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Taxonomic History (provided by Barry Bolton, 2017)

Distribution:

(based on species list records)
Neotropical Region: Americas, Central America, Costa Rica, Heredia

Distribution Notes:

Costa Rica: mid-elevation Atlantic slope.

Biology:

Longino notes:

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 500-1100m 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, and another in a canopy fogging sample. Workers have been collected as foragers on low vegetation.

Identification:

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.

Comments:

Named for Ronald Vargas C., ALAS Parataxonomist from 1992 to 2005.

Notes:

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.

References:

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.

Specimen Habitat Summary

Found most commonly in these habitats: 3 times found in montane wet forest, 1 times found in wet forest.

Found most commonly in these microhabitats: 1 times Wet forest. Strays on vegetation at site, all habitats., 1 times Primary forest gap. Nest in 1.25cm dia live melastome vine; entire nest contents, 1 times strays on refuge building, 1 times strays, 1 times Sobre Vegetacion.

Collected most commonly using these methods: 3 times search, 1 times Foggin, 1 times Sweeping.

Elevations: collected from 500 - 1100 meters, 950 meters average

Type specimens: Holotype Nesomyrmex vargasi: inbiocri002281227; Paratype Nesomyrmex vargasi: inb0003225385, jtlc000008515, jtlc000008516, jtlc000008517, jtlc000008518, jtlc000008519, inbiocri002281228, inbiocri002282019; paratype of Nesomyrmex vargasi: lacment144699

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