Strumigenys chyzeri

Identification
Bolton (2000) - A member of the Strumigenys loriae-group. The shape of the mandible in chyzeri often varies between populations and in some samples even varies between workers from the same nest-series. In particular, variation in the maximum width of the mandible in relation to its length in full-face view, is apparent. Also there is variation in the relative length and thickness of the preapical tooth, and the degree to which it overhangs the inner mandibular margin. To some extent the first of these seems usually to be size-related as larger individuals frequently have more slender mandibles and smaller individuals have stouter mandibles. These variations appear to have no significance in the species-rank taxonomy.

Newly synonymised above are Mann’s Solomon Islands species Strumigenys antaeus and the infraspecific Strumigenys foscior. Mann (1919) recognised that antaeus was very close to chyzeri but said that the “deeply excavated clypeus readily distinguishes antaeus from chyzeri Emery which has the anterior border arcuate.” In fact, type-material and all other samples of chyzeri have the clypeal margin the same shape as in antaeus. Series of antaeus are paler in colour than is usual, being dull brownish yellow where samples of chyzeri from most of its range are mid-brown to blackish brown, though paler samples are not unknown in both New Guinea and Australia. In fact, the type-series of foscior is considerably darker than antaeus and more closely approximates the usual shades seen in chyzeri.

In the regional fauna there are two other groups in which the preapical tooth of the mandible arises from the dorsal surface of the mandible rather than from its usual location on the inner margin, the wallacei-group and the fuarda-group. Neither of these has the complex shape of cephalic dorsolateral margin and head capsule possessed by chyzeri (see group diagnosis, above). There are other striking differences. For instance in the wallacei-group the ventral surface of head anteriorly has a single broad deep transverse trench that in profile occupies all the space between the posterior margin of the buccal cavity and the level of the eye; this represents a fusion of the postbuccal groove and the ventral preocular impression into a single exaggerated trench. In chyzeri the postbuccal groove and the preocular impression are separate. In fuarda the ventral surface of the head bears no impressions at all except for an extremely shallow feeble postbuccal groove.

Within the loriae-group the oddly placed and shaped preapical tooth is immediately diagnostic. In several collections workers of chyzeri have been found mounted upon the same pins as specimens of loriae, the two should not be confused.

Distribution based on Regional Taxon Lists
Australasian Region: Australia. Indo-Australian Region: Indonesia, New Guinea, Solomon Islands.

Nomenclature

 *  chyzeri. Strumigenys chyzeri Emery, 1897c: 576, pl. 14, figs. 4-6 (w.q.m.) NEW GUINEA. Senior synonym of antaeus, fuscior: Bolton, 2000: 859.
 * antaeus. Strumigenys antaeus Mann, 1919: 355, fig. 34 (w.) SOLOMON IS. Junior synonym of chyzeri: Bolton, 2000: 859.
 * fuscior. Strumigenys antaeus var. fuscior Mann, 1919: 357 (w.) SOLOMON IS. Junior synonym of chyzeri: Bolton, 2000: 860.

Worker
TL 2.5-3.2, HL 0.78-1.00, HW 0.65-0.87, CI 80-87, ML 0.36-0.50, MI 45-52, SL 0.44-0.59, SI 63-75, PW 0.30-0.39, AL 0.68-0.88 (35 measured). In full-face view preapical tooth of mandible arises from about the midwidth of the dorsal surface, at or close to the point where the mandible is broadest; preapical tooth very obviously not arising from the inner margin. From its origin the preapical tooth arcs medially across the mandible and up to half its length projects beyond the inner mandibular margin. In full-face view side of head in front of preocular impression convex but not expanded into a triangular or conical projecting process. Apical antennomere spindle-shaped, strongly constricted basally and narrowly articulated to preapical antennomere. In profile cephalic dorsum at highest point of vertex and near occipital margin with short stiff standing hairs; such hairs absent from concavity of transverse dorsal impression. Promesonotal standing pilosity stiff and short, restricted to a pair on pronotum close to anterodorsal margin, the humeral pair, and a single mesonotal pair. Pleurae and side of propodeum densely reticulate-punctate. Propodeal spines slender, straight or very shallowly upcurved. Dorsal (outer) surfaces of middle and hind basitarsi without erect long fine hairs. Lateral spongiform lobe of petiole little more than an extension of the collar. Ventral spongiform strip on petiole very reduced, in some samples present only beneath node, petering out beneath peduncle; in others present as a narrow crest that extends the length of the segment. Petiole node in dorsal view varying from broader than long to slightly longer than broad. Disc of postpetiole sometimes mostly smooth, varying from this to uniformly reticulate-punctate. Basigastral costulae shorter than to about equal to length of disc of postpetiole. Standing hairs on first gastral tergite short and stiff.

Type Material
Syntype workers, queen and male, PAPUA NEW GUINEA: Madang ( = Friedrich-Wilhelmshafen), and near Aitape ( = Berlinhafen) (L. Biro) [examined].