Leptogenys grohli Hamer, Lee & Guénard, 2024

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 grohli Hamer, Lee & Guénard sp. nov.

Figs 11 , 12 , 13 , 20 C

Diagnosis.

Head isosceles trapezoid, longer than wide; mandible linear, basal margin longer than masticatory margin; basal margin edentate, masticatory margin with one proximal and one apical tooth. Scape extending beyond posterior head margin by three tenths of its length; antennal flagellomere I longer than pedicel and antennal flagellomere II. Promesonotal articulation and notopropodeal sulcus present. Propodeum with a pair of broadly rounded, posterior facing cuticular lobes. In lateral view, petiole slightly longer than high, trapezoidal in shape with posterior margin higher than anterior margin; dorsum subtly convex, curving gradually downwards anteriorly. Head dorsum between eye, clypeus, and frontal lobe with numerous and dense hair-bearing micro-punctulae. Mesosomal dorsum smooth and shining with large, sparse punctures. Anteriormost point clypeal margin with a pair of stout, tubular peg-like setae and two decumbent hairs adjacent to the peg-like setae.

Description.

Head. In full face view, head isosceles shaped as trapezoid, longer than wide, widest at mandibular insertion; lateral margin subtly convex and subtly widening beyond eye to posterior margin; posterolateral corner of head blunt; posterior margin of head straight. Mandible linear, basal margin longer than masticatory margin; distinct angle between basal and masticatory margin present; basal margin weakly sinuous and edentate, masticatory margin with one proximal (formed by angle between basal and masticatory margin) and one apical tooth; gap formed between clypeus and mandible when closed. In lateral view, masticatory margin of mandible curves ventrad at apex; mandibular groove present, beginning 1 / 3 the width of the mandible from base, terminating at ventrolateral mandible apex. Mandalus ovoid, visible at base of mandible when closed. In full face view, anterior clypeal lobe broadly triangular, extending into intermandibular space; 1 / 5 of head length; terminating in an acute convex point; lateral clypeal margin gradually curving to lateral head margins with inconspicuous lobes; longitudinal clypeal carina present and conspicuous. Frontal lobes small, 2 / 3 of antennal condyle visible. Frontal groove short, terminating at anterior eye margin. Occipital carina present, extending to ventral surface meeting at an acute angle ventrally. Eye convex, located dorsolaterally in full face view; interrupting lateral head outline; length 1 / 4 of lateral head length; maximum number of ommatidia across maximum eye length 14 or 15. Antennae with ten flagellar segments; scape long, extending beyond posterior head margin by 3 / 10 of its length; scape reaching maximum width medially; antennal flagellomere I longer than pedicel and antennal flagellomere II; apical most flagellomere tapering to a point. Hypostomal teeth present; in ventral view, located laterally, adjacent to mandibular base. Palp formula 4: 4 (one worker dissected).

Mesosoma. In lateral view, promesonotum feebly to distinctly convex; promesonotum higher than propodeum; propodeal dorsal outline straight to feebly convex; dorsal surface longer than declivitous face; angle between dorsal and declivitous face gradually curving. In dorsal view, pronotum wider than long; pronotum wider than maximum propodeal width. Prosternal process present, anteriorly convex, and posteriorly acutely angled. Promesonotal articulation present but feebly impressed. Mesonotum wider than long. Notopropodeal sulcus present, impressed, with longitudinal cross-ribs. Angle between dorsal and lateral surfaces smoothly curved. Posterolateral propodeum at spiracular height with broadly rounded lobe that extend posteriorly; propodeal declivitous surface concave. In lateral view, mesometapleural suture deeply impressed, with cross-ribs; mesopleural margin of suture distinctly marginated. Mesopleuron not visibly divided into anespiternum and katerpisternum. Propodeal spiracle circular, located above midline of lateral propodeum surface within concave cuticular depression anterodorsally. Metapleural gland bulla circular. Distance between metapleural gland and spiracle greater than spiracle diameter. Legs long and slender; tarsomere one with concave cleaning comb basally. Mesotibia with one pectinate and one simple spur; simple spur 1 / 2 length of pectinate spur. Metatibia with one long pectinate spur and one simple spur; simple spur ~ 1 / 3 the length of the pectinate spur. All tarsal claws pectinate.

