Polyrhachis hashimotoi

Identification
Kohout (2007) - Polyrhachis hashimotoi is very similar to Polyrhachis xiphias Fr. Smith, 1863 from New Guinea and Polyrhachis shixingensis Wu & Wang described in 1995 from Shixing County of Guangdong Province, China and also collected on Dongkho I., Vietnam, by A.G. Radchenko (IZAS). The clypeus of all three species has a median carina arising from the truncate and shallowly emarginate clypeal margin. However, in P. shixingensis the carina is short, strongly raised and sharp, in P. xiphias it is weakly and evenly raised throughout its length and in P. hashimotoi it is rather flat and blunt anteriorly. The dorsum of the petiole in P. hashimotoi is distinctly higher than the bases of petiolar spines, which are situated below the convex summit of the petiole. In contrast, in P. xiphias and P. shixingensis the petiolar spines arise from the summit of the petiole.

Distribution based on Regional Taxon Lists
Indo-Australian Region: Borneo, Indonesia.

Castes
Sexuals and immature stages unknown.

Nomenclature

 *  hashimotoi. Polyrhachis hashimotoi Kohout, 2007c: 12, figs. 7, 8 (w.) BORNEO.

Worker
Dimensions of holotype: TL c. 6.95; HL 1.75; HW 1.47; CI 84; SL 1.62; SI 110; PW 1.03; MTL 1.84.

Mandibles with 5 teeth, reducing in length towards base. Anterior clypeal margin truncate, with truncate portion somewhat jagged, notched medially and laterally flanked by distinct denticles. Clypeus in profile weakly concave, with blunt carina that is more raised posteriorly; basal margin shallowly impressed medially, laterally represented by thin line. Frontal triangle distinct. Frontal carinae sinuate, with margins only weakly raised anteriorly; carinae flat, short and weakly converging posteriorly; central area relatively wide, almost flat with weakly marked frontal furrow. Sides of head in front of eyes rounding into mandibular bases; behind eyes rounding abruptly and narrowly onto virtually flat occipital margin. Eyes rather flat, breaking lateral cephalic outline in full face view. Ocelli lacking; their relative positions indicated by shallow punctures in cephalic sculpturation. Pronotum in dorsal view with lateral margins rounded without indication of humeral angles, margings very narrowly, but distinctly upturned; mesonotal dorsum with lateral margins converging posteriorly, their posterior angles distinctly raised and continuous medially, forming a transverse ridge that divides dorsum of mesonotum from somewhat stepped propodeum. Lateral margins of propodeal dorsum subparallel, extending posteriorly and forming relatively long, somewhat dorso-medially flattened spines, their inner margins continuous medially, forming, in dorsal view, a reverse, ‘U’ shaped ridge, that separates propodeal dorsum from concave declivity. Petiole with anterior face convex, posterior face weakly concave; dorsum rather acute, extending laterally and posteriorly and forming posteriorly directed, subparallel spines with their extreme tips bent weakly outwards. Anterior face of first gastral segment relatively low, weakly concave at base, narrowly rounding onto dorsum of segment.

Dorsum of head and mesosoma finely reticulate-punctate; sides of mesosoma very finely reticulate-wrinkled. Gaster very finely shagreened, rather polished.

Mandibles with numerous, rather short, curved, golden hairs near masticatory margins and piliferous pits towards their bases. Anterior clypeal margin with two long setae medially and few short setae fringing margin laterally. Clypeus with a few pairs of erect, medium length, golden hairs near anterior and basal margins. Frontal carinae and vertex each with a pair of shorter erect hairs. Fore coxae with several long, anteriorly directed, erect hairs; a few short, erect hairs fringing subpetiolar process anteriorly. Gastral apex and ventral apical segments with numerous, rather long, erect hairs. Closely appressed pubescence distributed sporadically over most of body, distinctly more abundant on gastral dorsum. Somewhat longer, semierect and curved, rather dense pubescence on anterior gastral venter.

Black; anterior portion of mandibles, except teeth, and legs, including coxae, medium to dark reddish-brown. Funiculi dark reddish brown at base, with subsequent segments progressively lighter and apical segments rather light yellow. Condylae and apical tarsal segments light yellow. Dorsum of gaster very dark reddish-brown with apical segments and venter blotched light to medium reddish-brown.

Type Material
HOLOTYPE: EAST MALAYSIA, SABAH, 10 km S of Danum Valley Field Centre, Reduced Impact Logging Project Area, 20.vii.-25.viii.1994, coll. (worker). Type deposition: Unique holotype in ITBC.

Etymology
Named in honour of Assoc. Prof. Dr Hashimoto Yoshiaki of the Museum of Human Activities, University of Hyogo, Japan, in appreciation of his excellent work in producing digital images of Bornean, Southeast Asian and Australian Polyrhachis for my ongoing work on taxonomy of the genus.