Formicidae, Hymenoptera, Insecta, Arthropoda, Animalia
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Additional images: SEM, face view; SEM, lateral view.
Range
Mexico to Colombia (Brown 1958, Lattke 1995). Costa Rica: widespread in wet forest between 500 and 2000m elevation, rare at lower elevations. Occurs from Cordillera de Guanacaste to Talamancas.
Identification
Pronotum separated from remainder of mesosoma by a very distinct suture, completely breaking the sculpture; anteroventral process of petiole square-cut, with sharp posterior angle; metanotal suture not impressed, not breaking sculpture, much weaker than promesonotal suture; mesonotum and dorsal face of propodeum forming even convexity; scapes surpassing margin of vertex by less than length of first funicular segment; petiole posteriorly inclined, the anterior face joining the dorsal face through a broad convexity that contrasts with a sharper angle between the posterior and dorsal faces, but posterior face perpendicular, not concave.
Natural History
This is the most common Gnamptogenys species above 500m elevation in wet forest leaf litter. It occurs at lower elevations (e.g. La Selva) but is less common there. It is frequently encountered foraging on the ground at night, and is common in samples of sifted leaf litter (Winkler samples). It nests in and under dead wood on the ground, under stones, and in soil. It may be polygynous: I observed a nest in Monteverde with two dealate queens. Observations of prey items include lepidopteran larvae, isopods, diptera (adults and larvae), and beetle larvae.
Nest observation from Guanacaste Province, Cerro Cacao: I discovered a nest in the soil of a steep bank at the side of a trail. Many workers were out foraging, and several workers were observed dragging a dead Camponotus albicoxus to the nest. I excavated the nest; it extended no more than 10cm horizontally back into the bank. There were several irregular galleries and chambers. One major chamber contained the queen.
Taxonomic Notes
There is variation in the size of the propodeal spiracle size. Some have very large spiracular openings, others have a distinct thickened rim that reduces the spiracular opening to a small pore. The character seems to be constant within colonies. I at first attempted to use this character as evidence of two species, and most material fell cleanly into one form or the other. However, 1) there was at least one intermediate specimen, 2) in all other respects the workers were similar or with discordant character variation, and 3) the two forms were both present in Monteverde and Penas Blancas, with no evidence of divergent distributions or habitats.
Type data
Holcoponera strigata Norton 1871:4. Type worker: Mexico, "temperate regions."
Literature Cited
Brown, W. L., Jr. 1958. Contributions toward a reclassification of the Formicidae. II. Tribe Ectatommini (Hymenoptera). Bulletin of the Museum of Comparative Zoology 118:175-362.
Lattke, J. E. 1995. Revision of the ant genus Gnamptogenys in the New World (Hymenoptera: Formicidae). Journal of Hymenoptera Research 4:137-193.
Norton, E. 1868. Description of Mexican ants noticed in the American Naturalist, April 1868. Communications of the Essex Institute 6:1-10.
John T. Longino, The Evergreen State College, Olympia WA 98505 USA.longinoj@evergreen.edu
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