erect setae, mostly similar in length, longest notably shorter than MOD. Body mostly concolorous dark brownish-black to black ( Figure 6 ).

Queen. Diagnosis. This caste is diagnosed by: (1) caste-specific morphology of the mesosoma related to wingbearing and presence of ocelli on head, (2) mesoscutum and mesoscutellum smooth and shiny, (3) inferior propodeal spines triangular, much shorter than superior propodeal spines, and (4) body mostly concolorous dark brownish-black to black ( Figure 7 ).

Measurements. (n = 2). HL 1.25–1.30; HW 1.02–1.12; MOD 0.26–0.33; OMD 0.20–0.24; SL 0.80–0.91; PNW 0.92–0.93; HFL 1.08–1.12; ML 1.56–1.63; PW 0.32–0.34; PPW 0.51–0.53. Indices: SI 71.43–89.22; CI 78.46–89.60; OI 25.49–29.46; HFI 100.00–105.88.

Description. With caste-specific morphology of the mesosoma related to wing-bearing and presence of ocelli on head. In full-face view, head elongate (CI = 78.46–89.60), posterior margin flat. Longitudinal rugae on cephalic dorsum extending to near posterior margin, rugae fine and dense medially, density decreasing laterally and becoming weakly rugoreticulate; vertex weakly rugoreticulate. Interrugae on cephalic dorsum weakly to moderately coriarious, weakly shining. Mandible with five to six teeth, dorsal surface convex, coarsely rugose, anterior margin flat to weakly convex. Psammophore poorly-developed, consisting of short to medium-length hairs scattered across ventral surface of head.

Mesoscutum, mesoscutellum, dorsum of propodeum smooth and shining; mesopluera, metapluera, propodeal sides longitudinally rugose; interrugae weakly coriarious, weakly shining. Superior propodeal spines welldeveloped with blunt tips, inferior propodeal spines triangular, wider than tall, about 0.5–0.7x the length of superior spines. In profile, petiolar node asymmetrical with anterior surface shorter than posterior surface, apex subangulate. In dorsal view, postpetiole wider than long. Posterior surface of petiolar node and dorsum of postpetiole weakly coriarious, weakly shining to smooth and shining. First gastral tergum smooth and shining. Most body surfaces with moderately abundant suberect to erect, yellowish setae; gaster with fewer setae. Entire body dark brownish-black to black; legs, posterior gastral terga often with brownish infusion ( Figure 7 ).

Male. Diagnosis. This caste is diagnosed by: (1) mesopleura, metapleura, pronotal sides and/or dorsum of propodeum with weak to strong rugae, (2) no hairs on ventral surface of head or those protruding from mandibles approach MOD, and (3) in profile, juncture between cephalic dorsum and posterior declivity (near posterior margin of ocelli) weakly angulate to rounded, posterior declivity weakly convex to weakly concave ( Figure 8 ).

Measurements —(n = 4). HL 1.06–1.19; HW 0.93–1.01; MOD 0.39–0.43; OMD 0.14–0.18; SL 0.29–0.35; HFL 1.15–1.25; ML 1.62–1.73; PW 0.27–0.30; PPW 0.40–0.43. Indices: SI 30.21–37.63; CI 80.87–90.57; OI 41.58–46.24; HFI 123.66–126.88.

Additional material examined. ARGENTINA: Chubut: Lago Fontana, Mar 4, 1948 ( FML). Río Negro: Tronador, no date ( MACN); San Carlos de Bariloche, Feb 8, 1964 ( MZUSP). Neuquén: Hua Hum, no date & Jan 25, 1949 ( FML; MHNG). CHILE: La Araucanía: Pucón, Volcán Villarica,> 1000 m, Dec 3, 1989 ( LACM). Los Lagos: Petrohue, Mar 1922 ( MLPA) ( Figure 5 B).

Etymology. The specific epithet, laevigatus (from Latin, laevigatus = smooth, glossy), is derived from the smooth, shiny surface over most of the body of this species.

Discussion. Patagonomyrmex laevigatus co-occurs with Pa. angustus and Pa. odoratus . Patagonomyrmex laevigatus is distinguished from Pa. angustus based on the following characters: (1) dorsum of promesonotum and posterior surface of petiolar node smooth and shining (both structures strongly granulate in Pa. angustus ), and (2) inferior propodeal spines triangular, shorter than superior propodeal spines (inferior propodeal spines elongate, length similar to that of superior propodeal spines in Pa. angustus ). In his key, Kusnezov (1951) separated Pa. laevigatus from Pa. odoratus based on the mostly concolorous blackish to black body (body orangish-brown with the gaster slightly darker in Pa. odoratus ). Kusnezov (1949, 1951) also indicated that longitudinal rugae on the cephalic dorsum were coarser in Pa. laevigatus than in Pa. odoratus , but I could not discern this difference. He also indicated the angle between the peduncle of the petiole and the anterior surface of the petiolar node was more rounded in Pa. laevigatus , and more angulate in Pa. odoratus . This character appeared to be very subtle and inconsistent, and thus was not a useful diagnostic trait. We did not find any morphological measurements that could be used to separate Pa. laevigatus from its two congeners.

Figures

FIGURE 5. Geographic distribution of: (A) Patagonomyrmex angustus (Mayr), (B) Patagonomyrmex laevigatus (Santschi), and (C) Patagonomyrmex odoratus (Kusnezov); the larger filled black circle in each panel (when present) denotes the type locality.

FIGURE 6. Photograph of Patagonomyrmex laevigatus (Santschi) worker: (A) frontal view of head, (B) lateral view of body, (C) dorsal view of body (CASENT 0103393). Photos taken by April Nobile and www. antweb. com.

FIGURE 7. Photograph of Patagonomyrmex laevigatus (Santschi) alate queen: (A) frontal view of head, (B) lateral view of body, (C) dorsal view of body (CASENT 0280992). Photos taken by Estella Ortega and www. antweb. com.

FIGURE 8. Photograph of Patagonomyrmex laevigatus (Santschi) male: (A) frontal view of head, (B) lateral view of body, (C) dorsal view of body (CASENT 0914809). Photos taken by Michele Esposito and www. antweb. com.