Strumigenys intermedia, 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 : 68-73

Strumigenys intermedia sp. nov.

urn:lsid:zoobank.org:act:E71526C0-CF69-4F74-83BD-6465452DAB2E

Figs 2A–B , 24–25 ; Tables 2 , 6

Diagnosis

Strumigenys intermedia sp. nov. can be distinguished from other species in the S. leptothrix -group by a combination of the following characters: cephalic dorsum with appressed stout and truncated setae; laterally-projecting seta present in full-face view; in profile view, erect setae present sporadically across cephalic dorsum, not restricted to area between highest point of vertex and occipital margin; pronotum marginated dorsolaterally; propodeal spines subtended by broad lamellae; femora, tibiae and basitarsi with long erect setae.

Etymology

The species is named after its sporadic erect setae on the cephalic dorsum in comparison with other existing species from the same species group, Strumigenys elegantula and Strumigenys jacobsoni , which have appressed setae only (except for area close to the occipital margin) and erect setae only, respectively. The epithet ‘ intermedia ’ is the nominative feminine singular of the Latin adjective ‘ intermedius ’ (meaning ‘intermediate’).

Type material

Holotype worker ( Fig. 24 )

HONG KONG • Lantau Island , Chep Lap Kok, AW 14R72; 22.2939° N, 113.9331° E; 22 m a.s.l.; 1 Oct. 2015; B.M. Worthington leg.; Winkler, 12 random; secondary forest; LKCNHM ANTWEB1010888 (collection code IBBL BMW00363 ).

Paratype workers

HONG KONG • 3 workers; same collection data as for holotype; HKBM ANTWEB1010889 to ANTWEB1010891 (collection code IBBL BMW00363 ) .

Additional material examined

MAINLAND CHINA – Hainan Province • 1 worker; Bawangling, BWLR8; 19.193492° N, 109.020000° E; 15 Jul. 2016; L. Wang leg.; Winkler , 4 corners; IBBL • 1 worker; Yinggeling, YGLK7; 19.091766° N, 109.536910° E; 1 Aug. 2016; L. Wang leg.; Winkler , 12 random; IBBL • 2 workers; Yinggeling, YGLK8; 19.091036° N, 109.535279° E; 1 Aug. 2016; L. Wang leg.; Winkler , 12 random; IBBL • 2 workers; Yinggeling, YGLK9; 19.092689° N, 109.534550° E; 1 Aug. 2016; L. Wang leg.; Winkler , 4 corners; IBBL .

