Key to Oriental Leptogenys

This worker key is based on K. Arimoto and S. Yamane, 2018 who in turn state "As supporting information, we update the key of Xu and He (2015) by adding information related to species described in Zryanin (2016), Arimoto (2017a, 2017b), and the current study."

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• Leptogenys
• Oriental and Australian Leptogenys species groups

1

• Hypostomal tooth present and visible in full-face view . . . . . 2

• Hypostomal tooth absent . . . . . 9

2

return to couplet #1

• Median lobe of clypeus without apical median extension. Body surface mostly with shagreened sculpture, without standing long hairs . . . . . 3

• Median lobe of clypeus with apical median extension. Body surface mostly with areolate-rugose sculpture, covered with standing long hairs . . . . . 4

3

return to couplet #2

• Head, mesosoma and gaster finely punctate, not pruinose (Sri Lanka, Indonesia, Madagascar) . . . . . Leptogenys falcigera

• Head, mesosoma and gaster densely pruinose, not punctate (Sri Lanka) . . . . . Leptogenys pruinosa

4

return to couplet #2

• Petiole in profile longer than or almost as long as high (LPI: 94–102); dorsal face of node subhorizontal (Malaysia) . . . . .Leptogenys breviloba

• Petiole in profile higher than long (LPI: 103– 122); dorsal face of node distinctly sloping anteriad . . . . . 5

5

return to couplet #4

• Head in full-face view shorter (CI: 88–101). Mandible curved near base, becoming straight apically. Clypeus with lateral lobe . . . . . 6

• Head in full-face view longer (CI: 77–83). Mandible distinctly curved throughout. Clypeus without lateral lobe . . . . . 8

6

return to couplet #5

• Head in full-face view almost as long as wide (CI: 98–101). Antennal scape distinctly long (SL: 1.83–1.95; SI: 115–121), surpassing posterior margin of head by two-fifths of its length. Median clypeal extension with truncate apex (Malaysia). . . . . .Leptogenys malayana

• Head in full-face view longer than wide (CI: 88–95). Antennal scape long (SL: 1.40–1.80; SI: 99–110), surpassing posterior margin of head by one-fifth to one-third of its length. Median clypeal extension with convex apex. . . . . . 7

7

return to couplet #6

• Head in full-face view slightly longer than wide (CI: 93–95). Clypeus with blunt angle between lateral lobe and median extension. Petiole in profile distinctly higher than long (LPI: 109– 118); anterior face of node ventrally vertical and dorsally forming continuous curve with dorsum (Malaysia) . . . . . .Leptogenys itoi

• Head in full-face view distinctly longer than wide (CI: 88–90). Clypeus smoothly incurved between lateral lobe and median extension. Petiole in profile slightly higher than long (LPI: 103– 108); node with anterior and dorsal faces forming continuous curve (Indonesia) . . . . . .Leptogenys modiglianii

8

return to couplet #5

• Petiolar node with anterior and dorsal faces forming continuous curve. Gastral segment II covered with scalloped depressions, which close to each other. Body covered with understory layer of short dense hairs (Indonesia) . . . . . .Leptogenys curva

• Anterior face of petiolar node ventrally vertical and dorsally forming continuous curve with dorsum. Gastral segment II smooth. Short hairs not forming understory layer (Malaysia) . . . . . .Leptogenys kanaoi

9

return to couplet #1

• Petiolar dorsal margin ends in blunt pointed tooth that projects beyond posterior margin (Vietnam) . . . . . .Leptogenys leleji

• Petiolar dorsal margin ends without pointed tooth . . . . . 10

10

return to couplet #9

• Masticatory margin of mandible with more than two teeth and denticles in addition to the apical one . . . . . 11

• Masticatory margin of mandible usually edentate, at most with one tooth in addition to the apical one . . . . . 24

11

return to couplet #10

• Head dorsum rugose throughout. First gastral segment coarsely reticulate-rugose (Myanmar, Laos, Vietnam, Thailand) . . . . . Leptogenys aspera

• Head dorsum punctate or mostly smooth and shiny, if anteriorly striate then at least posterior half smooth and shiny. First gastral segment smooth and shiny . . . . . 12

