Olfactory responses of two species of grasshoppers to plant odours

Electroantennogram (EAG) responses were recorded from two species of oedipo dine grasshoppers, Oedaleus decorus asiaticus L. (graminivorous) and Angara cris barabensis Pall. (forbivorous), to volatiles emitted by chopped leaves of ten plant species. Male O. d. asiaticus showed much stronger EAG respon ses than conspecific females and both sexes of A. barabensis. Sexual differ ences in EAG responses correspond to different numbers of antennal sensilla of both sexes and to certain behavioural and morphological factors as well . The overall EAG response profiles of the two grasshopper species to the t en plant odours were similar. However, adaptation to host odour might have occurred because of differences in their feeding habits. Females of the gra minivorous O. d. asiaticus possess a significantly higher olfactory sensiti vity for poaceous plant species than A. barabensis, while the forbivorous A . barabensis showed significantly higher EAG responses to Allium senescens (Liliaceae), and a tendency of high responses to composite plant species in comparison with O. d. asiaticus.