Probolomyrmex watanabei

Specimens have been collected from leaf litter. Little else is known about the biology of .

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, Singapore.

Nomenclature

 * . Probolomyrmex watanabei Tanaka, 1974a: 35, pl. 3 (w.) WEST MALAYSIA.
 * Type-material: holotype worker.
 * Type-locality: Malaysia: Pasoh Forest, 15.i.1972, no. 2509 (H. Watanabe).
 * Type-depository: MATC.
 * Eguchi, Yoshimura & Yamane, 2006: 32 (q.).
 * Status as species: Bolton, 1995b: 366; Eguchi, Yoshimura & Yamane, 2006: 32 (redescription).
 * Distribution: Malaysia (Peninsula).

Worker
Holotype: Head with somewhat convex genal border and shallowly concave occipital border, posterolateral corner rounded, anteromedian structure well agrees with the generic character. Antennal scape relatively long, slightly failing to reach the median occipital border. Funicular joints, except the basal and the terminal, more or less broader than long; the basal joint about one-fifth longer than broad, and the terminal joint almost as long as the three preceding ones together. Mandible small, elongate-triangular, with an acute apical tooth followed by a series of seven denticles, distal one of which is slightly enlarged. Labrum bilobed, with some (probably six, one of which is lost) clavate setae on the anterior surface, and with spine-like ones on the distal border. Maxillary palpus 4-segmented, the segments I-III nodiform, subequal in breadth, the segment IV (terminal) elongate, bulged medially and almost as long as the segments II & III together. Labial palpus 2-segmented, elongate and rather narrow, the segment I slightly arching and the segment II resembling in the shape to the maxillary segment IV. Relative length (width) of the segments of each maxillary and labial palpus as follow; 6.5 (4), 7 (4), 5.5 (4), 13 (3), and 8 (2.5), 16 (3). Labial and maxillary palpi with neither seta nor sensilla except the two spine-like setulae on the maxillary segment I, just as shown in the fig. Eyeless. Mesosoma, viewed from above, shallowly constricted between the pronotum and the mesonotum; pronotum rounded, much broader than the mesonotum, mesonotum and propodeum with subparallel sides. Mesosomal dorsum in profile shallowly but distinctly concave from the summit of the promesonotal convex dorsum to the propodeal dorsum. Mesosomal sutures absent on the dorsal surface and obsolesc,::mt on the lateral surface. Declivitous face of the propodeum strongly concave, marked off on each, lateral border by a low marginate carina, which is terminating dorsally in a distinct propodeal spine. Petiole slender, higher and broader posteriorly than anteriorly, dorsal profile arching, median posterodorsal border remarkably protruding just as shown in figs; posterior surface strongly concave, marked off on each lateral. border by a low obtuse carina. Subpetiolar process reduced as shown in fig. Gaster comparatively thick; its maximum width in dorsal view about 0.38 mm.

Fine shagreening punctures, about 0.005 mm. in diameter, well developed on everywhere except antennae and legs. Larger overlying punctures distinct, about 0.015-0.030 mm. in diameter, a little smaller and dense on the head, larger and dense on the both dorsal and lateral surfaces of the mesosoma and on the petiole, smaller and rather sparse on the gastric segments I & II, and reduced on other parts. Bristles very few, some stout ones on the mandibles, and a few spine-like ones about the cloacal orifice. Pubescence very minute, extremely dense on everywhere, especially on the antennae. Body entirely brownish to blackish red, opaque to subopaque; antennae, legs and gastric segments III-V somewhat yellowish, also opaque to subopaque.

Measurements and indices as follow (see TAYLOR, R. W., 1965, Trans. R. ent. Soc. Lond., vol.. 117, p. 351; or TAYLOR, 1967, Pac. Ins. Mon., vol. 13, p. 17) ; Head Length, 0.64 mm. ; Head Width, 0.42 mm.; Scape Length, 0.55 mm.; Weber's Length of Mesosoma, 0.92 mm.; Pronotal Width, 0.34 mm.; Dorsal Petiole Width, 0.18 mm.; Petiole Height, 0.23 mm.; Petiolar Node Length, 0.36 mm.; Cephalic Index, 66; Scape Index, 131; Petiolar Node Index, 53; Lateral Petiolar Index, 156.

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].