Myrmicinae, Formicidae, Hymenoptera, Insecta, Arthropoda, Animalia
Additional images: worker dorsal view (large); worker petiole, lateral view (large).
Costa Rica: Atlantic slope wet forest from 50m to 1600m (2000m?).
Basal margin of mandible flat, without a notch; face with a distinct fan of longitudinal rugae between frontal lobes, and rugose sculpture that extends from mandibular insertions to beyond compound eye; rest of face and promesonotum smooth and highly polished; propodeum shiny and polished like promesonotum, but with variably developed transverse rugae on dorsal face; legs red brown, contrasting with darker mesosoma.
Variation: There is a tendency for workers to be smaller and more strongly sculptured at lower elevation. However, an isolated worker from the 2000m site, tentatively identified as this species, is aberrant in several respects. It is relatively large. The facial sculpture is more extensive than on any other specimens, extending over about 3/4's of the face, leaving a narrow posterior strip that is smooth and polished. The pronotum, instead of being completely smooth, has feeble, thin, widely spaced, transverse striae. A specimen from Panama, Bocas del Toro, Fortuna-Chiriqui Grande road, 800m (D. Olson) has similar face sculpture but even heavier sculpture, with abundant transverse striae on the promesonotum and dorsal face of propodeum. However, it is smaller and with light-colored legs, like the typical form. This specimen is so different I have given it a different morphospecies code: JTL-014.
Similar species: Stenamma expolitum.
Stenamma JTL-013 occurs in mature wet forest habitats. It is a specialist inhabitant of clay banks. Colonies are most readily encountered on nearly vertical banks along stream margins, but may also occur along trail edges where they have been cut into hillsides.
In spite of ten collections of entire or nearly entire colonies, most with dealate queens, I have never found males or alate queens.
John T. Longino, The Evergreen State College, Olympia WA 98505 USA.email@example.com
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