12

return to couplet #11

• Head quadrate or subquadrate in full-face view, about as broad as long. Petiolar node longitudinally compressed and squamiform in lateral view, acute at summit, without distinct dorsal margin, the node above anterior and posterior articulations at least 2 times as broad as long in dorsal view . . . . . 13

• Head rectangular in full-face view, distinctly longer than broad. Petiolar node longitudinally thickened or elongate, roughly triangular or cubical in lateral view, dorsal margin long or narrowly convex, always distinct, the node above anterior and posterior articulations at most 1.5 times as broad as long in dorsal view . . . . . 15

13

return to couplet #12

• Head dorsum sparsely punctate throughout. Posterior head margin straight in full-face view. Apex of clypeus acutely toothed (India) . . . . . .Leptogenys dentilobis

• Head dorsum smooth and shiny. Posterior head margin weakly to strongly concave in full-face view. Apex of clypeus convex . . . . . 14

14

return to couplet #13

• Posterior head margin weakly concave, anterior half of head dorsum longitudinally striate, the striations reaching posterior eye margin. Antennal segments IV–VI about as broad as long. Subpetiolar process broad and triangular. Body color reddish brown (Myanmar, India, China) . . . . . .Leptogenys birmana

• Posterior head margin strongly concave, anterior third of head dorsum longitudinally striate, the striations not reaching posterior eye margin. Antennal segments IV–VI longer than broad. Subpetiolar process narrow and cuneiform. Body color brownish black (India, Sri Lanka, Vietnam) . . . . . .Leptogenys processionalis

15

return to couplet #12

• Petiolar node longitudinally elongate and horizontally triangular, distinctly longer than high in lateral view, about twice as long as broad in dorsal view. Masticatory margin of mandible with 14 irregular teeth and denticles (Laos) . . . . . .Leptogenys khammouanensis

• Petiolar node longitudinally thickened, erectly triangular or subcubical, about as high as long or distinctly higher than long in lateral view, about as broad as long or distinctly broader than long in dorsal view. Masticatory margin of mandible with less than 10 teeth and denticles . . . . . 16

16

return to couplet #15

• Petiolar node erectly triangular in lateral view, dorsal and anterior margins form a single arch, the two margins not separated by a distinct blunt angle . . . . . 17

• Petiolar node subquadrate in lateral view, dorsal and anterior margins not forming a single arch, the two margins separated by a distinct blunt angle . . . . . 18

17

return to couplet #16

• Head largely sparsely punctate and opaque. Posterior head margin weakly convex in full-face view. Metanotal groove not impressed in lateral view. Head, mesosoma and petiole black, gaster blackish brown (India) . . . . . .Leptogenys moelleri

• Head smooth and shiny. Posterior head margin weakly concave in full-face view. Metanotal groove distinctly impressed in lateral view. Body color reddish brown (Vietnam, China) . . . . . .Leptogenys davydovi

18

return to couplet #16

• Petiolar node thickly trapezoidal in lateral view, dorsal margin as long as or longer than anterior margin. Body color brownish yellow . . . . . 19

• Petiolar node thinly trapezoidal in lateral view, dorsal margin distinctly shorter than anterior margin. Body color reddish brown to black . . . . . 20

19

return to couplet #18

• Dorsal margin of petiolar node about as long as anterior margin in lateral view; the node relatively narrow in dorsal view, about 1.2 times as broad as long. Declivity of propodeum without transverse striation (Myanmar, China) . . . . . .Leptogenys crassicornis

• Dorsal margin of petiolar node longer than anterior margin in lateral view; the node relatively broad in dorsal view, about 1.4 times as broad as long. Declivity of propodeum with transverse striation (India) . . . . . .Leptogenys emiliae

20

return to couplet #18

• Head dorsum sparsely punctate throughout . . . . . 21

• Head dorsum mostly smooth and shiny . . . . . 22

21

return to couplet #20

• Head dorsum largely sparsely punctate. Antennae relatively shorter, scape surpassing posterior head corner by about one fifth of its length, antennal segments III–VI about as broad as long. Metanotal groove not impressed in lateral view. Body color brownish black (India, Myanmar) . . . . . .Leptogenys roberti

• Head dorsum finely sparsely punctate. Antennae relatively longer, scape surpassing posterior head corner by about one third of its length, antennal segments III–VI distinctly longer than broad. Metanotal groove distinctly impressed in lateral view. Body color black (Sri Lanka) . . . . . .Leptogenys yerburyi

