Leptogenys diminuta (F. Smith, 1857)

Hamer, Matthew T., Lee, Jonathan Hon Chung, Tse, Cheung Yau Leo, Silva, Thiago S. R. & Guénard, Benoit, 2024, The Leptogenys Roger, 1861 (Formicidae, Ponerinae) of Hong Kong SAR with additional records from Guangdong, China, ZooKeys 1202, pp. 169-211 : 169-211

Leptogenys diminuta (F. Smith, 1857)

Figs 4 B. 5 B, D. 6 B, 8 A, 10, 20 B

Ponera diminuta Smith, 1857 a: 69 (w.) Borneo (East Malaysia: Sarawak).

Lobopelta diminuta : Mayr 1862: 734.

Leptogenys diminuta : Emery 1895: 461.

Leptogenys diminuta bismarckensis [senior synonym] Forel, 1901 c: 7 (w.) New Guinea: Wilson 1958 c: 118; Bolton 1995 b: 231; Zhou 2001 a: 43. Of Leptogenys diminuta deceptrix Forel, 1901 m : 46 (w.): Xu and He 2015: 138. Of Leptogenys ferox Smith, 1865 a: 70 (w.) Indonesia: Wilson 1958 c: 118; Bolton 1995 b: 231; Zhou 2001 a: 43. Of Leptogenys hodgsoni Forel, 1900 f: 308 (w.) Myanmar: Xu and He 2015: 144. Of Leptogenys diminuta palliseri Forel, 1900 f: 307 (w. m.) India: Xu and He 2015: 138. Of Leptogenys diminuta santschii Mann, 1919: 299 (w. eq. m.) Solomon Is: Wilson 1958 c: 118; Bolton 1995 b: 231; Zhou 2001 a: 43. Of Leptogenys diminuta sarasinorum Forel, 1900 f: 307 (w.) Sri Lanka: Xu and He 2015: 138. Of Leptogenys simillima Smith, 1860 b: 104 (w.) Indonesia: Roger 1863 b: 19; Mayr 1863 a: 428; Bolton 1995 b: 231; Zhou 2001 a: 43. Of Leptogenys diminuta stitzi Viehmeyer, 1934 c: 310 : Wilson 1958 c: 118; Bolton 1995 b: 231; Zhou 2001 a: 43. Of Leptogenys diminuta striatula Emery, 1895 m : 461 (w.) Myanmar: Xu and He 2015: 138. Of Leptogenys diminuta woodmasoni Forel, 1886 d: 246 (w.) India: Xu and He 2015: 138. of Leptogenys diminuta yarrabahna Forel 1915 b: 29 (w. m.) Australia: Taylor 1988: 34; Bolton 1995 b: 231; Zhou 2001 a: 43.

Measurements.

Worker (n = 10): HL 1.53 – 1.62; HLL 1.15 – 1.33; HLA 0.34 – 0.39; HW 1.09 – 1.17; CML 0.36 – 0.41; SL 1.56 – 1.72; AII 0.22 – 0.225; AFI 0.29 – 0.34; AFII 0.23 – 0.32; EL 0.3 – 0.36; ML 0.67 – 0.83; PrL 0.85 – 0.99; PrH 0.57 – 0.72; PrW 0.81 – 0.89; WL 2.32 – 2.53; PeL 0.49 – 0.66; PeH 0.65 – 0.73; PeW 0.4 – 0.48; DPL 0.42 – 0.5; CI 70.01 – 74.19; CLI 23.53 – 26.32; SI 137.99 – 155.25; OI 24.21 – 27.27; LPI 107.12 – 135.85; DPI 84.24 – 103.9.

Ergatoid (n = 1): HL 1.59; HLL 1.29; HLA 0.39; HW 1.18; CML 0.43; SL 1.63; AII 0.25; AFI 0.32; AFII 0.24; EL 0.34; ML 0.83; PrL 0.94; PrH 0.66; PrW 0.89; WL 2.61; PeL 0.56; PeH 0.7; PeW 0.47; DPL 0.47; CI 74.15; CLI 26.66; SI 137.82; OI 26.43; LPI 124.73; DPI 99.57.

Morphological variation.

Studied specimens showed clear variation in dorsal head sculpturing, with the shape of concentric costulae medially ranging from broadly curved to angulate, and the regularity of costulae varying subtly among specimens. Additionally, we observed the presence of smooth patches in the middle of the head, with varying sizes among certain specimens; when present, these patches were between the concentric costulae. The dorsal margin of the node is completely foveate in most specimens, but fine costulae was observed in the ventral margin of the petiole of one specimen. Fine and faint costulae was also observed on the metapleuron of one specimen, contrary to the general pattern of rugulose sculpture found in other specimens of L. diminuta . Leptogenys diminuta is known to be a highly morphologically variable species, both on a wider geographical scope, as well as within Hong Kong. This is also reflected through the complex taxonomic history of this species and the numerous associated subspecies, either considered as valid or synonyms. Given such morphological diversity, L. diminuta is likely a species complex with numerous cryptic species found across its distribution ( Wilson 1958).

