Figures 3, 4, 12 - 16
Worker. Measurements (mm), holotype in parentheses: HW 0.95 - 1.00 (0.99); HL 1.04 - 1.11 (1.08); SL 1.11 - 1.13 (1.13); EL 0.19 - 0.21 (0.20); MSL 0.11 - 0.12 (0.11). SL / HL 1.03 - 1.08 (1.05). Number of ommatidia along long axis of eye ca. 10.
Structure. Similar to P. nigrita and P. pilidorsalis , but the following characteristics are useful to recognize P. batak . Mesal half of mandible rather extensively smooth with scattered punctures. Posterior face of propodeum superficially but extensively punctate. Both anterior and posterior faces of petiole distinctly punctate. Dorsal face of mesosoma without standing hairs or with at most five very short standing hairs. Gastral tergites 1 and 2 each with less than five standing hairs (excluding those along posterior margin of the tergites).
Queen. Small, head width ca. 0.85 mm. Similar in size and structure to the queen of P. pilidorsalis , but mesosoma dorsally and gastral tergites 1 and 2 virtually without standing hairs.
Male. Structure. Head small, much narrower than pronotum, posteriorly roundly narrowed. Clypeus apically almost straight; labrum produced anteriorly. Lower frons with a short longitudinal keel. Mandible reduced, basally widened. Eye large (maximum length 0.30 mm), strongly convex, with short standing hairs, mesally weakly emarginate. Ocelli small, diameter as long as the width of antennal segment 3; distance between posterior ocelli much longer than that between anterior and posterior ocelli. Scape as long as antennal segment 3; pedicel (segment 2) slightly longer than half the length of scape. Pronotum posterolaterally concave; mesoscutum large, much higher than pronotum; scutellum much narrower than mesoscutum, with a wide and deep furrow just behind mesoscutum; mesopleuron large, with a deep transverse groove of which the bottom has many striae. Propodeum lower than meso-metanotum, weakly rounded above; posterior face shallowly concave. Petiole relatively thin, in profile much narrowed above; subpetiolar process in profile with an apically acute posterior projection. Sculpture. Head only superficially punctate and shining. Pronotum, mesoscutum, scutellum and metanotum very weakly sculptured and somewhat shining; mesopleuron almost entirely smooth and strongly shining; metapleuron anteromedially coarsely puncto-striate; other part of metapleuron weakly sculptured. Propodeum very densely punctate except for concave posterior face that is only superficially sculptured. Anterior and posterior faces of petiole densely and irregularly sculptured; posterior face very weakly sculptured and somewhat shining. Gaster only superficially sculptured. Pilosity. Body rather densely covered with decumbent pubescence and obliquely standing short hairs; on mesopleuron the pilosity very sparse. Coloration. Body dark reddish brown, with slightly paler gaster and legs.
ADDITIONAL MATERIAL
SUMATRA: 26 w 2 q, same loc. (SU 02 - SKY- 85); 11 w 2 q, same loc. (SU 02 - SKY- 90); 16 w, Bt Lawang (lowland), G. Leuser N. P., Sk. Yamane (SU 02 - SKY- 87).
ETYMOLOGY
Named for the Batak tribe who live in the area of the type locality.
REMARKS
This species may be most closely related to P. pilidorsalis , from which it is easily distinguished by the lack of standing hairs on mesosoma and gastral tergites 1 and 2 (excluding those arising along posterior margins of the tergites) in the queen. It is also separable from the related P. nigrita by the smaller body (queen), and smaller ocelli and dark body color (male). On the other hand, in the worker caste, P. batak differs from P. pilidorsalis and P. nigrita only in the fewer numbers of standing hairs on mesosoma and tergites 1 and 2. This species nests in rotting wood / branches on the ground in secondary forests.
