Pheidole plagiaria

Indo-Malayan populations inhabit well-developed forests, and usually nest in rotting logs and wood fragments. On the other hand, Indo-Chinese populations often occur in forest edges and even in open lands adjacent to forests, and usually nest in the soil (Eguchi 2001). Heterick & Kitching (2022) collected this species in a ground malaise trap within a lowland dipterocarp forest in Brunei.

Identification
This species is characterized among Indo-Chinese species by the combination of the following features: in the major posterior margin of head in full-face view relatively widely and deeply concave; in the major the posteriormost part of the dorsum of vertexal lobe almost transversely rugose; in the major and minor the posterior slope of promosonotal dome with a prominence or mound; in the major outer surface of foretibia bearing relatively long decumbent-suberect hairs; in the minor median part of clypeus with a zigzag or ramified (but rarely straight) median carina which is usually accompanied with weak rugulae. The minor of this species is similar to that of Pheidole binghamii, but in the latter median part of clypeus has no rugula and the mound on the posterior slope of promesonotal dome has only a pair of hairs. (Eguchi 2008)

Distribution
Widely distributed in the Indo-Chinese, Indo-Malayan subregions and Austro-Malayan subregion.

Distribution based on Regional Taxon Lists
Indo-Australian Region: Borneo, Brunei Darussalam, Indonesia, Krakatau Islands, Malaysia, Philippines, Singapore. Oriental Region: Laos, Myanmar, Thailand, Vietnam. Palaearctic Region: China.

Worker
Minor

Nomenclature

 *  plagiaria. Pheidole plagiaria Smith, F. 1860b: 112 (s.w.) INDONESIA (Batjan I.). Senior synonym of divergens: Mayr, 1879: 675 (in key); of yomensis: Eguchi, 2008: 73. Current subspecies: nominal plus moica, palawanica, rectilineata. See also: Eguchi, 2001b: 88.
 * divergens. Pheidole divergens Mayr, 1867a: 97 (s.w.q.m.) INDONESIA. Junior synonym of plagiaria: Mayr, 1879: 675 (in key).
 * yomensis. Pheidole peguensis r. yomensis Forel, 1903c: 253 (s.) MYANMAR. Junior synonym of plagiaria: Eguchi, 2008: 73.

Type Material
Three major worker and three minor worker syntypes in. Arranged on three cards as follows:
 * Card 1. 1 major and 1 minor, labelled “Bac.” With Smith’s original label plus Donisthorpe det. labels.
 * Card 2. 2 majors, labelled “Bac. 26.” With Smith det. label “plagiaria.”
 * Card 3. 2 minors, labelled “Bac. 35.” With Smith det. label “plagiaria.”

Eguchi (2008):

Syntypes: 3 majors & 3 minors, “Bac” [Batjan, Indonesia], TYPE HYM: 983 1-2/6, 3-4/6 & 5-6/6, examined.

Pheidole divergens. Syntypes: major, minor, queen & male, Indonesia, not examined.

Pheidole peguensis r. yomensis. Syntype: 1 major, “Lower Burma Pegu Yoma 1 1900 Bingham” [Myanmer],, examined, designated as lectotype.

Current subspecies (Bolton, 1995): nominal plus moica Forel, 1911c: 222, syntype(s): major, Central part of Southern Vietnam, not examined; palawanica Stitz, 1925: 118, syntypes: 2 majors, “N. Palawan Binaluan Boettcher” [Philippines],, examined; rectilineata Viehmeyer, 1916b: 288–289, syntype(s): major, Sulawesi (in copal), not examined.

Worker
Eguchi (2008) - Major (n=5). — HL 1.65–1.89 mm, HW 1.59–1.77 mm, CI 91–98, SL 1.03–1.22 mm, SI 59–71, FL 1.42–1.70 mm, FI 85–99. Minor (n=5). — HL 0.79–0.93 mm, HW 0.67–0.75 mm, CI 81–85, SL 1.01–1.20 mm, SI 146–163, FL 1.12–1.36 mm, FI 162–181.

Major. — Head in lateral view not or only very weakly impressed on vertex; posterior margin of head in full-face view relatively widely and deeply concave; longitudinal rugulae running on the frons and then spreading posterolaterad as they run almost transversely on the posteriormost part of the dorsum of vertexal lobe; posterolateral face of head with oblique rugulae which run anteroventrad from dorsal face of vertexal lobe; frontal carina conspicuous; antennal scrobe inconspicuous or only weakly impressed; median longitudinal carina of clypeus present but weak, or rarely absent; median and submedian processes of hypostoma inconspicuous or absent; lateral processes conspicuous; outer surface of mandible covered with relatively long decumbent hairs; antenna with a 3-segmented club; maximal diameter of eye a little longer, as long as, or a little shorter than antennal segment X. Promesonotal dome in dorsal view transversely rugose with interspaces smooth to shagreened, or smooth to shagreened with sparse several transverse rugulae; the dome in lateral view with a low prominence or mound on its posterior slope; humerus of the dome not or hardly produced laterad; the dome at the humeri narrower than at the bottom; mesopleuron, metapleuron and lateral face of propodeum rugoso-reticulate, with enclosures punctured. Outer surface of foretibia bearing relatively long decumbent-suberect hairs. Petiole longer than postpetiole (excluding helcium); postpetiole not massive. First gastral tergite largely smooth and shining, but sometimes weakly punctured around its articulation with postpetiole.

Minor. — Frons and dorsal face of vertex smooth and shining, or very weakly punctured or rugoso-punctate; area between antennal insertion and eye rugose or rugoso-punctate; preoccipital carina well-developed; median part of clypeus with a zigzag or ramified (but rarely straight) median carina which is usually accompanied with weak rugulae; antenna with a 3-segmented club; scape extending far beyond posterolateral margin of head; maximal diameter of eye shorter than antennal segment X. Promesonotal dome smooth and shining, or in dorsal view concentrically rugose, with a median area smooth and shining or very weakly punctured; the posterior slope of the dome with a low mound which bears several (>2) standing hairs; humerus in dorso-oblique view not or hardly produced; mesopleuron, metapleuron and lateral face of propodeum punctured, usually overlain by weak rugoso-reticulation; propodeal spine horn-like or elongate-triangular, narrowly based, directing relatively upward. Petiole longer than postpetiole (excluding helcium); postpetiole not massive.

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