Subfamily FORMICINAE
Tribe FORMICINI

Polyergus ruber Trager, 2013

by Joe A. MacGown, uploaded 20 August 2014

Polyergus ruber, full face view of a worker (photo by James Lewis and Joe MacGown)
Polyergus ruber, lateral view of a worker (photo by James Lewis and Joe MacGown)
Polyergus ruber, dorsal view of a worker (photo by James Lewis and Joe MacGown)

Introduction
Polyergus workers can be easily recognized by their large size (approximately 4.0 - 7.0 mm long), yellowish-red to dark reddish-brown coloration, presense of three small ocelli, and sickle-shaped (falcate) mandibles with minute serrations on inner borders. Additionally characteristics of the genus are: eye convex, longer than wide, situated more than its greatest diameter from the mandibular base; frontal carina short, frontal area triangular, weakly defined; clypeus wider than long; mesosoma with distinct promesonotal suture; propodeum bluntly rounded where declivity meets base; petiole erect, thickened anteroposteriorly, more convex anteriorly than posteriorly, superior border blunt and subtruncate.

Polyergus species are obligatory or true slave-making ants. In nest founding, the female enters a nest of the host species, eventually kills the rightful queen, and uses the host workers to tend her brood. Polyergus colonies conduct slave raids on nests of various species of Formica, and workers of the host are taken and used by the Polyergus colony to feed and rear the brood and excavate the nest. Polyergus workers are incapable of surviving without slaves. In laboratory colonies, a colony without slaves will starve to death even when plentiful food is available. (Hedlund, 2007; King and Trager, 2007).

Taxonomic History (from Trager 2013, Bolton 2014)
Polyergus oligergus Trager, 2013: 528, figs. 39-41 (w.) U.S.A. Nearctic.

Identification
Worker Measurements (in mm) from Trager 2013 (for more comprehensive measurements, see Trager's paper). (N=26) HL 1.52–1.90 (1.65), HW 1.42–1.80 (1.64), SL 1.68–1.79 (1.71), WL 2.52–2.86 (2.66), TL 6.16–7.36 (6.75). Color clear red with some infuscation at tip of gaster and legs. Head matte to weakly shining, mesosomal matte on dorsum, but shining laterally, and gaster shining. Head longer than wide; vertex with numerous macrosetae (8–20); scape reaching and usually surpassing corners of vertex and gradually thickening distally. Pronoutum with 0–9 erect setae dorsally. Miesonotum weakly convex (in profile view). Propodeum evenly rounded to weakly obtuse in profile. Petiole narrow, with convex sides taht converge dorsally, dorsum rounded or flat medially, ocassionally slightly concave. First gastral tergite lacking pubescence, with sparse, weakly flexuous to straight pilosity.

Polyergus ruber is most similar to P. longicornis and P. lucidus. It differs from P. longicornis by being shinier and having less pilosity on the vertex, and it differs from P. lucidus by having longer appendages. Additionally, P. ruber differs in that its host is Formica biophilica.

Biology and Economic Importance
Polyergus ruber appears to exclusively use F. biophilica as a host,. Raids have been observed from early June to mid-August near 5 PM. Raiding parties are considered to be relatively large compared to some species, with 500 to 1000 individuals (Trager 2013).

Distribution (from Trager 2013)
USA: Georgia, Maryland, Mississippi, Missouri, and North Carolina.

Literature Cited
Forel, A. 1899. Formicidae. Biol. Cent.-Am. Hym. 3: 1-160.

Hedlund, K. S. 2007. The Ants: North America Catalog: Genus Polyergus. http://www.cs.unc.edu/~hedlund/playpen/dev/ants/catalog/ (accessed 6 June 2008).

King, J. R. and J. C. Trager. 2007. Natural history of the slave making ant, Polyergus lucidus, sensu lato in northern Florida and its three Formica pallidefulva group hosts. 14 pp. Journal of Insect Science 7: 42, available online: insectscience.org/7.42

Trager, J. C. 2013. Global revision of the dulotic ant genus Polyergus (Hymenoptera: Formicidae, Formicinae). Zootaxa 3722 (4): 501–548.

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