22

return to couplet #20

• Head distinctly longer than broad in full-face view, about 1.4 times as long as broad, posterior margin weakly convex. Inner margin of mandible distinctly denticulate (India) . . . . . .Leptogenys dalyi

• Head slightly longer than broad in full-face view, at most 1.2 times as long as broad, posterior margin straight or weakly concave. Inner margin of mandible edentate . . . . . 23

23

return to couplet #22

• Mandible with 5 teeth on the masticatory margin. Subpetiolar process semicircular, rounded at apex. Body color reddish brown (China) . . . . . .Leptogenys strena

• Mandible with 7–8 teeth and denticles on the masticatory margin. Subpetiolar process triangular, angled at apex. Body color black (India, Myanmar, China) . . . . . .Leptogenys lucidula

24

return to couplet #10

• Eye located posterior to mid-length of head . . . . . 25

• Eye located near mid-length of head . . . . . 27

25

return to couplet #24

• Gastral segments I–II longitudinally striate (Laos, Thailand, Cambodia, Myanmar) . . . . . .Leptogenys cyanicatena

• Gastral segments I–II smooth . . . . . 26

26

return to couplet #25

• Eye length in full-face view more than one-fourth of head lateral margin length. Outer margin of eye just breaking lateral outline of head. Head and petiolar node smooth except for anterior part of frons and gena weakly longitudinally striate (Malaysia) . . . . . .Leptogenys chalybaea

• Eye length in full-face view less than one-fourth of head lateral margin length. Eyes distinctly interrupts lateral outline of head. Head and petiolar node striate (Vietnam) . . . . . .Leptogenys atra

27

return to couplet #24

• Head dorsum striate throughout . . . . . 28

• Head dorsum punctate throughout or mostly smooth and shiny, at most punctate or rugose anterior to eyes . . . . . 29

28

return to couplet #27

• Clypeus with distinct longitudinal central carina. Sides of pronotum smooth, finely rugulose or finely reticulate; sides of mesothorax, metathorax and propodeum irregularly rugose (India, Sri Lanka, Myanmar, China, Philippines, Malaysia, Singapore, Indonesia, New Guinea, Solomon Islands) . . . . . .Leptogenys diminuta

• Clypeus without longitudinal central carina. Mesosoma regularly longitudinally striate (India, Myanmar, Thailand, Vietnam, China, Malaysia, Indonesia, New Guinea) . . . . . .Leptogenys kitteli

29

return to couplet #27

• Head dorsum punctate throughout . . . . . 30

• Head dorsum mostly smooth and shiny, at most punctate or rugose anterior to eyes.. . . . . 42

30

return to couplet #28

• First gastral segment mostly punctate . . . . . 31

• First gastral segment smooth and shiny . . . . . 35

31

return to couplet #30

• Head roughly rectangular in full-face view, not widening anteriorly, posterior margin roundly convex. Anterior apex of clypeus strongly convex . . . . . 32

• Head roughly trapezoidal in full-face view, distinctly widening anteriorly, posterior margin nearly straight. Anterior apex of clypeus truncate or nearly truncate . . . . . 33

32

return to couplet #31

• Posterior head margin weakly convex in full-face view. Dorsum of promesonotum almost straight in lateral view, metanotal groove narrowly impressed. Petiolar node trapezoidal in dorsal view, anterolateral corners narrowly rounded. Head, mesosoma, and petiole densely reticulate-rugose. Body color blackish brown. Total length 4–5 mm (India, Sri Lanka) . . . . . .Leptogenys hysterica

• Posterior head margin strongly convex in full-face view. Dorsum of promesonotum moderately convex in lateral view, metanotal groove widely impressed. Petiolar node nearly semicircular in dorsal view, anterolateral corners rounded. Head, mesosoma, and petiole densely punctate. Body color blackish brown. Total length 7.9–8.5 mm (China) . . . . . .Leptogenys hezhouensis

33

return to couplet #31

• Antennae relatively shorter, only one fourth of length of scape surpassing posterior head corner, segments 3 and 4 about equal. Anterior margin of petiolar node straight and vertical, anterodorsal corner narrowly rounded. Total length 5.2–5.7 mm (China) . . . . . .Leptogenys yandii

