Strumigenys loriae group

Strumigenys loriae group Bolton (2000)

Species

Malesian-Oriental-East Palaeartic

Strumigenys chyzeri also occurs in the Austral region.

Worker Diagnosis

Apical fork of mandible of 2 spiniform teeth; either without intercalary dentition or with 1-2 denticles or small teeth. Usually a single preapical tooth present (none in Strumigenys pachycephala). In full-face view inner margin of mandible straight to curved from base to about apical quarter but thereafter the margin abruptly becomes concave with respect to its previous line; preapical tooth when present located at proximal commencement of concavity or upon the concave section itself, or, in Strumigenys chyzeri, arising from the dorsal surface of the mandible rather than from its inner margin. MI 39-52.

Anterior clypeal margin usually with a conspicuous median impression or broadly V-shaped; in one species (Strumigenys odalatra) margin only very shallowly concave, almost transverse.

Scape slender and subcylindrical, not or only very slightly dorsoventrally flattened; short to moderate, SI 53-75.

Apical antennomere slender, tapering from midlength to base but, except in chyzeri, not narrowly articulated with the preapical antennomere.

Ventrolateral margin of head with a deep semicircular concavity immediately in front of eye, the ventrolateral margin broadest immediately anterior to this concavity and sometimes expanded into a lobe or tooth. Preocular concavity continues as a broad vertical groove up side of head immediately in front of eye and terminates dorsally as a roughly semicircular excavation in the upper scrobe margin. Preocular toward the midline.

Dorsolateral margin of head very irregular. In full-face view from front to back the margin shaped as follows: convex at frontal lobe, pinched in immediately behind frontal lobe, convex posterior to this (ventrolateral margin is usually strongly expanded below this convexity), deeply concave immediately above preocular impression, flared outward at nearly a right-angle immediately above eye, divergent posterior to this and the dorsum traversed from side to side by a broad depression.

Head capsule in profile with a broad concavity in the dorsal outline that extends from about the midlength to close to the occipital margin. In same view the ventral outline with a narrow postbuccal groove and a preocular impression in front of level of eye; behind level of eye ventral margin has a broadly U-shaped or V-shaped impression.

Scrobe poorly defined behind level of eye, usually obsolete or almost absent, without sharply defined margins and scarcely or not concave.

Propodeal declivity usually with a mere carina, rarely with a narrow and inconspicuous lamella the posterior (free) margin of which is concave and parallels the shape of the margin of the declivity.

Spongiform appendages of waist segments all present, small to moderate. Ventral spongiform curtain on petiole may be very slender or restricted to surface immediately below the node. Lateral lobe of petiole may be vestigial or little more than an extension of the posterior collar down the node.

Pilosity. Flagellate hairs or long fine simple hairs absent from head, alitrunk and first gastral tergite. Short stiff standing hairs present on cephalic dorsum, promesonotum, waist segments and first gastral tergite. Pronotal humeral hair short and stiff. Dorsal (outer) surfaces of middle and hind basitarsi usually without long erect hairs (present only in odalatra). Ground-pilosity on dorsum of head simple and very short, inconspicuous.

Sculpture. Dorsal surfaces of head, alitrunk and petiole finely densely reticulate-punctate; head and promesonotum often also with longitudinal fine rugulae. Pleurae and side of propodeum reticulate-punctate. Gaster unsculptured except for basigastral costulae.

Notes

The seven species included here are mostly confined to New Guinea but a few have wider distributions and one, Strumigenys chyzeri, extends its range into the Austral region. One species (Strumigenys loriae) is strongly polymorphic, an extremely rare occurrence in dacetines. Polymorphism may also occur in one or more of the related new species described below as their morphology closely resembles that of loriae, but material of each is currently restricted to a few roughly same-size individuals, so the undoubted presence or absence of polymorphism remains to be proved.

The shape of the apical portion of the mandible as described above is repeated in the omopyx and koningsbergeri groups. The former of these does not have the peculiarly shaped head capsule of the loriae-group and has the apical antennomere strongly constricted and extremely slender basally. Within the koningsbergeri-group a few species do have some or most of the strange modifications of the head capsule described above, but in these the scrobe is always markedly concave and has sharply defined margins, the pleurae and side of the propodeum are mostly to entirely smooth and the propodeal declivity has a broad lamella.

References

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