Formicinae, Formicidae, Hymenoptera, Insecta, Arthropoda, Animalia
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Additional images: worker scape (small, large).
Range
Southwestern USA, Mexico, Costa Rica. Costa Rica: Cordillera de Tilar‡n, Cordillera Volcanica Central.
Identification
Scape with macrochaetae inconspicuous, little longer than abundant suberect pubescence; first gastral tergite lacking appressed pubescence; color light to dark brown; face usually shagreened, with bluish reflections.
Natural History
In Costa Rica, this species is a strict cloud forest specialist. In the Monteverde area, it is one of the most abundant ants in the cloud forest on the ridge crest, at 1400-1800m elevation. Most Winkler samples from the forest floor contain workers, and baits placed on the forest floor will attract workers. The species decreases in abundance as one descends into the Pe–as Blancas Valley east of Monteverde. It is present at El Aleman, a site at 900m elevation. Just a few kilometers away at Refugio Eladio, at 800m elevation, I have never collected it, in spite of abundant Winkler sampling at the site.
Sampling by Project ALAS along the Barva transect in Braulio Carrillo National Park reveals a similar pattern. The species is abundant in the leaf litter at sites between 1000-1500m. It is absent from the 2000m site and the 500m site.
Although my sampling in the Cordillera de Talamanca is limited, I have taken a few Winkler samples from montane forest sites such as Wilson Botanical Garden and Estacion Biologica Pittier, and I have not found P. austroccidua. The Cordillera Volcanica Central may be the southern limit of this northern element in the Costa Rican fauna.
At the northern end of the range, in the United States, this species inhabits the tops of mountains, often island-like forested habitats surrounded by lowland deserts. In douglas fir forests and pine forests in the Huachuca Mountains and similar areas it nests under stones and dead wood (Trager 1984).
Literature Cited
Trager, J. C. 1984. A revision of the genus Paratrechina (Hymenoptera: Formicidae) of the continental United States. Sociobiology 9:49-162.
Page author:
John T. Longino, The Evergreen State College, Olympia WA 98505 USA.longinoj@evergreen.edu
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