Strumigenys circothrix group

Strumigenys circothrix group Bolton (2000)

Species

Malesian-Oriental-East Palaeartic

Worker Diagnosis

Mandibles in full-face view and at full closure narrow and tapering apically, masticatory margins engage only in the apical half of their length. Basalmost tooth at about the midlength of the exposed portion of the mandible. Proximal to basal tooth there is a distinct gap between the mandibles through which the labral lobes are visible. In ventral view outer margin of mandible without a prebasal inflected angle. MI 20-25.

Dentition. Basally with a dental row of 5 teeth, followed by an indeterminate number of minute denticles and a slightly enlarged apical tooth.

Basal lamella of mandible triangular, close to anterior clypeal margin in full-face view and partially exposed even when the mandibles are fully closed. A marked diastema present between basal tooth an d basal lamella, the diastema longer than the height of the basal tooth.

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

Clypeus with anterior margin transverse to very shallowly convex, broad, with distinct anterolateral angles. Outer margins of closed mandibles intersect the anterior clypeal margin close to or some distance mesad of the anterolateral angles.

Clypeal dorsum densely clothed with small broadly spatulate to suborbicular hairs. Lateral margins of clypeus fringed with a row of freely projecting anteriorly curved spoon-shaped hairs.

Preocular carina conspicuous in full-face view.

Ventrolateral margin of head between eye and mandible angular. Postbuccal impression small and shallow.

Cuticle of side of head within scrobe reticulate-punctate.

Scape short, SI 50-68, strongly dorsoventrally flattened, its leading edge with a prominent, broadly rounded to angulate subbasal angle that is by far the widest point of the scape.

Leading edge of scape with small spoon -shaped hairs that are either all curved toward the apex of the scape and quite closely applied to the surface, or with a hair that curves toward the base of the scape.

Pronotum without a median carina.

Propodeum with a pair of small teeth that are almost entirely confluent with the broad lamellae; at most only the extreme tip of each tooth is free.

Spongiform appendages of waist segments well developed. Base of first gastral sternite in profile with spongiform tissue extremely sparse to absent.

Pilosity. Pronotal humeral hair small and straight, weakly remiform to clavate apically. Cephalic dorsum densely clothed with conspicuous broadly spoon-shaped to suborbicular hairs; without standing hairs of any form. Mandibles and scapes dorsally with small scale-like to spoon-shaped hairs. Apically simple to weakly clavate standing hairs are present on first gastral tergite. Mesonotum with a single pair of short erect hairs. Hind tibiae and basitarsi without long erect fine hairs.

Notes

The two Japanese species currently referred to this group show some similarities to the North American pergandei group. However, the structure of the mandible and its dentition is very different so it seems best to leave Strumigenys circothrix and Strumigenys hiroshimensis in a group of their own.

References

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