Pheidole ajaxigibba

This species occurs in lowland rain forest of Costa Rica. A nest was collected in dead wood, in a dead horizontal tree trunk about 1 m above the ground. Minor workers have been collected in beating samples from low vegetation and in a Malaise trap.

Identification
Minor: face smooth and shining; head tapered posteriorly to narrow neck and strongly developed occipital carina; promesonotal groove deep and broad; mesonotum strongly protruding in lateral view; pronotum smooth and shining; katepisternum with faint foveolation and strong longitudinal rugulae; propodeal spines long, thin, about as long as posterior face of propodeum; gaster smooth and shining; abundant erect setae on mesosomal and gastral dorsum, tibiae; color yellow orange. Major: inner hypostomal teeth widely spaced, in form of small, inconspicuous denticles; scape base terete; face with foveolation overlain with reticulate rugulae throughout, these becoming more longitudinally oriented posteriorly; propodeal spines about two thirds length of posterior face of propodeum; gastral dorsum sericeous/striolate on anterior two thirds, fading to smooth and shiny posteriorly; face and sides of head covered with dense, decumbent, somewhat silky pubescence; abundant erect setae on mesosomal and gastral dorsum, tibiae.

Measurements, minor worker: HW 0.65, HL 0.89, SL 1.29, EL 0.15, WL 1.22, PSL 0.23, PTW 0.12, PPW 0.20, CI 73, SI 197, PSLI 35, PPI 161 (n=4).

Measurements, major worker: HW 1.38, HL 1.43, SL 1.23, EL 0.21, WL 1.57, PSL 0.24, PTW 0.23, PPW 0.37, CI 96, SI 89, PSLI 18, PPI 161 (n=4).

This species and Pheidole ajax are similar. Pheidole ajaxigibba differs in the much more produced mesonotum and the bright yellow color. It is allopatric with P. ajax, the two appearing to be complementary forms on the two sides of Costa Rica.

Distribution based on Regional Taxon Lists
Neotropical Region: Costa Rica.

Nomenclature

 *  ajaxigibba. Pheidole ajaxigibba Longino, 2019: 21, fig. 51 (w.) COSTA RICA.

Type Material

 * HOLOTYPE: 1 major worker, Costa Rica, Puntarenas: Sirena, Corcovado NP, 8.48067 -83.58885 ±1 km, 25 m, 29-Jun-2013, rainforest, nest in dead wood (J. Longino, JTL8286.1) [MUCR, unique specimen identifier CASENT0638172].
 * PARATYPES: major, minor workers: same data as holotype [CAS, DZUP, MCZC, USNM].

Etymology
Similar to P. ajax but with more pronounced mesonotum.