Pogonomyrmex barbatus

This species has large crater like mounds with a diameter of about 1 meter. They are cleared of vegetation and covered with gravel, if it is available. Brood and reproductives were found in the nests in July. They are extremely pugnacious and their sting is very painful. (Mackay and Mackay 2002)

Identification
This is usually an easily recognized species as it is large, red and aggressive. Occasionally it is difficult to distinguish specimens from those of Pogonomyrmex rugosus. The color usually works to distinguish this species (P. rugosus is dark with a con-trasting lighter gaster), but it may be necessary to examine the cephalic rugae to determine if they are fine or coarse as in P. rugosus. It can be separated from the other species, as it is much larger (total length over 8 mm, usually about 10 mm in total length). Workers from newly founded nests are small, and could be confused with Pogonomyrmex desertorum. The cephalic rugae are fine, but are not as fine as those of P. desertorum, which also has a shiny area at the posterior lateral corner, an area which is covered with rugae in P. barbatus. (Mackay and Mackay 2002)

Distribution
Southwestern United States and northern Mexico.

Distribution based on Regional Taxon Lists
Nearctic Region: United States. Neotropical Region: Mexico.

Habitat
Various habitats. Ranging from the edges of the desert and grasslands up to lower elevation pine forests, pinyon-juniper and oak forests, sagebrush and riparian habitats. It occurs in more mesic sites than P. rugosus.

Abundance
Quite common in northern Mexico.

Biology
An intermorphic queen has been described by Castano-Meneses & Vasquez-Bolanos (2007). These queens are characterized by less thoracic development, loss of wings, and absence of ocelli when compared to full queens. However, they have the same reproductive capacity in new colonies as do normal queens since they have the same number of ovarioles.

Genetics
The genome of P. barbatus (Smith et al. 2011) was used for a study examining how parasitic ants with no worker caste may have altered their genome to arrive at a workerless state. In comparison to ants with a full complement of castes, there appeared to be no loss of genes in the parasitic ants. This suggests regulatory differences and not sequence differences predominate in gains and losses of castes (phenotypes). (Smith et al. 2015)

Genetics
Pogonomyrmex barbatus has had their entire genome sequenced.

Palomeque et al. (2015) found class II mariner elements, a form of transposable elements, in the genome of this ant.

Other Ants
A host species for the workerless social parasite.

Nematodes
Pogonomyrmex barbatus is an intermediate host for the nematode, which lives in the stomach of the Texas horned lizard, Phrynosoma cornutum (Lee, 1957).

Nomenclature

 *  barbatus. Myrmica barbata Smith, F. 1858b: 130 (q.) MEXICO. Mayr, 1870b: 971 (w.); Mayr, 1887: 610 (m.); Wheeler, W.M. 1900b: 20 (l.); Taber, Cokendolpher & Francke, 1988: 51 (k.). Combination in Pogonomyrmex: Mayr, 1868b: 170. Senior synonym of molefaciens: Mayr, 1886c: 365; Creighton, 1950a: 119; Cole, 1968: 56; of nigrescens: Cole, 1968: 56. See also: Wheeler, G.C. & Wheeler, J. 1953a: 107; Petralia & Vinson, 1980: 381; Smith, D.R. 1979: 1353.
 * molefaciens. Myrmica (Atta) molefaciens Buckley, 1860b: 445 (w.q.) U.S.A. Emery, 1895c: 308 (m.). Combination in Pogonomyrmex: Mayr, 1886c: 365. Subspecies of barbatus: Forel, 1886b: xlii; Emery, 1895c: 308; Forel, 1901c: 128. Junior synonym of barbatus: Mayr, 1886c: 365; Creighton, 1950a: 119; Cole, 1968: 56.
 * nigrescens. Pogonomyrmex barbatus var. nigrescens Wheeler, W.M. 1902c: 389 (w.) U.S.A. Junior synonym of fuscatus: Creighton, 1950a: 119; of barbatus: Cole, 1968: 56.

