Anochetus lanyuensis

The collected specimens indicate that Anochetus lanyuensis inhabits coastal bushes, organic farms, primary forests, and nests in soil, sand, or under small stones. Although the genus of Anochetus is typically found in forests, this species exhibits a wide habitat range from natural forests to open areas such as farms or coasts.

Identification
Leong et al (2019) - Among the Anochetus graeffei species group, Anochetus lanyuensis can be distinguished from the other species by its large body size (HL + MdL ≥ 1.89 mm), longitudinally striate pronotal disc, large eye (EL = 0.16–0.21 mm, 12 ommatidia along the maximum diameter), weakly concave dorsal margin of the petiole in the frontal view, and relatively longer 2nd antennal segment (as long as the length of the 3rd and 4th segments combined). Anochetus lanyuensis is particularly similar to Anochetus ruginotus from the Philippines. Both species are easily distinguishable from the others in the graeffei group by the large body size (HL +MdL > 1.75 mm in Anochetus ruginotus; HL + MdL ≥ 1.89 mm in Anochetus lanyuensis) and the longitudinally striate pronotal disc (irregularly striate or smooth in the other species). Anochetus lanyuensis is distinguishable from Anochetus ruginotus through the following characteristics of the worker caste: in Anochetus lanyuensis, 1) larger eye [EL = 0.16–0.21 mm, 12 ommatidia along the maximum diameter; EL < 0.10 mm in Anochetus ruginotus; 2) mesonotum with weak transverse striae (strong reticulate striae in Anochetus ruginotus; 3) dorsal margin of the petiole weakly concave in the frontal view (convex in Anochetus ruginotus); 4) 2nd antennal segment as long as the 3rd and 4th segments combined (2nd antennal segment as long as the 3rd and 5th segments combined in Anochetus ruginotus); and 5) shorter setae on the gasteral surface (longer in Anochetus ruginotus).

Chen et al. (2019) - China: The species is similar to Anochetus ruginotus, but can be distinguished from the latter by the following characters: eyes larger with 12 ommatidia along the maximum diameter; dorsal outline of mesosoma straight.

Distribution
Known from Orchid Island, Taiwan.

Distribution based on Regional Taxon Lists
Oriental Region: Taiwan.

Nomenclature

 *  lanyuensis. Anochetus lanyuensis Leong, Tsai, Terayama, Shiao & Lin, 2018: 125, figs. 2-7 (w.q.) TAIWAN.

Worker
Holotype: EL 0.20 mm; HL 1.25 mm; HW 1.23 mm; SL 1.01 mm; MdL 0.76 mm; PrW 0.68 mm; PeH 0.61 mm; PeL 0.32 mm; WL 1.69 mm; TL 5.63 mm; CI 98, PI 55, MdI 61, SI 82. Paratypes (n=7): EL 0.16–0.21 mm; HL 1.23–1.32 mm; HW 1.16–1.23 mm; SL 1.00–1.09 mm; MdL 0.66–0.79 mm; PrW 0.65–0.70 mm; PeH 0.52–0.61 mm; PeL 0.27–30 mm; WL 1.54–1.72 mm; TL 5.33–5.74 mm; CI 93–95, PI 55–58, MdI 53–61, SI 86–89. Dealate queen: EL 0.39 mm; HL 1.23 mm; HW 1.26 mm; SL 1.02 mm; MdL 0.75 mm; PrW 0.76 mm; PeH 0.61 mm; PeL 0.31 mm; WL 1.75 mm; TL 5.84 mm; CI 102, PI 60, MdI 61, SI 81.

Head slightly longer than broad (CI: 93–98); widest at level of eyes, with deeply concave and strongly impressed ventral margin in full-face view; posterior 1/3 of head subparallel; posterodorsal corner forming dull angle and protruding posteriad; extraocular furrow gently incised. Mandible linear with shaft broadest at apical 1/3; dorsal margin without distinct teeth; apical portion with three distinct teeth; dorsal tooth longest and ca. 3.0 times as long as basal width; intercalary tooth distinct and triangular; ventral tooth ca. 2.5 times as long as basal width. Clypeus small, with gently concave anterior margin. Antenna long and slender; scape not exceeding posterior corner of head; 2nd segment 2.25 times (n = 8) as long as wide and as long as 3rd and 4th segments combined; 3rd to 11th segments each longer than wide, the ratio of 2nd to 5th segments nearly 2:1:1:1 in length from the base; terminal segment 3.97 times (n = 8) as long as wide. Eye flat and large (ca. 0.20 mm in maximum diameter), with about 12 ommatidia along the maximum diameter. In lateral view of mesosoma, dorsal outline of pronotum weakly convex anterior half and straight posterior half; dorsal outline from mesonotum to propodeum straight; posterolateral corner of propodeum dully angulate with straight posterior margin straight. In dorsal view of mesosoma, pronotal disc slightly wider than long, with acutely convex anterior margin, neatly convex lateral side, and straight posterior margin; anterolateral corner not forming an angle. Petiole higher than long, with acute triangular tip; anterior margin straight and posterior margin weakly convex; dorsal margin of petiole weakly concave in frontal view; subpetiolar process developed, with subtriangular ventral margin; in dorsal view, petiolar node about 0.75 times as long as wide, widest at midlength. Gaster oval; 3rd abdominal tergum subtrapezoid with slightly convex anterior margin and straight posterior margin; its length about 0.68 mm and 0.9 times (n = 8) as long as wide in dorsal view; 4th abdominal tergum subrectangular; its length about 0.61 mm and 0.8 times (n = 8) as long as wide in dorsal view. Sculpture Frons and vertex of head with many thin and longitudinal striae extending to posterior lobes; malar space and gena smooth and shining.

