Key to southeastern Asian Aenictus ceylonicus group species

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This worker key is based on Jaitrong, W. & Yamane, S. 2013. The Aenictus ceylonicus species group (Hymenoptera, Formicidae, Aenictinae) from Southeast Asia. Journal of Hymenoptera Research 31, 165-233.

Also included is Aenictus yangi, a species described in 2015,

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1

  • Mandible with 2-6 teeth/denticles between subapical and basal teeth (mandible with more than 4 teeth/denticles) . . . . . 2a
  • Mandible with 0-1 tooth/denticle between subapical and basal teeth (mandible with 3-4 teeth/denticles); Figure 1:A,B . . . . . 15
Lui et al. 2015. Figure 1.

2a

return to couplet #1

  • Dorsal face of propodeum mostly smooth and shiny; lateral face of propodeum partly smooth and shiny (Figure 2A); postpetiole entirely smooth and shiny . . . . . 2b
  • Propodeum entirely sculptured (Figure 2B); postpetiole entirely sculptured or with smooth and shiny small area on dorsal face . . . . . 6
Lui et al. 2015. Figure 2.

2b

return to couplet #2a

  • Metanotal groove noticeably present but weak; propodeal junction noticeably angulate with distinct tooth; subpetiolar process relatively elongate, subrectangular, and slightly projecting anteroventrally (Figure 3A) . . . . . Aenictus yangi
Liu-et-al-2015-9 Aenictus yangi hal.jpg
  • Character combination never as above; metanotal groove usually absent or strongly reduced, but always weaker than above; propodeal junction rounded to angulate without/with small tooth; subpetiolar process variable, ranging from strongly reduced and rounded to subrectangular, but never as elongate as above (Figure 3 B-E)) . . . . . 3
Lui et al. 2015. Figure 3.

3

return to couplet #2b

  • Declivity of propodeum with lateral carinae, but not demarcated basally by a transverse carina (Lombok) . . . . . Aenictus longicephalus
  • Declivity of propodeum shallowly concave, encircled with a rim . . . . . 4

4

return to couplet #3

  • Distal 2/3 of basal margin of mandible straight, proximal 1/3 narrowed toward base of mandible; anterior clypeal margin straight; petiole clearly smaller than postpetiole (Lombok) . . . . . Aenictus minipetiolus
  • Basal margin of mandible feebly concave; anterior clypeal margin concave; petiole larger than or as large as postpetiole . . . . . 5

5

return to couplet #4

  • Promesonotum strongly convex and sloping gradually to metanotal groove; subpetiolar process with angulate posteroventral corner; antennal scape relatively long (SI 78-86) (Bali) . . . . . Aenictus baliensis
  • Mesosoma almost flat dorsally or feebly convex; subpetiolar process lower, with its posteroventral corner rounded; antennal scape relatively short (SI 57-78) (Vietnam and Thailand) . . . . . Aenictus wiwatwitayai

6

return to couplet #2a

  • Vertex with 2 long standing hairs mixed with a few short appressed hairs; promesonotum with few appressed hairs and a few decumbent hairs (Sabah) . . . . . Aenictus appressipilosus
  • Vertex and promesonotum with dense standing or decumbent hairs . . . . . 7

7

return to couplet #2

  • Promesonotum entirely sculptured (punctate or reticulate) . . . . . 8

8

return to couplet #7

  • Promesonotum sparsely reticulate and shiny or superficially micropunctate (entire promesonotum looks shiny); antennal scape superficially shagreened; petiole cylindrical, clearly longer than high (S. Thailand) . . . . . Aenictus cylindripetiolus
  • Promesonotum densely punctate and matt; antennal scape micropunctate; petiole round or subangulate, almost as long as high (Vietnam and N. Thailand) . . . . . Aenictus thailandianus
Aenictus thailandianus side (www.niaes.affrc.go.jp).jpg

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9

return to couplet #7

  • With head seen in profile and dorsal view occipital corner produced as a small lobe (Sulawesi) . . . . . Aenictus gonioccipus
  • With head seen in profile occipital corner without such a lobe . . . . . 10

10

return to couplet #9

  • Masticatory margin of mandible with large acute apical tooth followed by a series of 6-7 denticles of two sizes, the larger alternating with 1-2 smaller; gap between anterior clypeal margin and mandibles relatively small or indistinct, with maximum width shorter than maximum width of mandible (S. Japan and Taiwan) . . . . . Aenictus lifuiae
Aenictus lifuiae side (www.niaes.affrc.go.jp).jpg
  • Masticatory margin of mandible with large acute apical tooth followed by a medium-sized subapical tooth, 2-5 denticles, and a medium-sized basal tooth; gap between anterior clypeal margin and mandibles relatively large and distinct, with maximum width longer than maximum width of mandible . . . . . 11

