Strumigenys mazu (Terayama, Lin & Wu, 1996)

Smithistruma mazu Terayama et al., 1996: 337, figs. 26, 27, 30, 31 (w.) TAIWAN.

Combination in Pyramica: Bolton, 1999: 1673. Combination in Strumigenys: Baroni Urbani & De Andrade, 2007: 123. Fig 6A–F, Fig 7A–F.

Diagnostic characters

Strumigenys mazu can be differentiated in the worker caste from its congeners by the reticulate-punctate sculpture on the cephalic dorsum and the absence of basigastral carinae [3, 25]. Additional characters include a truncated anterior clypeal margin and a well-defined upper scrobe margin [3].

Material examined

Specimen images examined (n = 1):

Holotype worker: Taiwan, Chilan, Yilan Hsien; 28.vii.1988; T2-F0-T4

Physical specimens examined (n =17):

1 worker: China; Hong Kong, Tai Po Kau; 02 November 1979; Coll. R.Winney; soil Berlese; NHMUK010639085 [NHMUK] • 1 worker: China; Guangxi, Diding; 1110 m a.s.l; 9 July 1999; Coll. J.F.Fellowes; JF0006 [HKBM] • 1 worker: China; Hong Kong, Tai Po Kau; 22.42007 114.1829; 290 m a.s.l; 2 July 2015; Coll. T.Tsang; Winkler ex. Leaf litter; ANTWEB1010081 [IBBL] • 1 worker: China; Hong Kong, Penny’s Bay; 22.31339101 114.036877; 5 m a.s.l; 25 October 2017; Coll. M.Pierce; Mini Winkler, ex leaf litter; WC-PB-INV-03 [IBBL] • 1 worker: China; Hong Kong, Kau Tam Tso; 22.5034 114.2459; 90 m a.s.l; 26 April 2022 Coll. A.I.Weemaels; Winkler ex. 0.5m² leaf litter; CASENT0764985 [IBBL] • 1 worker: China; Hong Kong, Tai Mo Shan; 22.42341 114.12825; 570 m a.s.l; 4 September 2022; Coll. M.T.Hamer; Winkler ex. random leaf litter; TMS1GC2−9 [IBBL] • 1 worker: China; Hong Kong, Tai Mo Shan; 22.42351 114.1281; 590 m a.s.l; 14 September 2022 Coll. M.T.Hamer & A.I.Weemaels; Winkler ex. 0.5m² leaf litter; TMS2T3W3-5 [IBBL] • 1 worker: China; Hong Kong, Tai Mo Shan; 22.42351 114.1281; 590 m a.s.l; 14 September 2022; Coll. M.T.Hamer & A.I.Weemaels; Winkler ex. 0.5m² leaf litter; TMS2T3W1-8 [IBBL] • 1 worker: China; Hong Kong, Tai Mo Shan; 22.42395 114.1292; 530 m a.s.l; 14 September 2022; Coll. M.T.Hamer & A.I.Weemaels; Winkler ex. 0.5m² leaf litter; TMS2T1W3-2 [IBBL] • 6 workers: China; Hong Kong, Tai Mo Shan; 22.42351 114.1281; 590 m a.s.l; 14 September 2022 Coll. M.T.Hamer; Hypogaeic Winkler, 1m² soil; ANTWEB1010145, ANTWEB1010147, ANTWEB1010148, ANTWEB1010149, ANTWEB1010150, ANTWEB1010151 [IBBL] • 1 worker: China; Hong Kong, Tai Mo Shan; 22.42351 114.1281; 590 m a.s.l; 14 September 2022 Coll. M.T.Hamer; Hypogaeic Winkler, 1m² soil; CASENT0745759 [ZRC] • 1 worker: China; Fujian, Quanzhou; 25.64504491 118.202877; 945 m a.s.l; 22 June 2023 Coll. L.Xuan; Winkler ex. 4 m² leaf litter; ANTWEB1010144 [IBBL] • 1 worker: China; Fujian, Quanzhou; 25.63946617 118.2267705; 1070 m a.s.l; 25 June 2023 Coll. L.Xuan; Winkler ex. 4 m² leaf litter; ANTWEB1010143 [IBBL].

Virtual dataset

Worker based virtual datasets contains surface volume rendering image stacks of PNG files for CASENT0745759, comprising stills of the head in full-face view, the mandibles in anteroventral view, the whole body in lateral and dorsal view, as well as individual images of both petiolar segments, and gaster both in dorsal view. Further, raw volumetric data (nii format), and a full 3D surface model (STL format) are made available for CASENT0745759, as well as CASENT0764985. All datasets are deposited on Zenodo (https://zenodo.org/records/14830376). 3D surface models of the whole body of CASENT0745759, and CASENT0764985 are also made available on Sketchfab (CASENT0745759; https://skfb.ly/pyFxI & CASENT0764985; https://skfb.ly/pyFxK).