HONG KONG • 3 workers; Islands District , Tung Ping Chau; 22.5382° N, 114.4365° E; 2 Oct. 2017; R. Cheung and B. Morgan leg.; Winkler, 12 random; IBBL ANTWEB1016277 • 2 workers; Kwai Tsing District , Tsing Yi Peak; 22.34312° N, 114.0999° E; 16 Mar. 2018; R. Cheung and M. Law leg.; Winkler, 4 corners; IBBL ANTWEB1016950 • 1 worker; Kwai Tsing District , Tsing Yi Peak; 22.34312° N, 114.0999° E; 16 Mar. 2018; R. Cheung and M. Law leg.; Winkler, 12 random; IBBL ANTWEB1016742 • 2 workers; Kwai Tsing District , Tsing Yi Peak; 22.34054° N, 114.10076° E; 16 Mar. 2018; R. Cheung and M. Law leg.; Winkler, 12 random; IBBL ANTWEB1016753 • 1 worker; Kwai Tsing District , Tsing Yi Peak; 22.33512° N, 114.10293° E; 16 Mar. 2018; R. Cheung and M. Law leg.; Winkler, 4 corners; IBBL ANTWEB1016764 • 1 worker; Lantau Island , Chep Lap Kok; 22.2939° N, 113.9331° E; 24 Mar. 2017; B.M. Worthington leg.; IBBL • 2 workers; Lantau Island , Chep Lap Kok; 22.2939° N, 113.9331° E; 20 m a.s.l.; 29 Jul. 2016; B.M. Worthington leg.; Winkler, 12 random; IBBL • 1 worker; Lantau Island , Penny’s Bay; 22.32589° N, 114.03385° E; 22 m a.s.l.; 13 Oct. 2017; M. Pierce leg.; pitfall trap; IBBL • 1 worker; Lantau Island , Penny’s Bay; 22.32589° N, 114.03385° E; 22 m a.s.l.; 13 Oct. 2017; M. Pierce leg.; pitfall trap; IBBL • 1 worker; Lantau Island , Sha Lo Wan; 22.2881° N, 113.9013° E; 6 May 2016; B.M. Worthington leg.; IBBL • 1 worker; Lantau Island , Shek Pik; 22.233° N, 113.888° E; 18 Aug. 2015; R.H. Lee leg.; pitfall trap; IBBL • 2 workers; Lantau Island , Shek Pik; 22.2309° N, 113.88606° E; 18 Aug. 2015; R.H. Lee leg.; IBBL • 1 worker; Tai Po District , Sha Lo Tung; 22.47708° N, 114.18195° E; 28 May 2015; R.H. Lee leg.; pitfall trap; IBBL • 1 worker; Tai Po District , Wu Kau Tang; 22.49645° N, 114.2441° E; 29 m a.s.l.; 28 Oct. 2015; T. Tsang leg.; IBBL • 1 worker; Tsuen Wan District , Tai Lam; 22.37564° N, 114.04408° E; 160 m a.s.l.; 3 Nov. 2017; M. Pierce leg.; pitfall trap; IBBL • 1 worker; Tsuen Wan District , Tai Lam; 22.37564° N, 114.04408° E; 160 m a.s.l.; 3 Nov. 2017; M. Pierce leg.; pitfall trap; IBBL • 2 workers; Tsuen Wan District , Tai Lam; 22.38109° N, 114.05457° E; 246 m a.s.l.; 11 Nov. 2017; M. Pierce and R.Cheung leg.; pitfall trap; IBBL • 2 workers; Tsuen Wan District , Tai Lam; 22.38109° N, 114.05457° E; 246 m a.s.l.; 11 Nov. 2017; M. Pierce and R.Cheung leg.; pitfall trap; IBBL • 1 worker; Tsuen Wan District , Tai Lam; 22.37579° N, 114.04408° E; 243 m a.s.l.; 14 Sep. 2016; R.H. Lee and M. Pierce leg.; Maxi Winkler; IBBL ANTWEB1009819 • 1 worker; Tsuen Wan District , Tai Lam; 22.37579° N, 114.04408° E; 243 m a.s.l.; 14 Sep. 2016; R.H. Lee and M. Pierce leg.; Maxi Winkler; IBBL ANTWEB1009821 • 1 worker; Tsuen Wan District , Tai Lam; 22.37579° N, 114.04408° E; 243 m a.s.l.; 14 Sep. 2016; R.H. Lee and M. Pierce leg.; Maxi Winkler; IBBL ANTWEB1009822 • 1 worker; Tsuen Wan District , Tai Lam; 22.37591° N, 114.04477° E; 225 m a.s.l.; 14 Sep. 2016; R.H. Lee and M. Pierce leg.; Maxi Winkler; IBBL ANTWEB1009844 • 13 workers; Tsuen Wan District , Tai Lam Country Park; 22.38091° N, 114.05324° E; 8 Nov. 2017; R. Cheung and M. Pierce leg.; Winkler, 12 random; IBBL • 80 workers; Tsuen Wan District , Tai Lam Country Park; 22.38109° N, 114.05511° E; 8 Nov. 2017; R. Cheung and M. Pierce leg.; Winkler, 12 random; IBBL ANTWEB1016468 • 1 worker; Yuen Long District , Lok Ma Chau; 22.51192° N, 114.06064° E; 31 May 2018; M. Wong leg.; pitfall trap; IBBL • 1 worker; Yuen Long District , Lok Ma Chau; 22.51378° N, 114.06301° E; 31 May 2018; M. Wong leg.; pitfall trap; IBBL • 1 worker; Yuen Long District , Mai Po Nature Reserve; 22.487° N, 114.039° E; 13 Sep. 1993; J. Fellowes leg.; pitfall trap; IBBL .

