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Strumigenys nathistorisoc group
Strumigenys nathistorisoc group Tang and Guénard (2023)
Species
Oriental and Sino-Japanese realms
"Malesian-Oriental-East Palaeartic" Bolton (2000)
Worker Diagnosis
MANDIBLE. In full-face view, and at full closure short and elongated-triangular, MI 30–34; in profile view, robust with apical half enlarged and curving downwards; masticatory margins engaged only at apical half of their lengths, basal half with prominent gap between mandibles. Basal lamellae low and broadly triangular, not fully visible at full closure; trap-jaw mechanism most likely absent.
DENTITION. Principal dental row with seven alternating long tapered teeth and reduced low and rounded teeth, four basalmost teeth separated by basal gap between mandibles and following three teeth fully engaging their counterparts from opposing mandible with mandibles at full closure; diastema present between basal lamella and first tooth; first tooth small and triangular, follows by reduced tooth or small denticle, third tooth tapered and larger, fourth tooth reduced, low and rounded, fifth and seventh teeth both tapered, subequal in size and largest among all teeth, sixth tooth reduced, low and rounded, almost squircle in shape and larger than third tooth; apex of mandible at down curvature, in anterior view, with crowded series of around 10–11 minute denticles, terminating in small conical apical tooth. Total dental count of 18 –19.
HEAD. Anterior clypeal margin broadly convex. Preocular carina conspicuous in full-face view; occipital carina present. Ventrolateral margin of head between eye and mandible usually marginate; postbuccal impression small.
ANTENNA. Scape short to moderate, SI 68–74, subcylindrical, marginated but not converging anteriorly to form thin lamella at leading edge.
MESOSOMA. In profile view, propodeal spines usually present; propodeal lamella may be present on declivity.
METASOMA. In profile view, petiole elongate and subclavate; petiolar peduncle may grade evenly into node, or node may have differentiated anterior face. Areolate processes (spongiform tissues) of metasoma well developed.
PILOSITY. Clypeal and mandibular dorsum usually with small appressed setae; upper scrobe margins, lateral and anterior clypeal margins usually with decumbent setae; leading edge of scape usually with appressed to decumbent apically-directed setae. Hairwheel present at mesopleural excavation. Pilosity of head and body variable; in dorsal view, lateral margins of mesosoma usually with posteriorly-directed decumbent setae.
SCULPTURE. Basigastral costulae usually short, no more than one fourth in length of first gastral tergite.
Notes
The Strumigenys nathistorisoc-group currently contains a single member found in the Oriental and Sino- Japanese realms. One undescribed species from Guangdong province of mainland China (specimens have previously been examined by us) also shares the characteristic dentition and likely belong to the same species group.
This group shares superficial resemblance with the S. leptothrix-group and S. kichijo-group, such as short and triangular mandibles, relatively elongated head (CI < 85) with well-developed occipital corners, and large eyes (OI > 10). It can be easily differentiated from the other groups by the combination of a prominent gap between the mandibles at the basal half and its unique dentition of seven alternating long tapered teeth and reduced low and rounded teeth. A conspicuous gap between mandibles is absent in S. leptothrix-group, while S. kichijo-group’s principal dental row is consistently triangular to elongated triangular throughout the mandible, not alternating between two different tooth shapes.
References
- Bolton, B. 2000. The ant tribe Dacetini. Memoirs of the American Entomological Institute. 65:1-1028.
- Tang, K. L., Guénard, B. 2023. Further additions to the knowledge of Strumigenys (Formicidae: Myrmicinae) within South East Asia, with the descriptions of 20 new species. European Journal of Taxonomy 907, 1–144 (doi:10.5852/ejt.2023.907.2327).