Strumigenys lasia group

Strumigenys lasia group Bolton (2000)

Worker Diagnosis
Mandibles in full-face view and at full closure elongate and narrow, only engaging at extreme apices; distal to apices with a broad space between the mandibles through which the conical labral lobes are visible. In ventral view outer margin of mandible without an inflected prebasal angle. MI 43 - 46.

Dentition. Inner margin of mandible with a crowded apical series of 9-10 minute denticles, and with 5-6 irregularly spaced low blunt denticles preceding them on the distal two-thirds of the blade. Proximal one-quarter to one-third of margin edentate to the basal lamella.

Basal lamella of mandible an evenly rounded low lobe, visible in full-face view when mandibles fully closed.

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

Clypeus with anterior margin shallowly convex medially between the mandibles proximal of the mandibular basal lamellae. Outer margins of mandibles intersect anterior clypeal margin at or very near the anterolateral clypeal angles.

Clypeus with anterior margin bearing a row of narrowly spatulate medially-curved unspecialised hairs that are the same shape and size as the other hairs on the clypeal dorsum.

Preocular carina conspicuous in full-face view.

Ventrolateral margin of head between eye and mandibular insertion broadly convex, the side rounding evenly into the ventral surface. Postbuccal impression very small.

Cuticle of side of head within scrobe reticulate-punctate.

Scape slender and long, SI 92 - 98, subcylindrical.

Leading edge of scape with curved hairs that are simple to very narrowly spatulate. Some of the narrowly spatulate hairs are curved toward the base of the scape.

Dorsolateral borders of pronotum and mesonotum marginate.

Spongiform appendages of petiole and postpetiole moderately developed. Base of first gastral sternite with hairs but without a pad of dense spongiform tissue.

Pilosity. Dorsolateral margin of head with two long flagellate hairs that freely project on each side, each arising from a blunt tubercle. Cephalic dorsum with 2-3 pairs of erect flagellate hairs and very dense fine anteriorly curved ground-pilosity. Humeral angle of pronotum with a long flagellate projecting hair that arises from a blunt tubercle; dorsolateral margin of alitrunk behind humeral angle with other flagellate hairs and promesonotal dorsum with very dense fine ground-pilosity. Dorsal surfaces of petiole, postpetiole and first gastral tergite with flagellate hairs and dense ground-pilosity.

The structure of the mandibles makes it apparent that Strumigenys lasia is directly derived from the lujae-group by reduction and specialisation of its shape and dentition; the two together apparently form a monophyletic unit. The mandibles of lasia appear long, but to some extent this is an optical illusion brought about because they are very narrow (Bolton, 1983).

The MI of lasia (43-46) is within the range shown by the lujae-group (MI 26-50), where the mandibles are elongate-triangular.