Leptanilla Emery, 1870

Griebenow, Zachary Hayes, Richter, Adrian, Economo, Evan P., Dang, An Van & Yamada, Aiki, 2025, Four new species of Leptanillinae (Hymenoptera: Formicidae) from northern Vietnam described with phylogenomics and micro-computed tomography, European Journal of Taxonomy 987, pp. 98-145 : 121-124

Genus Leptanilla Emery, 1870

Leptanilla Emery, 1870: 196 .

Scyphodon Brues, 1925: 93 , fig. 1. Synonymy by Griebenow (2024: 128).

Phaulomyrma Wheeler & Wheeler, 1930: 193 , figs 1–2. Synonymy by Griebenow (2021: 630).

Leptomesites Kutter, 1948: 286 , figs 1–7. Synonymy by Baroni Urbani (1977: 433).

Noonilla Petersen, 1968: 582 , figs 6–8. Synonymy by Griebenow (2024: 128).

Yavnella Kugler, 1987 (“1986”): 52, figs 14–22. Synonymy by Griebenow (2024: 128).

Diagnosis

Worker

1–4 medial mandibular teeth present. Ventromedial mandibular margin lacking teeth. Peg- or pencil-like chaetae absent from labrum. Dorsal mandibular articulation not visible in full-face view. Palp formula 1–2,1. Clypeus indistinct, not extending visibly between antennal toruli. Pair of medial chaetae absent from second protarsomere. Meso-metapleural suture absent; or if present, then unsculptured.Abdominal segments III–IV narrowly joined. Cuticular microsculpture present, scabriculous to areolate.

Gyne

Compound eyes repressed or present; if present then with 1–4 ommatidia. Mandible often falcate, rarely ( Leptanilla belantan Griebenow, 2024 ) with distinct masticatory margin; edentate, or with 1–2 subapical teeth. Wings and alar sclerites absent. Abdominal segment III not petiolate.

Male

Palp formula 1–2,1. Ocelli present or absent; if present, then almost always set on tubercle. Notauli absent. Pterostigma absent. Hindwing 1A absent. Volsellae present or absent; if present, then parossiculus and lateropenite insensibly fused. Cupula present or absent; if present, then annular. Penial sclerites medially fused, rarely ( Leptanilla astylina Petersen, 1968 ; Leptanilla TH 03) articulated.

Key to Leptanilla workers of the Eastern Palaearctic and Indo-Malaya

Condensed from Griebenow (2024: 148–149, 152–154), with the addition of taxa described since that publication ( Qian et al. 2024; Zhong 2024).

1. Clypeus with median process ( Fig. 3C ) ............................................................................................ 2

– Clypeus without median process ( Fig. 3A ) .................................................................................... 16

2. Clypeal process entire; length of abdominal postsclerites IV<combined length of abdominal postsclerites V–VIII .......................................................................................................................... 3

– Clypeal process emarginate to bilobed; length of abdominal postsclerites IV≥combined length of abdominal postsclerites V–VIII ........................................................................................................ 5

3. Posteriorly recurved subpetiolar process absent; PPI = 80–86 ........................................................... ......................................................................... Leptanilla buddhista Baroni Urbani, 1977 ( NEPAL)

– Posteriorly recurved subpetiolar process present; PPI = 122–138 ................................................... 4

4. CI = 72–74, SI = 49–56; outline of antennal torulus subcircular ( Zhong 2024: fig. 3c) .................... ............................................................. Leptanilla macauensis Leong et al., 2018 ( CHINA: Macau)

– CI = 67–70, SI = 63–66; outline of antennal torulus oblong, with protruding anteromedial angle ( Zhong 2024: fig. 3b) .............................. Leptanilla sichuanensis Zhong, 2024 ( CHINA: Sichuan)

5. Anterior margin of dorsal petiolar node emarginate in dorsal view ( Leong et al. 2018: fig. 13e–f) .. ........................................................................................................................................................... 6

– Anterior margin of dorsal petiolar node entire in dorsal view ( Leong et al. 2018: fig. 13a, d) ........ 7

