Probolomyrmex watanabei

Identification
Eguchi et al. (2006) - This species is well separated from related species by the following characteristics in the worker and queen: posterodorsal margin of petiolar node in dorsal view produced medially, and abdominal segment III in profile relatively strongly narrowed anteriad in the anterior 2/3. This species is most similar to Probolomyrmex longiscapus (see under P. longiscapus).

Distribution
Known only from Southern Malay Peninsula.

Distribution based on Regional Taxon Lists
Indo-Australian Region: Malaysia.

Nomenclature

 *  watanabei. Probolomyrmex watanabei Tanaka, 1974a: 35, pl. 3 (w.) WEST MALAYSIA. Eguchi, Yoshimura & Yamane, 2006: 32 (q.).

Worker
Eguchi et al. (2006) - HL, 0.64–0.72 mm; HW, 0.42–0.45 mm; SL, 0.52–0.60 mm; CI, 62–66; SI, 124–135; WL, 0.96–1.10 mm; PW, 0.33–0.38 mm; DPtW, 0.19–0.22 mm; DPtI, 57–60; PtH, 0.23–0.28 mm; PtNL, 0.34–0.40 mm; LPtI, 132–148 (N=6). Nontype workers examined here agree well with the original description (Tanaka, 1974). Palp formula also agrees with the holotype but we have not yet examined mandible and mouthparts in detail because only a few specimens are available.

Queen
Eguchi et al. (2006) - (dealate queen). HL, 0.69 mm; HW, 0.46 mm; SL, 0.57 mm; EL, 0.14 mm; CI, 67; SI, 124; EI, 30; WL, 1.12 mm; PW, 0.41 mm; DPtW, 0.23 mm; DPtI, 56; PtH, 0.28 mm; PtNL, 0.38 mm; LPtI, 136 (N=1). Body ferruginous brown; apical three segments of gaster yellowish. Head in full-face view with weakly convex sides and almost straight occipital border. Eye as long as the width of apical antennal segment. Antenna moderately long; scape when laid backward just reaching the level of anterior margin of lateral ocelli; relative lengths of antennal segments II–XII as in the worker (see Fig. 10H); segment III shorter than IV. Pronotum large; mesoscutum ca. 1.2 times as long as broad, in profile very weakly convex, without notauli; parapsidal lines fine but distinct; scuto-scutellar suture fine, very weakly and roundly curved posteriad; scutellum in profile with relatively steep posterior slope; axilla poorly separated from scutellum by an obscure impression but not by suture; mesopleuron (except its posteriormost part) well divided by a suture into anepisternum and katepisternum; metanotum with its median portion only weakly raised and laterally gently sloping; suture between metepisternum and propodeum absent; a distinct depression present metepisternum into anepisternum and katepisternum; orifice of metapleural gland small, opening posterolaterad; posterior margin of propodeal dorsum in dorsal view moderately concave; posterior face of propodeum margined laterally with a well-developed lamella which forms a triangular propodeal spine; outline from propodeal spine to propodeal lobe in profile strongly concave. Petiole including subpetiolar process much longer than high, in profile with strongly concave posterior outline (above the articulation with gaster), in dorsal view weakly widened posteriad, with the broadest point just before the posterior end; posterodorsal margin of petiolar node in dorsal view produced medially; subpetiolar process very poorly developed. Abdominal segment III (gastral segment I) in profile relatively strongly narrowed anteriad in the anterior 2/3; abdominal sternum III in profile rather strongly convex behind its midlength.

Type Material
Eguchi et al. (2006) - Holotype: worker, Pasoh Forest, Malaysia, 15/i/1972, H. Watanabe (Tanaka’s private collection) [not examined].