Strumigenys terroni group

Strumigenys terroni group Bolton (2000)

Species

Afrotropical-West Palaeartic

Worker Diagnosis

Mandibles in full-face view and at full closure narrowed to blades that engage only in the apical third or less of their length; proximal to this with an elongate triangular gap bordered by the masticatory margins and between which the labral lobes are visible. In ventral view outer margin of mandible without an inflected prebasal angle. MI 18-22.

Dentition. Basally with a dental series of 6 or 7 small to minute teeth followed by a relatively large tooth (the longest on the margin), then 3 small teeth, a slightly larger tooth, 4 minute denticles and a larger apical tooth, giving a total dental count of 16-17.

Basal lamella of mandible a very high narrow truncated triangle, completely concealed by clypeus when mandibles closed; basal lamella separated from the basal tooth by a long diastema.

Labrum terminates in a pair of elongate digitate to triangular narrow lobes.

Clypeus with anterior margin evenly shallowly concave across the entire width in full-face view; lateral margins feebly divergent posteriorly. Outer margin of mandible intersects anterior clypeal margin very close to clypeal anterolateral angles. In ventral view the lateral clypeal margins extend well beyond the outer margins of the fully closed mandibles through the basal third or more of their length.

Clypeal lateral and anterior margins with a continuous fringe of spatulate to spoon-shaped hairs that curve anteriorly on the lateral margins and toward the midline on the anterior margin. Dorsum of clypeus without standing hairs but with anteriorly directed minute flattened appressed hairs that are very inconspicuous.

Preocular carina conspicuous in full-face view.

Ventrolateral margin of head between eye and mandible sharply angular to marginate.

Cuticle of side of head within scrobe reticulate-punctate.

Scape short, SI 55-63, dorsoventrally flattened, the dorsum and ventre converging anteriorly so that the leading edge is a flange or even a thin lamella. Ventral surface of scape behind the leading edge concave.

Leading edge of scape with a row of spatulate or spoon-shaped hairs, most of which curve toward the base of the scape.

Pronotal dorsum without a median longitudinal carina.

Propodeum bidentate to bispinose, lamella on declivity vestigial; base of declivity with low bluntly triangular propodeal lobe.

Spongiform appendages large on petiole and postpetiole. Base of first gastral sternite in profile without a pad of spongiform tissue.

Pilosity. Very reduced; apart from fringing pilosity of clypeus and scapes at most with standing hairs on waist and first gastral tergite. Standing pilosity absent from cephalic dorsum and promesonotum; without long filiform or flagellate hairs anywhere on head, body or legs. Pronotal humeri without projecting specialized hairs. Ground-pilosity on head sparse, minute, appressed and very indistinct.

Sculpture. Dorsum of head behind clypeus shagreenate to finely reticulate-punctate. Pleurae finely superficially sculptured, not smooth and shining. Disc of postpetiole smooth.

Notes

Only two species of this remarkable group are known, both from Cameroun. The previously known species has been fully described by Bolton (1983). The group is directly derived from the chyatha-complex of the extensive emarginata group, which Strumigenys terroni and Strumigenys tethepa resemble in all respects except for the elongate and specialised mandibles. The two groups together form a purely Afrotropical monophyletic unit characterised by the form of the mandibular basal lamella and the construction and pilosity of the clypeus.

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.