Metasoma. In lateral view, petiole slightly longer than high, trapezoidal in shape with posterior margin higher than anterior margin; dorsum subtly convex, curving anteriorly; anterior face straight, ~ 1 / 2 as high as of posterior face. Peduncle absent. Spiracle small and circular, located laterally on anteromedial surface. In dorsal view, petiole distinctly longer than wide; posterior width twice the anterior width. Subpetiolar process present, located anteroventrally; process triangular with posterior margin longer than anterior margin, posteroventral angle acute. Semi-circular prora lobe present, pointed ventrally. Angle between anterior and dorsal surface of abdominal tergite III broadly rounded in lateral view. Abdominal tergite III widest posteriorly in dorsal view. Cinctus with numerous short, longitudinal cross-ribs. Sting present.

Sculpture. Mandibular dorsum with faint longitudinal striations across whole length. Clypeal dorsum laterally smooth, coarsely striate medially, with scattered hair-bearing punctae. Head dorsum between eye, clypeus, and frontal lobe with numerous, dense hair-bearing punctulae; punctations become larger and sparse posteriorly; ventrolateral head surface mostly smooth and shining with widely spaced hair-bearing punctations. Antennal segments with numerous, dense punctulae, lacking smooth regions. Mesosomal dorsum mostly smooth with large, sparse punctures; distance between punctures much larger than their diameter. Propodeal declivity with conspicuous transverse striations that do not extend to propodeal dorsum; posterior portion of declivity smooth. Lateral surface of pronotum mostly smooth and shining with large, sparse punctures. Mesopleuron anteroventral and ventral margins with short striations; striations crossing mesopleuron width ventrally; mesopleuron mostly smooth and shining with sparse punctures. Lateral propodeum with striations on ventral margin, around metapleural gland bulla, propodeal spiracle and posteroventral corner. All femora with hair-bearing punctures; punctures progressively denser apically on dorsal surface of profemur. All tibiae smooth and shining with dense punctulae and sparse macro hair-bearing punctures throughout. Petiole dorsum mostly smooth and shining with large hair-bearing punctures; lateral petiole surface smooth. Dorsum of first gastral tergite mostly smooth and shining with large, sparse, hair-bearing macro punctures; anterior face smooth and shining. Presternite IV imbricate. Abdominal segment IV with macro-punctures dorsally; sternite with very sparse macro punctures. Pygidium and hypopygium with sparse, hair-bearing macro punctures only.

Pilosity. Mandibular dorsum with stout erect hairs directed inwards along basal margin, and short, decumbent hairs on dorsum. Anteriormost point clypeal margin with pair of long, stout, tubular peg-like setae and two decumbent hairs adjacent to the peg-like setae; clypeal dorsum with numerous, long erect hairs as well as decumbent short hairs sparsely distributed across surface. Head dorsum, between clypeus, antennal foramen, and eye with dense, semi-decumbent, appressed hairs; hairs posteriorly sparse with suberect hairs only; head dorsolaterally with decumbent hairs directed anteriorly. Scape with numerous subdecumbent and suberect hairs; flagella with numerous suberect and decumbent hairs. Mesosomal dorsum with erect and suberect hairs sparsely distributed. Suberect and decumbent hairs present on lateral surfaces of pronotum and propodeum. Coxae with many decumbent hairs reaching highest density on ventral surface. Femora with suberect hairs dorsally and subdecumbent hairs ventrally; tibiae with dense, decumbent hairs dorsally, and sparse decumbent hairs ventrally. All tarsi I with stout and apically blunt hairs arranged in a series, surrounded by simple decumbent hairs. Petiolar dorsum with decumbent hairs; lateral petiole surface with sparse decumbent hairs, almost glabrous; subpetiolar process with numerous suberect and erect hairs. Prora with numerous, fine, short, erect hairs directed anteriorly. All abdominal tergites and sternites with sparsely distributed suberect and erect hairs. Pygidium and hypopygium with numerous long erect hairs.

Colour. Dark reddish brown across mesosoma, mandibles and legs distinctly paler red to orange in colour.

Ergatoid description.

