Key to Arabian Tetramorium

This worker key is based on: Sharaf, M.R., Aldawood, A.S. and Taylor, B. 2012. A New Ant Species of the Genus Tetramorium Mayr, 1855 (Hymenoptera: Formicidae) from Saudi Arabia, with a Revised Key to the Arabian Species. PLoS ONE. 7(2):e30811 doi:10.1371/journal.pone.0030811

They noted the following in regard to the Arabian Tetramorium:

With these two species, Tetramorium amalae and Tetramorium latinode, the T. shilohense group is recorded for the first time in Arabia and the squaminode group also is recorded for the first time from Saudi Arabia. T. latinode  was originally described from Yemen. Both species groups are mainly Afrotropical in distribution with seven and thirteen species for the shilohense and squaminode groups, respectively. Apparently, these two species are endemic to the chain of Alsarawat Mountains which extends to Yemen. This is supported by the degree of isolation characterizing this area of Arabia.

The finding of these two Afrotropical ant species groups in this area further supports the claim that Al Bahah region in southwestern Arabia biogeographically is Afrotropical and has a distinct history from the rest of the Arabia.

By comparison of the descriptions of Tetramorium jizane and Tetramorium yemene it is apparent also that these two species may be synonymous with the widely distributed invasive species Tetramorium simillimum and Tetramorium delagoense as the number of genae hairs overlap. We suspect that the records of Tetramorium khyarum and [[Tetramorium delagoense from Arabia are due to misidentifications but examination of the material mentioned by Collingwood & Agosti and comparison with appropriate type-material will be required.

Tetramorium bicarinatum is a cosmopolitan invasive species often imported with plant materials. The record from UAE [24] was the first for Arabia and our record, based on a single specimen collected from Riyadh without any specific data, is the first for Saudi Arabia.

Finally, the total of nineteen species of Tetramorium recorded from Arabia is a relative modest number considering the vastness of the region and the diversity of habitats. We expect additional collecting will reveal additional species.

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Tetramorium

1

 * Body hairs bifid or trifid (cosmopolitan species) . . . . . Tetramorium lanuginosum


 * Body hairs simple or barbulate but not bifid or trifid . . . . . 2

2
return to couplet #1
 * Eyes tiny consisting of only two ommatidia (Saudi Arabia . . . . . Tetramorium amalae


 * Eyes larger consisting of more than two ommatidia . . . . . 3

3
return to couplet #2
 * Anterior clypeal margin with a distinct median notch . . . . . 4


 * Anterior clypeal margin entire, without a median notch . . . . . 6

4
return to couplet #3
 * Smaller species, TL 2.25–2.37; colour light brown; propodeal spines short and strong (Yemen) . . . . . Tetramorium hirsutum


 * Larger species, TL 2.62–4.5; bicoloured species, body distinctly lighter than the dark gaster; propodeal spines long and acute . . . . . 5

5
return to couplet #4
 * Petiole squamiform, much higher than long in profile; body hairs barbulate; head length smaller HL 0.67–0.80; cephalic index greater CI 87–100 (Yemen & Saudi Arabia) . . . . . Tetramorium latinode


 * Petiole rectangular, not squamiform, distinctly longer than high in profile; body hairs simple; head length greater HL 0.80–1.00; cephalic index smaller CI 80–87 (cosmopolitan invasive species) . . . . . Tetramorium bicarinatum

6
return to couplet #3
 * SI 100 or more . . . . . 7


 * SI less than 100 . . . . . 9

7
return to couplet #6
 * Propodeum armed with a pair of strong and well developed spines; lateral portions of clypeus prominent as a tooth or crest on each side in full-face view. When viewed from above and behind the lateral parts of the clypeus arise to a high peak in front of the antennal insertions and then slope steeply down toward the median portion of the clypeus, sericeiventre group . . . . . 8


