Myrmicinae, Formicidae, Hymenoptera, Insecta, Arthropoda, Animalia
Above images are of holotype. Additional images: holotype worker, dorsal view (small, large); alternate face view (small, large); alternate lateral view (small, large); label (small, large).
Costa Rica: mid-elevation Atlantic slope.
Antennae 11-segmented; metasternal lobes subangulate; mandibles smooth and shining at inner half of upper surface; sides of thorax mostly smooth and shining but with some coarse rugae on lower side of propodeum; propodeal spiracles directed upward, highly visible in dorsal view; propodeal spine relatively large compared to Nesomyrmex JTL-009, and petiolar node relatively longer and lower.
Similar species: pleuriticus, JTL-009.
This species occurs in mid-elevation wet forest habitats. So far it is known only from the Volcan Barva transect in Braulio Carrillo National Park, from 1000-1100m elevation. I collected a nest in a treefall gap, in the 1.25cm diameter live stem of a melastome vine. It contained 32 workers, 1 dealate queen, and abundant brood of various sizes. One specimen was collected in a Project ALAS sweep sample. Workers have been collected as foragers on low vegetation.
Holotype worker: Costa Rica: Heredia Prov., 15 km SSE La Virgen (10¡17'N 84¡05'W), 1000 m elevation, 12.VII.1986, leg. J. Longino#1365, specimen code INBIOCRI002281227 (INBC).
10 Paratypes: worker and dealate queen, same data as holotype, specimen code INBIOCRI002281228 (JTLC); worker, same data as holotype but 9.VII.1986, leg. J. Longino#1380-s, JTLC000008515 (LACM), JTLC000008516 (MCZC), JTLC000008517 (UCDC), JTLC000008518 (CASC), JTLC000008519 (NMW); worker, Costa Rica: Heredia Prov., 16 km SSE La Virgen (10¡16'N 84¡05'W), 1100 m elevation, leg. R. Vargas C. 11/RG/RVC/009, INB0003225385 (INBC); worker, same data but 15-17.XI.2000, leg. J. Longino#4365-s, INBIOCRI002282019 (USNM); same data but 11.II.2001, leg. J. Longino#4385-s, LACM ENT 144699 (BMNH).
Worker: Antenna 11-segmented; eye with about 11 ommatidia across greatest diameter; mandible smooth and shiny to weakly striate; all surfaces of body shiny; generally smooth and polished except for about 5 longitudinal rugae between eye and antennal insertion, about 6 longitudinal rugae on promesonotum, a few longitudinal rugulae on dorsal face of propodeum, about 3 longitudinal rugae on ventral half of side of pronotum, irregular rugulae on katepisternum and side of propodeum, about 4 longitudinal rugae on side and dorsum of petiole; side and dorsum of pronotum flat, meeting at carinate right angle; propodeal spiracles large, horizontal, opening dorsally; inferior propodeal lobes large, produced as an acute but rounded angle; anteroventral margin of petiole with acute, ventrally-directed tooth; scapes with abundant erect setae, these shorter than maximum width of scape, and with abundant underlying suberect pubescence; face with abundant short erect setae, these about as long as setae on scapes; in full face view abundant short suberect setae projecting from sides of head and margin of vertex; mesosomal and petiolar dorsa with abundant flexuous setae, these longer than those on face, longest about as long as propodeal spines; postpetiole, gastral dorsum, femora, and tibiae with abundant erect setae, these about as long as those on scapes and face; color red brown.
Measurements (holotype): HL 0.764, HW 0.722, SL 0.603, MeL 0.938.
Named for Ronald Vargas C., ALAS Parataxonomist from 1992 to 2005.
This species keys to N. pleuriticus in Kempf (1959). The two species have a parapatric distribution on the Barva Transect in Braulio Carrillo National Park, N. pleuriticus occurring at La Selva Biological Station and the 500 m site, N. vargasi occurring around the 1100m site. Nesomyrmex vargasi differs from N. pleuriticus in the much smoother and shinier surface sculpture.
Kempf, W. W. 1959. A synopsis of the New World species belonging to the Nesomyrmex-group of the ant genus Leptothorax Mayr (Hymenoptera: Formicidae). Studia Entomologica (n.s.) 2:391-432.
Longino, J. T. 2006. New species and nomenclatural changes for the Costa Rican ant fauna (Hymenoptera: Formicidae). Myrmecologische Nachrichten 8:131-143.
John T. Longino, The Evergreen State College, Olympia WA 98505 USA. firstname.lastname@example.org
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