With characters of worker but: lateral head margin not straight, distinctly widening posteriorly noticeably more so than the worker. Mesosoma stout and robust not as elongated as in worker; promesonotum distinctly convex; propodeum shorter, ~ 1 / 3 longer than propodeal declivity. Petiole nodiform, distinctly higher than long in lateral view; about as wide as long in dorsal view. Metasomal segments III-VII enlarged, segment III wider than petiole. Same colours as the worker.

Measurements.

Worker holotype: HL 1.13; HLL 0.87; HLA 0.23; HW 0.72; CML 0.22; SL 1.20; AII 0.21; AFI 0.32; AFII 0.24; EL 0.23; ML 0.56; PrL 0.71; PrH 0.49; PrW 0.66; WL 1.92; PeL 0.68; PeH 0.61; PeW 0.38; DPL 0.64; CI 63.57; CLI 19.8; SI 167.31; OI 26.67; LPI 89.66; DPI 59.75.

Worker paratypes (n = 12): HL 1.12 – 1.18; HLL 0.86 – 0.90; HLA 0.20 – 0.23; HW 0.69 – 0.75; CML 0.21 – 0.23; SL 1.16 – 1.26; AII 0.19 – 0.24; AFI 0.31 – 0.36; AFII 0.22 – 0.26; EL 0.22 – 0.25; ML 0.54 – 0.57; PrL 0.66 – 0.74; PrH 0.49 – 0.55; PrW 0.64 – 0.69; WL 1.79 – 1.99; PeL 0.60 – 0.69; PeH 0.56 – 0.61; PeW 0.33 – 0.39; DPL 0.52 – 0.67; CI 61.36 – 64.17; CLI 18.65 – 20.43; SI 166.25 – 172.94; OI 26.14 – 28.93; LPI 85.02 – 93.55; DPI 55.5 – 65.71.

Ergatoid paratype (n = 1): HL 1.19; HLL 0.90; HLA 0.259; HW 0.80; CML 0.25; SL 1.19; AII 0.23; AFI 0.30; AFII 0.22; EL 0.25; ML 0.59; PrL 0.73; PrH 0.56; PrW 0.7; WL 1.88; PeL 0.50; PeH 0.62; PeW 0.49; DPL 0.50; CI 67.31; CLI 21.34; SI 148.06; OI 28.28; LPI 123.01; DPI 97.61.

Non-type workers (n = 10): HL 1.12 – 1.18; HLL 0.82 – 0.92; HLA 0.16 – 0.24; HW 0.7 – 0.75; CML 0.2 – 0.25; SL 1.17 – 1.34; AII 0.18 – 0.22; AFI 0.31 – 0.36; AFII 0.23 – 0.26; EL 0.22 – 0.27; ML 0.55 – 0.61; PrL 0.66 – 0.74; PrH 0.5 – 0.55; PrW 0.64 – 0.71; WL 1.81 – 1.97; PeL 0.63 – 0.69; PeH 0.54 – 0.67; PeW 0.36 – 0.4; DPL 0.57 – 0.67; CI 61.82 – 64.78; CLI 18.01 – 20.73; SI 163.69 – 179.7; OI 25.74 – 31.04; LPI 81.83 – 97.24; DPI 56.97 – 68.64.

Morphological variation.

A spectrum of mesosomal size was observed, which is reflected in the variation seen within the mesosomal measurements. Moreover, the longitudinal ridges across the notopropodeal sulcus differs across the specimens examined with some showing more ribbing than others. No relationship between the size of a specimen and the longitudinal ridges could be found. Variation in both morphometric and qualitative characters mentioned above differs within the colony type series.

Comparative notes.

Within Xu and He (2015), specimens of L. grohli will key to the couplet containing both L. peuqueti and L. confucii . Leptogenys grohli is distinguishable from L. peuqueti by the more linear lateral margins of the head than the convex lateral margins of L. peuqueti ; the smaller eye ( EL 0.22 – 0.27); and narrower head ( HW 0.70 – 0.75). Sculptural differences also occur, with L. grohli having greater density of punctures across the whole head, scapes, mesosomal, petiole and first two gastral tergites than L. peuqueti . Leptogenys peuqueti is generally larger in all aspects, with L. grohli being a smaller, more gracile species. Leptogenys grohli is also morphologically similar to L. confucii , a species known from Taiwan and Southern Japan, but can be differentiated by the conspicuously defined angle between the basal and masticatory margin of the mandible; a smaller, less conspicuous frontal indentation; more angulated posterior head corner, and the lack of sculpture across the whole mesopleuron and lateral propodeal surfaces.

