Polyergus breviceps Emery

Subfamily FORMICINAE
Tribe FORMICINI
Polyergus breviceps Emery

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

Polyergus breviceps, profile view of 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 4.0 - 6.0 mm. Color, dark reddish-brown sometimes with parts or all of gaster infuscated or blackish. Body subopaque to shining, but gaster opaque in appearance because of dense pubescence. Head approximately as wide as long, sides of head converge above eyes, occipital border feebly emarginate. Eye not noticeably convex, longer than wide, situated more than its greatest diameter from the mandibular base. Antennal scape short, not as long as length of interocular distance, and enlarged at apex forming a prominent club. Frontal carina short, diverging posteriorly. 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 short and stout, with distinct promesonotal suture. Mesonotum not strongly convex. Propodeum bluntly rounded where declivity meets base. Petiole erect, thickened anteroposteriorly, more convex anteriorly than posteriorly, superior border blunt and subtruncate. Mandibles, clypeus, pronotum, prosternum, coxae, trochanters, flexor surfaces of legs, petiole and gaster with erect hairs. Pubescence on body appressed, and sparse, except on gaster where it is dense. (Identification from Smith, 1947).

This species can be separated from other Polyergus species in the southeastern United States by its shorter antennal scapes, which are shorter than the interocular distance, clubbed appearance of antennal scape, and the more densely pubescent gaster.

Biology and Economic Importance
As with other Polyergus species, P. breviceps are obligate slave-makers. They have been reported to use the following species as hosts: Formica altipetens Wheeler, F. argentea Wheeler, F. fusca L., F. lepida Wheeler, F. montana Emery, F. neoclara Emery, F. neorufibarbis Emery, F. pallidefulva Latreille, and F. subpolita Mayr (Smith, 1979). I have also collected this species with F. subsericea Say in Arkansas.

Alates of this specie have been collected in the summer.

Distribution
Smith (1979) gives the distribution of this species as Ontario, Michigan. west to British Columbia south to Indiana, Illinois, Missouri, Kansas, New Mexico, Arizona, and California. The MEM has also collected this species in Conway County, Arkansas.

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, D. R. 1979. In Catalog of Hymenoptera in America north of Mexico. Smithsonian Institution Press, Washington D. C. Vol. 2, pp. 1323-1427.

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.

Links

AntWeb Images
Discover Life Images