Mandible smooth and shining. Antenna weakly microreticulate. Protonal dorsum longitudinally striate, with carinate anterior margin. Mesonotum opaque, with weak transverse striae. Mesopleuron smooth and shining, except anterior potion weakly striate. Metapleuron and propodeum with many transverse striae. Petiole smooth and shining. Gaster smooth and shining. Legs smooth.

Pilosity: Dorsum of head with scattered and short subdecumbent pubescences. Dorsum of alitrunk and petiolar node with short erect or suberect setae. Gaster with moderately abundant long suberect setae about 0.15–0.24 mm in length and moderately abundant decumbent setae about 0.04–0.08 mm in length. Antennae and legs with short pubescences.

Color: Body reddish brown; mandible and antenna brown; legs yellowish brown.

Chen et al. (2019) - TL5.33–5.84, HL 1.23–1.32, HW 1.16–1.23, CI 93–98, SL 1.00–1.09, SI 82–89, ED 0.16–0.21, PW 0.65–0.70, MSL 1.54–1.72, PL 0.27–0.32, PH 0.52– 0.61 (n=7) (After Leong et al., 2018).

In full-face view head longer than broad, posterior margin strongly concave. Mandibles linear, gradually broadened apically; inner margin without denticles; apical portion with three distinct teeth. Antennae 12-segmented; scapes not exceeding to posterior corners of head. Eyes moderate-size.

In lateral view mesosoma stout, dorsal outline of posterior half of pronotum and mesonotum straight. Posterolateral corners of propodeum obtusely angulate. Petiole thin, distinctly higher than long, with acute triangular tip; anterior margin straight, posterior margin distinct convex; subpetiolar process developed with subtriangular ventral margin. Dorsal margin of petiole weakly concave in anterior view. Frons and anterior part of vertex longitudinally striate extending to posterior lobes of head, remainder of head smooth and shining. Clypeus smooth and shining. Pronotum longitudinally striate. Mesonotum and propodeum transversely striate. mesopleuron smooth and shining. Petiolar node smooth and shiny except basal area faintly striate. Gaster smooth and shining.

Dorsum of body with abundant erect to suberect hairs and abundant decumbent pubescence; scapes and tibiae with scattered subdecumbent hairs dense pubescence. Body reddish brown; antennae, legs and petiole yellowish brown.

Queen
General shape and mandible similar to worker caste. Ocelli forming a right-angled triangle; median ocellus larger than lateral ocelli. Eye large and circular, with 20 ommatidia along the maximum diameter. Antennal scape not reaching posterior corner of head; 2nd segment almost as long as 3rd and 4th segments combined. In lateral view of mesosoma, dorsal outline of mesosoma well convex and arching from anterior margin of pronotum to posterior margin of propodeum; pro-mesonotal suture distinctly incised; transcutal suture distinct; mesopleural sulcus present; dorsolateral margin of propodeum forming a blunt angle. In dorsal view of mesosoma, pronotal disc with acutely convex anterior margin and broadly convex lateral margins; scutum inverted-subtrapezoidal; scutellum semicircular; metanotum with convex posterior margin; propodeal disc wider than long and widest at anterior end, with straight sides and posterior margin. Petiole similar to with worker caste. Gaster oval, first gastral tergum wider than long in dorsal view. Sculpture: Frons and vertex of head with many thin longitudinal striae extending to posterior lobes; maler space and genal area smooth and shining. Pronotum with oblique striae, excepting anteromedian portion smooth and shining. Scutum with longitudinal striae. Scutellum and metanotum smooth and shining. Mesopleuron smooth and shining. Propodeal disc and declivity with transverse striae. 3rd abdominal tergum largely smooth and shining, with a few shallow weak punctures. Pilosity: Similar to worker caste, but shorter and less abundant. Color: Body reddish brown; legs yellowish brown.

Type Material
Holotype: Worker, TAIWAN. Taitung County, Orchid Island, the coastal bush near the Lanyu airport. 10 IX 1997, W. H. Tsai (: CMAon001). Paratypes: 4 workers, same data as holotype (: CMAon003; NMNS: CMAon004; NIAES: CMAon005; : CMAon006) and 1 dealate queen, same data as holotype (NMNS: CMAon002). 2 workers, TAIWAN. Taitung County, Orchid Island, Hungtoushan. 16 IV 2015, J. J. Liu (: LCM00023; NTU: LCM00024). 1 worker, TAIWAN. Taitung County, Orchid Island, Yunghsing Organic Farm, IX 2015, F. C. Hsu (: LCM00025).

Etymology
Named after Orchid Island (Lanyu), the type locality of this new species.