Distribution.

So far L. grohli is only known from Hong Kong and Guangdong This species, however, should be expected from neighbouring Chinese provinces and is likely to have been misidentified previously as L. peuqueti .

Ecology.

The type series was collected by sifting and extracting leaf litter within an old growth secondary forest. Specimens were noted during leaf litter sample collection, with the nest located within the soil between the tree trunk and its roots. One ergatoid and 16 workers were obtained, likely representing most of the colony. Solitary foraging individuals have been observed and collected during daytime across Hong Kong, with specimens obtained from tree plantations to secondary forests and Feng Shui Woods. Group hunting behaviour was not observed in this species.

Material examined.

Holotype worker. China • 1 worker; Hong Kong SAR, Tai Po Kau Nature Reserve ; 22.4271, 114.1814; 160 m a. s. l.; 23 Aug. 2022; A. I. Weemaels & M. T. Hamer leg.; Secondary forest, Winkler ex. leaf litter; ZRC ANTWEB 1010093 .

Paratype workers: 12 workers: Same collection as holotype; ZRC ANTWEB 1010085 to ANTWEB 1010092 . Same collection data as holotype; HKBM ANTWEB 1010095 to ANTWEB 1010099 .

Paratype ergatoid: Same collection data as holotype; ZRC ANTWEB 1010094 .

