Pogonomyrmex wilsoni, 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 : 223-227

Pogonomyrmex wilsoni NEW SPECIES

( Figure 113 )

Distribution—112B

Holotype worker [ MNNC: CASENT0923341 ]: CHILE, Atacama Region, Huasco Province : Fdo. Marañón, 26 September 1977 (O. León coll.).

Worker diagnosis. Workers of this species are uniquely characterized by the following combination of features: (1) bicolored: head and gaster ferruginous orange; mesosoma blackish to black except for orangish to dark orangish pronotum, (3) anterior one-half to most of first gastral tergum moderately coriarious, dull to weakly shining, lacking striae, (4) superior propodeal spines long, length greater than distance between their bases, (5) rugae on cephalic dorsum relatively closely spaced, rugae on frontal lobes weakly converging, 1–2 pairs of medial rugae meet and end at posterior margin of frontal triangle, and (6) eyes relatively small (MOD/HL = 0.18–0.19) and situated relatively far from malar area (OMD/MOD = 1.52–1.53) ( Figure 113 ).

Measurements— holotype. HL 2.10; HW 2.27; MOD 0.38; OMD 0.58; SL 1.54; PNW 1.20; HFL 2.24; ML 2.25; PW 0.35; PPW 0.78. Indices: SI 67.84; CI 108.10; OI 16.74; HFI 98.68.

Description. Head wider than long (CI = 108.10), widest just posterior to eyes; posterior margin flat in fullface view. Longitudinal rugae on cephalic dorsum prominent, wavy to irregular, narrowly spaced; rugae on frontal lobes weakly converging, medial 1–2 pair of rugae meet and end at posterior margin of frontal triangle. In full-face view, medial rugae continuing to posterior margin of head; interrugae strongly granulate, dull, with a weakly beaded appearance. Posterior corners rugose, interrugae weakly granulate, weakly shining. Anterior margin of clypeus moderately concave, dorsum with numerous subparallel, longitudinal rugae. Numerous long, curved, bristle-like, cream-colored to light yellowish macrochaetae project from anterior margin of clypeus and basolateral margin of mandibles. Mandibles with six teeth; mandibular dorsum coarsely rugose. MOD ranging from 0.18–0.19× HL. In profile, eyes situated slightly anterior to middle of head, but relatively far from malar base (OMD = 1.52–1.53× MOD). In full-face view, eyes protruding slightly beyond lateral margins of head. Antennal scapes relatively long (SI = 67.84), just failing to reach to reaching posterior corners of head. Antennal scapes with weak longitudinal striae, interstriae weakly shining; basal flange well developed with carinate margin. Psammophore well developed.

Mesosomal profile flat to weakly convex; all mesosomal surfaces with prominent subparallel-parallel, irregular rugae to rugoreticulate. In dorsal view, humeral shoulders of pronotum enlarged, rounded. Dorsum of mesonotum rugoreticulate, pronotum rugoreticulate posterad with up to several irregular, transverse rugae along anterior margin that continue posteroventrally on pronotal sides. Promesonotal suture absent. Rugae on most of anepisternum traversing in various directions to weakly rugoreticulate; irregular, posterodorsally trending rugae on rest of mesopleura; irregular transverse rugae on dorsum of propodeum traverse ventrally or anteroventrally on sides. Superior propodeal spines long, length greater than distance between their bases, tips bluntly acuminate, spines connected by well defined keel. Inferior propodeal spines wider than high, apex weakly rounded to bluntly acuminate. Propodeal spiracles narrowly ovate facing posterad. Interrugae on mesosoma weakly to strongly granulate-punctate, dull to weakly shining. Legs weakly shining to shining.

