Pogonomyrmex brevispinosus

Occurs in California and Nevada.

Identification
Key to North American Pogonomyrmex

The new species appears to be most closely related to Pogonomyrmex subdentatus, but the differences between the two are so striking that I designate this affinity without much conviction. The features which identify the worker of Pogonomyrmex brevispinosus are very distinctive. From all other members of its complex it is separable by a well-defined combination of characters in all castes. In the worker, the frontal lobes are very large, broad, convex, and better developed than in any other species. The outer margin of each lobe is prominently, broadly, and evenly convex; and it is not at all angular, as in other species of the complex. Moreover, it is thin and uniform throughout and is completely devoid of a peripheral carina. The scape base (Pl. IV, Fig. 6), although resembling that of Pogonomyrmex occidentalis [Pl. IV, Fig. 1]), is nevertheless distinctive. The thorax, petiole, and post petiole have the characteristic type of sculpture that has been noted in the foregoing description of the new species. Epinotal armature varies from angles or denticles to short, pointed, robust spines. Body pilosity is delicate; on the thoracic dorsum the hairs are not coarse and clavate. In the female the thoracic contour is strongly interrupted, in lateral view, by the large, protruding mesonotum. In dorsal view, the mesonotum is broader mesally than laterally because of a median lobe which extends posteriorly. In addition, the epinotum of the female bears a pair of very weak angles. The male is characterized in part by the massive postpetiole which is approximately twice as broad as long. Furthermore, the frontal lobes are rather strong; they are more elevated and more prominent than in any other species in the complex. The paramere (Pl. X, Fig. 5) of the genitalia is quite distinctive. (Cole 1968)

Distribution
United States: Calfornia, Nevada.

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



Biology
At the type locality the nests were in very compact sandy soil, and each was marked by a low, circular crater 3 to 8 inches in diameter. The single central entrance was surrounded by a broad, low, loose pile of small pebbles and bits of dry twigs and leaves. The nests were comparatively shallow affairs. Some of the galleries were rather superficial and attained a depth of only about 5 inches from the soil surface, whereas others were at a depth of approximately one foot at the base of a single, central, vertical gallery. Fewer than two hundred workers were in a nest. They were sluggish and docile, and ambled to cover when disturbed. I was unable to elicit a stinging response. The sexes occupied shallow chambers at about 2 inches from the surface of the soil. Males were collected from nests at the type locality on August 5 (Cole leg.), at Wasco on October 26 (Barnes leg.), and at Kerman on November 5 (Stobbe leg.). Apparently, mating of this species occurs later in the season than does that of most other desert species. (Cole 1968)

Nomenclature

 *  brevispinosus. Pogonomyrmex (Pogonomyrmex) brevispinosus Cole, 1968: 89, pl.3, fig. 8; pl. 4, fig. 6; pl. 6, fig. 6; pl. 7, fig. 6; pl. 8, fig. 6; pl. 10, fig. 5; pl. 11, fig. 5 (w.q.m.) U.S.A. Taber, Cokendolpher & Francke, 1988: 51 (k.).

Worker
Mandible as shown in Pl. III, Fig. 8; blade not much broader distally than proximally; teeth rather blunt, irregular in size, shape, and spacing; apical tooth rather narrow, acme, longer than subapical tooth which is subequal to first basal; second basal notably shorter than first and third basals; penultimate basal much smaller than ultimate basal, which is not offset from mandibular margin; basal mandibular margin straight, apical margin nearly so.

Base of antennal scape as illustrated in Pl. IV, Fig. 6; basal enlargement well developed; superior lobe prominent, strongly and rather evenly convex, well set off from the shaft by a broadly rounded angle; inferior declivity interrupted by a weak point, meeting the shaft at a well-rounded angle; basal flange weak, extending for no more than one-half the distance between lip and apex of superior lobe; lip bipartite, strong, broad; curvature of shaft as in subdentatus.

