Pheidole rabo

This species inhabits usually well-developed forests but sometimes forest edges or bamboo forests, and nests under shelters (e.g., stones) or rarely in rotting logs on the ground.

Identification
Eguchi (2008) - This species is distinguishable among Indo-Chinese species by the combination of the following characteristics: in the minor head punctured dorsally and laterally; in the major frontal carina absent or inconspicuous (present just as rugulae); in the major antennal scrobe absent; in the major submedian processes of hypostoma well developed; in the minor maximal diameter of eye almost as long as or a little shorter than antennal segment X; in the minor scape exceeding posterior margin of head usually by almost the length of antennal segment II or more; in the minor mesosoma punctured; in the major and minor promesonotal dome in lateral view at most with an inconspicuous mound on its posterior slope.

This species is very similar to Pheidole parva, but distinguishable from the latter of which the minor has the following characteristics: scape exceeding posterior margin of head by less than half length of antennal segment II, or not reaching the posterior margin; maximal diameter of eye longer than antennal segment X.

Distribution
Widely distributed in Indo-Chinese and Indo-Malayan subregions.

Distribution based on Regional Taxon Lists
Indo-Australian Region: Borneo, Indonesia. Oriental Region: Thailand, Vietnam. Palaearctic Region: China.

Nomenclature

 *  rabo. Pheidole rabo Forel, 1913k: 28 (s.w.q.) INDONESIA (Sumatra). Senior synonym of tsailuni: Eguchi, Yamane & Zhou, 2007: 276. See also: Eguchi, 2001a: 21; Eguchi, 2001b: 102; Eguchi, 2008: 80.
 * concinna. Pheidole concinna Wheeler, W.M. 1928c: 13, fig. 1 (s.w.) CHINA. [Junior primary homonym of concinna Santschi, above.] Replacement name: tsailuni Wheeler, W.M. 1929f: 2.
 * tsailuni. Pheidole tsailuni Wheeler, W.M. 1929f: 2. Replacement name for concinna Wheeler, W.M. 1928c: 13. [Junior primary homonym of concinna Santschi, 1910c: 362.] Junior synonym of rabo: Eguchi, Yamane & Zhou, 2007: 276. See also: Eguchi, 2001a: 30.

Worker
Eguchi (2008) - Major (data from Eguchi, Yamane & Zhou 2007). — HL 1.11–1.53 mm; HW 1.06–1.42 mm; CI 91–95; SL 0.49–0.59 mm; SI 42–49; FL 0.65–0.87 mm; FI 58–67. Minor (data from Eguchi, Yamane & Zhou 2007). — HL 0.49–0.60 mm; HW 0.43–0.53 mm; CI 87–91; SL 0.45–0.53 mm; SI 100–108; FL 0.48–0.61 mm; FI 105–116.

Major — Head in lateral view not or very weakly impressed on vertex; frons longitudinally rugose; vertex rugoso-reticulate; dorsal and dorsolateral faces of vertexal lobe reticulate, with enclosures smooth to punctured; frontal carina absent or inconspicuous (present just as rugulae); antennal scrobe absent; median longitudinal carina on clypeus absent or conspicuous; hypostoma with low or inconspicuous median and well-developed submedian processes in addition to conspicuous (but sometimes reduced) lateral processes; outer surface of mandible (excluding area around the base) smooth or dimly rugose, sparsely with a (very) short appressed hairs; antenna with a 3-segmented club; maximal diameter of eye (a little) longer than antennal segment X. Promesonotal dome in lateral view at most with an inconspicuous mound on its posterior slope; humerus weakly produced laterad; the dome at the humeri as broad as or broader than at the bottom (or sometimes a little narrower than at the bottom). Petiole much longer than postpetiole (excluding helcium); postpetiole not massive. First gastral tergite weakly rugoso-punctate usually in its anterior 1/2 or more (at least around articulation with postpetiole).

Minor — Dorsum of head punctured dorsally and laterally, and often overlain by weak rugoso-reticulation dorsally; preoccipital carina very weak or inconspicuous dorsally; median part of clypeus smooth, weakly punctured or weakly reticulate; median longitudinal carina absent, inconspicuous or weak; antenna with a 3- segmented club; scape usually exceeding posterior margin of head by almost the length of antennal segment II or more (but sometimes by the half length of II); maximal diameter of eye almost as long as or a little shorter than antennal segment X. Dorsal and lateral faces of mesosoma punctured; punctation on dorsum of promesonotal dome often overlain sparsely by weak rugulae; promesonotal dome in lateral view at most with an inconspicuous mound on its posterior slope; humerus in dorso-oblique view produced weakly or very weakly; propodeal spine elongate-triangular. Petiole (much) longer than postpetiole (excluding helcium); postpetiole not massive.

Type Material
Eguchi (2008):

Lectotype: major, “No. 54a Maxwell’s Hill Taiping Malacca (v. Buttel)” [W. Malaysia],, examined; paralectotypes: 1 major & 2 minors, same data as the lectotype, MHNG, examined; 2 queens, “No 643 Bandar Baroe Sumatra Malacca (v. Buttel)”, MHNG, examined; original description also included syntype(s) from “Beras Tagi”, not examined.

Pheidole concinna. Lectotype:? major, “Laokay, Indo-China, 2-22-25, F. Silvestri”, MCZC cotype-20656, examined; paralectotypes: 1 major & 6 minors, same data as the lectotype, cotype-20656, examined.