Polyergus bicolor

Polyergus bicolor
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Insecta
Order:	Hymenoptera
Family:	Formicidae
Subfamily:	Formicinae
Tribe:	Formicini
Genus:	Polyergus
Species group:	rufescens-breviceps
Species:	P. bicolor
Binomial name
Polyergus bicolor Wasmann, 1901 Specimen Labels

This species lives in rotting logs, possibly preferring pine, with its host Formica subaenescens or less commonly Formica neorufibarbis (James Trager).

At a Glance

• Dulotic

Identification

P. bicolor is usually easily distinguished from other Nearctic species by its distribution, distinctive two-tone coloring and sparse pilosity. Northern (North Dakota, USA to British Columbia, Canada) populations of Polyergus mexicanus may exhibit similar coloration, but mexicanus is always more pilose. Bicoloration and reduced pilosity occur commonly in the small workers from young colonies of mexicanus, causing possible confusion. Nanitics of mexicanus are usually recognizable by their slender heads with a rounded vertex and longish appendages, and at least a pair of erect pronotal setae. Large workers of other breviceps-complex species also may appear somewhat bicolored, but only rarely is the bicoloration so neatly defined by a nearly completely dark gaster as in bicolor, and these others have more pilosity on the head and mesosoma.

Keys including this Species

• Key to Polyergus Species
• Key to US Polyergus species

Distribution

This species is apparently endemic to the upper Mississippi Valley, from the western Great Lakes region west to the Dakotas and southern Manitoba. In the past it was found in southern Wisconsin and as far south as Rockford, Illinois, but it has not been seen in this area in recent decades.

Latitudinal Distribution Pattern

Latitudinal Range: 44.34° to 44.1919°.

North Temperate	North Subtropical	Tropical	South Subtropical	South Temperate

• Source: AntMaps

Distribution based on Regional Taxon Lists

Nearctic Region: Canada, United States (type locality).

Distribution based on AntMaps

Distribution based on AntWeb specimens

Check data from AntWeb

Countries Occupied

Number of countries occupied by this species based on AntWiki Regional Taxon Lists. In general, fewer countries occupied indicates a narrower range, while more countries indicates a more widespread species.

Estimated Abundance

Relative abundance based on number of AntMaps records per species (this species within the purple bar). Fewer records (to the left) indicates a less abundant/encountered species while more records (to the right) indicates more abundant/encountered species.

Biology

Trager (2013): P. bicolor normally parasitizes Formica subaenescens, and normally nests with it in rotten stumps or fallen limbs in forests. Wheeler (1910) described raids occurring in early afternoon in a mature mesic forest in northern Illinois that originated from nests in stumps. Two samples examined in this study had Formica neorufibarbis hosts, also a denizen of moist woods, especially tamarack bogs in the eastern part of its range. Through the course of this study I was not able to obtain or study any specimens of bicolor (nor of its host F. subaenescens) collected within about the last 50 years, from bicolor’s historic range, and I am led to wonder if they have contracted northward due to climatic warming or other causes. Just before submitting this manuscript, in July 2013, I collected a sample in northern Wisconsin. As in the published records, this sample occupied a rotting log with F. subaenescens. The log was about 35 cm in diameter, with bark beginning to loosen and wood in transition from white to red rot. At first glance, the mixed colony bore a striking resemblance to a young colony of the locally common Formica aserva.

Castes

Images from AntWeb

Worker. Specimen code casent0281067. Photographer Shannon Hartman, uploaded by California Academy of Sciences.	Owned by CAS, San Francisco, CA, USA.

Worker. Specimen code casent0281068. Photographer Shannon Hartman, uploaded by California Academy of Sciences.	Owned by CAS, San Francisco, CA, USA.

Nomenclature

The following information is derived from Barry Bolton's Online Catalogue of the Ants of the World.

• bicolor. Polyergus rufescens subsp. bicolor Wasmann, 1901: 369 (w.q.m.) U.S.A. Junior synonym of breviceps: Wheeler, J. 1968: 163. Raised to species: Trager, 2013: 514.

Unless otherwise noted the text for the remainder of this section is reported from the publication that includes the original description.

Type Material

• Syntype, workers, Prairie du Chien, Crawford Co., Wisconsin, United States, 43°02′0″N 91°08′0″W, MCZ Type 22970, Museum of Comparative Zoology.
• Syntype, workers, male, Prairie du Chien, Crawford Co., Wisconsin, United States, 43°02′0″N 91°08′0″W, Los Angeles County Museum of Natural History.
• Syntype, workers, male, Prairie du Chien, Crawford Co., Wisconsin, United States, 43°02′0″N 91°08′0″W, USNM#59719, National Museum of Natural History.
• Syntype, queen, Prairie du Chien, Crawford Co., Wisconsin, United States, 43°02′0″N 91°08′0″W.

