Strumigenys jacobsoni

Known from a few wet forest and swamp collections, with each being collected from litter/ground sampling.

Identification
Bolton (2000) - A member of the Strumigenys leptothrix-group. A very distinctive densely hairy species, jacobsoni shares its propodeal structure, as described under Strumigenys leptothrix, with a number of other species of the region. Of these jacobsoni and leptothrix have abundant standing hairs on the cephalic dorsum, arising all over the surface from the posterior clypeal margin to the occipital margin and very conspicuous in profile. Both species also have straight freely projecting pilosity on the hind tibiae, a feature shared with Strumigenys alecto and Strumigenys elegantula, but in the last two species standing hairs on the dorsum of the head are restricted to the posterior portion. Apart from this the separation of alecto and elegantula from jacobsoni may easily be confirmed: alecto lacks pronotal margination (very conspicuous in jacobsoni), and elegantula has the mesopleuron uniformly densely reticulate-punctate and the pronotal dorsum lacks standing hairs (mesopleuron not reticulate-punctate in jacobsoni and pronotum with abundant standing hairs). S. jacobsoni separates from leptothrix as follows.

S. jacobsoni: SI < 75 (range 68-71). Leading edge of scape lacking straight projecting stiff simple hairs. Vertex predominantly longitudinally rugulose. With head in profile apex of occipital lobe projecting posteriorly as a thick flange separating curvatures of dorsal and ventral surfaces. Pronotum sharply marginate dorsolaterally, dorsum flat to concave; lateral faces of pronotum not projecting beyond marginations in dorsal view. Mesopleuron with at least vestiges of sculpture. Propodeal spines long, the lamellae broad. Dorsal outline of petiole in profile with peduncle grading into node through an evenly convex curve; node without a differentiated anterior face.

S. leptothrix: SI > 75 (range 79-80). Leading edge of scape with straight projecting stiff simple hairs. Vertex predominantly reticulate-punctate. With head in profile apex of occipital lobe more or less evenly rounded, not forming a thick posteriorly projecting flange. Pronotum weakly marginate dorsolaterally, dorsum shallowly convex; lateral faces of pronotum projecting beyond marginations in dorsal view. Mesopleuron completely smooth. Propodeal spines reduced to triangular teeth, the lamellae narrow. Dorsal outline of petiole in profile with peduncle separated from dorsum of node by a short but distinctly defined anterior nodal face.

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

Nomenclature

 *  jacobsoni. Strumigenys (Cephaloxys) jacobsoni Menozzi, 1939b: 180, fig. 4 (w.) INDONESIA (Sumatra). Brown, 1949d: 8 (q.). Combination in Smithistruma: Brown, 1948e: 105; in Weberistruma: Brown, 1949d: 8; in Pyramica: Bolton, 1999: 1673; in Strumigenys: Baroni Urbani & De Andrade, 2007: 122. See also: Bolton, 2000: 433.

Worker
Bolton (2000) - HL 0.68-0.78, HW 0.47-0.52, CI 67-71, ML 0.08-0.10, MI 12-14, SL 0.32-0.37, SI 68-71 (6 measured). Cephalic dorsum in profile densely clothed with elongate simple standing hairs that arise all over the surface from close to the posterior clypeal margin to the occipital margin, but are absent from the clypeus. In full-face view the dorsolateral margin of the head has numerous long fine freely projecting hairs throughout its length. Leading edge of scape with fine curved hairs that are directed toward the apex, without stiffly projecting straight hairs. Dorsum of head with scattered irregular longitudinal fine rugulae, the vertex also with weak punctulate sculpture present. Dentition discussed in introduction to group. Pronotum sharply marginate dorsolaterally, the dorsum transversely approximately flat to shallowly concave and its margins equipped with numerous long fine projecting hairs along their entire length. Mesopleuron not reticulate-punctate; sometimes more or less smooth but usually with traces of weak transverse rugulae. Dorsal surfaces of alitrunk, waist and gaster with abundant long fine standing hairs that are acute apically. All segments of legs with numerous very long fine projecting hairs that are erect to suberect and straight to feebly curved. The longest tibial hairs are very much longer than the maximum tibial width. Propodeum with a pair of spines that are subtended by broad lamellae, the latter merging into broadly rounded lamellate propodeal lobes at the base of the declivity. Spongiform appendages of waist well developed, the lateral lobe of the petiole very broad and extending far forward along the side of the node. Sculpture of pronotal dorsum variable; sometimes the surface completely smooth but more usually with some faint, almost effaced, punctation, very weak longitudinal rugulae, or both. Disc of postpetiole smooth.

Type Material
Bolton (2000) - Syntype workers, INDONESIA: Sumatra, Fort de Kock (E. Jacobson) [examined].