Pheidole yeensis

This species is more common in open lands, tillage and gardens than in woody habitats, and nests in the soil. In N. Vietnamese rural areas this species and Pheidole parva are the most dominant Pheidole species. Prominent wall built with soil usually surrounds the nest entrance. Workers actively forage on the ground, and prey and/or scavenge on small invertebrates including other ground-foraging ants, such as Odontoponera denticulata. (Eguchi 2008)

Identification
Eguchi (2008) - This species is characterized among Indo-Chinese species by the combination of the following features: in the minor dorsum of head and mesosoma sparsely bearing relatively thick standing hairs; in the major head in lateral view strongly impressed on vertex; in the major hypostoma at most with inconspicuous median and submedian processes; in the major and minor promesonotal dome in lateral view with a low mound on its posterior slope; in the major first gastral tergite longitudinally rugoso-punctate entirely.

This species is similar to Pheidole planifrons Santschi among Indo-Chinese species (see under P. planifrons).

Key to Pheidole of North Vietnam

Distribution
Known from the Indo-Chinese subregion.

Distribution based on Regional Taxon Lists
Oriental Region: Myanmar, Thailand, Vietnam. Palaearctic Region: China.

Nomenclature

 *  yeensis. Pheidole sulcaticeps r. yeensis Forel, 1902c: 179 (s.) MYANMAR. [Also described as new by Forel, 1902f: 544.] Bingham, 1903: 253 (w.). Subspecies of sulcaticeps: Emery, 1921f: 94. Raised to species: Bingham, 1903: 252; Wu & Wang, 1995: 102. See also: Eguchi, 2008: 107.

Worker
Eguchi (2008) - Major (n=5). — HL 2.01–2.09 mm; HW 1.77–1.83 mm; CI 85–89; SL 0.94–0.99 mm; SI 53–55; FL 1.55–1.61 mm; FI 87–88. Minor (n=5). — HL 0.73–0.93 mm; HW 0.58–0.77 mm; CI 79–83; SL 0.86–0.97 mm; SI 126–149; FL 0.97–1.23 mm; FI 160–170.

Major — Head in lateral view strongly impressed on vertex; frons rugose longitudinally, with interspaces weakly punctured; vertex and dorsal and dorsolaeral faces of vertexal lobe reticulate or rugoso-reticulate, with enclosures weakly punctured; frontal carina well developed, partly overhanging antennal scrobe; median longitudinal carina of clypeus absent, inconspicuous or weak; hypostoma without conspicuous median and submedian processes, but with conspicuous lateral processes; outer surface of mandible smooth excluding its basal area, bearing short appressed hairs; antenna with a 3-segmented club; maximal diameter of eye longer than antennal segment X. Promesonotal dome in dorsal view transversely rugoso-reticulate, with enclosures weakly punctured, in lateral view with a low or inconspicuous mound on its posterior slope; humerus very weakly produced laterad; the dome at the humeri a little narrower than or almost as broad as at the bottom. Petiole (a little) longer than postpetiole (excluding helcium); petiolar node in rear view weakly concave mediodorsally; postpetiole not massive. First gastral tergite longitudinally rugoso-punctate entirely.

Minor — Dorsum of head and mesosoma sparsely bearing relatively thick standing hairs; frons and vertex smooth or shagreened; dorsolateral part of head often rugoso-punctate weakly; preoccipital carina conspicuous dorsally and laterally; median part of clypeus largely smooth; median longitudinal carina of clypeus absent, or present but weak; antenna with a 3-segmented club; scape extending far beyond posterolateral margin of head; maximal diameter of eye almost as long as or shorter than antennal segment X. Promesonotal dome smooth entirely, or almost smooth dorsally and weakly rugoso-punctate dorsolaterally (and laterally); the dome in lateral view with a low mound on its posterior slope; humerus of the dome in dorso-oblique view not produced; mesopleuron, metapleuron and lateral face of propodeum well punctured. Petiole (a little) longer than postpetiole (excluding helcium); postpetiole relatively large but not massive.

Type Material
Eguchi (2008) - Syntype: 1 major, “Birmah (Bingham) Ye Valley CCI 14” [Myanmar],, examined, designated as the lectotype.