Tapinoma nigerrimum complex

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The species of the Tapinoma nigerrimum complex are easily separated from other Palaearctic species by cluster analyses of multiple characters. The following characters show the largest differences and may provide a simpler way for identification.

  • Workers: Large-sized and strongly size-polymorphic: The largest major workers of mature colonies have twice the cephalic width (CW) and ninefold the body mass of the smallest minor workers. CW may reach 1385 μm. Species of the Tapinoma simrothi complex are also rather size-polymorphic but CW does not exceed 1050 μm – this allows a separation of both species complexes in 20% of the individuals. Length to width ratio of second funiculus segment larger than in other species including the T. simrothi complex, IFu2900 1.74 - 2.06. The bilateral sum of pubescence hairs and smaller setae protruding at a few micron across margin of clypeal excision is larger than in other species, nExCly900 frequently 7 - 21.
  • Gynes: Much larger than in other species. CW in 58 specimens 1369 ± 59 [1251, 1530]. Species of the Tapinoma simrothi complex are next similar in size and show a small size overlap: CW in 29 specimens 1155 ± 67 [998, 1290]. With all measurements in mm, a safe separation of both species complexes is given by the discriminant D(5) = 30.01 CW - 19.27 CL + 27.42 dAN - 29.71 ExCly - 215.5 Fu2W - 2.05. Gynes of the T. nigerrimum complex have D(6) < -1 and those of the T. simrothi complex D(6) > 1.
  • Males: the genitalia show in ventral aspect a very broad basimere and a broad blade-like harpago (Fig. 11; Seifert 1984a: figs. 8, 9) which easily separates it from all other species complexes (Seifert 1984a: figs. 3-7). The members of the Tapinoma simrothi complex show in ventral aspect a gripper-like harpago and a narrower basimere (Seifert 1984a: figs. 6, 7).

References

Seifert, B., D'Eustacchio, D., Kaufmann, B., Centorame, M., Lorite, P., Modica, M.V. 2017. Four species within the supercolonial ants of the Tapinoma nigerrimum complex revealed by integrative taxonomy (Hymenoptera: Formicidae). Myrmecological News. 24:123-144.