Worker specimens (n =10): HW 0.31–0.34; HL 0.42–0.44; ML 0.07–0.09; SL 0.17–0.20; WL 0.42–0.46; PW 0.20–0.23; PL 0.20– 0.29; PH 0.10–0.12; DPW 0.11–0.13; DPL 0.06–0.10; DPPW 0.17–0.19; DPPL 0.11–0.13; ATL 0.30–0.34; TL 1.54–1.70

Indices: CI 71.76–79.30; MI 16.55–20.67; SI 51.84–57.48; PI 62.35–68.37; LPI 37.41–55.67; DPI 39.16–61.62; DPPI 138.21–161.82.

Female description

Material examined

Physical specimens examined (n =3):

1 alate gyne: CN-HK Tai Po Kau 22.4204 114.17577 295m 20−27.viii.2022 FIT Vane MTH ANTWEB1010079 [IBBL] • 1 dealate gyne: China; Hong Kong, Tai Mo Shan; 22.42351 114.1281; 590 m a.s.l; 14 September 2022 Coll. M.T.Hamer; Hypogaeic Winkler, 1m² soil ANTWEB1010146 [IBBL] • 1 dealate gyne: CN-HK Tai Mo Shan 22.42335 114.1282 598m 14.ix.2022 Winkler MTH/AIW. CASENT0745765 [ZRC] • 1 dealate gyne: CN-HK Tai Mo Shan 22.42335 114.1282 598m 14.ix.2022 Winkler MTH/AIW CASENT0745761 [IBBL] • 1 dealate gyne: CN-HK Tai Mo Shan 22.42335 114.1282 598m 14.ix.2022 Winkler MTH/AIW TMS2T3W1-9 ANTWEB1010080 [IBBL].

Virtual dataset

Strumigenys mazu gyne (CASENT0745761) cyber-material datasets consist of surface volume rendering image stacks of PNG files, comprising full-face views stills of the head in full-face view, as well as whole body in lateral and dorsal view. Further, raw volumetric data (nii format), and a full 3D surface model (STL format) are made available. All data is deposited on Zenodo (https://zenodo.org/records/14830376). A 3D surface model of CASENT0745761 is also made available on Sketchfab (https://skfb.ly/pyFxL).

Measurements

Gyne specimens (n =3): HW 0.35–0.37; HL 0.44–0.47; ML 0.09–0.10; SL 0.18–0.19; WL 0.53–0.58; PW 0.26–0.27; PL 0.25–0.27; PH 0.11-0.13; DPW 0.14; DPL 0.07; DPPW 0.21–0.22; DPPL 0.13–0.14; ATL 0.42–0.45; TL 1.86–1.97. Indices: CI 75.91–82.25; MI 18.92–23.3; SI 51.27–51.91; PI 72.68–75.92; LPI 43.53–53.04; DPI 55.69–56.28; DPPI 155.8–160.15.

Head

In full-face view, head longer than broad, broadest just anterior to posterior border. Mandibles triangular, reducing in width apically; basal masticatory margin with five stout triangular teeth, apical half with two smaller stout triangular teeth, followed by four smaller teeth and final acute apical tooth. Anterior clypeal border straight; posterior clypeal border narrowly inserted between antennal foramen. Antennae with six segments, including five funicular segments; scapes short, expanding apically; funiculus terminating in two-segment club, apical most segment conspicuously longer than broad. In lateral view, upper scrobe margin conspicuous and well defined, slightly overhanging lateral head surface. Eye present, comprising 25–30 ommatidia, located posteroventrally on lateral head surface. In lateral view scrobe present, as long as antennal scape. Preocular carina present, terminating just anterior of eye. Preocular cuticular strip conspicuous, running parallel to scrobe and terminating before median eye level. Postbuccal impression shallow, inconspicuous. Three ocelli present, distance between ocelli greater than ocelli diameter. Posterior border concave, with lamella extension within concavity directly anterior to head-pronotal neck articulation.

Mesosoma

In dorsal view, pronotum wider than long; anterior margin convex, slightly elevated from pronotal collar, posterior margin concave. Pronotum extending to lateral surface without dorsolateral margin. In dorsal view, anterior margin of mesoscutum convex and slightly elevated from pronotal surface; posterior margin straight, widest just in front of tegula; posterior lateral margins of mesoscutum converging towards mesoscutellum. Mesoscutum-mesoscutellum sulcus wide, weakly impressed. In dorsal view, mesoscutellum just longer than wide, widest point just anterior of middle; posterior margin convex. In posterodorsal view, metanotum visible as thin strip located below mesoscutellum and above the propodeum, terminating before tegula. Propodeum longer than wide, narrow; carinate margin present between metanotum and propodeum. One pair of spongiform tissue lobes present on metapleuron-propodeal margin. In lateral view, mesopleuron divided into anepisternum and katerpisternum by narrow sulcus. Katepistermum with sharp, anteriorly directed cuticular spur almost reaching posteroventral corner of pronotal side. Narrow sulcus separating katerpisternum and metapleuron. Metapleuron undivided, rectangular in shape. Metapleural lobe small; metapleural gland bulla small, oval shape, positioned and directed anterodorsally. Spiracle positioned high on upper metapleuron.