 * Propodeum unarmed, dorsum and declivity merely meeting in an angle, or at most with a pair of minute denticles at the junction of the two surfaces; lateral portion of clypeus not strongly modified as above (Ethiopia, North East Africa, Arabia), setigerum group . . . . . Tetramorium doriae

8
return to couplet #7
 * Propodeal dorsum in profile with one or more pairs of hairs arising from the surface between the metanotal groove and the base of the spines (Africa, Saudi Arabia and Yemen) . . . . . Tetramorium khyarum


 * Propodeal dorsum in profile without hairs, the posteriormost pair occurring at or before the metanotal groove (Arabia, Africa and the Malagasy region) . . . . . Tetramorium sericeiventre

9
return to couplet #6
 * Hairs on dorsal mesosoma and on first gastral tergite short, stout, and blunt apically, simillimum group . . . . . 10


 * Hairs on dorsal mesosoma and first gastral tergite fine and acute apically, or hairs absent from both these surface, caespitum complex . . . . . 14

10
return to couplet #9
 * Frontal carinae extend back to the posterior level of eyes and then are obscured by the cephalic sculpture . . . . . 11


 * Frontal carinae extend back beyond the posterior level of the eyes . . . . . 12

11
return to couplet #10
 * Genae with one long oblique hair, cephalic sculpture more widely spaced, scape index lower with SI 74 (Yemen) . . . . . Tetramorium yemene


 * Genae with two pairs of hairs, cephalic sculpture closely spaced, scape index higher with SI 83 (Saudi Arabia) . . . . . Tetramorium jizane

12
return to couplet #10
 * Frontal carinae weakly developed or reduced, either fading out posteriorly or uniformly weak, sometimes broken and usually not more strongly developed than the cephalic sculpture; antennal scrobes very feebly developed or absent; Palp formula 3,2 (a cosmopolitan invasive species) . . . . . Tetramorium caldarium


 * Frontal carinae long and strongly developed throughout their length, running back to the posterior margin of head, the carinae more strongly developed than the cephalic sculpture; antennal scrobes distinct; Palp formula 4,3 . . . . . 13

13
return to couplet #12
 * Side of head immediately behind the eyes with a single pair of projecting stout hairs; scapes relatively slightly longer (SI 84–92) (Africa, Malagasy region, Yemen, Palestine) . . . . . Tetramorium delagoense


 * Side of head immediately behind the eyes without such a hair, either hairless or with a number of fine decumbent to appressed hairs; scapes slightly shorter (SI 74–80) (a cosmopolitan invasive species) . . . . . Tetramorium simillimum

14
return to couplet #9
 * Dorsum of head with a distinct median depressed area (North east Africa and Middle East) . . . . . Tetramorium depressiceps


 * Dorsum of head without a median depression . . . . . 15

15
return to couplet #14
 * Petiole and postpetiole with distinct dorsal sculpture . . . . . 16


 * Petiole and postpetiole smooth and shining dorsally . . . . . 17

16
return to couplet #15
 * Metanotal groove deep; mesosomal pilosity restricted to pronotum and first half of mesonotum, propodeum bare; scape long (SL 0.78–0.87); petiole and postpetiole nodes coarsely sulcate (Russia & Arabia) . . . . . Tetramorium chefketi


 * Metanotal groove shallow but visible; mesosoma with abundant, stout and relatively long suberect hairs; scape shorter (SL 0.70–0.77); petiole and postpetiole nodes irregularly sculptured (Middle East) . . . . . Tetramorium syriacum

17
return to couplet #15
 * Head and mesosoma sculpture superficial, smooth in part (Saudi Arabia & Kuwait) . . . . . Tetramorium juba


 * Head and mesosoma entirely strongly sculptured . . . . . 18

18
return to couplet #17
 * Colour black; propodeal spines very short upturned; striae on posterior margin of head divergent (North Africa) . . . . . Tetramorium biskrense


 * Colour pale reddish yellow; propodeal spines acute and well developed; head striae longitudinal to the posterior margin of head (Oman & Yemen) . . . . . Tetramorium calidum