Strumigenys sauteri group

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Strumigenys sauteri group Bolton (2000)

Species

Malesian-Oriental-East Palaeartic

Worker Diagnosis

Mandibles in full-face view and at full closure short triangular to elongate and narrow. In the former the masticatory margins are serially dentate and engage throughout their exposed length. In the latter the margins are serially dentate throughout their length but fully engage only apically and the labral lobes are visible basally between the mandibles. In ventral view outer margin of mandible without an inflected prebasal angle. MI 6-22.

Dentition. Basally with a dental row of 7 or 9 teeth, the third or fifth tooth from the base the longest. Teeth 3 and 5 longer than 4; teeth 6 and 7 shorter than 5. Total dental count 12 or 14 (discussed in more detail below).

Basal lamella of mandible an apically rounded short triangle or a more elongate broadly convex lobe. In either case the height of the lamella subequal to the basal tooth, the two not separated by a diastema.

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

Clypeus with anterior margin distinctly concave. Clypeus broad, its anterolateral portions widely expanded and projecting as broad laminae on each side, the lateral projections extend outward far beyond the line of the outer margins of the mandibles. In full-face view the outer mandibular margins intersect the anterior clypeal margin a considerable distance mesad of the 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.

Clypeus without fringing pilosity on its anterior and lateral margins, the dorsum also without pilosity.

Preocular carina broad, conspicuous in full-face view.

Ventrolateral margin of head between eye and mandible sharply marginate, the margination terminates anteriorly in a small tooth or projecting angle. Postbuccal impression vestigial to absent.

Cuticle of side of head within the scrobe finely reticulate-punctate.

Scape dorsoventrally compressed and with a sharp leading edge, quite broad in dorsal view and the ventral surface concave.

Leading edge of scape lacks pilosity of any form or at most has sparse minute appressed pubescence that is directed toward the apex of the scape.

Pronotal dorsum without a median longitudinal carina.

Propodeum triangularly bidentate, the teeth subtended by a narrow carina or lamella on each side.

Spongiform appendages of waist segments well developed. Base of first gastral sternite in profile with a small pad of spongiform tissue, or spongiform tissue vestigial.

Pilosity. Pronotal humeral hair absent. Apicoscrobal hair absent. Head and body almost entirely devoid of hairs; standing pilosity entirely absent from head and alitrunk, ground-pilosity vestigial to absent; 1-3 pairs of simple short standing hairs at most present on postpetiole and extreme base of first gastral tergite. Dorsal (outer) surfaces of middle and hind tibiae without freely projecting hairs.

Sculpture. Dorsum of head behind clypeus, dorsal alitrunk and sometimes also sides of alitrunk, finely and densely punctate or reticulate-punctate.

Notes

The two previously described species of this group, Strumigenys sauteri and Strumigenys canina, formerly constituted the weak genus Pentastruma, reviewed by Brown & Boisvert (1979) and Ogata (1991), and now abandoned (Bolton, 1999). In the regions currently under consideration the members of this group are distinct because of their clypeal morphology and marked lack of pilosity. Such characters are, however, insignificant at genus-rank and have been evolved in several extralimital groups of species within Pyramica. In particular, a number of Afrotropical forms have a laterally expanded clypeus coupled with a concave anterior clypeal margin (emarginata group, terroni group). In both these groups there is also a marked tendency to reduce the body pilosity, but the clypeal margins are fringed with specialised hairs. In the marginata group the clypeus is expanded laterally and the clypeal margins lack fringing pilosity, but its anterior margin remains convex.

Dentition within the sauteri-group is of two forms. The first, found in Strumigenys arges, Strumigenys brontes and sauteri itself, shows a total dental count of 12. In these species the basal lamella is followed directly by 3 teeth that gradually increase in length. Tooth 4 is distinctly shorter than 3, and 4 is also shorter than 5. Teeth 6 and 7 are slightly shorter than 4 (markedly shorter than 5); tooth 7 is followed by 4 minute denticles and a slightly enlarged apical tooth. The dentition of canina differs from this as the mandible has become more elongate and the total dental count increased to 14. Teeth 1 and 3, following the relatively low elongate basal lamella, are longer than 2 and 4 but much shorter than 5, which is by far the longest and stoutest on the margin. This is followed by a much shorter tooth 6. Tooth 7 is slightly longer than 6, and 8 is small, about same length as 6. Tooth 9 is elongated, distinctly longer than 6-8 and 10-apex but shorter than 5. The mandible terminates apically in 4 minute denticles and a slightly enlarged apical tooth. All the currently known members of this group are confined to the Oriental region, ranging from Thailand through China to Taiwan and Japan.

References

Ogata, K. 1991b. A generic synopsis of the poneroid complex of the family Formicidae (Hymenoptera). Part II. Subfamily Myrmicinae. Bulletin of the Institute of Tropical Agriculture, Kyushu University. 14:61-149.

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