Stigmatomma draconis

Stigmatomma draconis was collected via litter and soil sifting within the lowland-montane floristic transition zone (500-550 m) in a secondary forest on the slopes of Tai Mo Shan at 525 m a.s.l. Though not pristine, owing to clear historic anthropogenic disturbance (e.g. tea terraces), the habitat has had a long history of reforestation and lack of human disturbance post-WWII. Here the leaf litter layer is deep, and samples rich in ant diversity (unpublished data). Further sampling at the site, and surrounding site did not reveal additional specimens.

Identification
Head quadrate, slightly wider than long (CI 106.71). Mandibles distinctly shorter than head (MI 52.75). Mandibular dentition asymmetrical; in full face view, left hand mandible with eight teeth, right hand mandible with nine teeth visible; pairs of teeth present; third tooth from apex short and recurved; preapical tooth blunt. Anterior clypeus margin with ten denticles; six median rectangular denticles; four-minute semi-rectangular denticles laterally. Supraclypeal area with confused sculpture. Total of eleven antennal segments. Lateral face of propodeum and declivitous face marginated. Mesepisternum divided into katepisternum and anepisternum. Hypopygium posteriorly with short stout setae.

Stigmatomma draconis is superficially similar to Stigmatomma pertinax, a species described from Northern India. The holotype specimen of S. draconis will key to S. pertinax within the key in Xu et al. (2012). Comparing both species, however, reveals clear morphological differences that we think provide adequate evidence to consider it as a separate species. Firstly, the third tooth from the apex is entirely differently shape in S. draconis: it is less apically protruding, recurved towards mandible base with a small acute apex (Fig. 7A-B). The preapical tooth is also differently shaped, being shorter, apically blunt and firmly attached to the mandible on its ventral margin (Fig 5C; Fig. 6D; Fig. 7A-B). Moreover, the S. draconis holotype has paired teeth, which the holotype of S. pertinax lacks (Fig 5C; Fig. 6D; Fig. 7B). It should be noted however that in S. draconis the left hand smaller, dorsal tooth in the first tooth pair, is absent, reducing the number of paired teeth on the left-hand mandible to eight. Baroni Urbani (1978) gave the number of mandibular teeth to be seven in the S. pertinax holotype. Interestingly, variation is seen in the mandibular teeth characters of other specimens determined to be S. pertinax (CASENT0172385 from India (CASENT0172395, CASENT0172385) and Nepal (CASENT0280668). Most variable is the third tooth from the apex, all which recurve towards the mandible base (unlike the holotype) but differ in length and overall size.

Additional differing morphological characters between S. pertinax and S. draconis include a less concave posterior head margin, more sculptured supraclypeal area and a less convex anterior clypeal margin. The anterior clypeal margin is also distinctly less convex than S. pertinax, and although, a less reliable character, the number of clypeal denticles is larger in S. draconis with a total of ten compared to eight in S. pertinax. In full face view it seems like a genal tooth is present in S. draconis. However, when seen in posterolateral and ventral view the extension originates from the posterolateral head capsule and is not an anterolateral extension of the gena (Brown 1960). In direct ventral view, minute teeth can also be seen (Fig. 6D). Baroni Urbani (1978) stated that the genal angles in the S. pertinax holotype were ‘well rounded’ and did not mention posterolateral cuticular extensions or minute ventral teeth. Unfortunately, these characters are not visible in the holotype image (CASENT0906831) but in full face view, such an extension seems absent unlike in S. draconis. Finally, both species are originating from two distant regions; the mid-eastern Himalayan foothills for S. pertinax and the lowland coastal region of Hong Kong for S. draconis.

Distribution based on Regional Taxon Lists
Palaearctic Region: China.

Nomenclature

 * . Stigmatomma draconis Hamer, Pierce & Guénard, 2023: 10, figs. 2B, 5A-C, 6A-F, 7B (w.) CHINA (Hong Kong SAR).

Type Material

 * Holotype worker from CHINA; Hong Kong SAR, New Territories, Tai Mo Shan Country Park, 22.42392803 114.129858, 525 m, 04 September 2022, Winkler of random leaf litter and soil, extracted over 6 days. Coll. M. T. Hamer & J. H. Park, det. M. T. Hamer & Benoit Guénard, Collection code; TMS1GC1-1, specimen code ANT-WEB1010999, ZRC.