Formicidae, Hymenoptera, Insecta, Arthropoda, Animalia
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Range
Honduras, Costa Rica, Panama, Colombia, Venezuela, French Guiana, Ecuador, Peru, Bolivia, Brazil (RJ, SP, BA), Puerto Rico, Dominican Republic, Cuba. Costa Rica: Atlantic lowland rainforest, to 1000m on Cordillera de Tilaran, to 800m on Cordillera Volcanica Central, to 1200m at San Vito (Wilson Botanical Garden).
Identification
Opening of propodeal spiracle viewed perpendicularly slit-shaped, more than twice as long as wide (spiracle is very small, and boss around spiracle is round, but actual orifice still slit-shaped); petiole scale-shaped, tapering dorsally to rounded summit; in lateral profile, posterior margin of anteroventral petiolar lobe square-cut or slightly produced as a subacute angle; mandible with 6 teeth, basal and masticatory margins not well-differentiated; lateral wings of clypeus divided by distinct transverse ridge, anterior portion distinctly concave and bent ventrad; head width about 0.8mm.
Similar species: stigma, cognata, JTL-011.
Natural History
This species occurs in mature rainforest, where it inhabits the leaf litter on the forest floor. I have most often encountered cauta in samples of sifted leaf litter (Winkler samples), but I have also collected workers from under dead wood on the ground, and from under epiphytes in old treefalls. I have never found any in the canopy or in recent treefalls, so I presume the ones I have found in old treefalls move there after the tree has fallen.
Type Data
Euponera (Trachymesopus) cauta Mann 1922:8. Holotype worker: Honduras, Lombardia (Mann) [USNM] (examined 1999).
Notes
When I first discovered that the Pachycondyla stigma complex could often be divided into a tramp species of open areas and coastlines (stigma s.s.) and a forest interior form, I used the name cauta for the latter. Roy Snelling discovered that two forms were sympatric on Cuba, and the forest interior form was probably Roger's succedanea. I used the name succedanea for the forest interior form, considering cauta a junior synonym. But Roy has now seen images of Roger's succedanea and concludes it is a junior synonym of stigma. Thus I return to referring to this species as cauta.
In Costa Rica, I have discovered two cauta-like forms, differing only in the form of the mandibles. One form has a mandible more like stigma, with 6 teeth, and one has a mandible more like cognata, with 7 or 8 teeth. I use cauta for the former and JTL-011 for the latter. In Atlantic slope rainforest, the two forms are ecologically distinct, with the former occurring in leaf litter on the forest floor, and the latter occurring in the canopy under epiphytes. In examining specimens of cauta from elsewhere in the Neotropics, I encounter variation in mandible shape and dentition, such that I cannot cleanly separate the two forms. Thus, a global definition of cauta would encompass both cauta and JTL-011 in Costa Rica. The form I call cauta in Costa Rica closely matches the type of cauta.
Literature Cited
Mann, W. M. 1922. Ants from Honduras and Guatemala. Proceedings of the U. S. National Museum 61:1-54.
Roger, J. 1863. Die neu aufgefuehrten Gattungen und Arten meines Formiciden-Verzeichnisses nebst Erganzung einiger frueher gegebenen Beschreibungen. Berl. Entomol. Z. 7:131-214.
Page author:
John T. Longino, The Evergreen State College, Olympia WA 98505 USA.longinoj@evergreen.edu
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