SONG PRODUCTION AND SONG RECOGNITION IN A GROUP OF SIBLING GRASSHOPPER SPECIES (CHORTHIPPUS DORSATUS, CH. DICHROUS AND CH. LORATUS: ORTHOPTERA, ACRIDIDAE)

ABSTRACT

1.	Chorthippus dorsatus, Ch. dichrous and Ch. loratus are closely related, sympatric grasshopper species (subfam. Gomphocerinae) with few morphological differences.
2.	Songs of males contain two elements: pulsed syllables produced during synchronous movements of the hindlegs (part A) and ongoing noise produced during alternating movements of the hindlegs (part B). Part A predominates in songs of Ch. loratus and part B in songs of Ch. dichrous. In Ch. dorsatus both parts contribute nearly equally to the songs.
3.	Ch. dichrous and Ch. loratus are Eastern species, while Ch. dorsatus occurs all over Europe including Spain and Italy. The songs of different populations of Ch. dorsatus in Europe are compared.
4.	Female stridulation of the three species is similar to male stridulation.
5.	Females prefer—expressed by their response songs—the conspecific signals over heterospecific ones. Discrimination, however, is not perfect.
6.	Tested with artificial song models, females of the different species differ clearly in their response functions for element numbers in part A, while Ch. dorsatus and Ch. dichrous females show nearly identical responses to varied durations of part B. Individuals of a Greek population with male song characteristics intermediate between Ch. dorsatus and Ch. dichrous show intermediate female response functions as well.