Is Tetrix bipunctata a single species with two subspecies, or is it else?

It is well known that the Palearctic species Tetrix bipunctata does occur in two brachypronotal forms that differ by the length of the hind wings. A form with long wings is present in northern Russia, Scandinavia, northern France, Belgium, Germany and the northern Alps. The other form with short wings occurs in Belgium, Germany, the southern Alps and at a few dispersed localities in Southern Europe (like the Sierra Nevada, northern Greece, etc.).

The former has been described as Tetrix bipunctata, while the latter has been named Tetrix kraussi. They were considered full species by Fischer (1948), who studied the populations of Schwaben (southern Germany) and subspecies by Nadig (1991) who studied the Swiss populations.

Some distributional facts are very puzzling:
- the boundary between the two forms in Engadin (Switzerland )is not the watershed of the Alps but a small zone of altitude 1000-2000 meters south of the Maloya pass, were they occur together
- in Germany there also is a small contact zone (esp. Diemeltal)
- in Belgium one form is present north of the Ardennes (on limestone rocks), the other south of the Ardennes (in old sand pits).

Another peculiarity is the fact that when the two species occur together, they have never been found in large populations of both morphs, which makes morphometric studies difficult. Whether this is a coincidence or part of the phenomenon is not known.

Apart from the difference in wing length no other characters have been found to distinguish both forms. It does not seem that the northern form is a hemi- brachypronotal, as does occur in the African genus Xerophyllum (these forms are distinguished by the longer pronotum and the smaller area scapularis).

H.Devriese, 20.11.2005

New research by A. Hochkirch and his team, presented during the 2008 meeting of the DGfO confirms the thesis that Tetrix bipunctata is a single species. Populations from Scandinavia (long wings) and Germany (both long and short wings) do not show any difference when studied with enzym techniques. The publication of the results is planned in 2009.

H. Devriese, 15.03.2009

Literature:
Devriese, H. , 1996 , Bijdrage tot de systematiek, morfologie en biologie van de West-Palearktische Tetrigidae , Nieuwsbrief - Lettre de contact Saltabel 15 : 2-38
Fischer, H. , 1948 , Die schwäbischen Tetrix-Arten (Heuschrecken) , Bericht der Naturforschende Gesellschaft Augsburg, 1948 : 40-87
Nadig, A. , 1991 , Die Verbreitung der Heuschrecken (Orthoptera: Saltatoria) auf einem Diagonalprofil durch die Alpen (Inntal-Maloja-Bregaglia-Lago di Como-Furche), Jahresbericht der Naturforschenden Gesellschaft Graubünden.
Schultes, A.M. , 2003 , Taxonomie, Verbreitung und Ökologie von Tetrix bipunctata (Linnaeus 1758) und Tetrix tenuicornis (Sahlberg 1893) (Saltatoria: Tetrigidae).