Rhopalothrix megisthmica

This species occurs in cloud forest habitats, from 1400–2000m elevation. All specimens are from Winkler or Berlese samples of sifted leaf litter. It is sympatric with Rhopalothrix isthmica at the type locality and with Rhopalothrix triumphalis on the slopes of Volcán Tacaná in Chiapas. At the type locality it was moderately abundant, occurring in 24 of 100 miniWinkler samples. (Longino and Boudinot 2013)

Identification
Differing from Rhopalothrix isthmica in larger size (HW > 0.73 versus < 0.69), and with propodeal tooth larger and more acute.

Distribution based on Regional Taxon Lists
Neotropical Region: Guatemala, Mexico.

Castes
Known only from the worker caste.

Nomenclature

 *  megisthmica. Rhopalothrix megisthmica Longino & Boudinot, 2013: 313, figs. 1B, 2C, 3F, 9, 16 (w.) GUATEMALA.

Worker
HW 0.73–0.83 (n=12); mandible with two or three teeth on masticatory margin (can vary within individuals, with two teeth on one mandible and three teeth on the other), second tooth from base 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; metanotal groove moderately to strongly impressed; propodeal tooth usually large and acute (shorter and obtuse on one specimen), infradental lamella evenly and shallowly concave; squamiform setae abundant on first gastral tergite, either uniformly covering entire tergite or covering at least 3/4 of posterior portion.

Type Material
Holotype, worker. Guatemala, Zacapa: 2 km SE La Union, 14.94460 −89.27726 ±57 m, 1550 m, 12 May 2009, cloud forest, ex sifted leaf litter (LLAMA Wm-B-03-1-05), unique specimen identifier CASENT0612564]. Paratypes (workers): same data as holotype but 14.94665 -89.27593 ±50 m (LLAMA#Wa-B-03-1-04), CASENT0614540; 14.94677 -89.27585 ±50 m (LLAMA#Wa-B-03-1-07) , CASENT0614546; 14.94723 -89.27707 ±50 m (LLAMA#Wa-B-03-1-45) , CASENT0612503; 14.95372 -89.27618 ±50 m, 1430 m (LLAMA#Wa-B-03-2-31) , CASENT0629572; , CASENT0629573; 3.5 km SE La Union, 14.95 -89.27 (unknown error), 1500 m, 4 Jun 1991 (R.S. Anderson#RSA91-050) , CASENT0603567; , CASENT0603699.

Etymology
Referring to its similarity to R. isthmica, differing mainly in larger size.

References based on Global Ant Biodiversity Informatics

 * Longino J. T. L., and M. G. Branstetter. 2018. The truncated bell: an enigmatic but pervasive elevational diversity pattern in Middle American ants. Ecography 41: 1-12.
 * Longino J. T., and B. E. Boudinot. 2013. New species of Central American Rhopalothrix Mayr, 1870 (Hymenoptera, Formicidae). Zootaxa 3616: 301-324.