Polyergus rufescens subsp. breviceps var. fusciventris Wheeler 1917: 555 (part). Unavailable name; following material referred here: CANADA, MANITOBA, South Cypress RM. Treesbank. (Wheeler) [USNM #59925, USNM ENT 00529453] (image examined by Trager, 2013).

Description

Worker

Trager (2013) - Syntype [LACM, red “type series” label, top specimen] HL 1.30, HW 1.28, SL 1.04, ½ VeM 0, ½ PnM 0, WL 1.96, GL 1.88, HFL 1.48, CI 98, SI 81, HFI 116, FSI 142, LI 3.26, TL 5.14.

(N=44) HL 1.24–1.66 (1.40), HW 1.24–1.74 (1.41), SL 0.92–1.16 (105), ½ VeM 0, ½ PnM 0–2 (0.58), WL 1.88–2.32 (2.08), GL 1.60–2.80 (2.07), HFL 1.40–1.68 (1.55), CI 97–105 (100), SI 64–81 (75), HFI 97–120 (110), FSI 137–158 (147), LI 3.12–3.98 (3.48), TL 4.83–6.58 (5.56).

Head subquadrate to suborbicular, its length and breadth about equal, sides often quite rounded; vertex concave, the concavity about half the head width in breadth, completely lacking vertex pilosity; scapes short, not reaching vertex corners, notably clavate in the apical third; pronotum lacking pilosity, or rarely with 1–2 dorsal erect setae; mesonotum profile flat or very weakly convex for most of its length; propodeum profile a rounded weakly obtuse angle; petiole with rounded sides, petiolar dorsum rounded, not at all or only feebly emarginate; first tergite moderately pubescent, with pilosity much like that of breviceps, in 4–5 transverse arrays; first tergite pilosity flexuous, subdecumbent.

Head matte; mesonotum matte; gaster matte to weakly shining.

Color of head, mesonotum and often petiole dull red, gaster very dusky red (nearly black); forelegs often redder than middle and hind legs; pilosity reddish brown, pubescence fine and grayish.

Etymology

Trager (2013) - Wasmann coined this name from the Latin nominal adjective “bicolor” meaning two-colored.

References

• de la Mora, A., Sankovitz, M., Purcell, J. 2020. Ants (Hymenoptera: Formicidae) as host and intruder: recent advances and future directions in the study of exploitative strategies. Myrmecological News 30: 53-71 (doi:10.25849/MYRMECOL.NEWS_030:053).
• Rericha, L. 2007. Ants of Indiana. Indiana Department of Natural Resources, 51pp.
• Trager, J.C. 2013. Global revision of the dulotic ant genus Polyergus (Hymenoptera: Formicidae, Formicinae, Formicini). Zootaxa 3722, 501–548.
• Wasmann, E. 1901. Neues über die zusammengesetzten Nester und gemischten Kolonien der Ameisen. [part]. Allg. Z. Entomol. 6: 369-371 (page 369, worker, queen, male described)
• Wheeler, J. 1968. Male genitalia and the taxonomy of Polyergus (Hymenoptera: Formicidae). Proc. Entomol. Soc. Wash. 70:156-164. [Erratum, Proc. Entomol. Soc. Wash: 156-164 (page 163, Junior synonym of breviceps)

References based on Global Ant Biodiversity Informatics

• Downing H., and J. Clark. 2018. Ant biodiversity in the Northern Black Hills, South Dakota (Hymenoptera, Formicidae). Journal of the Kansas Entomological Society 91(2): 119-132.
• Gregg, R.T. 1963. The Ants of Colorado.
• Smith M. R. 1947. A study of Polyergus in the United States, based on the workers (Hymenoptera: Formicidae). American Midland Naturalist 38: 150-161.
• Trager J. C. 2013. Global revision of the dulotic ant genus Polyergus (Hymenoptera: Formicidae, Formicinae, Formicini). Zootaxa 3722(4): 501-548.
• Wheeler G. C., and E. W. Wheeler. 1944. Ants of North Dakota. North Dakota Historical Quarterly 11:231-271.
• Wheeler J. 1968. Male genitalia and the taxonomy of Polyergus (Hymenoptera: Formicidae). Proc. Entomol. Soc. Wash. 70: 156-164.