Metasoma

In lateral view, petiolar peduncle short, node subclubate; dorsolateral margins with carinae, not smoothly rounded. Petiolar spiracle located just below node on posterolateral region of peduncle. In dorsal view, petiolar disc wider than long; postpetiolar disc wider than long, lateral margins converging on posterior margin in gradual arc. In lateral view, spongiform tissue massively produced around petiole and postpetiole; small spongiform tissue curtain present on ventral face of petiole. First gastral tergite long, as long as petiole and postpetiole combined; in dorsal view, anterolateral corners of first gastral tergite blunt.

Pilosity

Clypeus with short, simple decumbent and appressed setae directed anteriorly. Scapes with decumbent and appressed setae, alongside several long, erect, simple setae on lead edge of scape. Funicular segments with dense, short pubescence. Head dorsum with long, erect, simple setae slightly curved at apex; shorter, erect, simple setae also present among longer setae. In full-face view, eight long, erect simple setae located along upper scrobe margin arranged serially and directed anterolaterally. Corners of posterior head margin with medium length, subdecumbent and fully appressed simple setae, noticeably different to surrounded erect setae. Mesosomal dorsum covered in long, erect, simple setae, plus shorter, erect simple setae and semi-decumbent short, simple setae among erect, longer setae. Pronotal humeral seta long, erect, longer than surrounding setae and directed anterolaterally. Lateral mesosomal surface almost seta-less, some setae present on dorsolateral margin zone; short, simple setae present just above propodeal spiracle; katerpisternum and anasepsiternum entirely glabrate. Short, subdecumbant setae on anterior petiole face; petiole and postpetiole dorsum with long, simple setae. Gastral dorsum with long, erect simple setae, noticeably longer than those on mesosomal and head dorsa; gaster ventrally with medium length appressed setae and erect medium length setae. Coxa, trochanter, femur and tibia with numerous, dense and appressed long setae; several conspicuous long, projecting setae also present among the appressed setae.

Sculpture

Mandibular dorsum with dense micro-reticulation and non-reflective. Clypeus smooth centrally, with micro-punctures on periphery. Cephalic dorsum from posterior clypeal border to posterior lobes reticulate-punctuate; small region immediately behind posterior clypeal border smooth. Scapes and funicular segments with dense microsculpture. Pronotum partially smooth, with some microsculpture on lateral sides. Mesoscutum and mesoscutellum reticulate-punctate both dorsally and laterally. Katerpisternum, anespisternum and metapleuron smooth, partial microsculpture above metapleural gland bulla. Propodeal surface smooth. Petiolar peduncle laterally punctuate in the upper and smooth in the lower half; anterior face dorsally smooth. Petiole and postpetiole dorsally smooth. Gaster dorsally smooth; basigastral costulae present, short, hardly extending 1/5 th of the first gastral tergite.

Colour

Body and appendages reddish orange, spongiform tissue light yellow.

Distribution

Known from China (Hong Kong SAR, Guangxi Province, Fujian Province [New record]); Taiwan; Japan; Vietnam (Fig 1; Table 1).

Comments

Strumigenys mazu is the most widespread species within this species group, known from Japan, Mainland China (Fujian, Hong Kong SAR, Guangxi), Taiwan and Vietnam. Specimens were collected within leaf litter and soil, from broadleaf forest floors in Japan [24], and similarly in Hong Kong [22, 26]. Collection localities include high elevation sites, e.g., Tai Mo Shan (560 m a.s.l), as well as some lowland sites including Kau Tam Tso (93 m a.s.l) and Penny’s Bay (10 m a.s.l). Masuko [24] noted, on the basis of a single colony, that those were small, comprising a single queen and 19 workers, whereas the maximum number of individuals of S. mazu collected in one soil samples (1 m²) from Hong Kong was 44 and one dealate gyne. It is likely that this sample represented a single colony, especially given their rarity across Hong Kong. This species likely feeds on mites with Masuko [24] finding gamasid mites in field examinations of S. mazu nests, but under lab conditions also accepted collembolans and symphylans. A description of the gyne (Fig 7 A-F) is provided here. The first record of S. mazu from Fujian Province, China is also provided, where it was collected in two localities in Daiyunshan Nature Reserve within broadleaf forests at relatively high elevations (943–1074 m a.s.l). The occurrence of S. mazu in Fujian confirms the prediction of Tang & Guénard [26]. No records are yet known from Guangdong Province, but it seems very likely that this species should be present given its occurrence in Guangxi, Fujian, and Hong Kong.