Non-type workers (n = 35): China • 3 workers; Hong Kong SAR, Tai Po Kau ; 19 Jul. 1992; J. R. Fellowes leg.; HKBM MBS 006896 , MBS 006897 , MBS 006899 . • 2 workers; Guangdong Prov., Qi Mu Zhang ; 6 Apr. 1997; J. R. Fellowes leg.; HKBM MBS 015248 . • 1 worker; Hong Kong SAR, Lung Fu Shan ; 22.27876, 114.13728; 240 m a. s. l.; 24 Apr. 2015; R. H. Lee leg.; Plantation, Pitfall trap; IBBL RHL 00050 . • 2 worker; Hong Kong SAR, Lung Fu Shan ; 22.2784, 114.1378; 230 m a. s. l.; 30 Apr. 2015; R. H. Lee leg.; Plantation, Pitfall trap; IBBL RHL 00129 , RHL 00152 . • 1 worker; Hong Kong SAR, Shing Mun ; 22.39693, 114.153; 242 m a. s. l.; 14 May. 2015; R. H. Lee leg.; Feng Shui Forest, Pitfall trap; IBBL RHL 00401 . • 1 worker; Hong Kong SAR, Sunset Peak ; 22.26112, 113.95633; 575 m a. s. l.; 3 Jun. 2015; R. H. Lee leg.; Secondary forest, Pitfall trap; IBBL RHL 00892 . • 1 worker; Hong Kong SAR, Sunset Peak ; 22.26084, 113.95753; 575 m a. s. l.; 3 Jun. 2015; R. H. Lee leg.; Secondary forest, Pitfall trap; IBBL RHL 00894 . • 2 workers; Hong Kong SAR, Sunset Peak ; 22.26392, 113.95376; 470 m a. s. l.; 3 Jun. 2015; R. H. Lee leg.; Secondary forest, Pitfall trap; IBBL RHL 00906 , RHL 00908 . • 1 worker; Hong Kong SAR, Sunset Peak ; 22.26594, 113.95278; 440 m a. s. l.; 3 Jun. 2015; R. H. Lee leg.; Secondary forest, Pitfall trap; IBBL RHL 00931 . • 2 workers; Hong Kong SAR, Tai Po Kau ; 22.42613, 114.18178; 160 m a. s. l.; 14 Jul. 2015; R. H. Lee leg.; Plantation, Pitfall trap; IBBL RHL 00931 , RHL 02083 . • 1 worker; Hong Kong SAR, Tai Po Kau ; 22.42285, 114.18082; 200 m a. s. l.; 14 Jul. 2015; R. H. Lee leg.; Secondary forest, Pitfall trap; IBBL RHL 02128 . • 1 worker; Hong Kong SAR, Tai Po Kau ; 22.42706, 114.17999; 180 m a. s. l.; 14 Jul. 2015; R. H. Lee leg.; Plantation, Pitfall trap; IBBL RHL 02165 . • 2 worker; Hong Kong SAR, Tai To Yan ; 22.45479, 114.11821; 420 m a. s. l.; 4 Aug. 2015; R. H. Lee leg.; Secondary forest, Pitfall trap; IBBL RHL 02211 , RHL 02686 . • 3 worker; Hong Kong SAR, The Peak ; 22.27523, 114.13873; 370 m a. s. l.; 17 Aug. 2015; R. H. Lee leg.; Secondary forest, Pitfall trap; IBBL RHL 01090 , RHL 01099 , RHL 01106 . • 1 worker; Hong Kong SAR, The Peak ; 22.2767, 114.1423; 410 m a. s. l.; 17 Aug. 2015; R. H. Lee leg.; Secondary forest, Pitfall trap; IBBL RHL 02621 . • 2 worker; Hong Kong SAR, The Peak ; 22.27603, 114.14199; 410 m a. s. l.; 17 Aug. 2015; R. H. Lee leg.; Secondary forest, Pitfall trap; IBBL RHL 02636 , RHL 02639 . • 1 worker; Hong Kong SAR, The Peak ; 22.27495, 114.13828; 360 m a. s. l.; 17 Aug. 2015; R. H. Lee leg.; Secondary forest, Pitfall trap; IBBL RHL 02655 . • 1 worker; Hong Kong SAR, Tai Lam ; 22.3956, 114.0928; 420 m a. s. l.; 26–29 Oct. 2015; R. H. Lee leg.; Bamboo forest, Pitfall trap; IBBL RHL 02774 . • 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, General forager; IBBL RHL-SIA- 007 . • 1 worker; Hong Kong SAR, Mui Tsz Lam ; 22.3892, 114.2345; 220 m a. s. l.; 4 Oct. 2016; R. H. Lee leg.; Secondary forest, Pitfall trap; IBBL RHL 003304 . • 1 worker; Hong Kong SAR, Tai Po Kau ; 22.42613, 114.18178; 160 m a. s. l.; 6 Jun. 2017; R. H. Lee leg.; Secondary forest, Pitfall trap; IBBL RHL 03549 . • 1 worker; Hong Kong SAR, Tai Po Kau ; 22.42706, 114.17999; 180 m a. s. l.; 6 Jun. 2017; R. H. Lee leg.; Secondary forest, Pitfall trap; IBBL RHL 03555 . • 1 worker; Hong Kong SAR, Lung Fu Shan ; 22.2758, 114.13546; 250 m a. s. l.; 11 Oct. 2017; R. H. Lee leg.; Secondary forest, General forager; IBBL RHL-SIA- 095 . • 1 worker; Hong Kong SAR; Wong Lung Hang ; 22.2658, 113.9528; 440 m a. s. l; 11 May. 2023; M. T. Hamer leg.; Shrubland, General-forager IBBL ANTWEB 1010235 .

Etymology.

Named after the musician Dave Grohl, lead singer, guitarist, and songwriter of the rock band Foo Fighters, drummer of the rock bands Nirvana and Queens of the Stone Age among others, for his positive activism, and ever long musical accompaniment to both first and last author.

Figures

Figure 11. Leptogenys grohli holotype (ANTWEB 1010093) A lateral view B dorsal view C head in full face view.

Figure 12. Leptogenys grohli sp. nov holotype (all images are ANTWEB 1010093, other than C ANTWEB 1010092) close up sections A close up of head and mesosoma in lateral view B close up of right hand mandible in full face view C close up of right antennal scape in full anteroventral view D close up of petiole in lateral view E close up of propodeum, petiole and first gastral tergite in dorsal view.

Figure 13. Leptogenys grohli ergatoid queen (ANTWEB 1010094) A lateral view B dorsal view C head in full face view.

Figure 20. Distribution maps of Leptogenys species recorded from Hong Kong A L. binghamii B L. diminuta C L. grohli D L. kitteli. The base map displayed shows tree canopy cover with the darker green areas indicating greater tree cover.