Key to Indian Crematogaster

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This key to workers of Indian species of Crematogaster is based on Akbar et al. (2023) as updated by Dhadwal & Bharti (2024), and is modified from Bingham (1903), Blaimer (2012a), Hosoishi (2015, 2020) and Hosoishi & Ogata (2008, 2009a, 2009b, 2012, 2019).

1

  • Postpetiole globular, lacking median impression. Petiole in dorsal view more or less elongate-rectangular. Propodeal spiracle circular or subcircular. Antennae 11-segmented, antennal scapes often surpassing head margin, and antennae usually with a 2-segmented club, or lacking distinct club. Posterior head margin usually rounded (subgenus Orthocrema) => 2
  • Postpetiole bilobed, with more or less distinct median impression. Petiole in dorsal view flared to broadly oval, but not rectangular or ovo-rectangular. If petiole elongate-rectangular as above, then propodeal spiracle compressed oval. Antennae usually 11-segmented, rarely 10-segmented, antennal scapes of variable length; if antennae distinctly clubbed, then usually club 3-segmented (subgenus Crematogaster sensu stricto) => 3

2

return to couplet #1

  • Posterior portions of mesonotal dorsum forming short triangle-shaped process. Standing pilosity long and abundant on head, mesosoma, petiole, postpetiole and remains of the gaster. Basal flagellar segment (antennal segment III) longer than broad => Crematogaster binghamii
  • Posterior portions of mesonotal dorsum not forming short triangle-shaped process. Standing pilosity short and sparse. Basal flagellar segment (antennal segment III) broader than long => Crematogaster biroi

3

return to couplet #1

  • Reduced number of segments in maxillary and labial palps (palp formula 3, 3, 3, 2 or 2, 2). Ridge separating the lateral and ventral portions of the mesopleuron indistinct. Steeply raised pronotum, smooth and shiny body surface, short, appressed body setae (ranavalonae group) => 4
  • Maxillary and labial palp segments in workers not reduced usually 5, 3. Ridge separating the lateral and ventral portions of the mesopleuron distinct. Pronotum may or may not be as above, varying shape => 8

4

return to couplet #3

  • Scape with sparse setae. Propodeal spiracles as small as mesothoracic spiracles => Crematogaster aberrans
  • Scape with abundant setae. Propodeal spiracles large; diameter ca. 2 × as large as mesothoracic spiracles => 5

5

return to couplet #4

  • In dorsal view, postpetiole strongly bilobed, more than 2 × as broad as long (PPI 212–236) => 6
  • In dorsal view, postpetiole weakly bilobed, generally ca. 1.2 to 2 × as broad as long (PPI 125–200) => 7

6

return to couplet #5

7

return to couplet #5

  • Propodeal spines short; their length equal to or shorter than diameter of propodeal spiracles => Crematogaster dalyi
  • Propodeal spines long; distinctly longer than diameter of propodeal spiracles => Crematogaster sikkimensis

8

return to couplet #3

  • Undeveloped occipital carina not forming a distinct ridge; 2-segmented antennal club; postpetiole strongly bilobed => Crematogaster walshi
  • Occipital carina reduced but with distinct ridge; 3-segmented antennal club; postpetiole weakly bilobed => 9

9

return to couplet #8

  • Petiole diamond-shaped, broadest at mid-length, distinctly wider than postpetiole (PTWI 73–92); propodeal spines elongate, divergent (0.21–0.63 mm); postpetiole subglobular but without distinct longitudinal median sulcus; dorsal surface of head smooth and shiny; promesonotum smooth and shiny; mandible with four teeth; antennal club three-segmented; metanotal groove deep (ransonneti group) => Crematogaster ransonneti
  • Petiole not diamond shaped as above; spines not strongly developed as above; other character combination not as above => 10

10

return to couplet #9

  • Propodeum greatly inflated or mesonotum with posterolateral denticles; head large and broad, often medially depressed; postpetiole globular with a faint posterior impression (inflata group) => 11
  • Propodeum not greatly inflated neither mesonotum with posterolateral denticles; head not as large and broad as above; postpetiole of various shapes => 12

