Tettigonia cantans (Fuessly, 1775): avec ou sans Tettigonia viridissima Linné, 1758?

Tettigonia cantans: with or without Tettigonia viridissima? During the survey of the Orthoptera of the Famenne region (Belgium), a special attention was made to the distribution of the two species of Tettigonia. The border between the Ardennes and the Famenne is very suitable to study the different factors influencing the presence of these species. The regional and local distribution patterns can be explained by a combination of two previously formulated hypotheses. The regional distribution patterns are in perfect concordance with the differences in climate en ecology: Tettigonia cantans occurs on relatively cold and wet places, while T. viridissima is clearly exacting. On a more local scale it seems Tettigonia cantans has colonized the Ardennes only recently (historical hypothesis). It is supposed this colonization is still going on. Therefore, places suitable for T. cantans, but only inhabited by T. viridisiimia should be visited in the future. Our observations suggest intrespecific competition between the two species, with an advantage for T. cantans, as long as the ecological factors are suited for this species. Further ethological observations at sites inhabited by both species are needed to confirm this hypothesis.