Strumigenys jaitrongi, 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 : 74-77

Strumigenys jaitrongi sp. nov.

urn:lsid:zoobank.org:act:837012D2-8742-4566-B092-16D190593A07

Fig. 26 ; Tables 2 , 4

Diagnosis

Strumigenys jaitrongi sp. nov. can be distinguished from other species in the S. rostrata -group by a combination of the following characters: cephalic dorsum with small appressed obovate setae; mandibles with small basal gap; eye reduced to one ommatidium; pronotal humeral seta flagellate; in profile view, near occipital margin with four small claviform erect setae; mesonotal dorsum with a pair of similar setae; entire surface of mesosoma smooth and shinning except for mesonotal dorsum, which is areolate.

Etymology

The species is named after Dr Weeyawat Jaitrong in recognition of his remarkable work on Thai ants, and his hospitality during our journeys to Thailand that led to the discovery of the species. The name was created by adding the singular Latin genitive case suffix -i to the last name of a male person.

Type material

Holotype worker ( Fig. 26 )

THAILAND • Trang Province, Khao Chong, Site 37 (KCW37); 7.55471° N, 99.78834° E; 1 Jan. 2019; IBBL members leg.; Winkler, 4 corners; secondary forest; LKCNHM ANTWEB1011987 (collection code IBBL KCW-S37-sp2).

Paratype workers

THAILAND • 4 workers; same collection data as for holotype; HKBM ANTWEB1011948 , ANTWEB1011949 , ANTWEB1011985 , ANTWEB1011986 (collection code IBBL KCW-S37-sp2) .

Measurements

Holotype worker

TL 1.6, HL 0.43, HW 0.32, MandL 0.07, SL 0.20, EL 0.019, PW 0.20, ML 0.40, PL 0.19, PH 0.10, DPW 0.12, PPL 0.12, GL 0.38, CI 76, MI 17, SI 62, OI 6, LPI 53, DPI 61.

Paratype workers

TL 1.6–1.8, HL 0.42–0.43, HW 0.32–0.33, MandL 0.08, SL 0.19–0.21, EL 0.015 –0.021, PW 0.16–0.21, ML 0.40–0.46, PL 0.19–0.23, PH 0.10–0.12, DPW 0.11, PPL 0.12–0.14, GL 0.39–0.44, CI 77–79, MI 18–19, SI 58–63, OI 5–6, LPI 53–56, DPI 50–59 (n=4).

Worker description

HEAD. In full-face view, occipital margin broadly concave; occipital corners well developed, bluntly angular. Anterior clypeal margin broadly, weakly convex, with narrowly to moderately-rounded anterolateral angle; posterior clypeal margin converged at midpoint to form right angle (or just slightly smaller than right angle); preocular lamina wide. Scapes dorsoventrally flattened, converging anteriorly to form flange at leading edge; trailing edge shallowly concave. Mandibles in full-face view elongated-triangular; masticatory margins engaged across entire length, without diastema; but basalmost 1–2 tooth too small to reach counterpart from opposite mandible, leaving small basal gap between mandibles. Eye reduced to only one ommatidium.

DENTITION ( Fig. 26B ). (Only partially visible with all type specimens having their mandibles fully closed and obscured by setae along the inner mandible margins.) Principal dental row with six alternating reduced low and rounded teeth and long elongated-triangular teeth; first, third and fifth teeth low, with increase in size from basal to distal; second, third and sixth teeth long, subequal in size; apex of mandible at down curvature, in anterior view, with series of at least five small teeth or minute denticles, apical tooth inconspicuous, either obscured or reduced and, hence, indistinguishable from preapical denticles when mandibles fully closed. Total dental count of around 11–12.

MESOSOMA. In profile view, promesonotum broadly convex; pronotum not marginated dorsolaterally. In dorsal view, lateral margins of pronotum evenly convex. Propodeal spines short, broadly triangular, subtended on each side by broad lamella with weakly convex posterior margin that narrowed 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 about as long as node; petiolar node with differentiated anterior face, shorter than posterior face. In dorsal view, petiolar node broader than long, around 1.2–1.4 times as long; disc of postpetiole broader than long, around 1.4–1.6 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 te posterolateral angle of node in profile view; in dorsal view, the processes present along the lateral and posterior margins of the petiolar node, and surrounding th disc of postpetiole, thicker along lateral and posterior margins than on anterior margin.