Comparative notes.

Leptogenys diminuta resembles and is frequently confused with L. kitteli . However, L. diminuta can be readily separated from L. kitteli in Hong Kong based upon the often smooth to finely reticulate pronotum, the presence of a single tooth on the mandibular masticatory margin, as well as its much smaller size relative to L. kitteli .

Distribution.

A very wide ranging species, or species complex, known from numerous regions across Asia and Oceania, including the Australasian region ( Australia, New Guinea, Solomon Islands), the Indomalayan region ( Bangladesh, Borneo, mainland China [Guangdong (additional records provided here), Fujian, Hainan, Guangxi, Hunan, Hong Kong], India, Indonesia, Lanka, Laos, Malaysia, Myanmar, Nepal, Philippines, Singapore, Sri Lanka, Taiwan, Thailand, and Vietnam), as well as the Palaearctic region [part of southwestern China (Sichuan)] ( Wilson 1958; Bakhtiar and Chiang 2010;; Xu and He 2015; Bharti et al. 2016 Janicki et al. 2016; Guénard et al. 2017). The absence of this species from various countries and provinces (e. g., Cambodia and Guizhou, China) likely reflects lack of sampling efforts.

Ecology.

Leptogenys diminuta is a group-hunting species, forming long columns of workers that move through their habitat in search of prey. Colonies are moderately populous with 200–400 individuals per nest and move nesting locations throughout the year ( Ito 1997). Nest locations in Hong Kong have included rotting logs, underneath rocks and within leaf litter. The species has ergatoids (Fig. 10 D – E ) and likely disperses through colonial budding ( Ito 1997; Ito and Ohkawara 2000). Records are predominantly known from young to old growth secondary forests, and similar to L. peuqueti , it is one of the most frequently encountered Leptogenys in Hong Kong.

Material examined.