Measurements

Holotype worker

TL 2.8, HL 0.75, HW 0.55, MandL 0.11, SL 0.36, EL 0.078, PW 0.26, ML 0.65, PL 0.35, PH 0.14, DPW 0.12, PPL 0.21, GL 0.68, CI 73, MI 14, SI 65, OI 14, LPI 41, DPI 34.

Paratype workers

TL 2.5–2.6, HL 0.64–0.66, HW 0.46–0.48, MandL 0.08–0.09, SL 0.31–0.32, EL 0.074 –0.077, PW 0.23– 0.26, ML 0.63–0.65, PL 0.29–0.33, PH 0.13–0.14, DPW 0.11–0.12, PPL 0.17–0.21, GL 0.67–0.71, CI 71–73, MI 13–14, SI 66–67, OI 15–17, LPI 42–47, DPI 36–37 (n=3).

Worker description

HEAD. In full-face view, occipital margin deeply concave; occipital corners well developed and bluntly angular; occipital carina broad. Clypeus broader than long, around 1.2–1.4 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. 24B ). 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, mesosomal dorsum broadly, weakly convex; 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 deeply concave posterior margin broadening 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 1.6–1.9 times as long; disc of postpetiole slightly broader than long, around 1.1–1.2 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 and surface of scape covered with appressed stout and truncated setae; clypeal dorsum covered with appressed narrowly elliptic to acicular setae; mandibular dorsum covered with appressed acicular setae; masticatory margins each with row of medially-directed fine setae. Surface of funiculus covered with progressively finer setae. Lateral margin of occipital lobe with around 5–6 laterally-projecting setae, sometimes also 1–3 on upper scrobe margin; dorsolateral margin of head and leading edge of scape with decumbent setae; appressed setae present along occipital margin. In dorsal view, promesonotal dorsum sparsely with appressed setae; posteriorly-directed decumbent setae present along lateral margins; appressed setae present along margins of petiolar node and disc of postpetiole. Pronotal humeral seta long, straight and stout. In profile view, erect setae present sporadically across cephalic dorsum, not restricted to area between highest point of vertex and occipital margin; suberect to erect setae also present on mesonotal dorsum in three pairs, on petiole in two pairs, on disc of postpetiole as one pair and all over gastral tergites; ventral surface of head with decumbent setae; gastral sternites 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 fifth in length of first gastral tergite; rest of gaster smooth and shining.

Comments

Strumigenys intermedia sp. nov. is a member of the elegantula -complex in the S. leptothrix -group and shares all its characters ( Bolton 2000).

Aside from Strumigenys intermedia sp. nov., there are 12 other SEA species from the same species group ( S. ailaoshana , S. decumbens sp. nov., S. delicata sp. nov., S. densissima sp. nov., S. doydeei sp. nov., S. elegantula , S. jacobsoni , S. leptothrix , S. nankunshana , S. strummeri sp. nov., S. zanderi sp. nov. and S. zhenghuii sp. nov.) that share the following characters: propodeal spines present and subtended by broad lamellae, pronotum marginate dorsolaterally ( Table 6 ). Strumigenys decumbens , S. doydeei and S. zanderi can easily be differentiated from the other species for their complete lack of any erect to suberect seta on the cephalic dorsum in profile view. Among these three species, S. zanderi stands out for its further lack of any erect seta on the mesosomal dorsum, while there are at least a few pairs around the mesonotum in both S. decumbens and S. doydeei . Strumigenys decumbens can be differentiated from S. doydeei for all the setae on its middle and hind femora, tibiae and basitarsi are decumbent to appressed, while in S. doydeei there are numerous laterally-projecting erect setae.

