Pogonomyrmex sylvestris

Pogonomyrmex sylvestris inhabitits cloud forests at higher elevations (Lattke 1990). Since its description, P. sylvestris has been collected several more times in cloud forests of the eastern Venezuelan Andes close to Boconó, including a nest in a rotten log on the ground. (Lattke 2006)

Identification
Johnson (2015) - Within the P. sylvestris-group, the combination of: (1) six mandibular teeth, (2) eyes with hairs between ommatidia, (3) in profile, anterior margin of postpetiole not meeting helcium at a smooth, continuous angle, (4) in profile, procoxae finely imbricate, (5) femur and tibiae strongly coriarious, dull, and (6) medial clypeal region between antennal insertions with 4–8 coarse, sometimes wavy, longitudinal rugae, interrugae more or less shining uniquely characterize this species.

Pogonomyrmex sylvestris might co-occur with Pogonomyrmex striatinodus and Pogonomyrmex naegelii. Both of the former species occur in mesic forest habitats, while P. naegelii occurs in open, drier habitats. Pogonomyrmex sylvestris is distinguished from P. striatinodus by: (1) hairs between ommatidia, (2) clypeus lacks a medial carina, and (3) in profile, the anterior margin of postpetiole does not meet the helcium at smooth continuous angle. In P. striatinodus: (1) lacks hairs between the ommatidia, (2) the clypeus has a prominent medial carina, and (3) in profile, the anterior margin of postpetiole meets the helcium at smooth continuous angle. Pogonomyrmex sylvestris is distinguished from P. naegelii by: (1) hairs between ommatidia, (2) an elongate, triangular postpetiole, and (3) in profile, the petiolar node is flattened to weakly convex with a crest on the anterior margin that is elevated above the posterior surface. Pogonomyrmex naegelii: (1) lacks hairs between the ommatidia, (2) the postpetiole is nearly globular with the width and length similar, and (3) in profile, the petiolar node is convext and the anterior margin lacks a crest.

Distribution based on Regional Taxon Lists
Neotropical Region: Venezuela.

Biology
Johnson (2015) - Very little is known about the biology of P. sylvestris-group species. All three species are discussed together because they likely share a similar biology. Stray foragers comprise most collections for these three species. Few nests have been located: nests of Pogonomyrmex stefani consisted of a small exposed entrance (Lattke, 2006), one nest of P. sylvestris was in a rotten log (Lattke, 2006), and nests of Pogonomyrmex striatinodus are unknown. Diet and the sexual castes are unknown (except for the male of P. stefani) for all three species.

The P. sylvestris-group and P. sylvestris-group are sister groups that together form a clade that is sister to all other Pogonomyrmex (C.S. Moreau & the author, unpub. data). Consequently, obtaining information on the biology of P. sylvestris-group species (including diet, colony size and structure, phenotype of males and especially queens) would facilitate understanding the early evolution of the genus; queens would be especially interesting to collect given that Pogonomyrmex mayri has ergatoid queens. It is predicted that biology of these species is similar to that of P. mayri, which suggests that colonies are small (no more than several hundred workers) and that their diet consists of mostly dead arthropods and plant parts, but relatively few seeds (Kugler, 1979, 1984; Kugler & Hincapie, 1983).

All three species are known to occur only in northern South America (Venezuela, Colombia, and Ecuador), and they comprise the small group of South American congeners that inhabit mesophilic forests. Pogonomyrmex sylvestris and P. striatinodus are mid-elevation species—P. sylvestris has been collected only in premontane cloud forest habitats of Venezuela at elevations from 1000–1300 m, and P. striatinodus is only known from mesic forests at elevations from 1000–1525 m. Pogonomyrmex sylvestris occurs in the La Costa Xeric Shrublands and Venezuelan Andes Montane Forest ecoregions, and P. striatinodus occurs in Northwestern Andean Montane Forest ecoregion as defined by Olson et al. (2001). Alternatively, P. stefani is only known from two locations in the mesic lowland forests at elevations from 165–470 m, and its geographic distribution may be restricted to the Orinoco watershed of Venezuela (Lattke 2006); it occurs in the Llanos and Pantepui ecoregions as defined by Olson et al. (2001). None of these three species are known to occur proximate to one another.

Castes
Known only from the worker caste.

