Key to Palaearctic Tapinoma

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This key to workers of Palaearctic Tapinoma species only includes those occurring in outdoor habitats (based on Seifert et al., 2024).

This dichotomous key is workable until couplet 9 but this part of the key treated only 38% of the known Palaearctic species. The keying of species groups composed of cryptic species beginning with couplet 10 tried to reduce the number of time-consuming measurements while keeping the error rate reasonably low. Yet, many of the proposed solutions are questionable as they still imply a big workload. Overall, it appears better to numerically record the full set of 15 characters. This takes for the well-equipped, trained and experienced senior author Seifert about 25 minutes per specimen. It is recommended to run then the specimens under investigation as wild-card in a LDA using the data in supplementary information SI1 as reference for determination. Excluded from the key are cosmopolitan tropical tramp species such as Tapinoma melanocephalum and Tapinoma pithecorum which only occur in the considered geographical area in greenhouses.

1

  • Extremely small, SL < 475 µm. Clypeal excision absent or extremely shallow, ExCly <8 µm. Mainly Mediterranean zone of West Palaearctic. Figs. 9–11, Tab. 7 => Tapinoma pygmaeum
  • Larger, SL > 475 µm. Clypeal excision varying from very shallow to deep => 2
  • Seifert et al. (2024), Fig. 9. Tapinoma pygmaeum, head in full face view, Ollon / Switzerland, 2017.05.21.
  • Seifert et al. (2024), Fig. 10. Tapinoma pygmaeum, lateral view, Eekloo / Belgium, 2022.02.04.
  • Seifert et al. (2024), Fig. 11. Tapinoma pygmaeum, anterior head in dorsofronal view, Ollon / Switzerland, 2017.05.21.

2

  • Palaearctic eastwards to 60°E => 7
  • Palaearctic from 60°E to 120°E => 3

3

  • Based on image evaluation of two individuals from Tian Shan and Mongolia: Postocular index large, PoOc/CL >0.42. With all measurements in mm, discriminant 64.89*CL -49.21*CW -63.57*PoOc +20.81*SL -8.45 <0. Apparently a small, very short headed and short-scaped species with shallow clypeal excision, CS 693 and 720 µm, CL/CW 1.016 and 1.053, SL/CS 0.868 and 0.918, ExCly/CS 2.6 and 3.4%. Tian Shan, Mongolia. Figs. 12, 13; Tab. 7 => Tapinoma sinense
  • Discriminant > 0 => 4
  • Seifert et al. (2024), Fig. 12. Tapinoma sinense, type, head in dorsal view, Burgaltai / Mongolia, 1898.09.05; from www.antweb.org, photo Z. Lieberman.
  • Seifert et al. (2024), Fig. 13. Tapinoma sinense (type of T. emeryanum), lateral view, Ak Tash / Uzbekistan, from www.antweb.org, photo Z. Lieberman.

4

  • Second funiculus segment very short, IFu2 < 1.45. Clypeal excision very shallow and always much wider than deep ExClyL/W <0.66. Discriminant 6.469*IFu2 -1.946*ExClyL/W -11.268 <0. Small species from the montane zone of Sichuan /China => 5
  • IFu2 and ExClyL/W larger. Discriminant >0. Unknown from Sichuan => 6

5

  • Mesosoma rather thickset, ML/CS <1.335. Dorsal profiles of mesonotum and propodeum more strongly convex, metanotal depression deeper. Figs. 14–16, Tab. 7 => Tapinoma dabashanica
  • Mesosoma more slender, ML/CS > 1.335. Dorsal profiles of mesonotum and propodeum only feebly convex, metanotal depression shallower. Figs. 17–19, Tab. 7 => Tapinoma sichuense
  • Seifert et al. (2024), Fig. 14. Tapinoma dabashanica, holotype, head in full face view, Gaoguan / China, 2010.05.18.
  • Seifert et al. (2024), Fig. 15. Tapinoma dabashanica, holotype, lateral view, Gaoguan / China, 2010.05.18.
  • Seifert et al. (2024), Fig. 16. Tapinoma dabashanica, holotype, anterior head in dorsofronal view, Gaoguan / China, 2010.05.18.22.
  • Seifert et al. (2024), Fig. 17. Tapinoma sichuense, holotype, head in full face view, Jiuxiangzhen /China, 2009.07.08.
  • Seifert et al. (2024), Fig. 18. Tapinoma sichuense, holotype, lateral view, Jiuxiangzhen /China, 2009.07.08.
  • Seifert et al. (2024), Fig. 19. Tapinoma sichuense, holotype, anterior head in dorsofronal view, Jiuxiangzhen /China, 2009.07.08.