• Antennae relatively longer, one third or half of length of scape surpassing posterior head corner, segment 3 distinctly longer than segment 4. Anterior margin of petiolar node weakly convex and slope, anterodorsal corner broadly rounded . . . . . 34

34

return to couplet #33

• Eyes larger and occupying one third of head side. Antennae shorter, about one third of scape length surpassing posterior head corner. Head dorsum finely densely punctate. Dorsa of mesosoma, petiole and first gastral segment sparsely punctate with interspaces relatively shiny; sides of mesosoma and petiolar node longitudinally rugose, posterior two thirds of side of first gastral segment smooth and shiny, second gastral segment smooth and shiny. Total length 5–6 mm (India, Philippines) . . . . . .Leptogenys punctiventris

• Eyes smaller and occupying one fourth of head side. Antennae longer, nearly half of scape length surpassing posterior head corner. Head, mesosoma, petiole and first gastral segment densely punctate with interspaces coarsely reticulate-rugose and dull, second gastral segment sparsely punctate. Total length 9–10 mm (Myanmar, India, China) . . . . . .Leptogenys binghamii

35

return to couplet #30

• Petiolar node roughly conical in lateral view, without distinct dorsal margin, broader than long in dorsal view (India) . . . . . .Leptogenys jeanettei

• Petiolar node roughly trapezoidal in lateral view, dorsal margin long and slope down anteriorly, as broad as long or longer than broad in dorsal view . . . . . 36

36

return to couplet #35

• Clypeus truncate at apex (China) . . . . . .Leptogenys huapingensis

• Clypeus convex at apex, not truncate . . . . . 37

37

return to couplet #36

• Dorsal faces of head, mesosoma and petiolar node densely punctate and opaque . . . . . 38

• Dorsal face of head loosely punctate with interspaces relatively shiny, dorsal faces of mesosoma and petiolar node smooth and shiny . . . . . 39

38

return to couplet #37

• Inner margin of mandible roundly convex, basal corner bluntly angled. Pronotum densely punctate with sides longitudinally striate. Anterodorsal corner of petiolar node broadly rounded in lateral view. Body color black. Robust species with total length 7.1–7.8 mm (China) . . . . . .Leptogenys zhuangzii

• Inner margin of mandible nearly straight, basal corner rounded without clear angle. Pronotum finely rugulose with sides smooth and shiny. Anterodorsal corner of petiolar node narrowly rounded in lateral view. Body color blackish brown. Slender species with total length 4.5–5.0 mm (China) . . . . . .Leptogenys laozii

39

return to couplet #37

• Antennal segments relatively shorter, segment III about 1.5 times as long as broad, about as long as segment IV . . . . . 40

• Antennal segments relatively longer, segment III about 2.4–2.9 times as long as broad, distinctly longer than segment IV . . . . . 41

40

return to couplet #39

• Petiolar node higher than long in lateral view, with anterodorsal corner narrowly rounded. Mesopleuron and metapleuron mostly smooth and shiny. Body color black to blackish brown. Total length 4.5–5.2 mm (China) . . . . . .Leptogenys mengzii

• Petiolar node as high as long in lateral view, with anterodorsal corner broadly rounded. Mesopleuron and metapleuron mostly densely rugose and opaque. Body color reddish brown. Total length 5.6–6.4 mm (China) . . . . . .Leptogenys rufida

41

return to couplet #39

• Basal corner of mandible bluntly angled. Anterodorsal corner of petiolar node narrowly rounded. Body color black. Relatively smaller species with total length 5.5–5.7 mm (India) . . . . . .Leptogenys lattkei

• Basal corner of mandible rounded without clear angle. Anterodorsal corner of petiolar node broadly rounded. Body color blackish brown. Relatively larger species with total length 6.4–6.7 mm (India) . . . . . .Leptogenys transitionis

42

return to couplet #29

• Body color blackish brown, with metallic green iridescence. Total length 6.7 mm (India) . . . . . .Leptogenys stenocheilos

• Body color reddish brown to black, without metallic green iridescence . . . . . 43

43

return to couplet #42

• Petiolar node strongly elongate in lateral view, about 1.5 times as long as high . . . . . 44

• Petiolar node moderately to weakly elongate in lateral view, less than 1.2 times as long as high . . . . . 45

