Pogonomyrmex tenuipubens

Robert A. Johnson, 2015, A taxonomic revision of South American species of the seed-harvester ant genus Pogonomyrmex (Hymenoptera: Formicidae). Part I, Zootaxa 4029 (1), pp. 1-142 : 119-122

Pogonomyrmex tenuipubens

( Figure 62)

Pogonomyrmex (Ephebomyrmex) tenuipubens Santschi, 1936: 403 , fig. 4 (worker). Syntypes examined: 1 worker [FML], 1 worker [NHMB], ARGENTINA, Misiones: Loreto, #2055 (Dr. A. Ogloblin, 19 September 1933). NHMB worker here designated LECTOTYPE [CASENT0281113].

Ephebomyrmex tenuipubens (Santschi) : Kempf, 1972: 106, first combination in Ephebomyrmex. Pogonomyrmex tenuipubens Santschi : Bolton, 1995: 341, revived combination in Pogonomyrmex .

Worker. Diagnosis. Within the P. naegelii -group, the combination of: (1) approximately 16–20 fine, weak, longitudinal rugae between frontal lobes, (2) abundant, very short, delicate hairs on head (including psammophore) and mesosoma, maximal length similar to width of cephalic interrugae uniquely characterize this species ( Figure 62).

Measurements —lectotype (n = 1 paralectotype). HL 1.19 (1.23); HW 1.10 (1.16); MOD 0.27 (0.28); OMD 0.27 (0.27); SL 0.78 (0.75); PNW 0.77 (0.80); HFL 1.07 (1.15); ML 1.37 (1.38); PW 0.35 (0.37); PPW 0.50 (0.50). Indices: SI 70.91 (64.66); CI 92.44 (94.31); OI 24.55 (24.14); HFI 97.27 (99.14).

Redescription. Head elongate (CI = 92.44–94.31), widest just posterior to eye; posterior margin flat. Longitudinal rugae on cephalic dorsum fine and dense, slightly wavy; approximately 16–20 fine, longitudinal rugae between frontal lobes; in full-face view, medial rugae not diverging toward posterior corners of head. In profile, area posterior to eyes rugose, rugae converging between posterior margin of eye and vertex. Cephalic interrugae moderately granulate, weakly shining; vertex rugose. Anterior margin of clypeus moderately concave, dorsal surface with numerous fine, subparallel, longitudinal rugae; lateral lobe of clypeus lacking small lobe that projects from anterior margin of antennal fossa. Mandible with five teeth; mandibular dorsum coarsely rugose. Up to several moderately long, curved, bristle-like, yellow-brown to brownish hairs project from anterior margin of clypeus. MOD = 0.23x HL. In profile, eyes situated anterior to middle of head, OMD = 0.96–1.00x MOD. Antennal scapes moderately long (SI = 64.66–70.91), failing to reach vertex by approximately 2.0x length of basal funicular segment; entire scape strongly striate, dull. Basal flange of scape flattened, moderately well-developed with carinate margin. Psammophore poorly-developed, consisting of numerous very short hairs scattered across ventral side of head.

Mesosomal profile weakly convex; all mesosomal surfaces with weak, wavy to irregular rugae or rugoreticulate. Mesoepinotal sulcus not impressed. Dorsum and sides of pronotum with irregular rugae to rugoreticulate. Dorsum of mesonotum with irregular transverse rugae, mesopleura with irregular rugae angling posterodorsally; dorsum of propodeum with wavy, transverse rugae that traverse anteroventrally. Propodeum with moderately long, bluntly tipped spines connected by well-defined keel; spine length approximately 0.5-0.6x distance between their bases. Inferior propodeal spines well-developed, acuminate, length approximately 0.6x that of superior spines, width at base greater than length of superior spines; inferior and superior spines connected by a weak ruga. Propodeal spiracles ovoid to circular facing posterad. Interrugae on mesosoma moderately granulate, weakly shining. Legs weakly coriarious, weakly shining.

Peduncle of petiole about 0.7x as long as petiolar node, anteroventral margin weakly convex but lacking triangular process. In profile, petiolar node asymmetrical with anterior surface shorter than posterior surface, apex weakly rounded, anterior surface meeting peduncle at a right angle. In dorsal view, petiolar node longer than wide, widest near middle, narrowing to rounded anterior margin; maximal width of posterior surface slightly greater than distance between tips of superior propodeal spines; posterior surface and sides with weak transverse to oblique rugae, interrugae moderately granulate, weakly shining. Dorsum of postpetiole convex in profile; robust in dorsal view, widest at or near posterior margin, margins of posterior one-half mostly parallel, anterior one-half narrowing to broadly rounded anterior margin, maximal width greater than length, dorsum and sides moderately to strongly granulate-punctate, dull. Ventral process of postpetiole large, bulbous, height similar to dorsal portion of postpetiole. First gastral tergum smooth and strongly shining.

Short, thin, delicate, suberect, whitish pilosity moderately abundant on head, mesosoma, petiolar node, and postpetiole, hairs rarely longer than width of cephalic interrugae; one very long hair on each frontal lobe, length>MOD, and one to several long, coarse hairs occasionally present on posterior margin of head and pronotum. Moderately abundant short, appressed pilosity on scape plus several longer suberect hairs; abundant decumbent hairs on funicular segments. Legs with moderately abundant appressed setae; gastral terga with sparse, appressed, thin, delicate hairs that are longer than those on rest of body; posterior margin of second gastral tergum with several long erect hairs>MOD. Concolorous tan to tannish-brown with darker brownish gaster ( Figure 62).

Queen. Unknown .

Male. Unknown .

Additional material examined. PARAGUAY: Caaguazú: Pastoreo (see Fowler, 1981; not examined) ( Figure 56 C).

Etymology. Santschi named this species (Latin, tenui- = thin, narrow, or slender plus pubens = hair of an adolescent) for the fairly abundant, extremely short, fine pubescence over most of the body.

Discussion. Pogonomyrmex tenuipubens co-occurs with both P. abdominalis and P. naegelii . Pogonomyrmex tenuipubens can be distinguished from these two species based on the following characters: (1) P. tenuipubens has approximately 16–20 fine, weak, longitudinal rugae between the frontal lobes, and (2) very short, thin, delicate hairs on head (including psammophore) and mesosoma, their maximal length similar to width of cephalic interrugae. Both P. abdominalis and P. naegelii have: (1) approximately 8–10 coarse longitudinal rugae between frontal lobes, and (2) hairs on head (including psammophore) and mesosoma longer and coarse, their maximal length much longer than width of cephalic interrugae.

Biology. Pogonomyrmex tenuipubens appears to be uncommon given the very few times that it has been collected. Kusnezov (1951) and the author searched the type locality for this species: both found numerous colonies of P. naegelii but none of P. tenuipubens . Little is known about the biology of P. tenuipubens , but it is probably similar to that of P. naegelii .

Pogonomyrmex tenuipubens appears to inhabit low elevation sites (the type locality is at an elevation of about 65 m), and it is only known from the Alto Paraná Atlantic Forest ecoregion as defined by Olson et al. (2001) ( Figure 56 C).