Strumigenys leptothrix

A colony of this species was found in an oval cavity (1 x 1.5 cm) at a depth between 10 to 15 cm in soil near the root of a forest tree. It contained 82 workers, 64 larvae and a queen. (Ogata & Onoyama 1998)

Identification
Bolton (2000) - A member of the Strumigenys leptothrix-group. Within this group the seven species Strumigenys alecto, Strumigenys benten, Strumigenys elegantula, Strumigenys formosimonticola, Strumigenys jacobsoni, Strumigenys japonica and leptothrix have the propodeum armed with a pair of spines that are subtended by laminate lamellae rather than by narrow cuticular carinae. At the top of the declivity the lamella is fused with the ventral margin of the propodeal spine for a part of its length, but the apex of the spine is usually free. At the bottom of the declivity the lamella continues into rounded lamellate propodeal lobes that are obviously not elongate-triangular and acute.

Of these seven species only leptothrix has a series of straight simple hairs that project from the leading edge of the scape. With the head in profile only leptothrix and jacobsoni have numerous standing long hairs that arise all over the surface from the posterior margin of the clypeus to the occipital margin. At least the anterior half of the cephalic dorsum lacks such hairs in alecto, benten, elegantula, formosimonticola and japonica. Differences distinguishing leptothrix from jacobsoni are tabulated under the latter name.

Distribution based on Regional Taxon Lists
Oriental Region: Taiwan. Palaearctic Region: Japan.

Nomenclature

 *  leptothrix. Strumigenys (Cephaloxys) leptothrix Wheeler, W.M. 1929g: 55, fig. 7 (w.) TAIWAN. Terayama & Kubota, 1989: 787 (q.). Combination in Smithistruma (Weberistruma): Brown, 1948e: 107; in Weberistruma: Brown, 1949d: 8; in Pyramica: Bolton, 1999: 1673; in Strumigenys: Baroni Urbani & De Andrade, 2007: 122. See also: Bolton, 2000: 435.

Worker
Length nearly 3 mm.

Head 1 2/3 times as long as broad, at the clypeus only 3/5 as broad as its greatest posterior width, rounded behind, without posterior lobes, with only slightly concave but distinctly marginate occipital border. Eyes small, behind the middle and far down on the sides. Clypeus convex, nearly as long as broad, semicircular in front, its posterior border angular in the middle and concave on each side. Frontal carinae very short but continued back on each side of the head as a sharp margination bounding the antennal scrobe and joining the transverse occipital margination. Mandibles small, triangular, convex, nearly three times as long as broad, their apical borders with a series of nearly a dozen, slender crowded teeth, which grow gradually longer towards the base. Antennal scapes reaching to the posterior fifth of the head; funicular joints 2 and 3 subequal, longer than broad, together equal to the fourth, which is half as long as the terminal joint. Thorax long, with long, shallow mesoepinotal constriction, somewhat flattened above, high through the epinotum, very low through the pronotum. Seen from above the pronotum is regularly elongate-elliptical, longer and broader than the remainder of the thorax, with a distinct median carina. Promesonotal and mesoepinotal sutures represented by transverse impressions. Mesonotum and base of epinotum rectangular, parallel-sided, the former longer, the latter shorter than broad and both with a strong lateral margination which is continued back to the epinotal teeth. These are rather small, triangular, longer than broad at their bases and directed backward. Declivity of epinotum perpendicular, about as long as the base, marginate and furnished with a low spongiform lamella on each side. Petiole, with a low convex node, somewhat longer than broad and as long as the peduncle. Postpetiole broader than long, transversely elliptical. Both nodes are surrounded laterally and posteriorly with abundant spongiform material and the ventral surfaces of their segments have dependent spongiform masses fully as deep as the segments that bear them. Gaster elongate-elliptical, with straight; transverse anterior border. Legs rather long.

Shining; mandibles opaque, very finely and indistinctly striate; clypeus very finely longitudinally rugulose; head densely punctate, its surface uneven, with loose, interrupted and rather feeble longitudinal rugae. Sides of thorax very smooth and shining, dorsum of pronotum obscurely longitudinally striate; epinotum and petiole opaque and densely punctate; postpetiolar node shining, with several small longitudinal impressions. Gaster very smooth and shining; first segment with several short, coarse striae at the extreme base.

Hairs pale yellow, fine and conspicuously long, but not very abundant, erect both on the body and the extensor surfaces of the femora and tibiae. Hairs on the mandibles and clypeus very small and appressed, those on the latter squamiform.

Yellowish ferruginous; antennae, legs and gaster somewhat paler and more yellow; mandibles and border of clypeus brown.

Bolton (2000) - HL 0.72-0.78, HW 0.48-0.50, CI 64-67, ML 0.08-0.09, MI 11-12, SL 0.38-0.40, SI 79-80 (2 measured). Leading edge of scape with 2-4 anteriorly projecting straight suberect simple hairs that are about as long as the maximum width of the scape. Leading edge of scape also with a series of short fine apically-curved hairs. Dorsolateral margin of head in full-face view with numerous freely projecting long simple hairs. With head in profile the dorsum with numerous anteriorly sloping standing hairs that arise all over the surface from the posterior margin of the clypeus to the occipital margin. Dorsal surfaces of body with numerous simple standing hairs on all segments except propodeum. Femora and tibiae with freely projecting straight simple hairs that are erect to suberect. Pronotum bluntly and weakly marginate dorsolaterally, the margination not conspicuous in profile; in dorsal view the sides of the pronotum project laterally beyond the marginations. Pleurae and side of propodeum smooth and shining, without reticulate-punctate or rugulose sculpture. Propodeal teeth short and subtended by distinct lamellae. Petiole node in profile with a differentiated short anterior face and a long curved dorsum. Lateral spongiform lobe of petiole extends anteriorly to a point almost level with the anterior face of the node.

Type Material
A single specimen from Funkiko, Formosa.

Bolton (2000) - Holotype worker, TAIWAN: Funkiko (F. Silvestri) [examined].