Auditory behaviour of a parasitoid fly (Emblemasoma auditrix, Sarcophagidae, Diptera)

Females of the parasitoid fly Emblemasoma auditrix find their host cicada ( Okanagana rimosa) by its acoustic signals. In laboratory experiments, fly p honotaxis had a mean threshold of about 66 dB SPL when tested with the cica da calling song. Flies exhibited a frequency dependent phonotaxis when test ing to song models with different carrier frequencies (pulses of 6 ms durat ion and a repetition rate of 80 pulses s(-1)) However, the phonotactic thre shold was rather broadly tuned in the range from 5 kHz to 11 kHz. Phonotaxi s was also dependent on the temporal parameters of the song models: repetit ion rates of 60 pulses s(-1) and 80 pulses s(-1) and pulse durations of 5-7 ins resulted in the highest percentages of phonotaxis performing animals c oupled with the lowest threshold values. Thus, parasitoid phonotaxis is ada pted especially to the temporal parameters of the calling song of the host. Choice experiments revealed a preference of a song model with 9 kHz carrie r frequency (peak energy of the host song) compared with 5 kHz carrier freq uency (electrophysiologically determined best hearing frequency). However. this preference changed with the relative sound pressure level of both sign als. When presented simultaneously, E. auditrix preferred 5-kHz signals, if they were 5 dB SPL louder than the 9-kHz signal.