Pogonomyrmex subdentatus

All nests that I have seen were marked by low, irregular beds of sand or gravel with more than one entrance, and contained several hundred workers. The workers retreat rather rapidly toward cover when the nest is disturbed. I have never been able to elicit an attack response. (Cole 1968)

Identification
Pogonomyrmex subdentatus appears to be closely related to Pogonomyrmex salinus, from which it differs in the worker caste largely by the distinctive conformation of the scape base, the greater convexity of the thoracic dorsum, the more variable epinotal armature, the pronounced tooth or lobe on the petiolar peduncle, the broader postpetiole, the weaker cephalic and thoracic punctation, the less dull body surface, and the more shining surface of the first gastric segment which is apparently never either punctate or prominently shagreened. The dorsal thoracic contour of the worker is remarkably convex for a member of the occidentalis complex.

Distribution
United States – California, southwestern Oregon, western Nevada.

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

Biology
Wheeler and Wheeler (1986) found Anthicus lecontei Champion (Coleoptera: Anthicidae; det. EG. Werner) in a Pogonomyrmex subdentatus nest.

Nomenclature

 *  subdentatus. Pogonomyrmex subdentatus Mayr, 1870b: 971 (diagnosis in key) (w.) U.S.A. Cole, 1968: 111 (q.m.). See also: Shattuck, 1987: 175.

Worker
Cole (1968) - HL 1.60-1.77 mm, HW 1.48-1.90 mm, CI 92.5-107.3, SL 1.14-1.37 mm, SI 71.6-76.9, EL 0.42-0.46 mm, EW 0.23-0.27 mm, OI 26.0-26.3, WL 1.63-2.13 mm, PNL 0.38-0.19 mm, PNW 0.38-0.49 mm, PPL 0.38-0.49 mm, PPW 0.53-0.65 mm.

Mandible as shown in Pl. III, Fig. 6; dentition similar to that of owyheei (=Pogonomyrmex salinus); basalmost tooth not offset; basal mandibular margin straight. Base of antennal scape as illustrated in Pl. IV, Fig. 4; apex of superior lobe rather acute; basal flange straight, narrow, rather thin: extending distinctly beyond apex of superior lobe; superior declivity almost straight, meeting the shaft evenly at nearly a straight angle; lip narrow; point absent. Cephalic rugae rather dense, coarse, unevenly spaced; interrugal spaces densely and finely punctate, subopaque.

Contour of thorax, petiole, and postpetiole as in Pl. VI, Fig. 5; thorax notably convex; epinotal declivity short, nearly straight; epinotal armature variable, from denticles to long, sharp spines; contours of petiole and post petiole, in dorsal view, as shown in Pl. VII, Fig. 1; venter of petiolar peduncle with a prominent lobe or blunt spine; ventral process of postpetiole strong. Interrugal spaces of thorax densely punctate, subopaque; dorsum of petiolar and postpetiolar nodes subopaque, finely and densely punctate, with prominent, coarse, widely spaced, wavy, generally transverse fugae. Gaster finely and faintly shagreened. Body color a medium to rather deep ferrugineous red.

Queen
Cole (1968) - HL 1.56-1.71 mm, HW 1.56-1.75 mm, CI 100.0-102.3, SL 1.18-1.33 mm, SI 75.5-76.0, EL 0.42-0.49 mm, EW 0.23-0.28 mm, OI 26.9-28.7, WL 2.09-2.47 mm, PNL 0.42-0.53 mm, PNW 0.49-0.53 mm, PPL 0.42-0.49 mm, PPW 0.67-0.80 mm.

Conformation of mandible and scape base as in the worker. Cephalic rugae rather coarse, widely and unevenly spaced; interrugal spaces subopaque, densely and finely punctate. Thoracic sculpture similar to that of subnitidus; interrugal spaces subopaque. Epinotum armed with a pair of small, distinct, acute angles. Ventral process of petiolar peduncle strongly developed as a prominent lobe. In lateral view, petiolar node with anterior declivity convex; apex acute, with a strong nipple; dorsum flat, in terrupted by rugae. In dorsal view, petiolar node with coarse, widely and irregularly spaced, transverse, subparallel rugae confined chiefly to midregion; interrugal spaces densely punctate, subopaque. In dorsal view, postpetiolar node very densely and finely punctate and rather finely, irregularly, transversely rugose, the punctures tending to obscure the rugae, the surface dull. Gaster very finely shagreened, strongly shining. Body a concolorous, medium, ferrugineous red.

