Stigmatomma luyiae

The types, the only specimens of this species, were collected from the soil of a subtropical evergreen broad-leaved forest in Taiwan.

Identification
Hsu et al. (2017) - Workers of Stigmatomma luyiae can be distinguished from those of other Stigmatomma species by the combination of the following characters (asterisks flag putative unique characters within Stigmatomma):

1. Eleven antennomeres.

2. Mandibles as long as the head (MI: 100).

3. Mandibles’ baso-masticatory margin with a single row of teeth.

4. Mandibles with longer, jigsaw-tab-shaped median teeth.

5. *Anterior clypeal margin flat; modified setae or tubercular cuticular projections absent.

6. Anterior portion of the median area of the clypeus with seven stout, acuminate flattened-apex setae arranged in a single transversal row.

7. Frontal lobes closely approximated; median area of the clypeus extending posteriorly as a narrow longitudinal strip between the antennal sockets.

8. Antennal scrobe absent.

9. Genal teeth present, but minute.

10. Dorsal face of the head densely costate-foveolate, slightly catenated.

11. Head quadrate (CI: 100).

12. Mesepisternum divided into anepisternum and katepisternum.

13. Lamella absent on the ventral margin of the calcar of strigil.

14. *Anterior face of mesobasitarsus with round sulcus filled with microvilli-like projections.

15. One metatibial spur.

16. Sulcus absent on the anterior face of the metabasitarsus.

17. Fenestra absent on the subpetiolar process.

18. Stout spiniform setae absent on the hypopygium.

Stigmatomma luyiae is easily distinguished from most of its congeners in Asia due to its mandibles, which present only a single row of teeth instead of two rows. The only Stigmatomma species in that region sharing this character with the new species are those formerly classified as Bannapone (Eguchi et al., 2015): Stigmatomma caliginosum, Stigmatomma crypticum, Stigmatomma fulvidum, Stigmatomma mulanae, Stigmatomma pertinax, and Stigmatomma scrobiceps. Within this group, S. fulvidum possesses antennae with twelve antennomeres (Terayama 1987), while the antennae of the other species, including S. luyiae, have eleven antennomeres. Only S. luyiae and S. mulanae possess the median mandibular teeth in a jigsaw tab-shaped arrangement.

The diagnostic characters for setting apart Stigmatomma luyiae from S. mulanae are the presence/absence of cuticular projections and modified setae on the anterior margin of the clypeus, head shape, and relative size of the mandibles. In S. luyiae, the anterior clypeal margin is flat and bears neither tubercular projections nor stout setae. Instead, stout, acuminate flattened-apex setae rise from the anterior portion of the median area of the clypeus. Also, the head is quadrate (CI: 100), and the mandibles are as long as the head (MI: 100). In S. mulanae, the anterior margin of the clypeus presents tubercle-like cuticular projections, and each of which bears a stout, conic seta; the head is rectangular (CI: 84; Xu 2000); and the mandibles are shorter than the head (ML: 0.30, HL: 0.38; Xu 2000).

Distribution based on Regional Taxon Lists
Oriental Region: Taiwan.

Nomenclature

 *  luyiae. Stigmatomma luyiae Hsu, F. et al. 2017: 83, figs. 1-4, 8B (w.) TAIWAN.

Worker
Holotype: TL: 2.45 mm, HL: 0.5 mm, HW: 0.5 mm, HW2: 0.47 mm; SL: 0.3 mm, ML: 0.5 mm, WL: 0.6 mm, PPW: 0.24 mm, PnW: 0.31 mm, PtW: 0.24 mm, PtL: 0.16 mm, CI: 100, MI: 100, and SI: 60. Paratype: TL: 2.43 mm, HL: 0.48 mm, HW: 0.48 mm, HW2: 0.45 mm, SL: 0.29 mm, ML: 0.48 mm, WL: 0.6 mm, PPW: 0.22 mm, PnW: 0.32 mm, PtW: 0.24 mm, PtL: 0.16 mm, CI: 100, MI: 100, and SI: 60.

Head. Dorsal face of the head quadrate (CI: 100), bearing longer erect to suberect hairs, and numerous shorter suberect to subdecumbent pilosity; sculpture densely costate-foveolate, slightly catenated. Posterior margin of the head slightly concave in full-face view. Antenna with eleven antennomeres, bearing abundant erect to subdecumbent pilosity. Frontal lobes closely approximated: median area of the clypeus extending posteriorly as a narrow longitudinal strip between the antennal sockets. Antenna with eleven antennomeres. Antennal scrobes absent. Compound eyes absent Genal teeth present, but minute. Anterior clypeal margin flat; modified setae or tubercular cuticular projections absent. Anterior portion of the median area of the clypeus with seven stout, acuminate flattened-apex setae arranged in a single transversal row; longer median seta; each seta rises from a minute tubercle-like cuticular projection. Mandibles elongated, falciform; baso-masticatory margin with a single row of five teeth. Mandibular teeth arrangement, from base to apex: smaller blunt tooth; two longer jigsaw-tab-shaped teeth; long diastema; indistinct, acute pre-apical tooth, immediately followed by an acute apical tooth. Dorsal face of the mandibles costate. Mandibles with erect to subdecumbent pilosity. Mandibles as long as the head (MI: 100).

Mesosoma. Mesepisternum divided into anepisternum and katepisternum. Metanotal suture present. In profile, lateral margins of propodeal declivitous face are not continuous: ventral portion is raised. In the dorsal view, pronotum, mesonotum, and propodeum strigate-rugulose; declivitous face of the propodeum weakly strigate-rugulose. Posterolateral portion of the pronotum, mesepisternum, and posterolateral face of propodeum areolate; remainder of the lateral face of the propodeum strigate-rugulose-somewhat areolate; metapleuron imbricate. Mesosoma covered with erect to subdecumbent pilosity.

Legs. Lamella absent on the ventral margin of the calcar of strigil. Anterior face of calcar of strigil with squamiform microtrichia; posterior face with lanceolate microtrichia. Multiple spatulate, carinate setae on the anterior face of protibial apex, next to calcar of strigil. Multiple spatulate, carinate setae on the anterior face of probasitarsus. Mesotibial spur absent. Anterior face of mesobasitarsus with round sulcus filled with microvilli-like projections. One metatibial spur; pectinate; anterior and posterior faces glabrous. Sulcus absent on the anterior face of the metabasitarsus. Arolium present on pro-, meso-, and metapretarsus.

Metasoma. Subpetiolar process well developed and lobe-shaped; fenestra absent. Prora present. Stout spiniform setae absent on hypopygium. Petiolar tergite, laterotergite, and poststernite areolate/imbricate. Gaster imbricate; mostly covered with suberect pilosity.

Color. Head color orange-brown; body yellow-brown; apex of gaster and appendages yellowish.

Type Material
Holotype: worker, pinned. Original label: “TAIWAN: Nantou County, LFDP, 10.i.2015, F. C. Hsu col. CASENT0922349” Deposited at NMNS (National Museum of Natural Science). Paratype: worker, pinned. Original label: “TAIWAN: Nantou County, LFDP, 10.i.2015, F. C. Hsu col. ANTWEB1032000” Deposited at. Type locality. Lienhuachih Forest Dynamics Plot (LFDP), 23°55’01”N / 120°52’58”E, 770m, Nantou County, Taiwan, 10.i.2015, F. C. Hsu col., Winkler sample (sifted soil).

Etymology
The name luyiae is homage to Miss Lu-Yi Wang. The fieldwork that yielded specimens for this study could not have been completed without her participation.