Frontal lobes very large, broad, strongly convex, well elevated, completely obscuring antennal insertions in frontal view; outer margin thin, ecarinate, broadly and evenly convex. Cephalic rugae moderately strong, dense, well separated, weakly divergent into posterior corners of head. Interrugal spaces densely and finely punctate, subopaque.

Contour of thorax, petiole, and post petiole, in lateral view, as shown in Pl. VI, Fig. 6; thoracic dorsum weakly, broadly, and evenly convex. Epinotum armed with a pair of very short, angular, pointed spines; epinotal declivity very short, steep, concave. Thoracic rugae stronger and more widely spaced than cephalic rugae, those on pronotum wavy and arcuately transverse, those elsewhere transverse; interrugal spaces finely and sparsely punctate, rather shining. In lateral view. anterior declivity of petiolar node nearly straight, upper portion weakly convex, meeting the peduncle at a distinct, narrowly rounded angle; dorsum of node broadly and rather evenly convex; ventral process of petiolar peduncle absent; ventral process of postpetiole very strong, blunt. Petiolar and postpetiolar nodes viewed from above, as illustrated in Pl. VII. Fig. 6; petiolar node only slightly broader than long, the apex rather blunt; postpetiolar node, at widest point, a little more than half again as broad as long. Dorsum of petiolar node with a few irregularly spaced, moderately strong, transverse rugae; interrugal spaces densely and finely punctate, faintly striate, and opaque. Dorsum of postpetiolar node finely, sparsely, and transversely rugulose postenorly; faintly and densely striatopunctate; sub opaque. Gaster densely and finely shagreened, moderately shining.

Body a rather uniform, medium ferrugineous red; mandibular teeth and epinotal armature darker.

Variation in the worker is chiefly in the degree of development of epinotal armature and in body size. Epinotal armature varies from faint angles to prominent, short, pointed spines. Variation in size of the workers is as follows: HL 1.52-1.75 mm, HW 1.56-1.79 mm, CI 102.1-102.4, SL 1.18-1.25 mm, SI 71.5-77.6, EL 0.38-0.42 mm, EW 0.23-0.27 mm, OI 24.0-25.0, WL 1.67-1.82 mm, PNL 0.38-0.42 mm, PNW 0.38-0.42 mm, PPL 0.42-0.46 mm, PPW 0.53-0.61 mm.

Queen
Paratype. (Cole Coll. No. Cal-347). HL 1.79 mm, HW 1.82 mm, CI 101.7, SL 1.29 mm, SI 70.9, EL 0.42 mm, EW 0.28 mm, OI 23.4, WL 2.55 mm, PNL 0.49 mm, PNW 0.49 mm, PPL 0.46 mm, PPW 0.84 mm.

Mandible and scape base similar to those of holotype. Frontal lobes very strong, very broad, the anterior margin strongly convex. Cephalic rugae coarse, widely spaced, subparallel on vertex, diverging very weakly into occipital corners; interrugal spaces finely, sparsely, irregularly punctate, somewhat shinging.

In lateral view, thoracic contour strongly interrupted by the large, protruding metanotum. In dorsal view, metanotum broader mesally than laterally because of a posteriorly directed median lobe. Epinotum armed with a pair of very weak, blunt angles. Thoracic rugae dense, rather fine, closely spaced; longitudinal on scutum, scutellum, meso- and metathoracic sternites and episternites, and sides of pronotum; transverse on anterior surface of pronotum and on base of epinotum; absent from metanotum and declivity of epinotum; interrugal spaces very finely punctate, shining. Conformation and sculpture of petiole and postpetiole similar to those of worker, but apex of petiolar node strongly acute, with a prominent nipple. Gaster smooth and strongly shining; sparsely, finely, and faintly shagreened, the shagreening restricted to base of first segment.

Head, thorax, and appendages light ferrugineous red; petiole, postpetiole, and agaster darker, lightly infuscated.

HL 1.75-1.82 mm, HW 1.82-1.94 mm, CI 104.0-106.6, SL 1.29-1.33 mm, SI 66.5-78.6, EL 0.42-0.46 mm, EW 0.23-0.27 mm, OI 23.1-26.3, WL 2.66-2.70 mm, PNL 0.16-0.49 mm, PNW 0.49-0.53 mm, PPL 0.45-0.47 mm, PPW 0.84-0.89 mm.

