Key to Malagasy Tetramorium species groups

This key is based on: Hita Garcia and Fisher. 2011. The ant genus Tetramorium Mayr (Hymenoptera: Formicidae) in the Malagasy region – introduction, definition of species groups, and revision of the T. bicarinatum, T. obesum, T. sericeiventre and T. tosii species groups. Zootaxa. 3039: 1-72.

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 * Tetramorium species groups (species lists, diagnosiss, distributions, etc.)
 * Tetramorium

The key is for workers and includes this caveat: "The following key was developed on the basis of existing species groups (Bolton, 1979), with significant additions and modifications made in order to incorporate a substantial amount of new material. However, it should be noted that this key is only of preliminary nature, and that the ongoing revision of all species groups might lead to further changes."

True to their word some of these groups were updated in the following year: [[Media:Hita Garcia & Fisher 2012a.pdf|Hita Garcia, F. and B. L. Fisher. 2012. The ant genus Tetramorium Mayr (Hymenoptera: Formicidae) in the Malagasy region - taxonomy of the T. bessonii, T. bonibony, T. dysalum, T. marginatum, T. tsingy, and T. weitzeckeri species groups. Zootaxa. 3365: 1-123. PDF ]]. These changes are noted, in bold, as notes placed in relevant parts of the original 2011 key. With this in mind, the key does still work well for sorting many species to the species group level. Others, whether part of a newly suggested group that still awaits definitive revision studies or not, may not be resolved using this key.

'The T. tsingy'' group is not part of this key. Hita Garcia and Fisher (2012) - The members of the group possess an interesting character combination rendering them easily recognisable. The considerable lack of sculpture on head, mesosoma and waist segments, short to minute propodeal teeth, well-developed propodeal lobes, and an unsculptured petiolar node which is longer than wide, are not seen in any other species group.'''

1

 * Species with distinctly branched hairs, usually a mixture of simple, bifid, and trifid hairs (Fig. 2A, B) . . . . . T. obesum group


 * Species without branched hairs, hairs present neither bifid nor trifid, either with simple pilosity (Fig. 2C), or with reduced pilosity but short appressed pubescence (Fig. 2D) . . . . . 2

2
return to couplet #1
 * Antennae 12-segmented (Fig. 3A); sting appendage triangular to dentiform, acute apically (Fig. 3B) . . . . . 3
 * Antennae 11-segmented (Fig. 3C); sting appendage spatulate, broadened apically (Fig. 3D) . . . . . 7

3
return to couplet #2
 * Anterior clypeal margin with distinct median impression (Fig. 4A) . . . . . T. bicarinatum group


 * Anterior clypeal margin always entire and convex, never with distinct median impression (Fig. 4B, C) . . . . . 4

4
return to couplet #3


 * Propodeum armed with long to extremely long spines (PSLI 30–49), at least 2 to 3 times longer than metapleural lobes (Fig. 5A) . . . . . T. tosii group


 * Propodeum either unarmed (Fig. 5B), armed with small triangular teeth or denticles, or armed with medium-sized spines (Fig. 5C), propodeal spines at most only as long or weakly longer than metapleural lobes, more often propodeal spines distinctly shorter than metapleural lobes . . . . . 5

5
return to couplet #4
 * Lateral portion of clypeus prominent, raised to a tooth or denticle in full-face view (Fig. 4B); propodeal spines medium-sized and spinose, approximately of same length as metapleural lobes (Fig. 5C) . . . . . T. sericeiventre group


 * Lateral portion of clypeus never modified as above (Fig. 4C); propodeum either unarmed (Fig. 5B) or armed with small triangular teeth or denticles that are shorter than metapleural lobes (Fig. 6E, F) . . . . . 6

6
return to couplet #5
 * Head in full-face view relatively thin (CI < 80) and antennal scapes very long (SI > 120) (Fig. 6A); in general appearance head, antennae, and legs elongate and slender (Fig. 6E) . . . . . T. setigerum group


 * Head in full-face view relatively thicker (CI > 85) and antennal scapes conspicuously much shorter (SI < 92) (Fig. 6B, C, D); in general appearance more compact species with thicker heads and shorter antennae and legs (Fig. 6F) . . . . . T. simillimum group

7
return to couplet #2
 * Petiolar node and postpetiole strongly squamiform, petiolar node with anterior and posterior faces parallel and well developed, straight dorsum; petiole and postpetiole always completely unsculptured, smooth, and shining; standing pilosity scarce or absent on dorsal mesosoma and waist segments, first gastral tergite without standing pilosity (Fig. 7A) . . . . . T. weitzeckeri group


