Strumigenys disjuncta group

Strumigenys disjuncta group Bolton (2000)

Species

Malesian-Oriental-East Palaeartic

Worker Diagnosis

Mandibles in full-face view and at full closure triangular, with serially dentate masticatory margins that engage throughout their visible length or just fail to engage basally. In ventral view outer margin of mandible without an inflected prebasal angle. MI 14–23.

Dentition. Basally with a dental row of 6-8 teeth; these either approximately the same size or tooth 4 distinctly the tallest on the margin preapically. Distally with 3-4 denticles, a slightly larger preapical tooth and a much larger apical tooth that is separated from the preapical by a distinct cleft. Total dental count 12-13.

Basal lamella an elongate low strip that borders the mandibular inner margin; flattened or bluntly rounded dorsally, no taller than the basal most tooth that follows it, without a diastema.

Labrum terminates in a pair of narrow digitate to conical lobes.

Clypeus with anterior margin evenly arched-convex across its entire width, the margin continuous with the convex and posteriorly divergent lateral margins; without anterolateral angles.

Clypeal dorsum densely clothed with short spatulate to spoon-shaped hairs that are closely applied to the surface, without standing hairs; clypeal margins fringed with a row of anteriorly curved more narrowly spatulate hairs.

Preocular carina conspicuous in full-face view.

Ventrolateral margin of head between eye and mandible rounded or at most bluntly angular. Postbuccal impression broad and shallow to distinctly indented.

Cuticle of side of head within scrobe reticulate-punctate.

Scape moderate to long, SI 74-90, subcylindrical or weakly dorsoventrally flattened, the leading edge forming a sharp rim from which the hairs arise.

Leading edge of scape with a row of broad, spoon-shaped curved hairs that freely project anteriorly; one or more of these hairs may curve toward the base of the scape, or all may be directed toward the scape apex.

Pronotum not marginate dorsolaterally, the dorsum without a median longitudinal carina. Humeral angles not developed in dorsal view.

Propodeum bidentate, the teeth subtended by narrow but distinct carinae or lamellae.

Spongiform appendages of petiole reduced. Ventral strip beneath petiole extremely narrow, carinate or vestigial, may be absent anteriorly. Base of first gastral sternite with or without a pad or arcuate crest of spongiform tissue.

Pilosity. Pronotal humeral hair absent. Head and body with numerous short but quite stout, curved spatulate, spoon-shaped or remiform hairs that are closely applied to the surface or somewhat elevated. Pilosity conspicuous, dense on dorsal head and pronotum. In addition larger, more elevated curved hairs may occur on the vertex, mesonotum and base of the gaster, these being thickly remiform or even flattened clavate apically.

Sculpture. Dorsum of head behind clypeus and alitrunk everywhere densely coarsely reticulate-punctate, in particular entire side of alitrunk reticulate-punctate.

Basigastral costulae present on an otherwise smooth first gastral tergite.

Notes

The three known species of this very distinctive group come from Borneo and Aru Island, off New Guinea. They are striking species not only because of their coarse dense sculpture and dense, closely applied broad pilosity, but also because their heads in full-face view appear remarkably long, narrow and parallel-sided, much more so than is usual in this genus. The preocular carinae are almost parallel and the sides of the occipital lobes are only very weakly convex and do not diverge much posteriorly. These features, coupled with the vestigial nature of the petiole spongiform tissue, quickly identify members of this group.

References

Bolton, B. 2000. The ant tribe Dacetini. Memoirs of the American Entomological Institute. 65:1-1028.