Strumigenys emmae group

Strumigenys emmae group Bolton (2000)

Species

Austral

Strumigenys emmae also occurs in the Afrotropical, Malagasy, Malesian-Oriental-East Palaeartic and Neotropical-Nearctic regions.

Worker Diagnosis

Apical fork of mandible with 1 - 3 minute intercalary denticles (not visible when mandibles fully closed). Mandible with a long-conical to spiniform preapical tooth; there may also be a minute tumulus, denticle or shorter tooth between the preapical tooth and the apicodorsal tooth. Mandibles linear, usually broadest at about the basal third and outer margins convex at full closure. MI 26 - 42.

Anterior clypeal margin very broad, transverse to shallowly convex; anterolateral angles of clypeus project farther laterally than the outermost points of the fully closed mandibles.

Antenna with 4 or 6 segments; apical segment not constricted basally before its articulation with the preapical segment.

Leading edge of scape with all hairs spatulate or spoon-shaped and curved toward apex of scape. Scape slightly to distinctly flattened, broadest at about midlength; short to moderate, SI 52 - 73.

Preocular carinae very broad in full-face view, in profile short and terminating before level of the very small eye.

Upper scrobe margin sharply defined behind level of eye.

Ventrolateral margin of head in front of eye sharply defined, usually about straight or forming an even shallow curve, but with a deep broadly U-shaped preocular impression in one species (anchis). Postbuccal groove small and indistinct.

Propodeum with a small tooth that is almost fully engaged with a broad lamella, the latter extending down the declivity and without a ventral tooth.

Ventral surface of petiole with spongiform tissue. Base of first gastral sternite with a weak to moderate spongiform pad.

Pilosity. Pronotal humeral hair absent or present. Head with spatulate to broadly scale-like or orbicular hairs; upper scrobe margin fringed with similar hairs. First gastral tergite with short stiff simple to clavate hairs that are suberect to erect.

Sculpture. Head and alitrunk predominantly or entirely reticulate-punctate, frequently with a smooth area on mesopleuron that may also extend to metapleuron and side of propodeum. Base of first gastral sternite not longitudinally costulate.

Notes

The Austral region has seven species of this group, the pantropical tramp-species Strumigenys emmae and the six endemic Australian species. Previous speculation that this group was of Afrotopical origin (eg. Bolton, 1983) appears to be misplaced as the Austral region is the only one with species of this group other than the tramp emmae present in the fauna. Six of the seven species discussed here have 4-segmented antennae but one (Strumigenys pnyxia) has a plesiomorphic count of six. The 4-merous antennomere count is duplicated in a number of New Guinea-based species of the eurycera-group, previously associated with emmae in the now-abandoned genus Quadristruma, but all of those have the base of the first gastral sternite longitudinally costulate and have a characteristically shaped alitrunk.

References

Bolton, B. 1983. The Afrotropical dacetine ants (Formicidae). Bulletin of the British Museum (Natural History). Entomology. 46:267-416.
Bolton, B. 2000. The ant tribe Dacetini. Memoirs of the American Entomological Institute. 65:1-1028.