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Strumigenys wilsoniana group
Strumigenys wilsoni group Bolton (2000)
Species
Worker Diagnosis
Mandibles in full-face view and at full closure elongate and narrow, linear and shallowly curved; masticatory margins engage only in the apical third or so of their lengths. Proximal to this there is a large gap between the blades, through which the very long labral lobes are visible. Mandibles densely clothed with rows of pale spatulate hairs. MI 35.
Dentition. Inner margin of mandible in full-face view edentate from clypeal margin to about the midlength, where there is a conical tooth followed by a lower rounded tooth, whose apices do not meet those from the opposite mandible at full closure. Distal to these the teeth alternate between long conical and low rounded, into the down curvature of the vertical apical series. Apex of mandible in anterior view with a continuous series of teeth and denticles. Upper half of this series consists of alternating conical and rounded teeth, the lower half has a crowded series of minute denticles and terminates in a small apical tooth.
Basal lamella not visible with mandibles fully closed.
Labrum terminates in a pair of long narrow triangular to conical lobes.
Clypeus broad, with an evenly convex anterior margin. Dorsum of clypeus shallowly biconvex. Outer margins of fully closed mandibles in full-face view meet anterior clypeal margin at the anterolateral angles. In ventral view lateral margins of clypeus do not extend far beyond outer margins of mandibles.
Clypeal dorsum with longitudinal rows of broadly spatulate appressed hairs; without any other form of pilosity. Lateral margins of clypeus with hairs as dorsum, without a fringe of freely projecting hairs.
Preocular carina conspicuous in full-face view.
Ventrolateral margin of head between eye and mandible bluntly angular. Postbuccal impression broad and conspicuous.
Cuticle of side of head within the scrobe densely reticulate-punctate.
Scape short, SI 61-62, subcylindrical, the dorsum and ventre do not converge anteriorly to form a thin lamella at the leading edge. Ventral surface of scape convex.
Leading edge of scape with spatulate hairs that are directed toward the scape apex; spatulate hairs also abundant on dorsal surface of scape.
Pronotum without a median longitudinal carina, angulate but not marginate between dorsum and sides.
Petiole in profile elongate and subclavate. Dorsal outline of peduncle rounding evenly into the node through a shallow curve. In dorsal view petiole node longer than the disc of the postpetiole.
Propodeum with a pair of elongate acute narrowly triangular teeth, subtended on each side by a very narrow concave lamella that broadens slightly basally into a small rounded convex propodeal lobe.
Spongiform appendages of waist segments large, ventral lobe of postpetiole extensive. Base of first gastral sternite in profile apparently lacking a spongiform pad.
Pilosity. Pronotal humeral hair absent. Cephalic dorsum behind clypeus with longitudinal rows of appressed spatulate hairs; no other form of pilosity present. Dorsolateral margins of head with spatulate hairs as dorsum. Pilosity of dorsal alitrunk and waist segments sparse, spatulate; no standing hairs. A transverse row of 4 standing simple hairs present at the base of the first gastral tergite.
Sculpture. Basigastral costulae short and inconspicuous.
Notes
If it was not for the elongate, specialised mandibles the sole known species of this group, Strumigenys wilsoniana, would fall into the leptothrix group, with which it shares all other diagnostic characters at species-group level. It is apparent that wilsoni is yet another example of a species with long narrow mandibles that has evolved independently from a short mandibulate group within Pyramica.
References
- Bolton, B. 2000. The ant tribe Dacetini. Memoirs of the American Entomological Institute. 65:1-1028.