Nomenclature

 *  sylvestris. Pogonomyrmex sylvestris Lattke, 1991a: 305, figs. 1, 2 (w.) VENEZUELA.

Worker
Johnson (2015) - (n = 4). HL 1.24–1.32; HW 1.16–1.20; MOD 0.20–0.21; OMD 0.30–0.32; SL 0.88–1.03; PNW 0.81–0.84; HFL 1.13–1.34; ML 1.51–1.61; PW 0.21–0.21; PPW 0.42–0.46. Indices: SI 73.95–86.44; CI 90.91–94.40; OI 16.67–17.80; HFI 94.17–113.56. See also Lattke (1991).

Head elongate (CI = 90.91–93.55), widest just posterior to eye; posterior margin weakly concave. Cephalic dorsum rugoreticulate except for several irregular, medial, longitudinal rugae that become rugoreticulate near posterior margin. Cephalic interrugae smooth, shining; vertex rugoreticulate. Anterior margin of clypeus weakly convex with small medial tooth, dorsal surface between antennal insertions with 4–8 coarse, sometimes wavy, longitudinal rugae, interrugae more or less shining. Mandible with six teeth; mandibular dorsum coarsely rugose. Up to several moderately long, curved, bristle-like, yellowish hairs project from anterior margin of clypeus. Eyes small, MOD = 0.15–0.16x HL. In profile, eyes situated anterior to middle of head, OMD = 1.50–1.55x MOD; several short, delicate hairs project from between ommatidia. Antennal scapes moderately long (SI = 82.76–83.74), failing to reach vertex by less than length of basal funicular segment; entire scape with scattered, weak, longitudinal striae, strongly granulate-punctate, dull. Basal flange of scape well-developed with carinate margin. Psammophore poorly-developed, consisting of numerous short hairs (length similar to those on cephalic dorsum) scattered across ventral side of head.

Mesosomal profile strongly convex; all mesosomal surfaces rugoreticulate to vermiculate. Superior propodeal spines long, acuminate, bases not connected by well-defined keel, spines slightly shorter than distance between their bases. Inferior propodeal spines well-developed, acuminate, length similar to that of superior spines but with wider base. Interrugae on mesosoma moderately granulate, weakly shining to smooth, shining. Propodeal spiracles circular facing posterad. In profile, procoxae finely imbricate, dull. Legs strongly granulate-punctate, dull.

Peduncle of petiole about 0.6x as long as petiolar node, anteroventral margin with acuminate spine. In profile, petiolar node asymmetrical with anterior surface about 0.5x as long as posterior surface, apex forming a crest or tooth that is elevated above posterior surface; posterior surface flattened to weakly convex; anterior and lateral surfaces mostly smooth and shining; lateral surface nearly vertical, meeting posterior surface at or near a right angle. In dorsal view, petiolar node elongate (length >2.3x width), sides subparallel, weakly constricted near posterior margin, anterior one-third narrowing to subangulate tip; dorsum coarsely rugoreticulate, interrugae smooth and shining. Dorsum of postpetiole convex in profile, anterior margin with subangulate tip that overhangs connection to helcium; in dorsal view, nearly triangular, widest near posterior margin, narrowing to bluntly rounded anterior margin; lateral margins wider ventrally; dorsum moderately to strongly coriarious to moderately granulate, weakly shining, with several weak longitudinal rugae near anterior margin. First gastral tergum weakly coriarious, weakly shining to smooth and shining.

Short to long, flexuous, yellowish to golden hairs abundant on head; medium to long hairs abundant on mesosoma, petiolar node, postpetiole, gastral terga; longest hairs on head and mesosoma >MOD. Scape with abundant moderately long, suberect hairs; abundant decumbent hairs on funicular segments. Legs with moderately abundant, long, suberect setae. Head and mesosoma dark brown; petiolar node, postpetiole, gaster, legs slightly lighter brown to tan.

Type Material
Johnson (2015) - Holotype worker (not examined), VENEZUELA, Lara: 10 km SSE Barquisimeto (9°58’N 69°17’W), Parque Nacional Terepaima, 1100 m (J. Lattke leg., 13 September 1983).

Etymology
The specific epithet, sylvestris (sylva—Latin for forest), was derived from the type series being collected in cloud forest (premontane rain) habitats in Venezuela.