Peduncle of petiole about 0.8× as long as petiolar node, anteroventral margin flat to weakly curved, lacking a rounded process. In profile, posterior surface of petiolar node weakly convex; petiolar node asymmetrical with anterior surface shorter than posterior surface, apex weakly rounded. In dorsal view, petiolar node longer than wide, widest near rounded anterior margin, narrowing posterad. Posterior surface of petiolar node rugoreticulate posterad, anterior portion with irregular oblique to arcuate rugae the meet medially. Dorsum of postpetiole convex in profile; in dorsal view, widest near posterior margin, narrowing anterad, maximum width and length about equal. Rugae on dorsum of postpetiole weak, finer than those on posterior surface of petiolar node; rugae mostly longitudinal anterad, diverging to posterior corners posterad; interrugae on both surfaces weakly to moderately coriarious, weakly dull to weakly shining. First gastral tergum moderately to strongly coriarious over anterior one-half to most of segment, posterior margin mostly weakly shining to smooth and shining.

Erect, delicate, cream-colored pilosity moderately abundant on head, variable in length, many hairs 0.3–0.4× MOD. Moderately abundant suberect to semidecumbent hairs on scapes; abundant decumbent hairs on funicular segments. Legs with moderately abundant suberect to decumbent whitish to light yellowish setae. Head, petiole, postpetiole, gastral terga with moderately dense, erect whitish to yellowish setae that vary in length, at least several hairs approaching to exceeding MOD. Head and gaster orangish-brown; pronotum orangish to orangish-black; rest of mesosoma, petiolar node, postpetiole, legs blackish to black ( Figure 113 ).

Queen. Unknown.

Male. Unknown.

Additional material examined. None.

Etymology. The species is named to honor Dr. E. O. Wilson, who has made numerous contributions to the study of ants, and for his support to study Pogonomyrmex in South America.

Discussion. Pogonomyrmex wilsoni is a distinctive species that is not likely to be confused with any congeners. The combination of: (1) head and gaster orangish; mesosoma black with an orangish pronotum, (2) long superior propodeal spines, and (3) anterior one-half or more of first gastral tergum moderately coriarious, lacking striae, separate P. wilsoni from all congeners except P. santschii . Pogonomyrmex wilsoni is separated from P. santschii by: (1) larger (HW> 2.25 mm), (2) eyes placed relatively far from malar area (OMD/MOD> 1.50), (3) rugae between frontal lobes weakly converging, 1–2 pair of medial rugae meet and end at posterior margin of frontal triangle, (4) up to several irregular transverse rugae along anterior margin of pronotum that continue posteroventrally on sides of pronotum. In P. santschii : (1) smaller (HW <2.05 mm), (2) eyes placed relatively close to malar area (OMD/MOD <1.25), (3) rugae between frontal lobes subparallel-parallel, and (4) rugae along anterior margin of pronotum strongly irregular to rugoreticulate, never transverse, sides of pronotum rugoreticulate.

The type locality is uncertain as it was only given as Atacama: Fdo. Marañón. Fdo. is an abbreviation for Fundo, which is a country estate or farm. Riso Patron (1924) lists four locations for Marañon in Chile, but none of them are given as Fundo. All four locales are proximate to one another (70 o 43-47’S; 28 o 27-30’W), and all are indicated to be a short distance north of Vallenar. Muñoz-Schick (2008) also shows Marañon to be approximately 10 kilometers north of Vallenar, and this is presumed to be the type locality.

Biology. Nothing is known about the biology of P. wilsoni . Based on the above estimate, the type locality is at an elevation of approximately 570 m. This species occurs in the Chilean matorral ecoregion, as defined by Olson et al. (2001) ( Figure 112B ).

Figures

FIGURE 112. Geographic distribution of: (A) Pogonomyrmex weiseri, and (B) P. wilsoni. The large black circle in each panel denotes the type locality.

FIGURE 113. Photographs of Pogonomyrmex wilsoni holotype worker: (A) frontal view of head, (B) lateral view of body, and (C) dorsal view of body (CASENT0923341). Photographs by Michele Esposito from www.AntWeb.org.