11

return to couplet #10

  • Subpetiolar process subtriangular, its apex directed downward, anteroventrally not angulate; postpetiole elevated posteriorly; its posterior face much steeper than anterior face (Sumatra) . . . . . Aenictus itoi
  • Subpetiolar process subrectangular or low, convex in its ventral outline, anteroventrally always angulate; postpetiole with roundly convex dorsal outline . . . . . 12

12

return to couplet #11

  • Subpetiolar process rectangular, ventrally with anterior and posterior corners . . . . . 13
  • Subpetiolar process low, its ventral outline convex, almost straight or feebly concave, and anteroventral corner acutely angulate . . . . . 14

13

return to couplet #12

  • Posteroventral corner of subpetiolar process bluntly angulate (not spiniform); dorsal outline of propodeum weakly convex; metapleural gland bulla weakly sculptured and shiny (Vietnam) . . . . . Aenictus eguchii
  • Posteroventral corner of subpetiolar process acutely produced below (spiniform); dorsal outline of propodeum straight; metapleural gland bulla strongly sculptured (puncto-reticulate) and opaque (Borneo and Java) . . . . . Aenictus jawadwipa

14

return to couplet #12

  • Promesonotum in profile weakly convex; propodeal dorsum feebly convex; petiole sessile with low node, its posterior face encircled with a thin carina; postpetiole almost as long as petiole (Thailand) . . . . . Aenictus wilaiae
  • Promesonotum in profile strongly convex and forming a dome; propodeal dorsum clearly straight; petiole subsessile with high node, its posterior face not encircled with a carina; postpetiole slightly shorter than petiole (Philippines) . . . . . Aenictus pilosus

15

return to couplet #1

  • Mandible with 3 teeth including apical and basal teeth . . . . . 16
  • Mandible with 4 teeth including apical and basal teeth . . . . . 17

16

return to couplet #15

  • With head seen in profile occipital corner round; promesonotum in profile strongly convex and forming a dome; petiole almost as long as high, with high node, and almost as long as postpetiole (Vietnam and Thailand) . . . . . Aenictus watanasiti
  • With head seen in profile occipital corner roundly angulated (almost right- angled); promesonotum in profile with weakly convex or almost flat dorsal outline; petiole clearly longer than high, with low node, and slightly longer than postpetiole (Vietnam and Thailand) . . . . . Aenictus concavus

17

return to couplet #15

  • Dorsal and lateral faces of pronotum largely smooth and shiny; petiole almost as long as high; head slightly longer than or almost as long as broad (CI 90- 100) . . . . . 18
  • Dorsal and lateral faces of pronotum entirely sculptured (superficially puncto-reticulate, punctate to reticulate); petiole cylindrical, distinctly longer than high; head slightly shorter than broad (CI 102-112) . . . . . 20

18

return to couplet #17

  • Anterior clypeal margin distinctly concave; metanotal groove distinct, deep; foretibia relatively short, its length less than 0.5 times of head width; mesopleuron finely punctate without longitudinal rugulae (N. Vietnam) . . . . . Aenictus brevipodus
  • Anterior clypeal margin almost straight or feebly concave; metanotal groove indistinct; foretibia relatively long, its length about 0.9-1.0 times as long as head width; mesopleuron with some longitudinal rugulae . . . . . 19

19

return to couplet #18

  • Subpetiolar process low, ventral outline weakly convex, its anteroventral corner angulate (Thailand) . . . . . Aenictus khaoyaiensis
  • Subpetiolar process well-developed, subrectangular with convex ventral lamella, and with anterior and posterior corners acutely or bluntly angulated (Taiwan) . . . . . Aenictus formosensis

20

return to couplet #17

  • Subpetiolar process very low, with anterior and posterior denticles that protrude downward; head in full-face view rectangular, its posterior margin feebly concave (Thailand) . . . . . Aenictus maneerati
  • Subpetiolar process subrectangular or low, with its anteroventral corner acutely angulated and ventral outline straight or convex; head in full-face view subrectangular or rounded, its posterior margin weakly concave, almost straight or weakly convex . . . . . 21

21

return to couplet #20

  • Pronotum with central area superficially shagreened or rather smooth and shiny, and with lateral face reticulate and shiny; subpetiolar process low, with its anteroventral corner acutely angulate and ventral outline concave (Sumatra, Borneo and Java) . . . . . Aenictus sundalandensis
  • Pronotum micropunctate or reticulate and opaque (at most weakly shiny); subpetiolar process always low, with its anteroventral corner acutely angulate and ventral outline almost straight or convex . . . . . 22

22

return to couplet #21

  • Anterior portion of pronotum densely punctate, lateral face of pronotum finely reticulate (China, Hong Kong, Laos and Thailand) . . . . . Aenictus fuchuanensis