Pheidole obturaculum

This species occurs in cloud forest habitats. Minor and major workers recruit to ground baits.

Identification
Minor: face uniformly foveolate; promesonotum evenly arched; promesonotal groove not impressed; most of mesosoma foveolate, except for medial shiny patch on lateral pronotum; propodeal spines about one fourth length of posterior face of propodeum; gaster smooth and shining; abundant flexuous erect setae on mesosomal dorsum, tibiae, and gaster; color dark brown.

Major: inner hypostomal teeth stout, closely spaced; scape base flattened, curved at base, as wide at base as at apex; antennal scrobes pronounced, well-delimited dorsally and ventrally; face phragmotic, anterior frons, clypeus, and mandibles forming single, downturned, flattened surface; entire flat surface, including mandible surface, reticulate rugose; rest of face with faint foveolation, overlain with subparallel, longitudinal carinulae anteriorly, reticulate rugae posteriorly; propodeal spines about one third length of posterior face of propodeum; gastral dorsum smooth and shining; sides of head with abundant erect setae; abundant flexuous erect setae on mesosomal dorsum, tibiae, and gaster.

Measurements, minor worker: HW 0.56, HL 0.61, SL 0.54, EL 0.10, WL 0.76, PSL 0.04, PTW 0.12, PPW 0.16, CI 91, SI 98, PSLI 8, PPI 138 (n=2).

Measurements, major worker: HW 1.01, HL 1.36, SL 0.58, EL 0.16, WL 1.16, PSL 0.09, PTW 0.24, PPW 0.37, CI 74, SI 58, PSLI 9, PPI 159 (n=2).

This is clearly a member of the P. lamia complex, related to Pheidole lamia, Pheidole pelor, and Pheidole colobopsis. Pheidole lamia and P. pelor are smaller, light-colored species from the southern United States. The minor workers of P. colobopsis and P. obturaculum are very similar. The major worker of P. colobopsis has more strongly developed phragmosis, with head expanding anteriorly in both face and lateral view. The head of the major worker of P. obturaculum in face view is rectangular, not expanding anteriorly, and in lateral view the head is relatively less expanded anteriorly.

Distribution based on Regional Taxon Lists
Neotropical Region: Mexico.

Minor
Images from AntWeb

Nomenclature

 *  obturaculum. Pheidole obturaculum Longino, 2019: 51, fig. 33 (w.) MEXICO.

Type Material

 * HOLOTYPE: 1 major worker, Mexico, Veracruz: Las Cañadas, 19.1906 -96.99055 ±60 m, 1390 m, 1-Jul-2016, montane wet forest, at bait (ADMAC, Ba-F-07-1-04-09) [UNAM, unique specimen identifier CASENT0640871].
 * PARATYPES: major, minor workers: same data as holotype [UNAM]; Santuario, INECOL, Xalapa, 19.5123 -96.9357 ±60 m, 1330 m, 14-Jul-2016, cloud forest, at bait (ADMAC, Ba-F-09-1-03-03) [MCZC]; Ba-F-09-1-03-08 [CAS, USNM].

Etymology
Latin for stopper or plug, in reference to the phragmotic major worker.

References based on Global Ant Biodiversity Informatics

 * Longino J. T. 2019. Pheidole (Hymenoptera, Formicidae) of Middle American wet forest. Zootaxa 4599: 1-126