Pogonomyrmex subnitidus

The nests of Pogonomyrmex subnitidus are constructed in sand or in very loose sandy soil. They are surmounted by semicircular or circular craters or are marked by irregular beds of sand. Colony strength approximates that of Pogonomyrmex californicus. P. subnitidus is rather common within its range, and at some stations (e.g., San Fernando, California) it is sympatric with californicus. At such places the crater nests of the two species are indistinguishable. (Cole 1968)

Identification
In its shining interrugal areas and in color Pogonomyrmex subnitidus resembles Pogonomyrmex californicus. The scape base, frontal lobes (reduced), thoracic contour (broadly and weakly convex), and the shape of the petiole and postpetiole are quite different from their counterparts in californicus.

The epinotal armature of the subnitidus worker exhibits a considerable degree of variation, from distinct tubercles to well-developed, tapered spines that are fully as long as those of the "typical" occidentalis worker. Interrugal sculpture varies greatly, from sparse and very faint to dense and strong punctation.

Distribution
United States – coastal southern California to southcentral California, western Nevada. Mexico: Baja California

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

Biology
Wheeler and Wheeler (1986) found Araeoschizus armatus Horn (Coleoptera: Tenebrionidae; det. T.J. Spilman) in a Pogonomyrmex subnitidus nest in Nevada.

Zee and Holloway (2006) examined how the Argentine ant (Linepithema humile) raided nests of P. subnitidus in coastal southern California. The raids occurred sporadically and were not of great consequence during any individual raid. The harvestor ant would fend off the attack by closing off their nest and foraging would cease for the remainder of the day. There was also some mortality of P. subnitidus workers. The repeated effect of such raids over time and the increased threat to founding queens of this species in places where the Argentine ant occurs are likely to be decreasing the abundance of this species. Nests are under constant threat and over time may be destroyed as a result of repeated raids while the recruitment of new nests via queen founding may be greatly reduced where the Argentine ants co-occur with P. subnitidus.

Nomenclature

 *  subnitidus. Pogonomyrmex occidentalis var. subnitidus Emery, 1895c: 310 (w.) U.S.A. Cole, 1968: 115 (q.m.); Taber, Cokendolpher & Francke, 1988: 51 (k.). Raised to species: Wheeler, W.M. 1914e: 156. See also: Mackay, 1981: 25.

Worker
Cole (1968) - HL 1.29-1.90 mm, HW 1.29-1.94 mm, CI 100.0-102.1, SL 1.14-1.52 mm, SI 78.3-88.4, EL 0.27-0.46 mm, EW 0.15-0.27 mm, OI 20.9-24.2, WL 1.44-2.17 mm, PNL 0.30-0.49 mm, PNW 0.34-0.53 mm, PPL 0.38-0.49 mm, PPW 0.46-0.68 mm.

Mandible (Pl. III, Fig. 7) similar to that of owyheei, Pogonomyrmex salinus, and Pogonomyrmex subdentatus; basal most tooth not offset. Base of antennal scape as shown in Pl. IV, Fig. 5; superior and inferior lobes reduced; basal flange thin, straight, extending to acute apex of supeior lobe; lip well developed, rather strongly curved inward; inferior margin relatively straight, not interrupted by a point, and not making a distinct rounded angle with the shaft. Contours of thorax, petiole, and postpetiole, in lateral view, as illustrated in Pl. VI, Fig. 4; mesonotum broadly and weakly convex; base of epinotum as in occidentalis flattened or weakly concave; epinotal declivity somewhat longer than that of subdentatus, weakly concave. Epinotal armature varying from prominent tubercles to sharply pointed spines of variable length; venter of petiolar peduncle without a distinct process; anterior decltvity of petiolar node straight, the dorsum strongly convex, the nipple well developed, postpetiolar ventral process well developed. Petiole and post petiole, in dorsal view, as in Pl. VII, Fig. 5.

