Strumigenys rongi, 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 : 105-107

Strumigenys rongi sp. nov.

urn:lsid:zoobank.org:act:F6AD2DBA-D88F-4F14-99C8-C53F9BC305B2

Fig. 36 ; Tables 2 , 6

Diagnosis

Strumigenys rongi sp. nov. can be distinguished from other species in the S. leptothrix -group by a combination of the following characters: cephalic dorsum with appressed spatulate setae only; clypeal and mandibular dorsum with small spatulate to obovate setae; without any laterally-projecting seta in full-face view; pronotum marginated dorsolaterally; pronotal humeral seta absent; side of mesosoma mostly smooth and shining; in profile view, propodeal spines subtended by narrow lamellae; lateral lobe of petiole small and not reaching midpoint of node in profile; femora, tibiae and basitarsi with decumbent to appressed setae only.

Etymology

The species is named after mythological Vietnamese dragons (rồng) owing to its Vietnamese origin. The name was created by adding a suffix -i to the Vietnamese noun ‘rong’ for ease of pronunciation.

Type material

Holotype worker ( Fig. 36 )

VIETNAM • Lào Cai Province, Sa Pa, C ổng trời (B); 2000 m a.s.l.; 26 Apr. 2002; K. Eguchi leg.; mature forest; LKCNHM ANTWEB1010903 (collection code KUM Eg02-VN-098).

Paratype worker

VIETNAM • 1 worker; Lào Cai Province, Sa Pa, C ổng trời (E); 2100–2200 m a.s.l.; 2 May 2002; K. Eguchi leg.; mature forest; KUM ANTWEB1010904 (collection code KUM Eg02-VN-243) .

Measurements

Holotype worker

TL 3.1, HL 0.78, HW 0.51, MandL 0.13, SL 0.42, EL 0.109, PW 0.28, ML 0.88, PL 0.35, PH 0.19, DPW 0.15, PPL 0.16, GL 0.84, CI 65, MI 16, SI 82, OI 22, LPI 53, DPI 44.

Paratype worker

TL 3.1, HL 0.78, HW 0.50, MandL 0.13, SL 0.41, EL 0.095, PW 0.27, ML 0.85, PL 0.33, PH 0.17, DPW 0.15, PPL 0.21, GL 0.80, CI 65, MI 16, SI 81, OI 19, LPI 51, DPI 46 (n= 1).

Worker description

HEAD. In full-face view, occipital margin broadly concave; occipital corners well developed and bluntly angular; occipital carina narrow. Clypeus slightly broader than long, around 1.1–1.3 times as long, roughly resembling inverted diamond; anterior clypeal margin bluntly angular around midline. Scapes subcylindrical, marginated but not converging anteriorly to form thin lamella at leading edge. Mandibles in full-face view triangular; masticatory margins engaged across entire length, without diastema or gap between mandibles. In profile view, eye with five ommatidia in diameter.

MESOSOMA. In profile view, promesonotal dorsum broadly convex, propodeum more or less flat transversely; pronotum marginated dorsolaterally. In dorsal view, lateral margins of pronotum evenly convex. In profile view, propodeal spines elongated-triangular, subtended on each side by narrow lamella with concave posterior margin that broadens slightly basally into small rounded convex propodeal lobe. Metapleural gland bulla well developed.

METASOMA. In profile view, petiolar peduncle not grading evenly into node, but anterior face of petiolar node short and inconspicuous; petiolar node with broadly convex posterior face; petiolar peduncle about as long as node. In dorsal view, petiolar node slightly longer than broad, around 1.2–1.3 times as long; disc of postpetiole broader than long, around 1.5–1.7 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 small flap at posterolateral angle of node in profile and not reaching midpoint of node; in dorsal view, processes present along posterior margin of petiolar node, and surrounding disc of postpetiole, thicker along lateral margins than on anterior or posterior margin.

PILOSITY. Surface of scape with appressed subspatulate to spatulate setae; funiculus covered with appressed acicular to fine setae; cephalic dorsum covered with small spatulate setae; clypeal and mandibular dorsum covered with small spatulate to obovate setae; masticatory margins each with row of medially-directed fine setae. Leading edge of the scapes with decumbent setae. In full-face view, dorsolateral margin of head without any laterally-projecting seta. Pronotal humeral seta absent. In dorsal view, promesonotal dorsum sparsely with appressed subspatulate setae; lateral margins with posteriorly-directed decumbent setae. In profile view, cephalic dorsum without any erect seta; suberect to erect stout setae restricted to a few pairs on the mesonotal dorsum, petiolar node and disc of postpetiole, and all over gastral tergites; similar but suberect setae also present on gastral sternites; ventral surface of head with appressed to decumbent setae. Hairwheel present at mesopleural excavation, slightly elongated. Surfaces of femora, tibiae and basitarsi with decumbent to appressed stout setae, without any laterally-projecting erect seta.

SCULPTURE. Cephalic dorsum densely areolate-rugulose; surface of antennal scrobe, antenna and legs densely areolate. Pronotal dorsum predominantly, relatively weakly areolate, with weak longitudinal rugulae and long, weak, longitudinal median striation; dorsum of mesonotum, propodeum and petiolar node densely areolate-rugulose; side of mesosoma mostly smooth and shining with vestiges of sculpture around margins. Disc of postpetiole smooth and shining. Basigastral costulae absent to inconspicuous; rest of gaster smooth and shining.

Comments

Strumigenys rongi sp. nov. is a member of the S. leptothrix -group and shares all its characters ( Bolton 2000), and very likely belongs to the leptothrix -complex. The type specimens all have fully-closed mandibles and the view is obscured by setae along the inner margin of the mandible, making an accurate assessment of the dentition difficult. Placing the specimen against backlight suggests the presence of a principal dental row of around 7 teeth, followed by around 2 small teeth and 4 denticles, terminating in a small apical tooth.

Aside from Strumigenys rongi sp. nov., there are three other SEA species from the same species group ( S. japonica , S. megaera and S. scolopax ) that share the following characters: cephalic dorsum covered with appressed spatulatiform (plank-like, linear, elliptic, subspatulate, spatulate, oblanceolate, obovate or ovate) setae only, head without laterally-projecting seta in full-face view, propodeal spines present and subtended by narrow lamellae or carinae ( Table 6 ). Unlike all of the above three species, for S. rongi the side of the mesosoma is mostly smooth and shining (instead of fully sculptured as in S. megaera and S. scolopax , or mostly sculptured with a partially-smooth mesopleuron as in S. japonica ).

The type specimens of this new species have previously been reported as S. japonica due to their similarity ( Bui & Eguchi 2003). With the recognition of this new species, it is recommended that any other specimen collected from Vietnam that has previously been identified as S. japonica should be reexamined.

Geographic range

Vietnam (Lào Cai).

Ecology

Collected in mature forests at elevations from 2000 to 2200 m.

Figures

Fig. 36. Holotype worker (ANTWEB1010903) of Strumigenys rongi sp. nov. A. Full-face view. B. Profile view. C. Dorsal view.