6

  • Margin of clypeal excision forming a sharp cuticular edge beginning from its frontal corners caudad over at least 70% of its length and is in this area at same level as the adjacent clypeal surface It appears as if sharply punched out from a thin plane, plate. Fig.20, right). With all measurements in mm, discriminant 19.06*CW -19.92*CL +70.87*dAN -78.57*EL -0.085*nExCly +50.25*ExCly -110.38*ExOcc +113.82*Fu2L -110.03*Fu2W -16.97*MW + 3.184 < 0 [error 2.4% in 209 individuals, 0% in 67 nest sample means] => Tapinoma glabrella
  • Edge of clypeal excision slightly curving down below the level of adjacent clypeal surface, thus appearing rather blunt. Fig.20, left). Discriminant >0 [error 5.8% in 121 individuals, 0% in 39 nest sample means] => Tapinoma karavaievi

7

  • Second funiculus segment very short, Fu2L/CS <10.9%. With all measurements in mm, discriminant 134.18*Fu2L -14.42*CW -1.184 < 0. very small species, CS <0.65 mm, clypeal excision very shallow, ExCly/CS <3.5%. S Ukraine and S of European Russia. Figs. 21–23, Tab. 7 => Tapinoma kinburni
  • Fu2L/CS >10.9%. Discriminant >0. CS frequently >0.65 mm => 8
  • Seifert et al. (2024), Fig. 21. Tapinoma kinburni, head in full face view, Rybalche / Ukraine, 1982.06.08.
  • Seifert et al. (2024), Fig. 22. Tapinoma kinburni, lateral view, Rybalche / Ukraine, 1982.06.08.
  • Seifert et al. (2024), Fig. 23. Tapinoma kinburni, anterior head in dorsofronal view, Rybalche / Ukraine, 1982.06.08.

8

  • With all measurements in mm, discriminant 20.29*CL-101.78*dAN+23.03*ExCly+81.31*Fu2L-0.728 < 0. Head very short and with notably excavated posterior margin, mean CL/CW 1.035, ExOcc/CS 1.5%. Clypeal excision very shallow, mean ExCly/CS 3.75%. Distance of antennal socket rings large, dAN/CS 0.322. Only known from Greece and Turkey. Figs. 24–26 => Tapinoma festae
  • Discriminant > 0. Character combination strongly deviating => 9
  • Seifert et al. (2024), Fig. 24. Tapinoma festae, head in full face view, Izmir-Konak / Turkey, 2013.05.17.26.
  • Seifert et al. (2024), Fig. 25. Tapinoma festae, lateral view, Izmir-Konak / Turkey, 2013.05.17.
  • Seifert et al. (2024), Fig. 26. Tapinoma festae, anterior head in dorsofronal view, Izmir-Konak / Turkey, 2013.05.17.

9

  • Second funiculus segment more elongated, IFu2 1.912 ± 0.102. Clypeal excision with many pubescence hairs or small setae surpassing the upper margin of clypeal excision (Figs 1, 29), nExCly 16.2 ± 6.3. Usually large and very size-polymorphic, CW 0.938 ± 0.179 mm. With all metric data in mm, discriminant 0.119*nExCly -11.4*CL +11.11*CW +35.02*dAN +8.62*EL -28.01*ExCly +3.85*SL+32.35*ExClyW +19.79*ExOcc +135.45*Fu2L -253.50*Fu2W -12.60*MGr -10.54*ML-12.98*MW +6.15 > 0 [error 0.7% in 966 individuals]. T. nigerrimum group => 10
  • Second funiculus segment less elongated, IFu2 1.606 ± 0.107. Clypeal excision with fewer pubescence hairs or small setae surpassing the upper margin of clypeal excision, nExCly 4.8 ± 3.5. Smaller and less size-polymorphic, CW 0.757 ± 0.115 mm, specimens with CW >1.05 mm extremely rare. Discriminant < 0 [error 0.7% in 960 individuals] => 14

10

  • With all metric data in mm, discriminant -29.5*CW +51.53*dAN +26.6*EL -51.05*ExCly +25.1*ExClyW -29.98*ExOcc +56.41*Fu2L +141.54*Fu2W +63.37*MGR -10.1 > 0 [error 4.7% in 384 individuals]. Largely West and Central Mediterranean but introduced to Central and W Europe and Azerbaijan. Supercolonial. Tab. 3 => Tapinoma magnum
  • Discriminant < 0 [error 2.1% in 582 individuals] => 11

