Rhopalothrix isthmica

This species occurs in moderately seasonal to aseasonal wet forest, from sea level to 2000m elevation. All recent specimens are from Winkler or Berlese samples of sifted leaf litter. It is rare for ant species to occur across such a broad elevational spectrum, and given the considerable variability in setal pattern and wide geographic range, it may comprise multiple allopatric populations with unknown degrees of genetic divergence. In Honduras it was a rare cloud forest species at Comayagua and La Muralla and a rare lowland species along the north Caribbean coast. At La Union, in the mountains southeast of Zacapa, Guatemala, it was a rare species sympatric with the much more abundant Rhopalothrix megisthmica. In cloud forest on the slopes of Volcán Atitlán in western Guatemala it was abundant—occurring in 29 of 100 miniWinkler samples—and sympatric with the smaller Rhopalothrix atitlanica. (Longino & Boudinot, 2013)

Identification
Key to Rhopalothrix workers

Distribution based on Regional Taxon Lists
Neotropical Region: Costa Rica, Guatemala, Honduras, Nicaragua, Panama.

Castes
Known only from the worker caste.

Nomenclature

 *  isthmica. Acanthidris isthmicus Weber, 1941a: 188, figs. 4-7 (w.) PANAMA. Combination in Rhopalothrix: Brown & Kempf, 1960: 235.

Worker
Longino and Boudinot (2013) - HW 0.58–0.68 (n=13); mandible with three teeth on masticatory margin, middle tooth largest; subapical tooth with distinct reclinate denticle at base; subapical tooth about twice as long as apical tooth; intercalary teeth prominent, one closest to apical tooth about half as long as apical tooth; labrum trapezoidal, anterior lobes triangular, inner margins of lobes shallowly sloping to semicircular median notch; propodeal tooth acute to right-angled, infradental lamella evenly and shallowly concave; squamiform setae abundant on first gastral tergite, either uniformly covering entire tergite or covering varying extent of posterior portion, at least posterior half with abundant setae.

Type Material
Longino and Boudinot (2013) - Holotype, worker: Panama, Barro Colorado Island, 29 July 1938 (E.C. Williams, Jr. No.313(131)) ? (not examined).