Strumigenys lyroessa group

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Strumigenys lyroessa group Bolton (2000)


Malesian-Oriental-East Palaeartic

Worker Diagnosis

Apical dentition of mandible variable (see species-complexes, below); a single slender preapical tooth present. Mandible short, MI 27-36; in full -face view its basal quarter to third dorsoventrally flattened and its outer margin strongly expanded laterally. Mandible very obviously broadest in this vicinity, rapidly tapering distally to a very narrow apex; outer margins proximally converge to base and pass through a bulging inflected angle where mandible is broadest. ML only 0.80-1.00 X maximum width across outer margins of fully closed mandibles at broadest point. In profile line of mandible, with respect to long axis of head, sloping strongly upward from from base to apex; dorsal surface concave or more steeply angled downward in basal portion where it passes beneath the clypeus.

Basal lamella of mandible large, broad-based and roughly triangular in shape, usually with a blunt apex. In full-face view the anterior margin of the lamella is usually visible even when the mandibles are fully closed.

Anterior clypeal margin transverse to shallowly evenly convex.

Scape very short to moderate, SI 49-71; moderately to very conspicuously dorsoventrally flattened and with a sharp leading edge.

Apical antennomere not spindle-shaped, not strongly constricted basally, broadly articulated to preapical segment.

Ventrolateral margin of head continuous in front of eye, without trace of a preocular notch or impression. Head moderately to strongly dorsoventrally flattened, the dorsal and ventral surfaces without transverse impressions except for the shallow to vestigial postbuccal groove.

Dorsal outline of mesonotum in profile without a raised convex anterior portion and long, steeply sloping posterior portion.

Propodeal teeth subtended by a lamella that may be broad and conspicuous or reduced to a mere carina.

Spongiform appendages of waist segments all present; lateral lobe of petiole restricted to posterior portion in profile.

Pilosity. Standing hairs often absent or very sparse on dorsal alitrunk and first gastral tergite, less commonly numerous; when present always short, stiff and stubbly, simple or slightly expanded apically, or short-remiform. Flagellate or long filiform hairs absent from entire body. Apicoscrobal hair and pronotal humeral hair may be absent or present; when present they are short and stout.

Sculpture. Variable among species groups (see below). Head usually reticulate-punctate; alitrunk entirely reticulate-punctate to nearly smooth; disc of postpetiole smooth to coarsely reticulate-punctate. Gaster usually unsculptured except for basigastral costulae (sculptured only in Strumigenys hostilis).


The strange shape of the mandible immediately characterises this group. To a lesser extent the shape is paralleled in some members of the biroi group, and indeed the two may be closely related. However, the shape of the basal mandible is not as exaggerated in the biroi-group and in profile the line of the mandible is not markedly divergent from the line of the long axis of the head. Some species of the biroi-group also have thick spongiform tissue replacing the propodeal teeth and lamella.

The 18 species of this group fall into three unequal species complexes, defined below by their apical mandibular dentition and their sculpture. The lyroessa-complex contains those species closest related to the type-species of the now abandoned genus Labidogenys (Bolton, 1999).

elapoma complex

Apical fork of mandible with two spiniform teeth, the apicodorsal the larger; space between them bearing one or two intercalary denticles. Pleurae and side of propodeum entirely reticulate-punctate. Disc of postpetiole densely and sharply reticulate-punctate.

lyroessa complex

Apicodorsal tooth of mandible is subtended by a smaller apicomedian spiniform tooth which itself is subtended by two denticles and a short apicoventral spiniform tooth. Pleurae and side of propodeum entirely reticulate-punctate or with a smooth patch on the katepisternum. Disc of postpetiole densely and sharply reticulate-punctate.

prosopis complex

Apical fork of mandible with two spiniform teeth, the apicodorsal the larger; space between them bearing one or two intercalary denticles. Pleurae and side of propodeum entirely smooth, or at most with vestiges of sculpture around extreme periphery. Disc of postpetiole smooth and shining.