Strumigenys longidens, Tang & Guénard, 2023

Tang, Kit Lam & Guénard, Benoit, 2023, Further additions to the knowledge of Strumigenys (Formicidae: Myrmicinae) within South East Asia, with the descriptions of 20 new species, European Journal of Taxonomy 907, pp. 1-144 : 83-87

Strumigenys longidens sp. nov.

urn:lsid:zoobank.org:act:31CFF836-D330-4153-9D13-46AE068D2A2A

Fig. 28 ; Tables 2 , 9

Diagnosis

Strumigenys longidens sp. nov. can be distinguished from other species in the S. murphyi -group by a combination of the following characters: small suborbicular to orbicular setae restricted to clypeus and two rows immediately behind clypeus, absent in other parts of cephalic dorsum; inner margin of mandible with overhanging obovate setae; leading edge of scape with projecting spoon-shaped setae; mandible with six preapical teeth, all short except for fourth and sixth tooth, about as long as neighboring setae; apicodorsal tooth long and spiniform, overlapping outer margin of opposite mandible at full closure.

Etymology

The species is named after its long preapical dentition. The name was created by combining ‘ longi ’, the genitive masculine singular of Latin adjective ‘ longus ’ (meaning ‘long’), with the nominative singular of masculine Latin noun ‘ dens ’ (meaning ‘tooth’).

Type material

Holotype worker ( Fig. 28 )

VIETNAM • Đồng Nai Province , Cat Tien National Park, Site 19; 11.45683° N, 107.36852° E; 175 m a.s.l.; 4 Jun. 2018; IBBL members leg.; Winkler, 4 corners; secondary forest; LKCNHM ANTWEB1011950 (collection code IBBL CT-S19-4m2-sp12).

Paratype worker

VIETNAM • 1 worker; same collection data as for holotype; HKBM ANTWEB1011951 (collection code IBBL CT-S19- 4m 2-sp12) .

Additional material examined

VIETNAM – Đắk Nông Province • 1 worker; Nam Nung Reserve ; 12.18455° N, 107.76223° E; 878 m a.s.l.; 9 Jun. 2018; IBBL members leg.; Winkler; IBBL ANTWEB1011874 . – Đỗng Nai Province • 1 worker; Cat Tien National Park ; 11.45098° N, 107.36353° E; 160 m a.s.l.; 4 Jun. 2018; IBBL members leg.; Winkler, 4 corners; IBBL ANTWEB1011872 • 1 worker; Cat Tien National Park ; 11.45688° N, 107.36958° E; 175 m a.s.l.; 4 Jun. 2018; IBBL members leg.; Winkler, 4 corners; IBBL ANTWEB1011873 .

Measurements

Holotype worker

TL 1.8, HL 0.39, HW 0.45, MandL 0.20, SL 0.21, EL 0.018, PW 0.26, ML 0.45, PL 0.19, PH 0.11, DPW 0.13, PPL 0.13, GL 0.43, CI 116, MI 51, SI 46, OI 4, LPI 59, DPI 69.

Paratype worker

TL 1.9, HL 0.41, HW 0.48, MandL 0.22, SL 0.22, EL 0.014, PW 0.26, ML 0.47, PL 0.22, PH 0.12, DPW 0.14, PPL 0.14, GL 0.46, CI 118, MI 53, SI 46, OI 3, LPI 54, DPI 62 (n=1).

Worker description

HEAD. In full-face view, head wider than long; occipital margin broadly concave; occipital corner well developed; dorsolateral margins of head divergent on more than half of length, then abruptly converging towards center of head; anterior clypeal margin transverse. Scapes six-segmented, with well-developed subbasal lobe. Mandibles elongated and curvilinear, with six preapical teeth; all of them short and triangular to elongated-triangular, except for fourth and sixth teeth, longest and second longest respectively, spiniform and about as long as neighboring setae; apicodorsal tooth long and spiniform, overlapping outer margin of opposite mandible at full closure ( Fig. 28B ); basal lamellae low and broadly triangular, not fully visible at full closure. In anterior view of mandibles, enlarged extremity of mandibles composed of single apicodorsal tooth followed by series of very fine, compact, baleen-like mandibular setae, then single spiniform apicoventral tooth ( Fig. 28C ). Eye reduced to only one ommatidium.

MESOSOMA. In profile view, mesonotum forms conspicuous bulge, but not overhanging metanotal groove. In dorsal view, pronotum much wider than mesonotum and propodeum; anterior and lateral margins of pronotum convex. Propodeum unarmed, declivity on each side with broad lamella with weakly convex posterior margin narrowing slightly basally into rounded convex propodeal lobe. Metapleural gland bulla well developed.

