Pogonomyrmex saucius

This species nests under stones in open dry areas.

Identification
Johnson and Cover (2015) - The smaller Pogonomyrmex schmitti is the only congener known to occur in sympatry with P. saucius. Pogonomyrmex saucius is easily distinguished by the wavy to slightly irregular longitudinal rugae on the dorsum and sides of the mesosoma and posterior surface of the petiolar node. All other Hispaniolan congeners have rugoreticulate-vermiculate sculpturing on the mesosoma, and the posterior surface of the petiolar node is shining to strongly punctate or rugoreticulate, but never with prominent longitudinal rugae.

Worker. Small (HW = 1.22–1.33 mm), easily identified by the coarse regular to weakly irregular, subparallel longitudinal rugae on the dorsum and sides of the mesosoma and posterior surface of petiolar node.

Queen. With caste-specific morphology of the mesosoma related to wing-bearing and presence of ocelli on head. Small (HW = 1.15 mm), about the same size as conspecific workers; all surfaces of mesosoma and posterior surface of petiolar node with coarse longitudinal rugae.

Male. Head, dorsum of mesosoma, and posterior surface of petiolar node strongly granulate-punctate, dull; dorsum of postpetiole weakly granulate-punctate, weakly shining; notauli well-developed. Note that these characters might not be diagnostic because males of Pogonomyrmex aterrimus and Pogonomyrmex schmitti are unknown.

Distribution based on Regional Taxon Lists
Neotropical Region: Dominican Republic, Greater Antilles, Haiti.

Biology
In the Dominican Republic nests are found in open areas under rocks along the edge of forested areas.

From Wheeler and Mann (1914): Each of the nests contained a little heap of stored grain. It no doubt ranges over the territory about Lake Assuei. It is a more timid ant than Pogonomyrmex schmitti.

Johnson and Cover (2015) - Currently, P. saucius is known only from arid, semi-desert habitats at low elevations in south-central Hispaniola. Wheeler and Mann (1914) found nests under stones near sea level in a very arid area that contained desert vegetation such as cacti and thorny bushes; another collection label also indicated that specimens were collected in desert habitats (PS Ward #11730). Nests of P. saucius contained small numbers of seeds (Wheeler & Mann 1914). No information is available on colony size, but it is probably small (200–300 workers) (D. Lubertazzi, pers. comm.).

Little information is available relative to timing of sexual production or mating flights for P. saucius. One alate queen was collected on March 31, and the date for males was given as winter 1912–1913 (Wheeler & Mann 1914). The queen was small, similar to the size of workers. We also examined one aberrant intermorph-like queen (USNM) that had small wing buds, but her size and shape (especially the mesosoma) was similar to that of workers; she also lacked ocelli and distinct mesosomal sutures (see also Heinze et al. 1992; Johnson et al. 2007; Kusnezov 1951).

We also note that Wheeler & Mann described P. saucius as brownish-black. This coloration agrees with specimens in recent collections and indicates that over time workers in the syntype series have discolored to a light orangish-brown.

Nomenclature

 *  saucius. Pogonomyrmex (Ephebomyrmex) saucius Wheeler, W.M. & Mann, 1914: 29, figs. 10, 11 (w.m.) HAITI. Combination in Ephebomyrmex: Kempf, 1972a: 106; in Pogonomyrmex: Bolton, 1995b: 341.

Worker
Length: 5-5.5 mm.

Head subrectangular, a little longer than broad, with straight sides and feebly excised posterior border and the eyes just in front of the middle of its sides. Mandibles with 6 subequal teeth and rather convex external borders. Clypeus with straight, entire anterior border and a blunt, tooth-like projection on its upper surface on each side near the lateral border. Frontal area small, elongate-triangular. Antennal scapes not reaching to the posterior corners of the head; joints 2-7 of the funiculi as broad as long. Thorax shaped as in P. Schmitti and with similar spines on the epinotum and metasterna. Postpetiole, petiole and gaster also similar in structure, but the anterior surface of the petiolar node rises a little less abruptly from the peduncle and the posterior surface is more convex and, when seen from above, its anterior border is more pointed or acuminate in the middle.

Mandibles, head and thorax opaque. Mandibles striated; clypeus, head and thorax regularly longitudinally rugose, the interrugal spaces being finely and densely punctate. On the cheeks the rugm are rather far apart but are denser and diverge posteriorly on the posterodorsal portion of the head. The space enclosed by the four thoracic spines, is concave, smooth and shining. Petiole, postpetiole and gaster also smooth and shining, with small, sparse piligerous punctures, except the dorsal surface of the petiolar node, which is densely punctate and longitudinally rugose, the rugae converging anteriorly to the apex of the node. Antennal scapes and legs finely shagreened, the former opaque, the latter somewhat shining.

