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

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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