6. Dorsal petiolar node almost twice as long as wide in dorsal view; postpetiolar node longer than wide in dorsal view ................................ Leptanilla hypodracos Wong & Guénard, 2016 ( SINGAPORE)

– Length and width of dorsal petiolar node subequal in dorsal view; postpetiolar node distinctly wider than long in dorsal view ................... Leptanilla clypeata Yamane & Ito, 2001 ( INDONESIA: Java)

7. Length of metasomal setae bimodal ................................................................................................. 8

– Length of metasomal setae unimodal ..............................................................................................11

8. Mandible with four teeth, with most proximal tooth truncate ( Saroj et al. 2022: fig. 1e); ventromedian lamella of abdominal sternite II denticulate ....................................................................................... ............................................................... Leptanilla ujjalai Saroj et al., 2022 ( INDIA: West Bengal)

– Mandible with three teeth, with most proximal tooth not truncate; ventromedian lamella of abdominal sternite II not denticulate .................................................................................................................. 9

9. Longitudinal subpetiolar lamella absent ............................................................................................. ............................................................. Leptanilla dehongensis Qian et al., 2024 ( CHINA: Yunnan)

– Longitudinal subpetiolar lamella present ........................................................................................ 10

10. Lateral pronotal margins weakly convex in dorsal view; PPTI = 74–76 ............................................ ......................................... Leptanilla lamellata Bharti & Kumar, 2012 ( INDIA: Himachal Pradesh)

– Lateral pronotal margins strongly convex in dorsal view; PPTI = 85–86 .......................................... .................................................................... Leptanilla escheri ( Kutter, 1948) ( INDIA: Tamil Nadu)

11. PI>85 .............................................................................................................................................. 12

– PI ≤ 85 .............................................................................................................................................. 15

12. Mandible with three teeth, most proximal tooth acute ....................................................................... ....................................................... Leptanilla kunmingensis Xu & Zhang, 2002 ( CHINA: Yunnan)

– Mandible with four teeth, most proximal tooth blunt ..................................................................... 13

13. Meso-metapleural suture present laterally; PPI ≤ 87 ........................................................................... .................................................................... Leptanilla sapa Yamada sp. nov. ( VIETNAM: Lao Cai)

– Meso-metapleural suture absent laterally; PPI>87 ........................................................................ 14

14. Proximal mandibular tooth recurved, apex expanded ........................................................................ ........................................................ Leptanilla belantan Griebenow, 2024 ( MALAYSIA: Selangor)

– Proximal mandibular tooth sublinear, apex not expanded .................................................................. .............................................................. Leptanilla belantanoides sp. nov. ( VIETNAM: Ninh Binh)

15. Subpetiolar process present, angular; torular rim without areolate sculpture ( Griebenow 2024: fig. 27a) .............................. Leptanilla havilandi Forel, 1901 ( SINGAPORE; MALAYSIA: Sabah)

– Subpetiolar process absent; torular rim with medial and anterior areolate sculpture ( Griebenow 2024: fig. 27b)............................. Leptanilla thai Baroni Urbani, 1977 ( THAILAND: Khao Chong)

16. Mandible with two teeth ................................................................................................................. 17

– Mandible with 3–4 teeth ................................................................................................................. 18

17. Anterior margin of cranium with anterolateral clypeal projections; ventral vertices of abdominal sternites II–III projecting a subequal distance ventrad craniocaudal axis .......................................... ...................................................... Leptanilla kebunraya Yamane & Ito, 2001 ( INDONESIA: Java)

– Anterior margin of cranium entire; ventral vertex of abdominal sternite II distinctly lower on dorsoventral axis compared to ventral vertex of abdominal sternite III ............................................. ..................................................................... Leptanilla butteli Forel, 1913 ( MALAYSIA: Selangor)

18. Meso-metapleural groove present, impressed on dorsum of mesosoma ............................................ ............................................................... Leptanilla hunanensis Tang et al., 1992 ( CHINA: Hunan)

– Meso-metapleural groove absent from dorsum of mesosoma, sometimes impressed on sides ...... 19

