Key to workers of the Socotra Archipelago, Yemen

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This worker key is based on: Collingwood, C. A., Pohl, H., Guesten, R., Wranik, W. and van Harten, A. 2004. The ants (Insecta: Hymenoptera: Formicidae) of the Socotra Archipelago. Fauna of Arabia. 20:473-495. PDF

The following key uses a limited number of morphological features, most of them observable at low magnification under a stereo microscope. Included in the key are the 18 species positively identified and an additional, yet undetermined species of Monomorium for which workers have been available.

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1

  • Body with a single reduced or isolated segment (the petiole) between alitrunk and gaster . . . . . 2
  • Body with two distinct segments (the petiole and the postpetiole) between alitrunk and gaster . . . . . 8

2

return to couplet #1

Pachycondyla sennaarensis sam-hym-c000111a head 1.jpg
Pachycondyla sennaarensis sam-hym-c000111a profile 1.jpg

3

return to couplet #2

  • Very small (HW < 0.45 mm), whitish base of gaster contrasting with brownish-black body . . . . . Tapinoma melanocephalum
Tapinoma melanocephalum casent0173215 head 1.jpg
Tapinoma melanocephalum casent0173215 profile 1.jpg
  • Larger (HW > 0.45 mm), body colouration different . . . . . 4

4

return to couplet #3

  • Antennal insertions close to posterior clypeal margin . . . . . 5
  • Antennal insertions distant from posterior clypeal margin (genus Camponotus) . . . . . 6

5

return to couplet #4

Lepisiota spinisquama casent0912407 h 1 high.jpg
Lepisiota spinisquama casent0912407 p 1 high.jpg
Paratrechina longicornis casent0063128 head 1.jpg
Paratrechina longicornis casent0063128 profile 1.jpg

6

return to couplet #4

  • Body colour dull black, posterior margin of head with several hairs; one size class of workers . . . . . Camponotus acvapimensis
Camponotus acvapimensis casent0217601 h 1 high.jpg
Camponotus acvapimensis casent0217601 p 1 high.jpg
  • Body yellowish or bicoloured, posterior margin of head with two hairs at most; distinctly different small and large workers . . . . . 7

7

return to couplet #6

  • Underside of hind tibiae bordered by at least six spiny hairs . . . . . Camponotus hova
Camponotus hova casent0146188 head 1.jpg
Camponotus hova casent0146188 profile 1.jpg
Camponotus atlantis casent0249810 h 1 high.jpg
Camponotus atlantis casent0249810 p 1 high.jpg

8

return to couplet #1

  • Propodeum simply rounded without a pair of teeth or spines (genus Monomorium) . . . . . 9
  • Propodeum often with conspicuous spines, at least with a pair of blunt knobs . . . . . 13

9

return to couplet #8

  • Propodeum dorsally with transversely striate sculpture (may be faint in small specimens), body colour either dark brown, or yellow, contrasting with predominantly dark gaster . . . . . 10
  • Propodeum dorsally with very faint shagreened or punctate sculpture or unsculptured, body uniformly pale yellowish to brownish yellow . . . . . 11

10

return to couplet #9

Monomorium destructor casent0104076 head 1.jpg
Monomorium destructor casent0104076 profile 1.jpg
Monomorium mayri casent0249904 h 1 high.jpg
Monomorium mayri casent0249904 p 1 high.jpg

11

return to couplet #9

  • Small to minute ants (HW < 0.40 mm) with small eyes (diameter less than 0.25 times the HW), petiolar and postpetiolar node not wider than long in dorsal view . . . . . 12
  • Larger ants (HW > 0.50 mm) with comparatively larger eyes (diameter greater than 0.27 times the HW), petiolar and postpetiolar node clearly wider than long in dorsal view . . . . . Monomorium nimihil
Monomorium nimihil casent0922181 h 1 high.jpg
Monomorium nimihil casent0922181 p 1 high.jpg

12

return to couplet #11

13

return to couplet #8

  • Dimorphic ants- major workers have broad heads and stout mandibles with two apical teeth and one basal tooth, minor workers have narrow heads and mandibles with seven or more evenly spaced teeth (genus Pheidole) . . . . . 14
  • Monomorphic ants — mandibles With four or five evenly spaced teeth . . . . . 15

14

return to couplet #13

  • Postpetiolar node distinctly higher than petiolar riode, petiole with a ventral translucent projection in major workers, head without any rugulose sculpture in minor workers . . . . . Pheidole lamellinoda
Pheidole lamellinoda casent0907920 h 1 high.jpg
Pheidole lamellinoda casent0907920 p 1 high.jpg
  • Postpetiolar node at most as high as petiolar node, petiole without a ventral projection, usually some longitudinal rugae around eye in minor workers . . . . . Pheidole indica
Pheidole indica casent0281665 h 1 high.jpg
Pheidole indica casent0281665 p 1 high.jpg

15

return to couplet #13

  • Body dorsum entirely without erect hairs (genus Cardiocondyla) . . . . . 16
  • Body dorsum with several to many erect hairs (genus Tetramorium) . . . . . 17

16

return to couplet #15

Cardiocondyla emeryi casent0102968 head 1.jpg
Cardiocondyla emeryi casent0102968 profile 1.jpg
Cardiocondyla longiceps focol0738 h 1 high.jpg
Cardiocondyla longiceps focol0738 p 1 high.jpg

17

return to couplet #15

  • Dorsal outline of alitrunk evenly curved without metanotal groove, whole body covered in long fine acute hairs . . . . . Tetramorium lanuginosum
Tetramorium lanuginosum casent0125328 head 1.jpg
Tetramorium lanuginosum casent0125328 profile 1.jpg
  • Alitrunk outline rather flat with shallow metanotal groove, head and alitrunk with scattered short blunt hairs . . . . . 18

18

return to couplet #17

Tetramorium caldarium casent0102738 head 1.jpg
Tetramorium caldarium casent0102738 profile 1.jpg
Tetramorium simillimum casent0173318 head 1.jpg
Tetramorium simillimum casent0173318 profile 1.jpg