Stigmatomma luyiae, Hsu, Feng-Chuan, Esteves, Flavia A., Chou, Lien-Siang & Lin, Chung-Chi, 2017

Hsu, Feng-Chuan, Esteves, Flavia A., Chou, Lien-Siang & Lin, Chung-Chi, 2017, A new species of Stigmatomma from Taiwan (Hymenoptera, Formicidae, Amblyoponinae), ZooKeys 705, pp. 81-94 : 81-85

Stigmatomma luyiae sp. n.

Material.

Holotype: worker, pinned. Original label: "TAIWAN: Nantou County, LFDP, 10.i.2015, F. C. Hsu col. CASENT0922349" Deposited at NMNS.

Paratype: worker, pinned. Original label: "TAIWAN: Nantou County, LFDP, 10.i.2015, F. C. Hsu col. ANTWEB1032000" Deposited at TARI.

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).

Diagnosis.

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.

Description.

Holotype measurements (Figure 1): 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 measurements: 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 (Figs 1A, 2A). Posterior margin of the head slightly concave in full-face view. Antenna with eleven antennomeres, bearing abundant erect to subdecumbent pilosity (Figs 1A, 2 C–D). Frontal lobes closely approximated: median area of the clypeus extending posteriorly as a narrow longitudinal strip between the antennal sockets (Figs 1A, 2 B–C). Antenna with eleven antennomeres (Figs 1A, 2A, C–D). Antennal scrobes absent (Figs 1A, 2A, C). Compound eyes absent (Figs 2C, D). Genal teeth present, but minute. Anterior clypeal margin flat; modified setae or tubercular cuticular projections absent (Figure 2B). 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 (Figure 2B). Mandibles elongated, falciform; baso-masticatory margin with a single row of five teeth (Figs 1A, 2A). 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 (Figs 1A, 2A, C). Dorsal face of the mandibles costate (Figs 1A, 2A). Mandibles with erect to subdecumbent pilosity (Figs 1A, 2A). Mandibles as long as the head (MI: 100).

Mesosoma. Mesepisternum divided into anepisternum and katepisternum (Figs 1B, 3A). Metanotal suture present (Figure 1D). In profile, lateral margins of propodeal declivitous face are not continuous: ventral portion is raised (Figs 1B, 3A). 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 (Figure 3A). Mesosoma covered with erect to subdecumbent pilosity (Figure 3A).

Legs. Lamella absent on the ventral margin of the calcar of strigil (Fig. 4A, B). Anterior face of calcar of strigil with squamiform microtrichia; posterior face with lanceolate microtrichia (Fig. 4 A–B). Multiple spatulate, carinate setae on the anterior face of protibial apex, next to calcar of strigil (Figure 4A). Multiple spatulate, carinate setae on the anterior face of probasitarsus (Figure 4A). Mesotibial spur absent (Figure 4C). Anterior face of mesobasitarsus with round sulcus filled with microvilli-like projections (Figure 4D). One metatibial spur; pectinate; anterior and posterior faces glabrous (Fig. 4 E–F). Sulcus absent on the anterior face of the metabasitarsus (Figure 4E). Arolium present on pro-, meso-, and metapretarsus.

Metasoma. Subpetiolar process well developed and lobe-shaped; fenestra absent (Figs 1C, 3B). Prora present (Figs 1C, 3B). Stout spiniform setae absent on hypopygium (Figure 3D). Petiolar tergite, laterotergite, and poststernite areolate/imbricate (Figs 3 B–C). Gaster imbricate; mostly covered with suberect pilosity (Figs 1C, 3B, D).

Color. Head color orange-brown; body yellow-brown; apex of gaster and appendages yellowish (Figure 1).

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.

Other castes.

Unknown.

Distribution.

To date, Stigmatomma luyiae sp. n. was only collected in the soil of a subtropical evergreen broad-leaved forest, which is part of the Machilus-Castanopsis vegetation zone, in Taiwan (Figure 5).

Discussion.

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): S. caliginosum (Onoyama, 1999), S. crypticum ( Eguchi et al., 2015), S. fulvidum (Terayama, 1987), S. mulanae (Xu, 2000), S. pertinax (Baroni Urbani, 1978), and S. scrobiceps (Guenard et al., 2013). 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 (Fig. 8 A–B).

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 (Figure 2B). 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 (Figure 8A); the head is rectangular (CI: 84; Xu 2000); and the mandibles are shorter than the head (ML: 0.30, HL: 0.38; Xu 2000).