Workers (n = 67): China • 1 worker; Hong Kong SAR, Sunset Peak ; 25 Jul. 1992; J. R. Fellowes leg.; IBBL MBS 006900 . • 3 worker; Hong Kong SAR, Kadoorie Farm ; 10 Aug. 1996; J. R. Fellowes leg.; IBBL MBS 006880 , MBS 006881 , MBS 006882 . • 1 worker; Hong Kong SAR, Lantau , Tei Tong Tsai; 5 Nov. 1996; J. R. Fellowes leg.; HKBM MBS 015302 . • 3 workers; Guangdong Prov., Gu Tian ; 10 Apr. 1997; J. R. Fellowes leg.; HKBM MBS 006883 , MBS 006884 , MBS 006885 . • 2 workers; Hong Kong SAR, The Peak ; 27 Jun. 1999; SK. Yamane leg.; SKYC ANTWEB 1010191 , ANTWEB 1010192 . • 1 worker; Hong Kong SAR, Victoria Park ; 27 Jun. 1999; SK. Yamane leg.; SKYC MBS 006607 . • 1 worker; Hong Kong SAR, Kadoorie Farm Botanical Garden ; 6 Sep. 1999; J. R. Fellowes leg.; HKBM MBS 015275 . • 1 worker; Hong Kong SAR, Kadoorie Farm Botanical Garden ; 448–480 m a. s. l.; 21 Sep. 1999; J. R. Fellowes leg.; HKBM MBS 015282 . • 1 worker; Hong Kong SAR, The Peak ; 10 Sep. 2000; SK. Yamane leg.; SKYC ANTWEB 1010193 , ANTWEB 1010195 , ANTWEB 1010196 , ANTWEB 1010197 . • 1 worker; Hong Kong SAR, Kadoorie Farm Botanical Garden; 22.42947, 114.12145; 350 m a. s. l.; 3 Jul. 2011; P. S. Ward leg.; Secondary forest, Hand collection; IBBL ANTWEB 1010181 . • 1 worker; Hong Kong SAR, Lin Fa Shan ; 22.39963, 114.09654; 423 m a. s. l.; 18 Jul. 2015; T. Tsang leg.; Winkler leaf litter Ex; IBBL TT 01320 . • 1 worker; Hong Kong SAR, Tai Lam ; 22.3952, 114.09072; 440 m a. s. l.; 26 Oct. 2015; R. H. Lee leg.; Shrubland, Hand collection; IBBL RHL 01371 . • 1 worker; Hong Kong SAR, Ng Tong Chai ; 22.42415, 114.13185; 420 m a. s. l.; 26 Jun. 2016; R. H. Lee leg.; Secondary forest, Hand collection; IBBL RHL 02822 . • 1 worker; Hong Kong SAR, Lung Fu Shan ; 22.2758, 114.13546; 260 m a. s. l.; 30 Jun. 2016; R. H. Lee leg.; Secondary forest, Hand collection; IBBL RHL-SIA- 008 . • 1 worker; Hong Kong SAR, Clear Water Bay ; 22.2918, 114.30208; 114 m a. s. l.; 19 Jul. 2016; M. Pierce leg.;, ground forager; IBBL ANTWEB 1017020 . • 1 worker; Hong Kong SAR, Tai Po; Lam Tseun ; 22.43449, 114.11728; 171 m a. s. l.; 30 Aug. 2016; M. Pierce leg.; forest, Hand collection; IBBL ANTWEB 1009148 . • 1 worker; Hong Kong SAR, Tai Po; Lam Tseun ; 22.43449, 114.11728; 171 m a. s. l.; 30 Aug. 2016; M. Pierce leg.; forest, Hand collection; IBBL ANTWEB 1009378 . • 1 worker; Hong Kong SAR, Lung Fu Shan ; 22.2811, 114.1369; 150 m a. s. l.; 5 Oct. 2016; B. Worthington leg.;, Hand collection (night); IBBL BMW 02340 . • 1 worker; Hong Kong SAR, Tsing Yi ; 22.3405, 114.1003; 300 m a. s. l.; 12 Feb. 2017; R. H. Lee leg.; Open rock, general forager; IBBL RHL 003394 . • 1 worker; Hong Kong SAR, Hatton Road ; 22.2792, 114.1365; 237 m a. s. l.; 12 Feb. 2022; M. T. Hamer leg.; Young secondary, Hand collection; IBBL ANTWEB 1010183 . • 1 worker; Hong Kong SAR, Pok Fu Lam ; 22.25988, 114.13944; 213 m a. s. l.; 13 Jun. 2022; M. T. Hamer leg.;, Hand collection; IBBL ANTWEB 1010184 . • 3 workers; Hong Kong SAR, Ngong Ping ; 22.25298, 113.90457; 455 m a. s. l.; 4 May. 2023; M. T. Hamer leg.; Secondary forest, Hand collection; IBBL ANTWEB 1010128 , ANTWEB 1010129 , ANTWEB 1010130 . • 1 worker; Hong Kong SAR, Wong Lung Hang ; 22.26368, 113.95375; 400 m a. s. l.; 11 May. 2023; M. T. Hamer leg.; Young secondary forest, Hand collection; IBBL ANTWEB 1010133 , ANTWEB 1010134 . • 1 worker; Hong Kong SAR, Yi O ; 22.22342, 113.84714; 13 m a. s. l.; 20 Jun. 2023; M. T. Hamer leg.; Young secondary forest, Winkler leaf litter Ex; IBBL ANTWEB 1010126 , ANTWEB 1010127 . • 1 worker; Hong Kong SAR, Ngong Ping SSSI ; 22.25252, 113.90662; 455 m a. s. l.; 29 Jun. 2023; M. T. Hamer leg.; Secondary Forest, Hand collection; IBBL ANTWEB 1010124 . • 2 workers; Hong Kong SAR, Tai Mo Shan ; 22.40403, 114.1069; 471 m a. s. l.; 22 Aug. 2023; C. Y. L. Tse leg.; Secondary forest, ex. Nest; IBBL MTH 243 . • 1 worker; Hong Kong SAR, Tai Mo Shan ; 22.40384, 114.10549; 491 m a. s. l.; 26 Aug. 2023; C. Y. L. Tse leg.; Secondary forest, Gen. forager; IBBL MTH 80 , MTH 242 . • 4 workers; Hong Kong SAR, Tai Mo Shan ; Kap Lung Forest Trail ; 22.41084, 114.10423; 450 m a. s. l.; 3 Sep. 2023; M. T. Hamer leg.; Secondary forest, ex. decaying log; IBBL MTH 222 . • 5 workers; Hong Kong SAR, Nei Lak Shan ; 22.26524, 113.9064; 500 m a. s. l.; 6 Sep. 2023; M. T. Hamer leg.; Young Secondary Forest, Hand coll. in trail; IBBL MTH 303 . • 5 workers; Hong Kong SAR, Tai Mo Shan ; 22.40452, 114.10645; 490 m a. s. l.; 27 Sep. 2023; M. T. Hamer leg.; Secondary forest, un. rock; IBBL MTH 574 .

Ergatoid: China • 1 ergatoid; Hong Kong SAR, Tai Mo Shan ; Kap Lung Forest Trail; 22.40422, 114.10591; 470 m a. s. l.; 22 Aug. 2023; C. Y. L. Tse leg.; Nest ex.; IBBL ANTWEB 1010180 .

Figures

Figure 4. Mandibular masticatory margin differences A Leptogenys strena (ANTWEB 1010114) B L. diminuta (GYOT 070).

Figure 10. Leptogenys diminuta worker (ANTWEB 1010183) and L. diminuta ergatoid (ANTWEB 1010180) A worker specimen in lateral view B worker specimen in dorsal view C worker specimen in full face view D ergatoid in lateral view E ergatoid in lateral view and F ergatoid in dorsal view.