11

  • With all metric data in mm, discriminant 19.04*CL +57.56*dAN -108.18*EL +22.02*ExCly +35.61*ExClyW +26.49*ExOcc -55.39*Fu2L +158.80*Fu2W+22.53*MGr-18.71*ML-12.96*MW +10.40 > 0 [error 0.6% in 161 individuals]. S France and Spain. Not anthropogenously spread. Usually monodomous colonies => 12
  • Discriminant < 0 [error 0.7% in 421 individuals]. Largely West and Central Mediterranean but introduced to Central and NW Europe. Supercolonial => 13

12

  • With all metric data in mm, discriminant 47.25*SL -27.067*CW -28.67*ExCly -0.067*nExCly +87.18*MGr -14.728 > 0 [error 9.6% in 73 individuals, 21 nest-sample means fully separable with D > 0.15]. S France and N Spain. Tab. 3 => Tapinoma nigerrimum
  • Discriminant < 0 [error 4.5% in 88 individuals, 27 nest sample means fully separable with D < 0.15]. Central and S Spain. Figs 27–29, Tab. 3 => Tapinoma hispanicum
  • Seifert et al. (2024), Fig. 27. Tapinoma hispanicum, holotype, head in full face view, Prado del Rey / Spain, 2021.10.20.
  • Seifert et al. (2024), Fig. 28. Tapinoma hispanicum, holotype, lateral view, Prado del Rey / Spain, 2021.10.20.28.
  • Seifert et al. (2024), Fig. 29. Tapinoma hispanicum, holotype, anterior head in dorsofronal view, Prado del Rey / Spain, 2021.10.20.

13

  • With all metric data in mm, discriminant 19.44*CL -113.55*dAN +45.86*ExCly +21.53*SL -39.59*ExOcc -150.05*Fu2L+379.6*Fu2W +21.17*MGr -16.89 < 0 [error 6.2% in 210 individuals and 1.6% in 61 nest sample means]. Tab. 3 => Tapinoma darioi
  • Discriminant > 0 [error 8.5% in 211 individuals and 1.5% in 63 nest sample means]. Tab. 3 => Tapinoma ibericum

14

  • Clypeal excision very shallow and wider than deep, ExCly/CS 4.98 ± 0.67%, ExClyL/W 0.726 ± 0.087. With all metric data in mm, discriminant 54.85*Excly -28.27*dAN -0.04*nExCly -16.46*SL -41.23*ExClyW +38.87*ExOcc +173.50*Fu2L -44.53*Fu2W -4.94*MW + 5.144 < 0 [error 1.2% in 168 individuals] => 15
  • Clypeal excision deeper and at least as deep as wide, ExCly/CS 10.09 ± 1.97%, ExClyL/W 1.752 ± 0.456. Discriminant > 0 [error 3.1% in 782 individuals] => 16

15

  • Workers almost inseparable. Males separable by genital morphology: with all data in mm, discriminant 15.35*SPExc +10.52*SPdT -30.12*dSPST -5.22 < 0 [error 0% in 25 specimens]. Figs. 30–33, Tabs. 2, 6 => Tapinoma madeirense
  • Workers almost inseparable. Males separable by genital morphology: discriminant > 0 [error 1.3% in 77 specimens]. Fig. 34, Tabs. 2, 6 => Tapinoma subboreale
  • Seifert et al. (2024), Fig. 30. Tapinoma madeirense, head in full face view, Belem / Portugal, 2018.03.25.
  • Seifert et al. (2024), Fig. 31. Tapinoma madeirense, lateral view, Belem / Portugal, 2018.03.25.
  • Seifert et al. (2024), Fig. 32. Tapinoma madeirense, anterior head in dorsofronal view, Belem / Portugal, 2018.03.25.30.
  • Seifert et al. (2024), Fig. 33. Tapinoma madeirense, male genital in ventral view, Meio da Serra / Madeira, 2002.06.22.
  • Seifert et al. (2024), Fig. 34. Tapinoma subboreale, male genital in ventral view, Percile / Italy, 2013.06.23.

16

  • Margin of clypeal excision forming a sharp cuticular edge beginning from its frontal corners caudad over at least 70% of its length and is in this area at same level as the adjacent clypeal surface. It appears as if sharply punched out from a thin plane plate (Fig.20, right). With all metric data in mm, discriminant 17.96*CL +74.89*dAN -58.54*EL +72.71*ExCly -15.85*SL -30.07*ExClyW -48.23*ExOcc +43.34*Fu2L -6.606*ML -19.41*MW -0.265 < 0 [error 4.3% in 369 individuals and 0% in 124 nest sample means]. T. erraticum group => 17
  • Edge of clypeal excision slightly curveing down below the level of adjacent clypeal surface, thus appearing rather blunt (Fig.20, left). Discriminant > 0 [error 5.1% in 414 individuals and 0.8% in 134 nest sample means]. T. simrothi group => 19

