Strumigenys elegantula ( Terayama & Kubota, 1989 )

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 : 47-49

Strumigenys elegantula ( Terayama & Kubota, 1989)

Figs 2C , 16 ; Table 2

Smithistruma elegantula Terayama & Kubota, 1989: 788 , figs 23-27 (w.q.) TAIWAN. Indomalaya.

Pyramica elegantula – Bolton 1999: 1673.

Strumigenys elegantula – Baroni Urbani & De Andrade 2007: 119.

Diagnosis

Strumigenys elegantula can be distinguished from other species in the S.leptothrix -group by a combination of the following characters: cephalic dorsum with appressed plank-like to subspatulate setae; laterally-projecting seta present in full-face view; in profile view, erect seta on cephalic dorsum restricted to area between highest point of te vertex and occipital margin; pronotum marginated dorsolaterally; propodeal spines subtended by broad lamellae; femora, tibiae and basitarsi with long erect setae.

Material examined

HONG KONG • 1 worker; Lantau Island , Penny’s Bay; 22.32589° N, 114.03385° E; 22 m a.s.l.; 10 Oct. 2017; M. Pierce leg.; pitfall trap; IBBL ANTWEB1009804 • 1 worker; same collection data as for preceding; 13 Oct. 2017; M. Pierce leg.; pitfall trap; IBBL ANTWEB1009733 • 4 workers; same collection data as for preceding; IBBL ANTWEB1011994 to ANTWEB1011997 • 1 worker; same collection data as for preceding; IBBL ANTWEB1009764 • 2 workers; North District , Lai Chi Wo; 22.527° N, 114.258° E; 8 May 2015; R.H. Lee leg.; Winkler; IBBL • 1 worker; Tsuen Wan District , Tai Lam Country Park; 22.38091° N, 114.05324° E; 8 Nov. 2017; R. Cheung and M. Pierce leg.; Winkler, 4 corners; IBBL ANTWEB1016431 .

THAILAND – Trang Province • 5 workers; Khao Chong, Site 17 (KCW17); 7.26719° N, 99.65431° E; 28 Dec. 2018; IBBL members leg.; Winkler, 4 corners; IBBL ANTWEB1011959 • 1 worker; same collection data as for preceding; IBBL ANTWEB1011998 .

Measurements

Workers

TL 2.3–2.5, HL 0.57–0.63, HW 0.41–0.45, MandL 0.08–0.10, SL 0.27–0.32, EL 0.06–0.07, PW 0.20– 0.25, ML 0.56–0.62, PL 0.29–0.32, PH 0.12–0.14, DPW 0.09–0.11, PPL 0.16–0.19, GL 0.61–0.77, CI 71–73, MI 13–17, SI 66–72, OI 14–16, LPI 40–43, DPI 30–35 (n=9).

Worker redescription

HEAD. In full-face view, occipital margin broadly concave; occipital corners well developed and bluntly angular; occipital carina broad. Clypeus slightly broader than long, around 1.1–1.3 times as long, roughly resembling inverted diamond. 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; basal lamellae low and broadly triangular, not fully visible at full closure. In profile view, eye with four ommatidia in diameter.

DENTITION ( Fig. 2C ). Principal dental row with eight alternating short triangular and long spiniform teeth (i.e., four consecutive pairs of teeth, each pair consists of short tooth followed by long tooth), second and third pairs subequal in size and longer than other pairs (short tooth of one pair compares with short tooth of another pair only, same for long tooth); followed by 3–4 small teeth and, at down curvature in anterior view, series of four minute denticles, terminating in small apical tooth. Total dental count of 16–17.

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

METASOMA. In profile view, petiolar peduncle grading evenly into node, and about as long as (or slightly shorter than) node. In dorsal view, petiolar node longer than broad, around two times as long; disc of postpetiole broader than long, around 1.4–1.5 times as long. Areolate processes (spongiform tissues) present on both petiole and postpetiole; ventral lobes of petiole and postpetiole extensive; lateral lobe of petiole forming moderately extensive 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 and posterior margins than on anterior margin.