METASOMA. In profile view, petiolar node high; petiolar peduncle not grading evenly into node, and longer than node, around 1.3–1.5 times as long; petiolar node with differentiated anterior face. In dorsal view, petiolar node broader than long, around 1.3–1.5 times as long; disc of postpetiole broader than long, around two times as long. Areolate processes (spongiform tissues) present on both petiole and postpetiole; ventral lobes of petiole and postpetiole extensive; lateral lobe of petiole merely a flap at posterolateral angle of node in profile; in dorsal view, processes present along lateral and posterior margins of petiolar node, and surrounding disc of postpetiole, thicker along lateral margin than on anterior or posterior margin.

PILOSITY. In full-face view, cephalic dorsum (including along dorsolateral margin of head), clypeal dorsum, mandibles and surface of scape with very short appressed pubescence, those on cephalic dorsum mostly apically acute; small suborbicular to orbicular setae on head restricted to clypeus and two rows immediately behind clypeus, absent in other parts of cephalic dorsum. Anterior clypeal margin with six small appressed shoehorn-shaped to spoon-shaped setae, medially-directed; labrum and inner margin of mandible with overhanging obovate setae; leading edge of scape with row of projecting spoon-shaped setae, arranged in crescendo fashion; larger setae present on subbasal lobes, and progressively smaller setae present until about two-third of scape; mostly curved and apically directed, except for largest seta, posited on subbasal angle and anteriorly directed. In profile view, promesonotal dorsum, petiolar node, disc of postpetiole with short appressed pubescence, without any standing seta; ventral surface of head also with similar setae; first gastral tergites sparsely with erect claviform setae against short appressed pubescence, notably with one row close to anterior margin and another row close to posterior margin; remaining gastral tergites each with a pair of erect remiform setae; ventral surface of gaster with suberect to erect simple fine setae. Surface of legs with short decumbent pubescence; apical portion of tibiae bearing some spatulate to obovate setae. Hairwheel present at mesopleural excavation, well developed.

SCULPTURE. Surface of head (including antennal scrobe), mandibles, antennae, legs and petiole densely areolate. Side of pronotum and mesosomal dorsum areolate-rugulose, rugulae on pronotal dorsum directional towards midline. Pleurae, side of propodeum and disc of postpetiole mostly smooth and shining, with vestiges of sculpture around margins. Basigastral costulae short, around one fifth in length of first gastral tergite; rest of gaster smooth and shining.

Comments

Strumigenys longidens sp. nov. is a member of the S. murphyi -group and shares all its characters ( Bolton 2000). It can be distinguished from other members of the species group by the combination of a limited distribution of small orbicular setae on the cephalic dorsum, and long apicodorsal as well as preapical teeth ( Table 9 ).

Apart from Strumigenys longidens sp. nov., there are two other species in the species group ( S. dyschima ( Bolton, 2000) and S. formosa ( Terayama et al., 1995)) that also share the character whereby orbicular setae on the cephalic dorsum are restricted to only a handful of rows immediately behind clypeus. In contrast, for S. hemisobek ( Bolton, 2000) , orbicular setae are completely absent; for S. nannosobek ( Bolton, 2000) , its orbicular setae are limited to the clypeal dorsum only; for S. murphyi (Taylor, 1968) , its orbicular setae cover the entire area from behind the clypeus to the transverse crest on the vertex. Strumigenys longidens can be distinguished from S. dyschima and S. formosa by its long and spiniform apicodorsal tooth (instead of short and not overlapping outer margin of opposite mandible at full closure). Strumigenys longidens also has areolate-rugulose sculpture on the pronotal dorsum (instead of longitudinal costulate as in S. dyschima ). Strumigenys longidens (TL 1.8–1.9, HW 0.45–0.48) is a slightly larger species than S. formosa (TL 1.6, HW 0.38) or S. dyschima (TL 1.5, HW 0.37).

Strumigenys longidens sp. nov. can further be distinguished from S. murphyi , which also has a long and spiniform apicodorsal tooth, by its preapical teeth. For S. longidens , the longest preapical teeth are spiniform and about as long as the neighboring obovate setae that overhang the inner margin of the mandible ( Fig. 28B ), while in S. murphyi , the preapical teeth are all short and never comparable in length with the neighboring setae.

Geographic range

Vietnam (Đắk Nông, Đồng Nai).

Ecology

Collected in secondary forest at elevations from 160 to 878 m.

Figures

Fig. 28. Holotype worker (ANTWEB1011950) of Strumigenys longidens sp. nov. A. Full-face view. B. Mandible close-up. C. Mandible close-up in anterior view. D. Profile view. E. Dorsal view.