17

  • Depth of clypeal excision larger, ExCly/CS 8.82 ± 1.35%. Minimum distance of the inner margins of antennal socket rings smaller, dAN/CS 0.286 ± 0.008. With all metric data in mm, discriminant 18.61*CL -37.88*CW +72.70*dAN +43.16*EL -84.94*ExCly +0.111*nExCly +58.18*MGr -10.30 <0 [error 5.9% in 340 individuals and 1.7% in 116 nest sample means] => 18
  • Depth of clypeal excision lower, ExCly/CS 5.90 ± 0.66%. Minimum distance of the inner margins of antennal socket rings larger, dAN/CS 0.301 ± 0.005. Discriminant > 0 [error 0% in 29 individuals and 0% in 8 nest sample means]. South Turkey to South Israel. Tab. 2 => Tapinoma israele

18

  • Second funiculus segment and scape longer, Fu2L/CS 14.28 ±0.40%, SL/CS 1.017 ±0.022. Eye shorter, EL/CS 0.260 ± 0.007. With all metric data in mm, discriminant 47.8*CL +121.79*EL -21.92*SL -39.55*ExClyW -187.68*Fu2L -11.68*ML -13.5*MW +0.16*nExCly -6.69 <0 [error 0.8% in 131 individuals]. Europe east to 24°E. Figs. 35–37, Tab. 2 => Tapinoma erraticum
  • Second funiculus segment and scape shorter, Fu2L/CS 13.41 ±0.40%, SL/CS 0.987 ±0.025. Eye longer, EL/CS 0.271 ± 0.009. Discriminant > 0 [error 0.5% in 209 individuals]. Palaearctic from 11.3°E to 82.3°E. Fig. 20, right; Tab. 2 => Tapinoma glabrella
  • Seifert et al. (2024), Fig. 35. Tapinoma erraticum, neotype, head in full face view, Nespouls-Faugère / France, 2008.07.02.
  • Seifert et al. (2024), Fig. 36. Tapinoma erraticum, neotype, lateral view, Nespouls-Faugère / France, 2008.07.02.32.
  • Seifert et al. (2024), Fig. 37. Tapinoma erraticum, neotype, anterior head in dorsofronal view, Nespouls-Faugère / France, 2008.07.02.
  • Seifert et al. (2024), Fig. 20. Clypeal excision of Tapinoma karavajevi (left) and T. glabrella (right); the broad white reflexion in the left picture indicates the blunt margin of clypeal excision.

19

  • With all metric data in mm, discriminant 0.045*nExCly+63.44*PoOc -35.80*dAN +64.72*EL +68.58*ExCly -30.02*SL -23.56*ExClyW +94.64*ExOcc -33.70*Fu2L -96.79*Fu2W -28.09*MGr +2.305 > 0 [error 3.9% in 205 individuals and 0 % in 66 nest sample means]. Mediterranean region from 10° W to 16°E but occasionally introduced farther east => 20
  • Discriminant < 0 [error 4.3% in 208 individuals and 1.5% in 68 nest sample means]. South Palaearctic from 33°E to 73°E => 21

20

  • With all metric data in mm, discriminant 17.82*CW -30.01*CL -82.78*dAN +86.78*ExCly +35.53*SL +64.0*ExClyW -125.50*Fu2W +1.36 < 0 [error 6.0% in 84 individuals and 0 % in 26 nest sample means]. Mediterranean zone between 9 and 16°E, few introductions outside this area. Figs. 38–40, Tab. 5 => Tapinoma insularis
  • Discriminant > 0 [error 7.4% in 121 individuals and 0 % in 40 nest sample means]. Mediterranean zone between 10°W and 10°E. Tab. 5 => Tapinoma simrothi
  • Seifert et al. (2024), Fig. 38. Tapinoma insularis, holotype, head in full face view, Portopalo / Italy, 2013.04.02.
  • Seifert et al. (2024), Fig. 39. Tapinoma insularis, holotype, lateral view, Portopalo / Italy, 2013.04.02.
  • Seifert et al. (2024), Fig. 40. Tapinoma insularis, holotype, anterior head in dorsofronal view, Portopalo / Italy, 2013.04.02.

21

  • With all metric data in mm, discriminant 0.111*nExCly -77.37*CL +75.45*PoOc +56.02*dAN+117.44*EL +30.22*SL +83.70*ExClyW -70.58*ExOcc -140.86*Fu2L -214.17*Fu2W +79.04*MGr +13.60*MW -3.077 < 0 [error 5.7% in 87 individuals and 0% in 28 nest sample means]. Tab. 5 => Tapinoma phoeniceum
  • Discriminant > 0 [error 4.1% in 121 individuals and 0% in 39 nest sample means]. Tab. 5 => Tapinoma karavaievi

References

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