Pogonomyrmex mayri

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 : 98-104

Pogonomyrmex mayri

( Figures 49–51)

Pogonomyrmex (Janetia) mayri Forel, 1899 a: 61 (worker, male, in footnote). Syntypes examined: 2 workers [AMNH], 2 workers, 1 male [NMW], 3 workers [USNM], 3 workers [ZSM], COLOMBIA, Magdalena: Ciénega; Wheeler & Wheeler, 1953: 112 (larvae); Kugler, 1979: 170, figs. 1–8 (queen). NMW worker here designated LECTOTYPE [CASENT0173358].

Pogonomyrmex (Forelomyrmex) mayri Forel : Wheeler, 1913: 80 (first combination in Forelomyrmex). Pogonomyrmex mayri Forel : Brown, 1973: 180 (Forelomyrmex synonomized under Pogonomyrmex [provisional]); Snelling, 1981: 395 (Forelomyrmex synonomized under Pogonomyrmex ).

Worker. Diagnosis. See above.

Measurements —lectotype (n = 12). HL 2.12 (1.78–2.19); HW 1.90 (1.63–1.94); MOD 0.31 (0.26–0.30); OMD 0.47 (0.45–0.55); SL 1.63 (1.50–1.74); PNW 1.47 (1.13–1.34); HFL 2.60 (2.03–2.71); ML 2.55 (2.13–2.49); PW 0.37 (0.34–0.43); PPW 0.69 (0.54–0.70). Indices: SI 85.79 (77.72–104.82); CI 89.62 (87.69–96.63); OI 16.32 (14.51–16.96); HFI 136.84 (121.56–140.41). See also Kugler (1979).

Redescription. Head weakly elongate to elongate (CI = 87.69–96.63), widest just posterior to eyes, narrowing to vertex; posterior margin strongly concave medially, broadly V-shaped. Cephalic dorsum, sides, and vertex rugose, rugae variable in height; in full-face view, medial rugae not diverging toward posterior corners of head. Cephalic rugae deeply incised, interrugae strongly granulate, dull. Anterior margin of clypeus convex with medial triangular tooth, dorsum of clypeus with numerous subparallel, wavy, longitudinal rugae similar to those on cephalic dorsum. Mandible with six teeth; mandibular dorsum coarsely rugose. Up to several moderately long, curved, bristle-like, amber to brownish hairs project from anterior margin of clypeus and basolateral margin of mandibles. Eyes small, MOD = 0.13–0.17x HL. In profile, eyes situated anterior to middle of head, OMD = 1.52– 2.00x MOD; no hairs project from between ommatidia. Antennal scapes long (SI = 77.72–104.82), reaching to surpassing vertex by less than length of basal funicular segment; entire scape with weak longitudinal striae, interstriae strongly granulate, dull. Basal flange of scape well-developed with recurved, carinate margin. Psammophore poorly-developed, consisting of numerous short hairs scattered across ventral side of head.

Mesosomal profile strongly convex; all mesosomal surfaces with wavy, deeply incised rugae that vary in height. Transverse rugae on pronotal sides curving dorsally, anteriorly, and posteriorly, transverse rugae on pronotal collar; dorsum of propodeum with transverse rugae that traverse to propodeal spiracle then angle posterad over metapleural lobe. Superior propodeal spines long, acuminate, bases connected by well-defined keel, spines longer than distance between their bases; inferior propodeal spines well-developed, acuminate, length approximately 0.3–0.5x that of superior spines; declivitous surface of propodeum transversely rugose. Propodeal spiracles narrowly ovate facing posterad. Rugae and interrugae on mesosoma strongly granulate, dull. Legs strongly granulate, dull.

Peduncle of petiole about 0.5x as long as petiolar node, anteroventral margin varying from broad translucent process to triangular acuminate spine. In profile, petiolar node asymmetrical with anterior surface approximately one-half as long as posterior surface, apex angulate, posterior surface flattened; all surfaces rugose. In dorsal view, petiolar node elongate, approximately twice as long as wide, lateral margins weakly convex posteriorly, nearly vertical medially, concave anteriorly, anterior one-third narrowing to acuminate tip; anterior portion of posterior surface weakly depressed below margins. Dorsum of postpetiole convex in profile, anterior margin narrowing to helcium; robust in dorsal view, longer than wide; widest near posterior margin, narrowing to truncate anterior margin; dorsum and sides coarsely rugose; ventral process strongly granulate, dull. Rugae and interrugae on posterior surface of petiolar node and dorsum of postpetiole strongly granulate, dull. First gastral tergum with fine longitudinal striae, dull.

Short to long, erect, amber to brownish hairs abundant on head, longest>MOD; mostly medium-length hairs abundant on mesosoma, petiole node, postpetiole, and gastral terga, longest approaching MOD. Scape with abundant medium-length, suberect hairs; abundant subdecumbent hairs on funicular segments. Legs with moderately abundant, short to medium-length, suberect setae. Body concolorous dark reddish-brown to dark brownish-black, or with postpetiole, gaster, legs slightly lighter reddish-brown ( Figure 49).

Ergatoid Queen. Diagnosis. See above.

Measurements —(n = 2). HL 1.50–1.51; HW 1.44–1.52; MOD 0.27–0.28; OMD 0.43–0.47; SL 1.03–1.14; PNW 1.14–1.18; HFL 1.64–1.65; ML 1.99–2.02; PW 0.70–0.74; PPW 1.20–1.25. Indices: SI 71.53–75.00; CI 96.00–100.66; OI 18.42–18.75; HFI 108.55–113.89. See also Kugler (1979) ( Figure 50).

