Pogonomyrmex saucius Wheeler & Mann 1914

Johnson, Robert A. & Cover, Stefan P., 2015, A taxonomic revision of the seed-harvester ant genus Pogonomyrmex (Hymenoptera: Formicidae) on Hispaniola, Zootaxa 3972 (2), pp. 231-249 : 239-240

Pogonomyrmex saucius Wheeler & Mann 1914

( Figures 6–8 )

Pogonomyrmex (Ephebomyrmex) saucius Wheeler & Mann, 1914: 29 , figs. 10, 11 (worker, male); Olsen, 1934, plate 7, fig. 2. Syntypes examined: 4 workers, 1 male [AMNH], 1 worker [LACM], 5 workers, 1 male [MCZ], 1 worker [MHNG], 14 workers [USNM]; HAITI, about one-half mile east of Manneville (W.M. Mann leg, winter 1912–1913) (LACM worker here designated LECTOTYPE [LACMENT181990]).

Ephebomyrmex saucius (Wheeler & Mann) ; Kempf, 1972: 106. First combination in Ephebomyrmex .

Pogonomyrmex saucius Wheeler & Mann ; Bolton, 1995: 341. Revived combination in Pogonomyrmex .

Worker. Diagnosis. 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 ( Figure 6 ).

Measurements — 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. Diagnosis. 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 ( Figure 7 ).

Measurements (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.

Description. 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 ( Figure 7 ).

Male. Diagnosis. Head, dorsum of mesosoma, and posterior surface of petiolar node strongly granulatepunctate, dull; dorsum of postpetiole weakly granulate-punctate, weakly shining; notauli well-developed ( Figure 8 ). Note that these characters might not be diagnostic because males of P. aterrimus and P. schmitti are unknown.

Measurements. (damaged, unable to measure).

Additional material examined. DOMINICAN REPUBLIC. Pedernales: Pedernales, May 27, 2008 (A Clark; RAJC); Cabo Rojo, 5 m, Sept 9, 1992 (PS Ward; MCZ, UCDC); Parque Nacional Jaragua, 5 m, Mar 31, 2012 (D Lubertazzi; MCZ). HAITI. Quest: Mannville, 1954 (WM Mann; LACM, USNM).

Etymology. 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.

Discussion and biology. The smaller P. schmitti is the only congener known to occur in sympatry with P. saucius ( Figure 5 ). 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.

Currently, P. s a uc i us is known only from arid, semi-desert habitats at low elevations in south-central Hispaniola ( Figure 5 ). 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 (see discussion under taxonomy, morphology, and ecology). 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.

Figures

FIGURE 5. Geographic distribution for (A) Pogonomyrmex aterrimus (▲), P. “ darlingtoni ” (■), and P. saucius (●), and (B) P. schmitti (●). The bold line down the left-center of the map is the border between Haiti and the Dominican Republic; lighter lines are the first administrative divisions in each country. Both maps are drawn on the same geographic area so that distribution patterns are directly comparable.

FIGURE 6. Photograph of Pogonomyrmex saucius Wheeler & Mann worker: (A) frontal view of head, (B) lateral view of body, and (C) dorsal view of body (MCZ-ENT 00511548). Photographs by Michele Esposito from www. antweb. org.

FIGURE 7. Photograph of Pogonomyrmex saucius Wheeler & Mann alate queen: (A) frontal view of head, (B) lateral view of body, and (C) dorsal view of body (MCZ-ENT 00511553). Photographs by Michele Esposito from www. antweb. org.

FIGURE 8. Photograph of Pogonomyrmex saucius Wheeler & Mann paralectotype male: (A) frontal view of head, (B) lateral view of body, and (C) dorsal view of body (CASENT 0217245). Photographs by Erin Prado from www. antweb. org.