Agavekar et al. (2017) - Twelve-segmented antennae; anterior clypeal margin complete and unspecialized; eyes of moderate size; antennal scapes of moderate length, not surpassing posterior head margin; antennal scrobes absent; frontal carinae very short to almost completely reduced; base of first gastral tergite not concave in dorsal view, without tubercles or teeth on each side; pilosity on dorsal surfaces of body erect to suberect with long and stout hairs; sting appendage dentiform.
Agavekar et al. (2017) - As noted by Bolton (1977), the Tetramorium caespitum group is the only endemic Tetramorium species group in the Palearctic, and it is widely distributed throughout all of Eurasia. Currently, it contains around 80 species and subspecies but this count has to be taken with a lot of caution and does not likely represent a realistic number. Compared to all other Tetramorium species groups, the Tetramorium caespitum group has never been comprehensively revised. Despite some recent small-scale revisionary treatments (Csosz, Radchenko & Schulz, 2007; Csosz & Schulz, 2010), its taxonomic situation can be classified as chaotic and no reliable identification resources exist for the group as a whole.
So far, only one species of the group is known from India: Tetramorium nursei. It occurs in Northwestern India representing the only genuine Palearctic component within the Indian Tetramorium fauna. It should be noted that the record of Tetramorium nursei from Kerala (Saranyan et al., 2013) is extremely dubious and very likely a misidentification. Species of the Tetramorium caespitum group are adapted to temperate and arid subtropical climate, thus not likely to occur in the Western Ghats.
Tetramorium ferox species complex
Based on Csösz and Schulz 2011.
- Tetramorium aegeum
- Tetramorium densopilosum
- Tetramorium diomedeum
- Tetramorium ferox
- Tetramorium feroxoides
Species belonging to the T. ferox-complex within the caespitum-group can be defined by the combination of the following characters.
- petiole and postpetiole relatively broad (CS/PEW > 2.31, CS/PPW > 1.93), in T. aegeum and T. diomedeum very broad.
- head, mesosoma and waist moderately sculptured; dorsum of both petiolar node and postpetiole medially shiny.
- first gastral tergite smooth (excluding T. aegeum, for which 1st gastral tergite is imbricate); several long, erect hairs always appear on first gastral tergite.
- propodeum in profile flat, sloping down at an angle of approximately 45°.
- propodeal teeth small, developed as triangular denticles, in contrast to a prominent propodeal lobe.
- mandibles smooth and shiny.
- petiole and postpetiole wide.
- mesosoma low, with flattened dorsum (seen in profile); scutum (seen from above) somewhat narrowed anteriorly and does not completely cover the pronotum, so that humeri (i. e. anterolateral pronotal angles) are easily visible.
- head, mesosoma and waist moderately sculptured or smooth.
- petiole and postpetiole with some very long thin hairs, in contrast to the first gastral tergite which is generally without long erect hairs.
- head and mesosoma moderately sculptured.
- sides of petiole and postpetiole angulate in dorsal view.
- stipes of genitalia curved inwards at the tip, and with flattened apical plate (seen in caudal view)
Tetramorium caespitum species complex
Based on Wagner et al. 2017.
See details here.
Tetramorium chefketi species complex
Based on Csösz & Schulz 2007.
- Tetramorium alternans
- Tetramorium anatolicum
- Tetramorium annectens
- Tetramorium chefketi
- Tetramorium exile
- Tetramorium forte
- Tetramorium moravicum
- Tetramorium rhodium
- Tetramorium sanetrai
- Tetramorium sulcinode
- Tetramorium syriacum
a) polygonal striae are continuous on 1st gastral tergite, and is sometimes microreticulate basally. Polygonal striation: interstices marked by feeble anastomosing striae (Fig. 8.), compare to microreticulation: interstices marked by very feeble elevated structures, like rugulae (Fig. 6, 7.);
b) head, alitrunk and waist coarsely sculptured, dorsum of petiolar node and postpetiole coarsely rugose and/or reticulate.
c) petiole and postpetiole relatively narrow (CS/PEW and CS/PPW, Table 1);
d) ground surface on the frons is usually coarsely microreticulate;
e) alitrunk is low, dorsum is flattened in profile;
f) scutum in dorsal view is somewhat narrowed anteriorly and does not cover completely the pronotum, humeri are well visible;
g) head, alitrunk and waist are coarsely sculptured, and petiole and postpetiole dorsum coarsely rugose or/and reticulate;
h) polygonal striae disrupted on 1st first gastral tergite, sometimes microreticulate basally;
i) mandibles are longitudinally striate;
j) petiole and postpetiole are relatively narrow (WAIST, Table 2);
k) head and alitrunk with usually coarsely sculpture, ground surface microreticulate;
l) sides of petiole and postpetiole not angulate as in the ferox species complex (in dorsal view);
m) first gastral tergite usually smooth and shiny, or feebly striate;
n) stipes of genitalia blunt, curved inwards at the top, with flattened apical plate (in caudal view)
The newly defined chefketi species complex may not strictly reflect the phylogenetic relationship of the above-mentioned species. T. sulcinode and T. annectens possess several autapomorphic characters (e.g. relatively large eyes and a long psammophore) what probably may lead to place them into a separate group in a future.
Tetramorium semilaeve species complex
This problematic species-complex lacks a modern taxonomic revision.