Leptanilla macauensis

Leptanilla macauensis  was collected with a Winkler extractor from the upper layer of soil consisting of fine sand, soil and leaf litter. It should be noted that within the same sample a geophilomorph centipede and two ant species (Pheidole megacephala, and Tapinoma indicum) were also collected. The sampling site was located near the stairs set on hillside in Ilha Verde Hill (Fig. 11A), which had a small secondary forest of about 4.3 ha in area. Moreover, the hill was surrounded by highly urbanized areas, isolated as an island, which is thought to be difficult for the permanently wingless Leptanilla queen to colonize (see Bolton 1990). (Leong et al. 2018)

Identification
Leong et al. (2018) - Leptanilla macauensis  can be easily distinguished from other species in the Oceanian, Oriental and Sino-Japanese regions (Holt et al. 2013) by a combination of the following characteristics: clypeus posteriorly not demarcated from frons; clypeal margin with a distinct median lobe and two developed lateral lobes; a total of 3 distinct teeth present on masticatory margin of mandible; metanotal groove absent; subpetiolar process forming a small and hook-like spine. Moreover, basitarsus of foreleg with about 10 thick and erect hairs on the ventral surface, whereas basitarsus of foreleg with densely comb-like hairs in Leptanilla morimotoi, which is similar in some aspects to the new species. Furthermore, Leptanilla macauensis is relatively small compared with other congeners from the Oriental and Sino-Japanese regions based on average head width.

So far, only two records of Leptanilla have been found in southeastern China. Regarding the first record, Leptanilla sp. cf. japonica from Hong Kong (CASENT0914941, Antweb. org 2017), L. macauensis can be distinguished from Leptanilla sp. cf. japonica by the combination of the following conditions; posterior margin of head concave in the former but almost straight in the latter; distinct median clypeal lobe present in the former but absent in the latter; propodeal dorsum glabrous in the former but with distinct hairs in the latter; and body larger in the former (HL: 0.25–0.26 mm, HW: 0.18–0.19 mm; n=4) than in the latter (HL: 0.19 mm, HW: 0.13 mm; n=1).

Distribution based on Regional Taxon Lists
Palaearctic Region: China.

Nomenclature

 *  macauensis. Leptanilla macauensis Leong, Yamane & Guénard, 2018: 4 (w.) CHINA.

Worker
Holotype: HL: 0.25; HW: 0.18; MaL: 0.09; SL: 0.10; PnW: 0.13; PnH: 0.12; MW: 0.10; PtL: 0.09; PtW: 0.07; PtH: 0.09; PpL: 0.07; PpW: 0.08; PpH: 0.10; WL: 0.32; TL: 1.12; CI: 72, SI: 49, MaI: 55, PI: 84, PHI: 78, PPI: 118, PPHI: 80. Paratypes (n=3): HL: 0.25–0.26; HW: 0.18–0.19; MaL: 0.10–0.11; SL: 0.09–0.11; PnW: 0.12–0.13; PnH: 0.09–0.11; MW: 0.10–0.11; PtL: 0.08; PtW: 0.07; PtH: 0.09; PpL: 0.07; PpW: 0.08; PpH: 0.10; WL: 0.31–0.33; TL: 1.12–1.14; CI: 72–74, SI: 49–56, MaI: 51–56, PI: 84–88, PHI: 78–81, PPI: 118–124, PPHI: 80–86.

Head. In full-face view (Fig. 2), head rectangular, distinctly longer than broad (CI: 72–74), with moderately concave posterior margin and weakly convex lateral margin, with posterolateral corners rounded. Clypeus (Fig. 3) not posteriorly separating from frons; anteromedian portion of clypeus forming a roundly raised disc of which anteromedian margin is armed with a pair of triangular extensions (Fig. 4); the disc separated from antennal socket by deep furrow: three short anterior lobes extended from clypeus, clearly differentiated from raised disc; the median lobe separated by distinct gap from lateral lobes (Fig. 3). Eyes absent. Masticatory margin of mandible (Fig. 4) with a total of three distinct teeth; basal tooth strong and upward-directed; preapical tooth almost as large as basal tooth; apical tooth very strong. Antenna 12-segmented; scape rather short and widest at its middle portion, not reaching mid-length of head; pedicel cone-shaped, distinctly narrowed toward base; each of 3rd to 11th segments very short, distinctly broader than long; 12th segment almost twice as long as broad, 2.7 times as long as each of 10th and 11th segments.

