An unusual song-pattern in the Chorthippus mollis group (Orthoptera: Acrididae): local variant or hybrid population?

Summary

Published accounts of geographical variation in the songs of Orthoptera are briefly reviewed. An unusual song-pattern produced by an isolated alpine population of a grasshopper belonging to the Chorthippus mollis group is described and illustrated with oscillograms. Both the song and morphological characters of this population are compared with those of typical C. mollis and C. biguttulus. The status of the population is discussed and it is concluded that the balance of evidence favours the hypothesis that it is a hybrid population resulting from a cross between these two species.