Stigmatomma pagei

The type locality of S. pagei, Tai Po Kau Headland, Hong Kong SAR, China, is unique as it is a typical lowland coastal woodland of exceeding quality which is now absent in Hong Kong. The headland, now a Site of Special Conservation Interest, owes its quality to a remnant pre-war Feng Shui relict woodland, post-World War II reforestation, and 60 years with little human disturbance (Kendrick & Barretto 2006). Stigmatomma pagei was collected within what is thought to be this remnant woodland site. Whether S. pagei is relic of lowland forests in Hong Kong pre-deforestation is unknown, however sampling from higher elevation secondary and other forests habitats in Hong Kong has thus far failed to reveal additional specimens. Moreover, Tai Po Kau Headland has produced numerous new species as well as rare genera and species in Hong Kong.

Identification
Head longer than broad (CI 87.00). Mandibles shorter than head length (MI 67.19). Clypeus with a total of six clypeal denticles; four-minute rectangular denticles; two conical bilobed denticles. Metanotal groove weakly impressed. Mesepisternum divided into katepisternum and anepisternum. Dorsolateral margin of propodeum marginated; margin begins posterior to mesonotum and extends along the whole propodeum dorsolateral margin including its declivitous face. Metapleuron and anterior area of the lateral surface of the propodeum with long longitudinal striae. In dorsal view, pronotum and propodeum bisected longitudinally by smooth cuticle with scarce punctuation. Metanotal groove weakly impressed.

Within Hong Kong, S. pagei is most morphologically similar to Stigmatomma amblyops and, assuming the presence 12 segments to the antennae, would key to this species in Xu & Chu (2012). However, numerous morphological characters differentiate both species. Firstly, the different mandible tooth composition with each tooth pair being closer together in S. pagei but more evenly spaced along the masticatory margin in S. amblyops (Fig 3A; Fig. 9C; Fig. 10C). The mandible is also distinctly convex medially (between first and final tooth pair) within S. pagei but conspicuously more linear in S. amblyops (Fig 3A; Fig. 9C; Fig. 10C). The lack of a marginated dorsolateral propodeal margin and metanotal groove in S. amblyops differs with S. pagei (Fig. 10A; Fig. 10E). Stigmatomma amblyops has a conspicuous genal tooth which is inconspicuous in S. pagei (Fig. 3A; Fig. 9C; Fig. 10D). Moreover, the median clypeal denticles are longer and distinctly extending beyond the anterior clypeal margin in S. amblyops, while the median clypeal denticles hardly projecting forward at all in S. pagei (Fig. 3A; Fig. 9C; Fig. 10C). No other species resembles S. pagei in continental Asia and eastern Asian islands. A single specimen from Borneo (CASENT0280663; bmnh-f) on AntWeb does show close morphological similarities with S. pagei, including marginated dorsolateral propodeal margin and a distinctly striate propodeal lateral surface. Both differ in terms of sculpturing and setae density, however, this is particularly obvious on the mesosomal dorsum, as well as the degree to which the posterior head margin in full face is concave. Other characters such as the anterior clypeal denticle characters and mandibular dentition are difficult to differentiate in bmnh-f due to mandible and head positioning.

Unfortunately, the holotype specimen (the only known specimen of this species) of S. pagei was damaged upon collection. The specimen has lost all funicular segments on both antennae and the majority of palp segments (Fig. 9C). The left-hand mandible has also become dissociated at the point of articulation with the head (Fig. 9C). It is likely the specimen acquired this damage during its time in the collection liquid (70% ethanol). Due the long sampling period (7 days), water evidently entered the pitfall and diluted the ethanol, contributing to specimen decomposition. Here and within the key, we assume the funicular segment count is twelve due to the close resemblance to S. amblyops and bmnh-f, as well as it’s dissimilarity to eleven antennal segmented species within the former Bannapone genus (Guénard et al., 2013; Liu et al., 2017). The palps are also highly damaged, rending segment counting impossible. Moreover, the accumulation of organic matter within and between segments as well as between striae obscured the true sculpture of the anepisternum, the posterior sculpture of the pronotal lateral area and the posterior setae on the hypopygium.

Distribution based on Regional Taxon Lists
Palaearctic Region: China.

Nomenclature

 * . Stigmatomma pagei Hamer, Pierce & Guénard, 2023: 14, figs. 2C, 9A-C, 10A-F (w.) CHINA (Hong Kong SAR).

Type Material

 * Holotype worker from CHINA; Hong Kong SAR, New Territories (Tai Po), Tai Po Kau Headland, 22.43471 114.19264, 74 m, pitfall trap (70% ethanol), 7-day sample time, 18-24 August 2022. Coll. M. T. Hamer & T. S. R. Silva, Determined by M. T. Hamer and Benoit Guénard. Collection code; TPK4SQ4PF3-8; specimen code; ANT-WEB1010972, ZRC.