Mesosoma. Mesosoma with promesonotal suture deeply incised, without metanotal groove, with dorsum in lateral view flat but interrupted by promesonotal suture. Pronotal neck in dorsal view gradually narrowed anteriad, with weakly convex anterior margin; pronotal disc (pronotum excluding the neck) in dorsal view almost as long as broad, with weakly convex anterior margin, roundly convex lateral margin, and weakly convex posterior margin; posterolateral corner of the disc produced posteriad (Fig. 6A). Propleuron in lateral view (Fig. 7) triangular in shape. Mesonotum in dorsal view with round anterolateral corner and straight lateral margin. Metapleuron clearly separated from mesopleuron by distinctly incised suture, with a deep pit at upper most point, but not demarcated from lateral face of propodeum; metapleural gland orifice large and oval (Fig. 8).

Metasoma. Petiolar node (abdominal segment II) in dorsal view (Fig. 5) rectangular, clearly longer than broad (PI: 84–88), with weakly concave straight anterior, moderately convex posterior, and convex lateral margins; petiolar node in lateral view (Fig. 7) with steep and slightly convex anterior and posterior margins, and with roundly convex dorsal margin; petiolar spiracle located close to anterior margin of tergite; ventral margin of sternite convex, with shallow median indentation; subpetiolar process poorly developed as a small and hook-like spine (Fig. 9). Postpetiolar node (abdominal segment III) in dorsal view sub-circular, broader than long (PPI: 118–124), with almost straight anterior margin and weakly convex posterior margin, in lateral view sub-round dorsally; sternite large, bulging ventrally, not clearly differentiated from tergite, but postpetiole with anterior incision; spiracle located behind the incision. Abdominal segment IV (gastral segment I) in dorsal view slightly longer than broad, narrowed anteriad; anterior margin widely concave and notched; lateral margin convex.

Sculpture. Body extensively smooth and shinning; punctation generally sparse and superficial. Head superficially punctate, with smooth interspace; disc of clypeus smooth; mandible deeply punctate on outer surface; antenna densely punctate, with interspaces smooth. Pronotal neck with about 10 transverse striae (Fig. 6A); anteromost section of mesonotum bearing some strong and transverse striae; upper half of mesopleuron, metapleuron and lateral face of propodeum with superficial punctuation; lower half of mesopleuron reticulate-striate; area around metapleural gland orifice nearly transversely striate; petiolar node superficially punctate on its dorsum; lower half of the node and pre- and poststernite of petiole reticulate-punctate; postpetiolar node superficially punctuate on dorsum; pre- and poststernite of postpetiole transversely striate; gastral tergites almost smooth, at most with sparse and superficial punctation.

Pilosity. Head including mandible with dense hairs, with some portions glabrous (Fig. 6C, condition can be variable among specimens); antenna with dense short erect and suberect hairs. Hair condition on mesosoma heterogeneous; pronotum with dense short hairs mixed with sparser, longer hairs; mesonotum, and dorsa of propodeum and waist with most hairs relatively long and often slanting, with reduced pilosity of short hairs; venter of waist with sparse, relatively long hairs. Gastral tergites with dense suberect hairs and few short decumbent hairs; sternites with sparely distributed and long suberect hairs. Foreleg with a few decumbent hairs on outer surface of femur, and scattered hairs on tibia; basitarsus with about 10 thick and suberect hairs on ventral surface (Fig. 6D). Mid- and hind legs with dense decumbent hairs on femora (more hairs on outer face), and extremely dense hairs on tibiae.

Coloration. Body yellowish brown; antennae and legs lighter.

Type Material

 * Paratypes. Four workers from the same Winkler extractor sample as the holotype, “CML20170125a, LCM00003” in SKYC, “CML20170125a, LCM00001” in CAS, “CML20170125a, LCM00002” in SBSHKU, “CML20170125a, LCM00040 in SBSHKU (kept in 95% alcohol; head separated with the mesosoma and bited on a minor of Pheidole megacephala).
 * Paratypes. Four workers from the same Winkler extractor sample as the holotype, “CML20170125a, LCM00003” in SKYC, “CML20170125a, LCM00001” in CAS, “CML20170125a, LCM00002” in SBSHKU, “CML20170125a, LCM00040 in SBSHKU (kept in 95% alcohol; head separated with the mesosoma and bited on a minor of Pheidole megacephala).

Etymology
The specific epithet is given after the type locality (Macau).