Strumigenys acheron

Identification
Bolton (2000) - A member of the Strumigenys extemena-group. Within this group acheron, Strumigenys aello and Strumigenys tarbosyne possess erect hairs on the vertex and also on the dorsal alitrunk. On the head pilosity is restricted to a single transverse row behind the highest point in acheron, but in aello and tarbosyne a pair or second row is present more anteriorly, at the highest point of the vertex.

Elsewhere in the group Strumigenys deinognatha, Strumigenys extemena and Strumigenys ocypete altogether lack standing hairs on the vertex, and these three species, together with  Strumigenys podarge and Strumigenys atopogenys, do not have any erect hairs on the dorsal alitrunk.

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

Nomenclature

 *  acheron. Pyramica acheron Bolton, 2000: 416 (w.) BORNEO. Combination in Strumigenys: Baroni Urbani & De Andrade, 2007: 110

Worker
Bolton (2000) - Holotype. TL 1.6, HL 0.40, HW 0.37, CI 93, ML 0.12, MI 30, SL 0.18, SI 49, PW 0.23, AL 0.45. Leading edge of scape rounded at broadest point, the edge with a continuous row of small, spatulate to spoon-shaped hairs that are all curved toward the apex of the scape and diminish in size toward the scape apex; without a single enlarged freely projecting hair at the broadest point. Dorsum of head with a thick, blunt transverse ridge running from side to side at about the highest point of the vertex. In full-face view the ridge best developed in the middle third of the head width. In profile the ridge very conspicuous at the highest point of the vertex where it forms a blunt crest, the anterior face of which is almost vertical. Outline of dorsum sloping steeply behind the ridge and with a transverse row of 4 short straight erect hairs in front of the occipital margin; without hairs on the crest of the ridge itself. Erect pilosity otherwise absent from cephalic dorsum. Eye small, partially concealed in holotype but apparently with only 3-4 ommatidia in total. Clypeus with minute and very indistinct appressed pubescence, its median area more or less shining. Dorsum of head behind clypeus finely and densely reticulate-granular to reticulate-punctulate. Dorsolateral margination of pronotum with a short straight hair projecting from just behind the humeri. Mesonotum with a single pair of short straight erect hairs anteriorly; alitrunk otherwise without standing pilosity. Dorsa of petiole, postpetiole and first gastral tergite with numerous short erect simple hairs. Legs with minute appressed pilosity only, directed toward the apices of the segments. Dorsum of pronotum between marginations more or less smooth centrally but with granular sculpture peripherally. Mesonotum markedly narrowed dorsally and finely punctulate; propodeal dorsum smooth. Pleurae and side of propodeum mostly smooth and shining, with weak granular sculpture near the upper margins. Mesonotal convexity very distinctive in profile. Propodeal declivity with broad lamellae. Petiole node in dorsal view much broader than long, weakly punctulate anteriorly but the sculpture fading out posteriorly. Disc of postpetiole smooth and shining.

Type Material
Bolton (2000) - Holotype worker, Malaysia: Sabah, Poring Hot Springs, 500 m., 13.v.1987, no. 23 (Lobl & Burckhardt).