Pogonomyrmex mohavensis Johnson

ROBERT A. JOHNSON, RICK P. OVERSON & CORRIE S. MOREAU, 2013, A New Species of Seed-harvester Ant, Pogonomyrmex hoelldobleri (Hymenoptera: Formicidae), from the Mohave and Sonoran Deserts of North America, ZOOTAXA 3646 (3), pp. 201-227 : 220-221

Pogonomyrmex mohavensis Johnson

(Figures 2, 9)

Pogonomyrmex mohavensis was described from workers at several locations in California and Nevada (Johnson & Overson, 2009).

Alate queens were recently collected from a nest in California: Kern County, Hwy 43 at 17.6 km N Wasco, Sept 15, 2011; 35 o 45.0'N 119 o 20.7'W, 80 m (RAJ #4805; specimens in RAJC), and they are described herein. The nest was in disturbed roadside habitat surrounded by agricultural fields. Workers in this nest were significantly larger than those collected at previous locations; HW ranged from 1.31-1.67 mm in the description of the species, while those at the present location ranged from 1.91-2.05 mm (n = 9).

Worker.

Diagnosis. Pogonomyrmex mohavensis is characterized by: (1) cephalic rugae not forming circumocular whorls, but rather extending more or less directly to the vertex or converging only slightly near the vertex, (2) mandible with six teeth (a seventh sometimes occurs as a denticle between the basal and sub-basal teeth), and (3) interrugal spaces on pronotal sides smooth and shining to slightly punctate and moderately shining.

Queen

Diagnosis. As in worker diagnosis, but with caste-specific structures related to wing-bearing, presence of small ocelli on head, and as illustrated in Figure 9. Mandible with six teeth or with a seventh tooth that occurs as a denticle between the basal and sub-basal teeth. All mesosomal surfaces except for mesoscutum and mesoscutellum with prominent rugae; sculpturing absent on mesoscutum and mesoscutellum except for scattered punctures or with faint longitudinal striae. Posterior face of petiole with coarse transverse, oblique, or longitudinal rugae, dorsum of postpetiole with weaker transverse rugae. Base of scape noticeably flattened; superior and inferior lobes very well developed, wider than width of scape base.

Measurements (mm)-(n = 2). HL 1.91-1.95; HW 2.01-2.08; MOD 0.43-0.43; OMD 0.49-0.57; SL 1.36- 1.38; PNW 1.52-1.62; HFL 1.91-2.00; ML 2.60-2.70; PW 0.74-0.74; PPW 0.89-0.90. Indices: SI 66.35-67.66; CI 105.24-106.67; OI 20.67-21.39; HFI 95.02-96.15.

Description. As in worker diagnosis, but with caste-specific structures related to wing-bearing, presence of small ocelli on head, and as illustrated in Figure 9. Dorsum and sides of head with strong, widely spaced rugae, in side view rugae converging near or slightly anterior to vertex, interrugal spaces smooth and strongly shining. In full-face view, head slightly broader than long, posterior margin flat. Mandible with six teeth on one queen, the other with a seventh tooth that occurred as a denticle between the basal and sub-basal teeth (Figure 9), dorsal surface coarsely rugose, strongly shining. Eye not large (OI = 20.67-21.39), MOD ranging from 0.22-0.23x HL. Base of scape noticeably flattened; superior and inferior lobes very well developed, wider than width of scape base.

Mesosoma as described above, propodeum unarmed; in side view, juncture of dorsum of propodeum and propodeal declivity rounded to subangulate, sides and dorsal surface rugose, shining, posterior surface smooth and strongly shining. Petiolar peduncle long, ventral margin straight. In side view, petiolar node asymmetrical with anterior surface shorter than posterior surface. Apex of node weakly rounded. Postpetiole broader than long. Posterior face of petiole with coarse transverse, oblique, or longitudinal rugae, dorsum of postpetiole with weaker transverse rugae, interrugal spaces weakly to moderately punctate, sub-shining. Gastric tergites weakly coriarious to mostly smooth and shining. Most body surfaces with moderately abundant coarse suberect to erect white setae. Entire body concolorous light to dark ferruginous orange.

Male. Unknown.

Discussion. The queens of P. mohavensis and P. hoelldobleri are very similar. The best characters to separate queens of these two species appear to be: (1) number of teeth (seven in P. hoelldobleri , six or with a seventh tooth that occurs as a denticle between the basal and sub-basal teeth in P. mohavensis ), (2) sculpturing (posterior face of petiole and dorsum of postpetiole weakly to moderately granulate or with weak tranverse rugae in P. hoelldobleri ; posterior face of petiole with coarse transverse, oblique, or longitudinal rugae, dorsum of postpetiole with weaker transverse rugae in P. mohavensis ), and (3) conformation of the base of the scape (base of scape rounded, superior and inferior lobes poorly developed in P. hoelldobleri ; base of scape noticeably flattened, superior and inferior lobes well developed in P. mohavensis ). The queens of P. mohavensis also were significantly larger (HW = 2.01- 2.08 mm) than those of P. hoelldobleri (HW = 1.44-1.79 mm). However, these queens of P. mohavensis are likely to be significantly larger than those in other parts of their range where the workers are much smaller.