PILOSITY. In full-face view, cephalic dorsum with small appressed obovate setae; clypeal dorsum also with appressed obovate setae, slightly smaller and more densely packed; mandibular dorsum with appressed fine setae. Surface of scape with appressed fine setae, and sparsely with a few small appressed oblanceolate setae near leading edge; funiculus densely covered with short fine setae. Laterally-projecting seta absent (one claviform seta around each occipital corner may appear so, but in fact originating from cephalic dorsum at angle instead of on dorsolateral margin of head, hence not truly laterally-projecting); lateral margin of occipital lobe with appressed spoon-shaped setae; lateral and anterior clypeal margins with small spoon-shaped setae, medially directed; leading edge of scape with row of projecting spoon-shaped setae, all curved except for third basalmost seta, which posited on subbasal angle, mostly straight and is longest among all; three setae immediately following straight seta basally directed; all other setae apically directed. In dorsal view, promesonotal dorsum, petiolar node and disc of postpetiole with small appressed subspatulate to obovate setae. Pronotal humeral seta long and flagellate. In profile view, immediately in front of occipital margin near midline with two pair of long, slightly curved claviform erect setae; similar setae also present on mesonotum in a pair; disc of postpetiole with two pairs of remiform erect setae, a pair of similar setae also present on first gastral tergite near anterior margin; petiole and sparsely across gastral tergites with long erect or looped flagellate setae; gastral tergites also further with short appressed fine setae; gastral sternites with erect to suberect setae; ventral surface of head with appressed setae. Hairwheel present at mesopleural excavation. Surface of femora, tibiae and basitarsi with appressed subspatulate to plank-like setae; surfaces of middle and hind basitarsi with long projecting flagellate seta.

SCULPTURE. Surface of head (including antennal scrobe), antennae and legs areolate. Entire surface of mesosoma smooth and shinning, except for mesonotal dorsum, which is weakly areolate. Dorsum of petiolar node and disc of postpetiole mostly smooth and shining. Basigastral costulae short, around one fourth in length of first gastral tergite; rest of gaster smooth and shining.

Comments

Strumigenys jaitrongi sp. nov. is a member of the S. rostrata -group and shares all its characters ( Bolton 2000). Strumigenys jaitrongi , as well as some other Oriental and Sino-Japanese species from the S. rostrata -group (e.g., S. atropos ), have a dentition consisting of alternating short and long teeth, which is different from the dentition of other species within the species group (e.g., S. claviseta sp. nov., S. nepalensis ). Strumigenys jaitrongi and these species may constitute a separate species group of their own due to their unique dentition.

Strumigenys jaitrongi sp. nov. can be distinguished from other Oriental and Sino-Japanese species in the species group by the following characters ( Table 4 ): antennae are 6-segmented (instead of 4-segmented as in S. nepalensis ); mandibles have a small basal gap between them (instead of having a prominent gap that spans almost their entire length as in S. nepalensis , or a complete absence of such a gap as in other species); eyes are greatly reduced (unlike S. emeswangi , S. incerta , S. nepalensis or S. rostrataeformis ); in profile view, the cephalic dorsum of the worker has four erect claviform setae (instead of two such setae as in S. claviseta sp. nov., remiform as in S. atropos or S. subterranea , or completely absent as in the other species); the pronotal dorsum is completely smooth and shining (unlike S. nepalensis , S. emeswangi , S. incerta or S. rostrataeformis ); the mesonotal dorsum is weakly areolate (instead of smooth and shining as in S. atropos ); the pronotal humeral seta is flagellate (instead of stout as in S. atropos or S. nepalensis , or remiform as in S. rostrataeformis , or claviform as in S. claviseta sp. nov.).

Comparing S. jaitrongi sp. nov. with S. claviseta sp. nov. and S. subterranea , the first gaster tergite of S. jaitrongi has a mix of appressed setae, erect flagellate setae, and a pair of erect remiform setae close to the anterior margin (erect remiform seta is absent in S. subterranea , while there are erect claviform setae only in S. claviseta ).

Geographic range

Thailand (Trang).

Ecology

Collected in secondary forest.

Figures

Fig. 26.Type specimens ofStrumigenys jaitrongi sp. nov.A, C–D. Holotype worker (ANTWEB1011987). B. Paratype worker (ANTWEB1011985). A. Full-face view. B. Mandible close-up. C. Profile view. D. Dorsal view.