Male. Diagnosis. This caste is diagnosed by: (1) CI <75.0, (2) neck elongate, flattened dorsally (3) in dorsal view, postpetiole>1.5x as long as wide, (4) in dorsal view, petiolar node elongate (>2x as long as wide), (5) funiculi with numerous suberect hairs, and (6) notauli absent, presence indicated only by short black lines that indicate underlying apophyses ( Figure 51).

Measurements —(n = 10). HL 1.49–1.72; HW 1.06–1.23; MOD 0.30–0.36; OMD 0.15–0.19; SL 0.22–0.37; HFL 1.47–2.03; ML 1.96–2.41; PW 0.28–0.36; PPW 0.50–0.65. Indices: SI 20.18–34.91; CI 66.25–74.52; OI 27.52–32.08; HFI 134.51–178.30. See also Kugler (1979).

Additional material examined. COLOMBIA: Atlantico: Puerto Colombia, 1970 (USNM). Bolívar: Santa Marta Mountains, Jul 7, 1920 & 1954 (LACM; MCZ; USNM). Cesar: Santa Marta Mountains, Valledupar, Jul 4, 1920 (LACM). Magdalena: Mamatoco, Jun 16, 1976 (LACM; MCZ); Río Frio, Feb 1924 & Mar 20, 1928 (LACM; MCZ; USNM); 5 km SE Río Frio, 50–200 m, Aug 15, 1985 (LACM); 2 km E Orihueca, 20 m, Aug 17, 1985 (LACM); Parque Nacional Tayrona, Guairaca, Mar 11, 1977 (LACM); Parque Nacional Tayrona, near Neguanje, 60 m, Jun 30, 1976 (MCZ); Santa Ana, Feb 1924 (USNM); Manantial, May 29, 1976 (MCZ); Cienega, no date (MZUSP; USNM); Digrera, base of mountains near Santa Marta, 100 m, Aug 23, 1976 (LACM; MCZ). Prov. Unknown : Santa Marta Mountains, Jul 31, 1920 (MCZ). Questionable locales: VENEZUELA: no loc, no date (FML; MCZ). Taber (1998) indicated that he had examined a specimen from Guyana (MCZ), but these specimens were unavailable to examine ( Figure 52).

Etymology. This species was named to honor Dr. Gustav Mayr, who erected the genus Pogonomyrmex in 1868.

Discussion. Pogonomyrmex mayri is a distinctive species that is easily diagnosed by the above characters. Pogonomyrmex naegelii is the only congener known to occur in Colombia.

Biology. Pogonomyrmex mayri is one of the more well-studied South American species of Pogonomyrmex . This is a phylogenetically basal species in the genus that is most closely related to P. sylvestris -group species (C.S. Moreau & R.A. Johnson, unpub. data).

Nests are typically located in soil at the base of trees or shrubs, or occasionally in cracks at the base of rocky outcrops or high on sandy beaches. Nests have one large (1–3 cm diameter), irregularly-shaped entrance, and the nest is normally covered by dry leaves, a log, or a stone; the nest lacks a crater, mound, or tumulus. Nests contain two to three chambers and range from 15–22 cm deep. Nest density ranges from approximately 50–150/ha; density decreases at elevations>100 m (Kugler & Hincapie, 1983).

Workers of P. mayri are diurnal scavengers that forage on the surface of the leaf litter or bare soil. Diet varies seasonally; more insects (especially termites and isopods) are harvested during the wet season (probably because of increased availability), while flower and leaf fragments are more commonly harvested during the dry season. Dead and dry arthropods comprise>50% of the harvested items in both seasons, but larger insects that struggle are avoided; seeds account for a small portion of the diet (ca. 10%) regardless of season. Colonies are small and consist of from 200–900 workers plus 25–270 larvae and pupae, and up to 28 males. Thus, overall colony size ranges from 284–1020 individuals (Kugler, 1984; Kugler & Hincapie, 1983).

No information is available on timing or location of mating flights or method of colony founding. However, males are relatively common in nest excavations, and they have been collected on vegetation outside the nest in March, April, June, September, October, and November; this suggests that P. mayri has a very different type of mating flight and mating behavior than is known for all congeners. Colonies have one ergatoid queen (known from 2 of 10 excavated colonies). Nothing is known about production of ergatoid queens (Kugler & Hincapie, 1983). Interestingly, ocelli were not visible on either of two examined ergatoid queens indicating that the ocelli are vestigial or absent, and Kugler (1979) did not mention ocelli in his description of the ergatoid queen.

The geographic range of P. m ay r i appears to be restricted to desert and dry deciduous forest habitats, mostly below 200 m, on the northwestern, western, and possibly southern end of the Sierra Nevada de Santa Marta, but it is also known to occur in more mesic habitats at elevations up to 835 m (Guerrero & Sarmiento, 2010; Kugler, 1979, 1984; Kugler & Hincapie, 1983). Pogonomyrmex mayri is only known to occur in northeastern Colombia in the Guajira-Barranquilla Xeric Scrub and Sinú Valley Dry Forest ecoregions as defined by Olson et al. (2001), with one additional record from the Magdalena-Urabá Moist Forests ecoregion ( Figure 52).

I have also examined workers labelled as having been collected in Venezuela (FML; MCZ); no further locality information was listed on either pin. Additionally, Taber (1998: 97) indicated that he had examined workers from Guyana (MCZ). Both records are considered dubious without further verification, especially given that P. mayri has not been collected from potential habitats in western Venezuela (J. Lattke, pers. comm.).