Male
Cole (1968) - HL 1.29-1.33 mm, HW 1.37-1.48 mm, CI 103.8-106.2, SL 0.65-0.76 mm, SI 48.0-51.1, EL 0.49-0.53 mm, EW 0.61-0.76 mm, OI 37.9-39.9. WL 2.13-2.51 mm, PNL 0.38-0.42 mm, PNW 0.49-0.76 mm, PPL 0.38-0.53 mm, PPW 0.68-0.80 mm.

Mandible as shown in Pl. VIII, Fig. 4; with 5 (less often 4) teeth; apical tooth rather short; subapical and basal teeth approximately of same size; ultimate basal tooth not offset from the broadly and evenly concave basal mandibular margin. Cephalic rugae fine, especially around compound eyes, rather closely and unevenly spaced; interrugal spaces subopaque to opaque, densely and finely punctate.

Scutum, scutellum, and sides of thorax rather shining, finely, irregularly, longitudinally striate, the interspaces largely without sculpture; epinotum very faintly, finely, unevenly punctate, delicately striate, moderately shining. Epinotal armature a pair of weak angles. Venter of petiolar node without a process; ventral process of postpetiole strongly developed. Contour of petiole and post petiole, viewed dorsally, as in Pl. XII, Fig. 11. Petiolar and postpetiolar nodes rather shining, densely and strongly shagreened.

Gaster very smooth and shining, without shagreening. Paramere as shown in Pl. X, Fig. 4 and Pl. XI, Fig. 4; apex convex. Head, thorax, legs (except tibiae and tarsi), and antennal scapes dark blackish brown; antennal flagella, tibiae, tarsi, petiole, postpetiole, and gaster notably lighter.

Type Material
Type locality: California.

References based on Global Ant Biodiversity Informatics

 * Branstetter M. G. 2012. Origin and diversification of the cryptic ant genus Stenamma Westwood (Hymenoptera: Formicidae), inferred from multilocus molecular data, biogeography and natural history. Systematic Entomology 37: 478-496.
 * Cole A. C., Jr. 1966. Keys to the subgenera, complexes, and species of the genus Pogonomyrmex (Hymenoptera: Formicidae) in North America, for identification of the workers. Annals of the Entomological Society of America 59: 528-530.
 * Johnson R. Personnal Database. Accessed on February 5th 2014 at http://www.asu.edu/clas/sirgtools/resources.htm
 * La Rivers I. 1968. A first listing of the ants of Nevada. Biological Society of Nevada, Occasional Papers 17: 1-12.
 * Mallis A. 1941. A list of the ants of California with notes on their habits and distribution. Bulletin of the Southern California Academy of Sciences 40: 61-100.
 * Olsen O. W. 1934. Notes on the North American harvesting ants of the genus Pogonomyrmex Mayr. Bulletin of the Museum of Comparative Zoology 77: 493-514.
 * Santschi F. 1911. Formicides récoltés par Mr. le Prof. F. Silvestri aux Etats Unis en 1908. Bullettino della Società Entomologica Italiana 41: 3-7.
 * Shattuck S. O. 1987. An analysis of geographic variation in the Pogonomyrmex occidentalis complex (Hymenoptera: Formicidae). Psyche (Cambridge) 94: 159-179.
 * Ward P. S. 1987. Distribution of the introduced Argentine ant (Iridomyrmex humilis) in natural habitats of the lower Sacramento Valley and its effects on the indigenous ant fauna. Hilgardia 55: 1-16
 * Wetterer, J. K.; Ward, P. S.; Wetterer, A. L.; Longino, J. T.; Trager, J. C.; Miller, S. E. 2000. Ants (Hymenoptera: Formicidae) of Santa Cruz Island, California. Bulletin of the Southern California Academy of Sciences 99:25-31.
 * Wetterer, J.K., P.S. Ward, A.L. Wetterer, J.T. Longino, J.C. Trager and S.E. Miller. 2000. Ants (Hymenoptera:Formicidae) of Santa Cruz Island, California. Bulletin of the Southern California Academy of Science 99(1):25-31.