Cephalic and thoracic rugae variable, moderately to very coarse, narrowly to widely spaced; interrugal spaces strongly shining; interrugal punctation absent to prominent; when present, fine, sparse to dense, but not obscuring the shining surface. Petiolar and postpetiolar nodes shining, densely and finely punctate, frequently irregularly and weakly striate or rugulose. Body color a uniform light to medium ferrugineous red.

Queen
Cole (1968) - HL 1.82-1.94 mm, HW 1.82-2.01 mm, CI 100.0-103.6. SL 1.33-1.48 mm, SI 73.1-73.6, EL 0.42-0.29 mm, EW 0.27-0.31 mm, OI 23.1-25.3, WL 2.70-3.04 mm, PNL 0.46-0.57 mm, PNW 0.53-0.61 mm, PPL 0.49-0.61 mm, PPW 0.76-0.91 mm.

Conformation of base of antennal scape as in the worker. Cephalic rugae unevenly and moderately closely spaced; interrugal spaces shining, without punctures or with very fine indistinct ones confined to areas around compound eyes.

Thoracic rugae somewhat finer and more closely spaced than cephalic rugae, chiefly longitudinal, but transverse on epinotum where they are finer on basal surface than on sides; infraspinal facet smooth, strongly shining; interrugal spaces on sides of prothorax shining, bearing rugules; interrugal spaces elsewhere smooth and shining. Epinotal spines short, sub triangular, very sharp, directed strongly backward and only weakly upward. Ventral peduncular process of petiole a rather weak, elongate, longitudinal carina. In lateral view, anterior declivity of petiolar node straight, apex rather acute, dorsum distinctly convex. Petiolar and postpetiolar nodes, viewed from above, densely and finely shagreened, weakly and irregularly striolate, strongly shining. Body color a nearly uniform, deep, ferrugineous red.

Male
Cole (1968) - HL 1.29-1.52 mm, HW 1.41-1.63 mm, CI 107.3-10792, SL 0.68-0.72 mm, SI 44.2-48.2, EL 0.49-0.53 mm, OI 34.9-37.9, EW 0.31-0.38 mm, WL 2.28-2.51 mm, PNL 0.38-0.12 mm, PNW 0.49-0.57 mm, PPL 0.57-0.65 mm, PPW 0.76-0.87 mm.

Mandible as shown in Pl. VIII, Fig. 5; with 4 (rarely 5) teeth; dentition similar to that of subdentatus; basal most tooth not offset. Cephalic rugae prominent, rather fine, wavy, closely spaced; interrugal spaces weakly punctate, moderately shining.

Anterior declivity of pronotum very short, concave, with a prominent, broad, elongate impression. Scutum massive, its anterior declivity long; finely, unevenly, rather densely rugulose; interrugal spaces moderately shining, nearly free of sculpture except for piligerous punctures. Scutellum and base of epinotum sparsely and finely striate, shining. Midportion of metanotum with a strong, broad impression. Epinotal declivity smooth, strongly shining. Epinotum armed with a pair of strong tubercles, angles, or prominent, robust denticles. Petiolar node, in lateral view, with a gentle anterior declivity which slopes evenly from the peduncle in a long, broad curve; apex nearly flat, set off from the short posterior declivity by a well-rounded angle; venter of peduncle without a process, with 1 or 2 long, straight, slender hairs. Postpetiolar node, in lateral view, broadly convex, anterior declivity longer and slightly less steep than posterior declivity; ventral process moderately to strongly developed as a well-rounded lobe. Petiolar node, in dorsal view, rather short; notably broader than long; its sides sloping rather strongly from center to the acute, but not pointed, apex. Postpetiolar node, in dorsal view, notably broader than long; rather strongly attenuated anteriorly; posteriolateral margins subparallel. Petiolar and postpetiolar nodes mostly smooth, strongly shining, weakly shagreened, and faintly striolate posteriorly. Paramere of genitalia as illustrated in Pl. X, Fig. 6 and Pl. XI, Fig. 6. Head and thorax dark blackish brown; petiole, postpetiole, and gaster paler.

Type Material
Type locality: San Diego County, California.