PILOSITY. In full-face view, cephalic dorsum with appressed setae, ranging from plank-like setae near occipital margin to subspatulate setae near posterior clypeal margin; clypeal dorsum covered with short narrowly elliptic setae; mandibular dorsum covered with small narrowly elliptic to acicular setae; masticatory margins each with row of medially-directed fine setae. Lateral margin of occipital lobe with around 5–6 laterally-projecting setae; dorsolateral margin of head and leading edge of scape with decumbent setae; appressed setae present along occipital margin. Surface of scape covered with appressed acicular setae; funiculus covered with appressed, progressively finer setae. In dorsal view, promesonotal dorsum sparsely with appressed setae; posteriorly-directed decumbent setae present along lateral margins; petiolar node sparsely with appressed setae. Pronotal humeral seta straight and stout, longer than other setae on pronotal dorsum. In profile view, erect setae on cephalic dorsum restricted to area between highest point of vertex and occipital margin; erect stout setae present on mesonotal dorsum as three pairs, on petiole, on disc of postpetiole, and all over gastral tergites; ventral surface of head with decumbent setae; gastral sternites sparsely with suberect to decumbent setae. Hairwheel present at mesopleural excavation. Surfaces of middle and hind femora, tibiae and basitarsi with long stout erect setae.

SCULPTURE. Cephalic dorsum, clypeal dorsum and ventral surface of head sparsely reticulate-rugulose, with spaces between rugulae densely areolate-rugulose; surface of antennal scrobe, antenna and legs densely areolate. Promesonotal dorsum predominantly, relatively weakly areolate, with weak longitudinal rugulae and long, weak, longitudinal median striation; propodeal dorsum densely areolate-rugulose; dorsum of petiolar node transversely rugulose. Side of pronotum mostly smooth and shining, with weak rugulae around margins; pleurae and side of propodeum densely areolate-rugulose. Disc of postpetiole smooth and shining. Basigastral costulae short, around one fourth in length of first gastral tergite; rest of gaster smooth and shining.

Geographic range

Mainland China (Guangdong, Guangxi, Hong Kong), Taiwan, Thailand (Chiang Mai, Mukdahan, Trang).

Ecology

Collected in Fengshui wood, semi-open forest, reclaimed land and rubber plantation.

Comments

After the description of Strumigenys intermedia sp. nov. and Strumigenys doydeei sp. nov., some of the specimens that were once recognized as S. elegantula are now re-identified accordingly. As such, we have revised the description of S. elegantula , based on photos of the type specimen from Taiwan, as well as the specimens from Hong Kong and Thailand. See Strumigenys intermedia for a detailed comparison between the species.

Specimens from Macau and the majority of those from Hong Kong are now re-identified as S. intermedia sp. nov., while CASENT0285186 from Chaiyaphum Province of Thailand (inspected by Bolton (2000) and currently recorded on AntWeb) ( Fig. 15A–C ) should be S. cf. doydeei sp. nov. instead. Specimens from Guangdong and Guangxi provinces of mainland China should be revisited to verify their identification. However, with the confirmation of its presence in Hong Kong ( Fig. 16A–C ) and Thailand ( Fig. 16D–F ), the geographic range of the species is unlikely to be drastically changed after the revision. Its presence in Fujian Province of mainland China, as well as Laos and Vietnam is likely.

After a careful examination of our specimens with opened mandibles, we have determined that S. elegantula has a different dentition pattern in comparison with S. leptothrix ( Fig. 2C ) and should be placed in a separate species complex. Specimens from Taiwan should be checked if they have the same dental morphology. See the species group section for detailed discussion.

Figures

Fig. 2. Mandible close-ups of workers from the elegantula-complex in the Strumigenys leptothrix-group. A–B. S. intermedia sp. nov. (TT01353). C. S. elegantula (Terayama & Kubota, 1989) from Hong Kong (RHL00290). D. S. jacobsoni Menozzi, 1939 from Vietnam (ANTWEB1011973).

Fig. 16. Workers of Strumigenys elegantula (Terayama & Kubota, 1989) in full-face, profile and dorsal views. A–C. Worker from Hong Kong (ANTWEB1009804). D–F. Worker from Thailand (ANTWEB1011998).

Fig. 15. Workers of Strumigenys cf. doydeei sp. nov. in full-face, profile and dorsal views. A–C. Worker from Thailand (CASENT0285186, taken by Cong Liu). D–F. Worker from Yunnan, mainland China (CASENT0715043, taken by Takumi Uchima, Environmental Science Section, OIST).