Polyergus sanwaldi

Only recently described (2013) as a distinctive species, this ant exclusively raids colonies of Formica dolosa.

Identification
Polyergus sanwaldi closely resembles Polyergus longicornis, but has consistently shorter appendages and more northern (and apparently allopatric) distribution.

Identification Keys including this Taxon

 * Key to Polyergus species
 * Key to US Polyergus species

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



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Biology
I have studied samples of this ant originating from Massachusetts to northwestern Indiana and southern North Dakota. All samples originated from localities with deep, sandy soil. It seems likely it could be found in intervening sandy soil locations, such as the Oak Openings of Ohio or black oak savannas of northern Illinois, Wisconsin and southern Minnesota.

Goodloe and Sanwald (1985) and Goodloe, Sanwald and Topoff (1987) studied this ant in their work on host specificity of “lucidus.” The host of this species is exclusively Formica dolosa (reported as F. schaufussi). These authors determined experimentally that mated gynes from colonies of sanwaldi were not accepted into groups of F. incerta workers, and likewise that gynes of lucidus were not accepted into groups of F. dolosa, while gynes introduced to groups of workers of the species of Formica in their home-nest most often were accepted. In the field, raids of the two species, again, were conducted only on the respective host species in the Polyergus home nest. Their papers were my first clue that lucidus, sensu lato might in fact be more than one species. The habitat of this species is sandy or sandy loam prairies and old fields, and sandy oak and pine savannas.

Nomenclature

 *  sanwaldi. Polyergus sanwaldi Trager, 2013: 530, figs. 42-44 (w.q.m.) U.S.A.

Worker
Holotype HL 1.80, HW 1.67, SL 1.60, ½ VeM 15, ½ PnM 4, WL 2.76, GL 2.68, HFL 2.24, CI 93, SI 96, HFI 134, FSI 134, LI 4.56, TL 7.24.

Paratypes (N=5) HL 1.72–1.80 (1.76), HW 1.63–1.74 (1.70), SL 1.62–1.64 (1.63), ½ VeM 11–15 (12.75), ½ PnM 2–4 (3), WL 2.68–2.83 (2.75), GL 2.12–2.24 (2.19), HFL 2.20–2.32, CI 95–99 (96), SI 93–101 (96), HFI 126–135 (132), FSI 134–143 (137), LI 4.44–4.60 (4.51), TL 6.67–6.76 (6.70).

(N=31) HL 1.52–1.90 (1.65), HW 1.42–1.80 (1.56), SL 1.50–1.79 (1.60), ½ VeM 3–12 (7.03), ½ PnM 0–4 (1.19), WL 2.36–2.86 (2.55), GL 1.69–2.60 (2.23), HFL 2.08–2.44 (2.20), CI 92–97 (95), SI 97–113 (103), HFI 134–150 (1.41), FSI 124–145 (138), LI 3.88–4.76 (4.20), TL 5.96–7.36 (6.43).

Head rounded hexagonal, its length greater than breadth; with conspicuous vertex pilosity, about 20–30 setae; scapes falling slightly short of, to slightly surpassing vertex corners, faintly clavate in the apical third or gradually thickening apically; pronotum with 3–10 dorsal erect setae; mesonotal profile flat; propodeal profile subquadrate; petiole straight- to slightly convex-sided, petiolar dorsum evenly convex; first tergite lacking pubescence; first tergite pilosity sparse (usually < 10 macrosetae), straight, suberect, often deciduous (indicated only by macrosetal sockets in many specimens).

Head matte; mesonotum matte with only slightly smoother pronotal sides; gaster weakly shining.

Color mostly red with darker, brown appendages, and similarly dark lower lateral mesosoma, and posterior portions of tergites.

Etymology
This species is named for Raymond Sanwald, who led to its discovery through his interest in Polyergus, and his willingness to host years of studies by Howard Topoff and his students on the Polyergus species resident at Ray’s Medford (Long Island) NY “Ant Ranch.”