11

return to couplet #10

12

return to couplet #10

  • Strongly sculptured body; metanotal groove deep; postpetiole distinctly bilobed; body setae stout; mandible with four teeth; 3-segmented antennal club; propodeal spines developed; petiole broader anteriorly (rothneyi group) => Crematogaster rothneyi
  • Character combination not as above => 13

13

return to couplet #12

  • Petiole flared with sharp dorsolateral margin; postpetiole bilobed, with a broad median longitudinal impression; pronotum with angular margins; mesonotum convex and posterolaterally margined (rogenhoferi group) => 14
  • Character combination not as above => 15

14

return to couplet #13

  • Pronotum reticulate; propodeal spines directed downward => 14a
  • Pronotum longitudinally striate; propodeal spines upcurved => Crematogaster flava

14a

return to couplet #14

  • Petiole as long as broad, sides angular in the middle in dorsal view; propodeal spine curved posteriorly in dorsal view => Crematogaster rogenhoferi
  • Petiole longer than broad, sides weakly convex in dorsal view; propodeal spines straight, directed posterolaterally in dorsal view => Crematogaster gadagkari

15

return to couplet #13

  • Head smooth and shining, at most with fine striae => 16
  • Head entirely sculptured => 25

16

return to couplet #15

  • Propodeal spines relatively long => 17
  • Propodeal spines short => 21

17

return to couplet #16

18

return to couplet #17

  • Propodeal spines cone shaped, straight => 19
  • Propodeal spines horn shaped, down curved (brunnea species complex) => Crematogaster brunnea

Crematogaster brunnea is a complex species group consisting of six species. General characters are reddish brown colouration, head smooth and shining with faint striations near base of antennae and gena, head wider than the mesosoma, the vertex slightly emarginated; mesosoma in lateral view finely striated longitudinally, metanotum deeply concave with acute spine; petiole heart shaped, flattened above; postpetiole globose and biturberculate dorsally; gaster smooth and shining.

Crematogaster contemta (often as Crematogaster brunnea contemta) is a light bicoloured yellowish subspecies with darker brown gaster, propodeal spines small sharply pointed, thick at the base, directed downward.

Crematogaster brunnea nicevillei is a darker subspecies with smaller spines, deep metanotal groove, raised mesonotum and faintly striate gena.

Crematogaster brunnea nilgirica is restricted to southern India with prominent striations on head and mesosomal dorsum, propodeal spines large, diverging, fronto clypeal sulcus more or less pointed.

Crematogaster brunnea rabula is a dull brownish coloured subspecies with pronotum and propodeum dorsally feebly striate, propodeal spines short, pointed, thick at base diverging outwards.

Crematogaster brunnea ruginota is a light yellowish brown coloured subspecies with deep metanotal groove, strongly raised pro- and mesonotum, propodeal declivity truncate, propodeal spines smaller, pointed, thick at base, directed upward.

19

return to couplet #18

  • Reddish brown species; mesosomal dorsum longitudinally striate; propodeal spines larger and thicker => Crematogaster hodgsoni
  • Blackish brown species; mesosomal dorsum reticulate, propodeal spines smaller and thinner => 20

20

return to couplet #19

  • Pronotum flat dorsally, rounded anteriorly; pro-mesonotal suture obsolete; mesonotum medially depressed => Crematogaster pradipi
  • Pronotum raised, angular anteriorly; pro-mesonotal suture prominent; mesonotum medially raised => Crematogaster anthracina

21

return to couplet #16

  • Propodeal spines reduced, tuberculate => Crematogaster bonnieae
  • Propodeal spines well-developed, never tuberculate => 22

22

return to couplet #21

23

return to couplet #22

24

return to couplet #24

25

return to couplet #15

  • Propodeal spines distinctly longer than metanotum; mesosoma finely sculptured => 26
  • Propodeal spines short; mesosoma strongly sculptured => 27

26

return to couplet #25

  • Dark maroon species; petiole diamond shaped; postpetiole heart shaped, abdomen strongly striate longitudinally => Crematogaster kirbii
  • Light brown species; petiole heart shaped; postpetiole globular, abdomen smooth not striate longitudinally => 28

27

return to couplet #25

28

return to couplet #25

References

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