Polyergus montivagus Wheeler

Subfamily FORMICINAE
Tribe FORMICINI
Polyergus montivagus Wheeler

Polyergus montivagus, full face view of a worker (click image to enlarge).
Photo courtesy of http://www.antweb.org/

Polyergus montivagus, profile view of a worker (click image to enlarge).
Photo courtesy of http://www.antweb.org/

Overview
Polyergus workers can be easily recognized by their large size (approximately 4.0 - 7.0 mm long), yellowish-red to dark reddish-brown coloration, and possession of sickle-shaped (falcate) mandibles with minute serrations on inner border.

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)

Identification
Overall length approximately 6.5 mm. Color, yellowish-red, apex of gaster lacking or with only weak infuscation, appendages slightly darker than body. Head and alitrunk subopaque, gaster shining. Head slightly longer than wide, cheeks slightly concave, sides of head converge above eyes, occipital border mostly straight to feebly emarginate. Eye convex, longer than wide, situated more than its greatest diameter from the mandibular base. Antennal scape 1.3-1.4 times length of interocular distance, and gradually enlarged as toward the apex (but not club-like as in P. breviceps). Frontal carina short, frontal area triangular, weakly defined. Ocelli small. Clypeus twice as wide as long or more, subcarinate, anterior border broadly emarginate medially. Mandible falcate, flattened and with minute serrations along inner border. Alitrunk with distinct promesonotal suture; metanotal groove strongly impressed. Propodeum bluntly rounded where declivity meets base. Petiole erect, thickened anteroposteriorly, more convex anteriorly than posteriorly, superior border blunt and subtruncate. Mandibles, clypeus, underside of head, pronotum, prosternum, coxae, trochanters, flexor surfaces of legs, petiole and gaster with scattered erect hairs; occipital lobes lacking erect hairs or with only one or two each. Pubescence on body fine, appressed, and sparse. (Identification from Smith, 1947).

This species can be separated from P. longicornis by its lack of infuscation at the apex of gaster and lack of erect hairs on the occipital lobes, both of which are present in P. longicornis. It differs from P. lucidus in that the head and alitrunk are subopaque, whereas, in P. lucidus, the entire body is shining. Polyergus montivagus differs from P. breviceps by having much longer scapes, scapes in P. breviceps are not as long as interocular distance; by not having the antennal scapes terminating in a club (scapes in P. breviceps enlarged distally forming a club); and by having sparse pubescence on the gaster, whereas, pubescence on gaster of P. breviceps is dense).

Biology and Economic Importance
Polyergus montivagus has been reported to utilize Formica pallidefulva as hosts (King and Trager, 2007).

This species poses little in the way of economic importance, as is rarely encountered. However, if provoked or handled worker can inflict a somewhat painful bite.

Distribution
This species has been reported from Colorado and Florida (King and Trager, 2007; Smith, 1947), and it has been collected In Mississippi in Chickasaw, Lowndes, and Oktibbeha Counties (MEM records).

Literature Cited
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

Smith, M. R. 1947. A Study of Polyergus in the United States, based on the workers (Hymenoptera: Formicidae). The American Midland Naturalist 38: 150-161.

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