19. Clypeus with median emargination ................................................................................................ 20

– Anterior clypeal margin entire, sublinear to convex ....................................................................... 23

20. Abdominal tergite IV not narrowed anteriorly in dorsal view ( Griebenow 2024: fig. 36b); clypeal margin protruding well anterad antennal toruli .................................................................................. ........................................... Leptanilla oceanica Baroni Urbani, 1977 ( JAPAN: Ogasawara Islands)

– Abdominal tergite IV narrowed anteriorly in dorsal view ( Griebenow 2024: fig. 36a); clypeal margin not protruding well anterad antennal toruli .................................................................................... 21

21. Abdominal tergite II trapezoidal in dorsal view, narrowing posteriorly; abdominal sternite III nearly planar ................................................. Leptanilla qinlingensis Qian et al., 2024 ( CHINA: Shaanxi)

– Abdominal tergite II rectangular in dorsal view, not narrowing posteriorly; abdominal sternite II convex ............................................................................................................................................. 22

22. Mandibular teeth equidistant ( Zhong 2024: fig. 13a) ......................................................................... ........................................................................ Leptanilla taiwanensis Ogata et al., 1995 (TAIWAN)

– Proximal mandibular tooth slightly removed from remaining teeth ( Zhong 2024: fig. 13b) ............. .............................................................. Leptanilla beijingensis Qian et al., 2024 ( CHINA: Beijing)

23. Mandible with four teeth (subapical tooth sometimes difficult to distinguish) .............................. 24

– Mandible with three teeth ............................................................................................................... 25

24. Most proximal mandibular tooth large and distinct; abdominal tergite IV distinctly narrowed anteriorly in dorsal view .................. Leptanilla tanakai Baroni Urbani, 1977 ( JAPAN: Yakushima)

– Most proximal mandibular tooth small and indistinct; abdominal tergite IV not distinctly narrowed anteriorly in dorsal view ..................... Leptanilla japonica Baroni Urbani, 1977 ( JAPAN: Honshu)

25. Petiole distinctly wider than long .................. Leptanilla yunnanensis Xu, 2002 ( CHINA: Yunnan)

– Petiole not distinctly wider than long ............................................................................................. 26

26. Anterior margin of clypeus convex in full-face view ..................................................................... 27

– Anterior margin of clypeus linear in full-face view ....................................................................... 28

27. Mesothorax anteriorly constricted in dorsal view .............................................................................. ................................................................. Leptanilla besucheti Baroni Urbani, 1977 ( SRI LANKA)

– Mesothorax not anteriorly constricted in dorsal view ........................................................................ ................................................................ Leptanilla morimotoi Yasumatsu, 1960 ( JAPAN: Kyushu)

28. Pedicel length and width subequal .... Leptanilla okinawensis Terayama, 2013 ( JAPAN: Okinawa)

– Pedicel distinctly longer than wide ................................................................................................. 29

29. Meso-metapleural suture absent; subpetiolar process absent posteriorly, abdominal sternite II linear in profile view ...................................... Leptanilla kubotai Baroni Urbani, 1977 ( JAPAN: Shikoku)

– Meso-metapleural suture present on side of mesosoma, absent from dorsum; abdominal sternite II convex in profile view ............................. Leptanilla phthirigyna sp. nov. ( VIETNAM: Ninh Binh)

Figures

Fig. 3. Volume renderings of Leptanilla Emery, 1870 crania, focusing on the cephalic sucking pump (green) and clypeofrontal muscles (red, orange). Dotted lines delimit frons from clypeus, with blue dotted ovals marking relevant muscle origins. Infrabuccal pouch and epipharynx connecting the pump to the mouthparts not shown. A. Leptanilla charonea López, Martínez & Barandica, 1994, dorsal view. B. L. charonea, sagittal cross-section. C. L. belantanoides sp. nov., dorsal view. D. L. belantanoides, sagittal cross-section. Abbreviations: ci1 = Musculus (M.) clypeopalatalis; bu1 = M. clypeobuccalis; bu2 = M. frontobuccalis anterior. Scale bars = 0.03 mm.