Hairs dark brown, short, stiff, moderately abundant, erect on the body, somewhat more oblique on the scapes and legs. Gula without ammochaetae.

Brownish black; mandibles, except their teeth and borders, sides of clypeus, cheeks, antennm, legs, thoracic spines, peduncle of petiole, anterior border and sides of postpetiole and a band across the anterior border of the first gastric segment, red.

Tip of gaster and margins of posterior gastric segments narrowly yellowish.

Johnson and Cover (2015) - lectotype (n = 10 + 2 paralectotypes). HL 1.33 (1.26–1.37); HW 1.33 (1.22–1.33); MOD 0.28 (0.25–0.30); OMD 0.33 (0.28–0.34); SL 1.01 (0.90–1.01); PNW 0.90 (0.87–0.95); HFL 1.22 (1.02–1.31); ML 1.63 (1.56–1.81); PW 0.50 (0.42–0.53); PPW 0.58 (0.51–0.62). Indices: SI 75.94 (68.42–79.51); CI 100.00 (94.57–101.53); OI 21.05 (19.84–24.00); HFI 91.73 (79.07–102.46).

Queen
Johnson and Cover (2015) - (n = 1). HL 1.23; HW 1.15; MOD 0.29; OMD 0.28; SL 1.00; PNW 1.01; HFL 1.27; ML 1.71; PW 0.41; PPW 0.55. Indices: SI 86.96; CI 93.50; OI 25.22; HFI 110.43.

With caste-specific morphology of the mesosoma related to wing-bearing and presence of ocelli on head. In full-face view, head longer than broad (CI = 93.50), posterior margin flat. Longitudinal rugae on cephalic dorsum prominent, wavy to irregular; interrugae strongly granulate, dull. Mandible with six teeth, dorsal surface coarsely rugose. Eye relatively small, situated anterior to middle of head. Antennal scape moderately to strongly granulate, dull. Psammophore poorly-developed, consisting of short hairs scattered across ventral side of head.

All mesosomal surfaces with subparallel, regular to weakly irregular longitudinal rugae except for sides and dorsum of propodeum where rugae converge posterad. Propodeum with long, well-developed superior and inferior spines, inferior spines about the same length as superior spines. In profile, petiolar node asymmetrical with anterior surface notably shorter than posterior surface, apex of node weakly angulate. In dorsal view, petiolar node slightly longer than wide, widest near middle, tapering to a rounded to spatulate anterior margin. Anterior surface of petiolar node smooth and shining; posterior surface with coarse regular to weakly irregular longitudinal rugae, interrugae weakly granulate, shining. In dorsal view, postpetiole widest near posterior margin, tapering to anterior margin, maximum width about equal to length; all surfaces strongly coriarious, dull. First gastral tergum strongly coriarious, dull. Moderately abundant yellowish-brown to brownish hairs on entire body, longest hairs on head and mesosoma shorter than MOD. Body mostly concolorous dark brown; legs, antennae, and mandibles lighter; postpetiole and first gastral tergum with an iridescent blue to purplish reflection.

Male
Length 4-4.5 mm.

Head slightly longer than broad, with large eyes and ocelli, narrowest through the cheeks, which are straight, rounded and broader behind the eyes. Mandibles like those of the worker but smaller. Clypeus convex, without lateral tooth-like projections. Antennal scapes scarcely four times as long as broad, somewhat curved and dilated at the base; first funicular joint a little longer than broad, second as long as the scape, joints 3-9 subequal, a little more than twice as long as broad; joints 10 and 11 shorter, terminal joint nearly as long as the two preceding together. Thorax robust, through the wing insertions as broad as the head. Mesonotum with well-marked Mayrian furrows, convex in front, flattened behind; epinotum and: metasterna unarmed, the former rounded without distinct bas3 and declivity. Petiole long; its node rounded in profile, constricted behind; its peduncle with III distinct ventral tooth. Postpetiole similar to that of the worker. Fore wing with a discal and two cubital cells.

Head, thorax and petiole opaque, finely and densely punctate, head and thorax also longitudinally rugulose above and on the sides of the epinotum. Mandibles, postpetiole and gaster shining, the mandibles coarsely and sparsely punctate and at the base finely striate. Legs rather shining, finely shagreened.

Pilosity similar to that of the worker.

Black; tips of mandibles, funiculi tibim, tarsi, bases and tips of femora, red; genitalia brown. Wings grayish hyaline, with brown veins and stigma.

Type Material
Described from numerous workers and two males taken from a couple of colonies nesting in the ground beneath stones along the very arid trail leading from Manneville to the Dominican border, about half a mile from the former place.

Etymology
Johnson and Cover (2015) - Wheeler did not give information regarding the derivation of this name. The specific epithet, saucius (Latin, sauci = wounded, injured, weakened) might refer to the behavior of disturbed workers feigning death, as occurs in some related species.