Male
Paratype. (Cole Coll. No. Cal-347). HL 1.26 mm, HW 1.45 mm, CI 115.1, SL 0.71 mm, SI 48.9, EL 0.51 mm, EW 0.34 mm, OI 40.5, WL 2.47 mm, PNL 0.6 mm, PNW 0.56 mm, PPL 0.39 mm, PPW 0.82 mm.

Mandible as shown in Pl. VIII. Fig. 6; with 5 teeth; similar to that of subdentatus, but apical tooth and masticatory margin longer and more oblique and teeth more irregular in size and spacing. Vertex of head rather strongly elevated meso•longitudinally, in lateral view bearing a rather sharp elevation on midoccipital border. Frontal lobes and frontal carinae moderately well developed, stronger than those of other species in the complex.

Scape length equal to combined lengths of first three flagellar segments. Front of head weakly, longitudinally rugose, the rugae irregular and rather closely spaced; interrugal spaces finely granulose, moderately shining. Area behind eyes with weak, irregular, broken rugulae; interrugal spaces finely and densely granulose, subopaque. Median lobe of clypeus and frontal area finely and irregularly granulose and rugulose, subopaque. Mandibles irregularly, longitudinally striate, densely and finely granulose.

Thoracic contour, in lateral view, notably broken by the strongly elevated scutellum which extends well above the scutum and by the large, subtrianglilar, strongly protruding metanotum which is widely separated from both scutellum and epinotum. In dorsal view, enlarged mid portion of metanotum not depressed, transversely rather short, anterioposteriorly much broadened, contrasting sharply with the narrower lateral portions; mid portion of metanotum with a small. posteriorly directed spinelike process on mid-posterior margin. Epinotum with a pair of very weak, blunt angles.

Thoracic sculpture poorly developed; pronotum, scutum. scutellum, base of epinotum, and sides of thorax with sparse, very weak, unevenly spaced rugulae and striae, the surface mostly smooth, moderately shining, finely and densely granulose. In lateral view, anterior declivity of petiolar node meeting the peduncle at a very weak, rounded, obtuse angle; posterior declivity subequal in gradient and length to anterior declivity, meeting the apex at an even, well-rounded angle; apex of node strongly and evenly convex. Postpetiolar node, in lateral view, with a long, evenly and gently sloping anterior declivity meeting the rather strongly convex apex; posterior declivity steep and very short, about one-fourth the length of anterior declivity. Viewed from above, petiolar node notably broader than long; covered with minute, irregular, broken striae, shining, without a median impression; apex very broadly and rather evenly convex. Postpetiolar node slightly more than twice as broad as long; sculpture like that of petiolar node; ventral process well developed, blunt.

Paramere of genitalia as shown in Pl. X, Fig. 5 and Pl. XI, Fig. 5. Gaster shining, very finely shagreened.

Head, thorax, petiole, and postpetiole dark brown; gaster and appendages lighter.

HL 1.22-1.37 mm, HW 1.14-1.62 mm, CI 111.1-115.2, SL 0.76-0.84 mm, SI 51.7-52.8, EL 0.49-0.51 mm, EW 0.30-0.34 mm, OI 35.8-40.5, WL 2.33-2.74 mm, PNL 0.38-0.41 mm, PNW 0.53-0.57 mm, PPL 0.39-0.49 mm, PPW 0.81-0.84 mm.

Type Material
Type locality. Bakersfield (20 mi. N.), California. Large series of paratype workers were collected by the writer on July 21, 1956 (Cole Coll. No. Cal-47, Cal-48, Cal-49); large series of workers as well as of males and females were collected at the same station by the writer on August 5, 1959 (Cole Coll. No. Cal-346, Cal-347, Cal-348).

The Holotype and long series of paratypes are in my collection. Paratypes will be deposited in the, , , , and in the collections of W S. Creighton and R. E. Gregg.