44

return to couplet #43

• Antennal scape relatively shorter, surpassing posterior head corner by about two fifths of its length. Petiolar node elongate trapezoidal in lateral view, with very short but distinct anterior margin. Body color reddish brown. Relatively smaller species with total length 6.5–7 mm (India) . . . . . .Leptogenys assamensis

• Antennal scape very long, surpassing posterior head corner by half of its length. Petiolar node triangular in lateral view, without anterior margin. Body color black. Large species with total length 13–13.5 mm (China) . . . . . .Leptogenys pangui

45

return to couplet #43

• Petiolar node moderately elongate, as long as high or distinctly longer than high in lateral view . . . . . 46

• Petiolar node weakly elongate, distinctly higher than long in lateral view, about 1.3-1.4 times as high as long. . . . . . 49

46

return to couplet #45

• Clypeus truncated at apex. Lager species with total length 8–11 mm . . . . . 47

• Clypeus convex at apex. Smaller species with total length 4.5–7 mm . . . . . 48

47

return to couplet #46

• Dorsal faces between eyes and antennal sockets smooth and shiny, without longitudinal rugae. Propodeal declivity transversely striate, not smooth. Petiolar node relatively broader in dorsal view, about 1.3 times as long as broad. Relatively smaller species with total length 8–10 mm (India, Sri Lanka, Philippines, China) . . . . . .Leptogenys chinensis

• Dorsal faces between eyes and antennal sockets longitudinal rugose and opaque. Propodeal declivity smooth and shiny, without transverse striations. Petiolar node relatively narrower in dorsal view, about twice as long as broad. Relatively larger species with total length 9–11 mm (Indonesia, Vietnam, China) . . . . . .Leptogenys kraepelini

48

return to couplet #46

• Petiolar node distinctly longer than high in lateral view. Sides of mesothorax, metathorax, and propodeum mostly smooth and shiny. Body color black. Relatively larger species with total length 5.9–6.3 mm (Vietnam, Myanmar, India, Sri Lanka, Bangladesh, Philippines, Singapore, Indonesia, China) . . . . . .Leptogenys peuqueti

• Petiolar node as high as long in lateral view. Sides of mesothorax, metathorax, and propodeum mostly irregularly rugose and opaque. Body color black, gaster blackish brown. Relatively smaller species with total length 4.5 mm (Japan, China, Taiwan) . . . . . .Leptogenys confucii

49

return to couplet #45

• Clypeus truncated at apex. Eyes relatively smaller and occupying one fourth of head side. Petiolar node relatively longer in lateral view, about 1.3 times as high as long, dorsal margin distinctly longer than anterior margin, anterodorsal corner narrowly rounded, the node obviously longer than broad in dorsal view (China) . . . . . .Leptogenys laeviterga

• Clypeus pointed and strongly convex at apex. Eyes larger and occupying one third of head side. Petiolar node relatively higher in lateral view, about 1.4 times as high as long, dorsal margin as long as anterior margin, anterodorsal corner broadly rounded, the node as broad as long in dorsal view (China) . . . . . .Leptogenys sunzii

References

• Arimoto, K. (2017b) Redescription of Leptogenys aspera (André, 1889) (Hymenoptera, For­micidae, Ponerinae) from Southeast Asia. Japanese Journal of Systematic Entomology, 23(1):15 – 19.
• Arimoto, K. 2017. Taxonomy of the Leptogenys modiglianii species group from southeast Asia (Hymenoptera, Formicidae, Ponerinae). ZooKeys 651: 79–106 (doi:10.3897/zookeys.651.10366).
• Arimoto, K., Yamane, S. 2018. Taxonomy of the Leptogenys chalybaea species group (Hymenoptera, Formicidae, Ponerinae) from Southeast Asia. Asian Myrmecology 10, e010008 (DOI 10.20362/am.010008).
• Xu, Z.-H., He and Q.-J. 2015. Taxonomic review of the ponerine ant genus Leptogenys Roger, 1861 (Hymenoptera: Formicidae) with a key to the Oriental species. Myrmecological News. 21:137-161.
• Zryanin, V.A. 2016. A remarkable new species of Leptogenys Roger, 1861 (Hymenoptera: Formicidae) from Vietnam. Euroasian Entomological Journal 1: 50–54.