BUSH-CRICKET SONG STRUCTURE AND PREDATION BY THE ACOUSTICALLY ORIENTING PARASITOID FLY THEROBIA-LEONIDEI (DIPTERA, TACHINIDAE, ORMIINI)

Males of most bushcricket species produce acoustic advertisement signa ls to attract females for mating. These signals can also increase cons picuousness to predators. In the genus Poecilimon (Orthoptera: Phanero pterinae) males are attacked by the parasitoid fly Therobia leonidei ( Diptera: Tachinidae: Ormiini) which locates males by their calls. In G reece T. leonidei parasitizes several Poecilimon species with differen t song structures: we examined whether host choice is related to song structure by comparing parasitism rates in two closely related Poecili mon species. One of these species produces monosyllabic songs, the son gs of the other species being polysyllabic. The tachinid fly parasitiz ed the polysyllabic species to a greater extent. We demonstrate in a f ield-experiment that this preference for the polysyllabic species does not depend on local adaptations of the fly. The most probable explana tion for the preference of the fly for the polysyllabic singing specie s seems to be better detection of longer songs. This result is discuss ed in the context of male song evolution.