Strumigenys stheno

The lone known specimen of this species, the holotype worker, was found in a lowland forest litter-sample.

Identification
Bolton (2000) - A member of the Strumigenys leptothrix-group. Only two species in this group, Strumigenys euryale and stheno, have narrow acute propodeal spines that are subtended by narrow carinae and terminate at the base of the declivity in rounded, non-lamellate, propodeal lobes. In Strumigenys medusa, Strumigenys megaera, Strumigenys rudinodis, Strumigenys scolopax and Strumigenys scylla the propodeum is bispinose and the declivity is margined with narrow carinae, but the propodeal lobes are acutely triangular, usually narrowly so. In Strumigenys alecto, Strumigenys benten, Strumigenys elegantula, Strumigenys formosimonticola, Strumigenys jacobsoni, Strumigenys japonica and Strumigenys leptothrix the propodeal spines or teeth are engaged ventrally by relatively broad lamellae that run down the declivity to laminate propodeal lobes, and in Strumigenys assamensis the declivity has only a broad lamina, there being no trace of spines or teeth.

The presence of a very conspicuous raised median crest on the anterior half of the clypeus in euryale immediately separates it from stheno, where the clypeus is evenly shallowly convex. Only stheno and leptothrix have a row of stiff, anteriorly projecting simple hairs on the leading edge of the scape. Apart from the differences in propodeal morphology mentioned above, these two are distinguished by the presence of hairs arising on the posterior clypeal margin in stheno (absent in leptothrix), and by the presence in leptothrix of a short but distinctly differentiated anterior face to the petiole node. In stheno the dorsal outline of the petiole peduncle and the dorsum of the node are confluent through a continuous convex even curvature.

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

Nomenclature

 *  stheno. Pyramica stheno Bolton, 2000: 440, figs. 274, 297 (w.) INDONESIA (Sulawesi). Combination in Strumigenys: Baroni Urbani & De Andrade, 2007: 128

Worker
Holotype. TL 3.1, HL 0.76, HW 0.54, CI 71, ML 0.10, MI 13, SL 0.38, SI 70, PW 0.32, AL 0.83. Leading edge of scape with a spaced row of 3-4 straight simple anteriorly projecting stiff hairs as well as short apically-directed appressed simple hairs. With head in full-face view the dorsolateral margin with abundant freely projecting long simple hairs (at least 15 on each side between frontal lobe and occipital corner). Most of vertex finely reticulate-punctate but behind highest point the surface predominantly longitudinally rugulose. With head in profile the entire surface behind the clypeus with fine standing hairs numerous; hairs shortest just behind the clypeus, longest at about highest point of vertex where they are almost as tall as the maxi m u m depth of the head. Posteriormost margin of clypeus with a few erect simple hairs that are noticably longer than those on the vertex immediately posterior to the clypeus. Occipital corner in profile evenly broadly rounded. Eye with 5-6 ommatidia in the longest row. Dentition discussed in introduction to group. All dorsal surfaces of body with numerous long fine simple hairs. Dorsal (outer) surfaces of middle and hind tibiae with numerous extremely long freely projecting simple hairs, the longest of which are at least twice the maximum tibial width; all other leg segments have similar projecting hairs. Pronotum marginate dorsolaterally, the dorsum flat and with sparse weak longitudinal rugulae. Propodeum with a pair of narrow acute straight spines that are subtended by narrow carinae, not lamellae. At base of declivity the carinae terminate in narrow broadly rounded propodeal lobes. Sides of alitrunk with scattered rugulose sculpture, without reticulate-punctate areas. Lateral spongiform lobe of petiole extensive, extending forward alongside of node almost to its anterior margin. Disc of postpetiole smooth but with faint traces of costulate sculpture at extreme lateral edges.

Paratypes. TL 3.0-3.1, HL 0.72-0.74, HW 0.52, CI 70-72, ML 0.08-0.10, MI 11-14, SL 0.36-0.38, SI 69-73, PW 0.30-0.32, AL 0.78-0.81 (3 measured).

Type Material
Holotype worker, Indonesia: Sulawesi Utara, Dumoga Bone N. P., ii.1985, 200-400 m., lowland rainforest, 2 m-sq. sample of litter, sample BB1 (P.M. Hammond).

Paratypes, 3 workers with same data as holotype but samples BB1, BB3 and BB4 respectively (BMNH, ).