Key to Tetramorium species groups of India

This worker key is based on: [[Media:Agavekar, G., Hita Garcia, F., Economo, E.P. 2017. Taxonomic overview of the hyperdiverse ant genus Tetramorium in India with descriptions and X-ray microtomography.pdf|Gaurav Agavekar, G., Hita Garcia, F., Economo, E.P. 2017. Taxonomic overview of the hyperdiverse ant genus Tetramorium Mayr (Hymenoptera, Formicidae) in India with descriptions and X-ray microtomography of two new species from the Andaman Islands. PeerJ 5:e3800 (DOI 10.7717/peerj.3800).]]

It is almost certain that future collecting in India will yield additional undescribed species. The key provided by Bharti & Kumar (2012) is a good foundation for the identification of most of the currently known Indian species. Here we provide a newly developed and illustrated species group key that allows a straightforward placement of species into their respective species group, and can be used to supplement the existing species level keys. This is especially useful when dealing with undescribed species.

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 * Tetramorium
 * India
 * Tetramorium of India

1

 * Species with distinctly branched (bifid, trifid, or very rarely quadrifid) hairs (Figs. 3A and 3B) . . . . . 2


 * Species without branched hairs, hairs present neither bifid, trifid, nor quadrifid, either with simple pilosity (Fig. 3C), or with reduced pilosity but short appressed pubescence (Fig. 3D) . . . . . 3

2
return to couplet #1
 * Pilosity on first gastral tergite predominantly erect with hairs simple, bifid, or a combination of both (Fig. 3E) . . . . . Tetramorium obesum group


 * Pilosity on first gastral tergite predominantly suberect with trifid or very rarely quadrifid hairs (Fig. 3F) . . . . . Tetramorium walshi group

3
return to couplet #1
 * Antennae 11-segmented (Fig. 3G) . . . . . 4


 * Antennae 12-segmented (Fig. 3H) . . . . . 5

4
return to couplet #3
 * Antennal scrobes present and well-developed with margin all-around (Fig. 4A); antennal scapes shorter (SI 65–75); petiolar node in profile high rectangular nodiform with moderately rounded anterodorsal and posterodorsal angles (Fig. 4B) . . . . . Tetramorium angulinode group


 * Character combination never as above, especially antennal scrobes, if present, always much less conspicuous than above, and without well-developed posterior and ventral margins (Fig. 4C) . . . . . Tetramorium tortuosum group

5
return to couplet #3
 * Head in full-face view distinctly cordate (Fig. 4D); lateral portion of clypeus modified into a low ridge in front of the antennal insertions (Fig. 4D); median cephalic and clypeal carinae/rugae absent (Fig. 4D) . . . . . Tetramorium melleum group


 * Head in full-face view never cordate as above (Fig. 4E); lateral portion of clypeus modified into a sharp and high ridge in front of the antennal insertions (Fig. 4E); median cephalic and clypeal carinae/rugae usually present, at least one of them (Fig. 4E) . . . . . 6

6
return to couplet #5
 * Sting appendage spatulate (Fig. 4F); frontal carinae very short, ending shortly behind level of posterior clypeal margin (Fig. 4G); antennal scrobes absent . . . . . Tetramorium fergusoni group


 * Sting appendage triangular to dentiform, but never spatulate (Fig. 4H); frontal carinae usually conspicuous and much longer than above, rarely short or absent (Fig. 4I); antennal scrobes present or absent . . . . . 7

7
return to couplet #6
 * Base of first gastral tergite with anterodorsal angles projecting as a pair of blunt teeth or horns (Fig. 5A) . . . . . 8


 * Base of first gastral tergite without anterodorsal angles projecting as a pair of blunt teeth or horns (Fig. 5B) . . . . . 9

8
return to couplet #7
 * Eyes moderately to strongly reduced, at most with five or six ommatidia in the longest row, usually just two or three. (Fig. 5C) . . . . . Tetramorium inglebyi group


 * Eyes moderately to well-developed and conspicuously much larger than above, at least with 10 or 11 ommatidia in the longest row (Fig. 5D) . . . . . Tetramorium mixtum group

9
return to couplet #7
 * Frontal carinae very short to almost completely reduced and antennal scrobes absent (Fig. 5E) . . . . . Tetramorium caespitum group


 * Frontal carinae variably developed, but never reduced or absent as above (Fig. 5F) . . . . . 10

10
return to couplet #9
 * Hairs on mesosomal dorsum equal to or shorter than maximum antennal scape width and stout apically (Fig. 6A) . . . . . Tetramorium simillimum group


 * Hairs on mesosomal dorsum usually significantly longer than maximum antennal scape width, if short then fine and acute apically (Fig. 6B) . . . . . 11

11
return to couplet #10
 * Anterior clypeal margin with distinct median impression, small in some species but always distinct (Fig. 6C) . . . . . Tetramorium bicarinatum group


 * Anterior clypeal margin complete, without median impression (Fig. 6D) . . . . . 12

12
return to couplet #11
 * Propodeal spines comparatively longer; metatibiae with conspicuous suberect to erect hairs on outer surface (Fig. 6E) . . . . . Tetramorium ciliatum group


 * Propodeal armament variable, ranging from almost absent to short teeth/spines, but always shorter than above; metatibiae with (usually) appressed to (rarely) decumbent hairs on outer surface (Fig. 6F) . . . . . Tetramorium tonganum group