Strumigenys eurycera group

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Strumigenys eurycera group Bolton (2000)

Species

Malesian-Oriental-East Palaeartic

Worker Diagnosis

Apical fork of mandible of 2 teeth, with a single intercalary denticle or small tooth. A single preapical tooth present, this tooth spiniform and longer than the maximum width of the linear mandible. MI 33-46.

Anterior clypeal margin broad, more or less transverse or with a very small median indentation.

Antenna with 4 segments. Scape slightly to extremely flattened; SI 60-70.

Preocular carinae broad and conspicuous in full-face view.

Scrobe short and shallow or vestigial behind level of eye; upper scrobe margin short and weakly defined or not defined behind level of eye, the dorsum rounding evenly into the side.

Ventrolateral margin of head in front of eye without a preocular notch or impression, weakly angular or rounding into ventral surface. Postbuccal groove extremely shallow to vestigial.

Propodeal dorsum more or less flat anteriorly but posteriorly abruptly angled downward and sloping steeply to the tooth; the latter short-triangular and subtended by a narrow carina on the declivity.

Spongiform lobes of waist segments present but lateral lobe of petiole small. Base of first gastral sternite almost bare or with a weak diffuse pad of spongiform tissue.

Pilosity. Variable but any standing hairs present are short and simple; no flagellate or bizarre pilosity. Pronotal humeral hair absent or present. Middle and hind tibiae and basitarsi without long projecting erect hairs. First gastral tergite with short simple hairs that are suberect to erect.

Sculpture. Head and alitrunk reticulate-punctate, sometimes with a smooth area on mesopleuron that may also extend on to metapleuron. Disc of postpetiole sculptured. Base of first gastral sternite with longitudinal costulae.

Notes

The four species recognised in this group are immediately defined by their 4-segmented antennae, strangely angled propodeal dorsum and costulate base of the first gastral sternite. Members of the group are currently known only from New Guinea and nearby islands.

The nominal species of this group, Strumigenys eurycera, was earlier associated with Strumigenys emmae in the now abandoned genus Quadristruma, because both species happened to have 4-merous antennae. At present 7 species are known in the predominantly Australian emmae group and it is obvious that this group and the eurycera group achieved 4-merous antennae by independent evolutionary events. One emmae-group species (Strumigenys pnyxia) retains 6-merous antennae; it does not show the strangely shaped propodeum or costulate first sternites characteristic of the eurycera-group.

References

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