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Strumigenys xenomastax group
Strumigenys xenomastax group Bolton (2000)
Species
Malesian-Oriental-East Palaeartic
Worker Diagnosis
Mandibles in full-face view and at full closure elongate-subtriangular; teeth occupy only the apical third or so of each mandible and are few in number. Proximal to basal tooth the margin edentate to basal lamella and with a large gap between the mandibles, through which the apices of the labral lobes are visible. In ventral view outer margin of mandible with an inflected prebasal angle. MI 20-22.
Dentition. Consists of only 6 teeth that occupy approximately the apical third of the exposed length of the mandible. The basal tooth and second tooth are largest and narrowly conical; second tooth is followed by 4 small teeth, of which the apical pair is smallest. A long, shallowly concave diastema is present between basal tooth and basal lamella.
Basal lamella of mandible higher than long, narrowly subrectangular, slightly broader basally than at apex; its anterior margin visible in full-face view with the mandibles fully closed.
Labrum terminates in a pair of short broad lobes, their anterior margins truncated; in ventral view each lobe appears almost square.
Clypeus with anterior margin broad and transverse, the outer margins of the mandibles intersect the clypeal margin at the anterolateral angles at full closure.
Clypeal dorsum with appressed short simple hairs, the lateral clypeal margins with a few similar but very slightly elevated hairs that are directed anteriorly.
Preocular carina visible in full-face view.
Ventrolateral margin of head between eye and mandible weakly angulate, not strongly marginate. Postbuccal impression broad and distinct.
Cuticle of side of head within scrobe reticulate-punctate.
Scape short, SI 60-66, subcylindrical, without a sharp leading edge.
Leading edge of scape with a row of minute inconspicuous simple hairs that are all directed toward the apex of the scape and are almost appressed.
Pronotum without a median longitudinal carina.
Propodeum with a narrow lamella on the declivity that terminates dorsally in a small triangular tooth.
Spongiform appendages of waist segments present but small. Base of first gastral sternite in profile with a distinct pad of diffuse spongiform tissue.
Pilosity. Pronotal humeral hair absent.
Notes
The single minute New Guinean species in this group appears to be a derivative of the Australian anderseni group, none of which have yet been discovered in New Guinea but which may occur there. The two groups are very similar but compared to the anderseni-group xenomastax has:
1 narrowed the mandibles without lengthening them,
2 elongated the diastema between basal tooth and basal lamella,
3 developed a marked gap between proximal portions of mandibles,
4 narrowed and lengthened the basal lamella,
5 retained the same low number of teeth but altered their proportions and distribution.
The eye is still relatively large in xenomastax but is somewhat smaller than that seen in the anderseni-group; xenomastax has retained reticulate-punctate sculpture in the scrobes, a feature mostly or entirely lost from the anderseni-group.
References
- Bolton, B. 2000. The ant tribe Dacetini. Memoirs of the American Entomological Institute. 65:1-1028.