 * Character combination never as above; petiole and postpetiole variably shaped, especially postpetiole never squamiform as above (Fig. 7B, C, D, E, 8C, D); if petiole squamiform and postpetiole weakly squamiform, then petiolar dorsum reduced and strongly tapering backwards posteriorly (Fig. 7F) . . . . . 8

8
return to couplet #7
 * Pronotum anterodorsally with distinct protuberance or bulge (Fig. 8A, B) . . . . . T. bonibony group (in part)


 * Pronotum anterodorsally without any protuberance or bulge (Fig. 8C, D) . . . . . 9

9
return to couplet #8


 * Anterior face of mesosoma usually well-developed and anterodorsal angle distinct (Fig. 9.A); dorsum of mesosoma, especially on pronotum, with strong reticulate-rugose sculpturation; colouration variable . . . . . New species group 1 (in parts)

Hita Garcia and Fisher (2012) - The newly created T. bonibony species group defined what was provisionally said to be this New Species group 1.


 * Anterior face of mesosoma not well-developed and anterodorsal angle absent, generally with a very short anterior portion rounding smoothly onto the dorsum (Fig. 9.B); either species dark brown to black and with almost reduced sculpturation on mesosomal dorsum, or species yellow to brown with weak irregular sculpturation on mesosomal dorsum . . . . . T. marginatum  group

10
return to couplet #4


 * Frontal carinae never running to posterior head margin, generally ending between posterior eye margin and posterior head margin, though closer to posterior eye margin, often curving down ventrally and forming posterior margin of antennal scrobe; propodeal spines always short to medium-sized and elongate-triangular to triangular (Fig. 10.A) . . . . . T. ranarum group

'(Hita Garcia and Fisher 2012) T. plesiarum and several undescribed species do not fit well within the T. ranarum'' group. Tetramorium plesiarum and allies all possess a distinct and sharply defined antennal scrobe, whereas the scrobe is at most shallowly developed in all other T. ranarum group members. This character seems to be of high diagnostic importance since it is absent in all other Malagasy species groups. For this reason, we consider T. plesiarum and allies to belong to a group distinct from the T. ranarum group.'''


 * Frontal carinae usually running back to posterior head margin or ending shortly before; propodeal spines always long and spinose (Fig. 10.B) . . . . . 11

11
return to couplet #10
 * Petiolar node distinctly higher than long and usually weakly to distinctly wider than long; node in profile antero-posteriorly compressed, squamiform to high nodiform; sculpturation on both waist segments often weakly developed but generally present (Fig. 11.A) . . . . . T. dysalum group


 * Petiolar node generally longer than high, only rarely roughly as long as high or weakly higher than long, node never antero-posteriorly compressed, generally rectangular nodiform and rarely clublike; both waist segments distinctly sculptured (Fig. 11.B, 11.C) . . . . . T. tortuosum group

'Hita Garcia and Fisher (2012, 2013) - Tetramorium kelleri is not a member of the T. tortuosum'' group. T. kelleri, along with Tetramorium ankarana, form the newly created T. kelleri species group.'''

12
return to couplet #2


 * Anterior clypeal margin with distinct median impression (Fig. 11.A) . . . . . T. bicarinatum group
 * Anterior clypeal margin always entire and convex, never with distinct median impression (Fig. 12.B, 12.C) . . . . . 13

13
return to couplet #12


 * Propodeum armed with long to extremely long spines, at least 2 to 3 times longer than propodeal lobes (Fig. 13.A) . . . . . T. tosii group
 * Propodeum either unarmed, armed with small triangular teeth or denticles, or armed with medium-sized spinose spines, propodeal spines at most only as long or weakly longer than propodeal lobes, more often propodeal spines distinctly shorter than propodeal lobes (Fig. 13.B, 13.C) . . . . . 14

14
return to couplet #13


 * Lateral portion of clypeus prominent, raised to a tooth or denticle in full-face view (Fig. 14.A); propodeal spines medium-sized and spinose, roughly of same length as propodeal lobes . . . . . T. sericeiventre group


 * Lateral portion of clypeus never modified as above (Fig. 14.B); propodeal spines usually strongly reduced to small triangular teeth or denticles that are shorter than propodeal lobes . . . . . T. simillimum group