Among the remaining 10 species that have erect to suberect setae on the cephalic dorsum ( S. ailaoshana , S. elegantula , S. delicata sp. nov., S. densissima sp. nov., S. intermedia sp. nov., S. jacobsoni , S. leptothrix , S. nankunshana , S. strummeri sp. nov. and S. zhenghuii sp. nov.), S. jacobsoni , S. leptothrix and S. strummeri can easily be differentiated from the others for, in profile view, they have suberect to erect setae only on the cephalic dorsum and without any appressed seta. In S. jacobsoni and S. leptothrix , they also have long erect setae across the mesosomal dorsum, while in S. strummeri , erect setae are restricted to a few pairs around the mesonotum only. Refer to Bolton’s comments under S. jacobsoni ( Bolton 2000) for a detailed comparison between S. jacobsoni and S. leptothrix .

Strumigenys ailaoshana and S. nankunshana subsequently stand out from the remaining species with their distinct sculpture on the promesonotal dorsum. The promesonotal dorsum of S. ailaoshana is predominantly longitudinally-striated, whereas that of S. nankunshana is predominantly transversely-striated, while for the other five species this sculpture is areolate-rugulose, sometimes with additional weak longitudinal striations.

The remaining five species all have both appressed and erect setae on the cephalic dorsum in profile view. For S. delicata sp. nov., S. intermedia sp. nov. and S. zhenghuii sp. nov., erect setae appear sporadically throughout the cephalic dorsum, not limited to any particular region on their heads, while for S. densissima sp. nov. and S. elegantula , erect setae are restricted to the area between the highest point of the vertex and the occipital margin only. Comparing appressed setae on the cephalic and clypeal dorsum for S. delicata , S. intermedia and S. zhenghuii , for S. delicata they are all fine and apically acute; for S. intermedia those on the cephalic dorsum are stout and truncated, and those on the clypeal dorsum mostly narrowly elliptic; for S. zhenghuii those on the cephalic dorsum are mostly subspatulate, and those on the clypeal dorsum mostly linear to narrowly elliptic. Among the three species, S. zhenghuii further stands out for the side of the mesosoma completely smooth and shining (in comparison it is mostly sculptured in the other two species); S. delicata stands out for its numerous laterally-projecting setae on the dorsolateral margin in full-face view (in comparison there are only around 5–6 for the other two species).

Comparing the final pair, S. densissima sp. nov. and S. elegantula , appressed setae on both the cephalic and clypeal dorsum are fairly consistently stout and truncated for S. densissima , while for S. elegantula , they are plank-like to subspatulate on the cephalic dorsum, and narrowly elliptic on the clypeal dorsum. Setae on the funiculus are also comparatively finer and denser in S. densissima than in S. elegantula .

With the records from Hainan Province ( Fig. 25 ), Hong Kong ( Fig. 24 ) and Macau, this species is likely more widespread in southern mainland China. Its presence in Guangdong Province is very likely.

Geographic range

Mainland China (Hainan, Hong Kong, Macau).

Ecology

Collected from a wide range of habitats, including secondary forest, disturbed secondary forest, Fengshui wood, rubber plantation, mixed woodland, shrubland, grassland, managed grassland and reclaimed land.

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. 24. Specimens of Strumigenys intermedia sp. nov. A, C–D. Holotype worker (ANTWEB1010888). B. Non-type worker (TT01353). A. Full-face view. B. Mandible close-up. C. Profile view. D. Dorsal view.

Fig. 25. Worker of Strumigenys intermedia sp. nov. from Hainan, mainland China (HNA-00188). A. Full-face view. B. Profile view. C. Dorsal view.