Worker
Cole (1968) - HL 1.98-2.43 mm, HW 2.05-2.70 mm, CI 103.6-111.1, SL 1.33-1.71 mm, SI 63.3-68.4, EL 0.42-0.53 mm, EW 0.23-0.34 mm, OI 21.2-21.8, WL 2.24-2.89 mm, PNL 0.46-0.65 mm, PNW 0.49-0.68 mm, PPL 0.42-0.65 mm, PPW 0.34-0.91 mm.

Mandible as shown in Pl. III, Fig. 17; teeth short, robust, blunt; apical and subapical teeth generally longer than others; ultimate basal tooth longer and broader than penultimate, slightly but distinctly offset from the moderately convex basal margin.

Base of antennal scape like that of rugosus (Pl. IV, Fig. 15), moderately strongly curved in proximal one-half its length, somewhat constricted but not flattened along the bend. Basal enlargement broad and strong; apex of superior lobe varies from blunt and subtruncate to subacute; gradient of superior declivity variable, but generally rather steep and forming a strong angle with the flange; lip strong and hook. shaped, its margin thin and directed distad and strongly inward forming a prominent concavity; point present or absent, when present varying from weak to strong; basal flange narrow, straight, extending from lip to apex of superior lobe; lateral surface of basal enlargement strongly, evenly, broadly, and longitudinally impressed, forming a prominent, moderately deep, elongate, saucerlike depression, the lower margin of which is bordered by the longitudinal peripheral carina (when present), the proximal extension of which forms the point.

Contour of thorax, petiole, and postpetiole as portrayed in Pl. V, Fig. 1. Epinotal spines always present, varying from short to long. Petiole and postpetiole in dorsal view as shown in Pl. VII, Fig. 17.

Cephalic rugae moderately to very fine, rather even, moderately to closely spaced; interrugal spaces shining to subopaque, without sculpture, or with fine punctures and/or foveae, often with granulations and sometimes with a few broken rugulae. Thoracic rugae fine, rather even, and closely set to moderately coarse and irregular; often strongest on pronotum, where they may be wavy but do not form strong reticulations with deep interrugal spaces. Interrugal spaces of thorax shining to subopaque, with or without punctures. Rugae on petiolar and postpetiolar nodes moderately fine to coarse, rather even, not forming coarse reticulations.

Body color varying from a concolorous light ferrugineous to very deep red.

Queen
Cole (1968) - HL 2.13-2.17 mm, HW 2.93-3.01 mm, CI 118.6-125.1, SL 1.63-1.67 mm, SI 54.9-55.6, EL 0.57-0.61 mm, EW 0.30-0.38 mm, OI 23.1-25.1, WL 3.80-3.81 mm, PNL 0.68-0.76 mm, PNW 0.68-0.84 mm, PPL 0.61-0.68 mm, PPW 0.95-0.99 mm.

Essentially similar to the worker, but with the usual female characters. Cephalic and scutal rugae rather fine, closely spaced. Scutellum smooth, very shining, longitudinal striae weak or absent. Epinotal spines short, prominent, robust, sharp. Dorsum of petiolar node rugose, the rugae not forming reticulations. Body color light to deep ferrugineous red.

Male
Cole (1968) - HL 1.60-2.09 mm, HW 2.09-2.36 mm, CI 112.9-130.6, SL 0.84-0.87 mm, SI 35.5-41.6, EL 0.61-0.61 mm, EW 0.42-0.46 mm, OI 29.2-29.2, WL 3.46-3.57 mm, PNL 0.49-0.53 mm, PNW 0.84-0.99 mm, PPL 0.57-0.65 mm, PPW 1.10-1.18 mm.

Mandible as shown in Pl. VIII, Fig. 11. Outer surface of base of antennal scape strongly flattened or broadly concave. Paramere as illustrated in Pl. X, Fig. 10 and Pl. XI, Fig. 11; inner dorsal bonier with a deep, rather broad emargination which strongly separates the terminal lobe from the base. Body gcnerally a concolorous clear yellow.