Polyergus vinosus

A southwestern North American species found in a number of coastal and near-coastal habitats. Its biology is relatively poorly known but it appears it exclusively raids colonies of Formica moki.

Identification Keys including this Taxon

 * Key to Polyergus species
 * Key to US Polyergus species

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

This species is endemic to the Californian vegetation zone of southern California and northern Baja California, Mexico, and is also found on Santa Cruz Island, California.



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Biology
Polyergus vinosus is a species of mature chaparral, coast live oak woodland and savanna, rocky wooded canyons and oak-gray pine woodlands of the southern California coast hills. As far as known, its exclusive host species is Formica moki, and the nests have the host species’ usual cryptic placement among rocks, often near streams or along wet-weather drainages, and sometimes with a lightly thatched superstructure. Only a few raids have been observed, but from unpublished observations by Les Greenberg (U. C. Riverside, pers. comm.) and Geoff Trager (then a student at UC Santa Barbara, pers. comm.), we know that the raids take place in early to mid summer, in the latter half of the afternoon. The raiding season may begin and end earlier than that of species from colder, summer-rainy climates.

Nomenclature

 *  vinosus. Polyergus vinosus Trager, 2013: 520, figs. 18-20 (w.q.m.) U.S.A.

Worker
Holotype HL 1.39, HW 1.34, SL 1.34, ½ VeM 0, ½ PnM 3, WL 2.16, GL 1.93, HFL 1.72, CI 96, SI 100, HFI 128, FSI 128, LI 3.55, TL 5.48.

Paratypes (N=4) HL 1.39–1.64 (1.51), HW 1.34–1.60 (1.46), SL 1.32–1.40 (1.37), ½ VeM 0, ½ PnM 3–6 (3.80), WL 2.16–2.40 (2.27), GL 1.64–2.44 (2.02), HFL 1.72–1.95 (1.83), CI 95–98 (97), SI 88–100 (94), HFI 122–128 (125), FSI 128–139 (134), LI 3.55–4.04 (3.78), TL 5.48–6.48 (5.81).

(N=36) HL 1.23–1.67 (1.43), HW 1.20–1.60 (1.40), SL 1.14–1.41 (1.27), ½ VeM 0–2 (0.11), ½ PnM 0–7 (3.43), WL 1.93–2.48 (2.18), GL 1.64–2.82 (2.14), HFL 1.55–2.00 (1.73), CI 95–103 (98), SI 80–100 (91), HFI 113–133 (124), FSI 128–142 (136), LI 3.23–4.15 (3.60), TL 4.26–6.97 (5.69).

Head truncate-ovate, its length usually slightly greater than breadth; scapes long for the breviceps species group (SI usually 85–95, never < 80), nearly reaching or even surpassing vertex corners, weakly clavate or gradually thickening in the apical third; pronotum with 0–6 (less often, up to 12, especially Santa Cruz Island population) dorsal macrosetae; mesonotum with profile weakly convex for most of its length, notably convex and “bulging” in the largest workers; propodeum subquadrate with a rounded angle; petiole sides rounded and converging dorsad, petiolar dorsum flat or even shallowly concave; first tergite densely pubescent; first tergite pilosity a relatively sparse 6–20 flexuous, mid-anterodorsal, suberect macrosetae and sometimes a few widely spaced ones in the posterior tergal half.

Head weakly shining; mesonotum weakly shining beneath fine gray pubescence; gaster weakly shining beneath fine gray pubescence.

Color mostly orange-red to wine red with scarcely any infuscation of gaster or appendages.

The most significant variation in this species is the greater pronotal pilosity of the Santa Cruz Island population, with ½ PnM 6–12, contrasting with 1–4 (rarely 5 or 6) on the mainland. Workers of Baja California are paler tan-orange in color (as in Fig. 6, possibly faded in preservation), and have a more rounded propodeal profile.

Etymology
“Vinosus” is Latin for red-wine-colored. Somewhat ironically, much of its habitat may be threatened by the conversion of its southern California oak woodland habitat to vineyards.