Are differences in song responsible for assortative mating between subspecies of the grasshopper Chorthippus parallelus (Orthoptera: Acrididae)?

Chorthippus parallelus parallelus and C. p. erythropus mate assortatively in the laboratory. Previously it had been assumed that differences in the songs of the males would be responsible for this assortment. However, in the present study, C. p. erythropus females continued to mate assortatively, and readily, with males that had been made dumb by the removal of their wings. Furthermore, this assortment broke down, and matings occurred less readily, following the removal of the antennae of both sexes. With C. p. parallelus the converse applied, i.e. assortment continued after the antennae were removed and mating occurred less readily in the absence of song. This implies that a substantial degree of differentiation (a change in the main channel of communication) has occurred between the mate recognition systems of these subspecies without leading to speciation.