Phonotaxis during walking and flight: are differences in selectivity due to predation pressure?

Female selectivity was tested in Tettigonia viridissima during two differen t phonotaxis situations; compensated walking and tethered flight. For two o f the three temporal parameters that are important for call recognition in T viridissima, selectivity was similar in the two situations. Selectivity f or the third parameter (minimum interval duration between the double pulses ) was much higher during walking than during flight: walking females respon ded only to stimuli with intervals of 28 ms or longer, while call models wi th intervals of 18 ms were attractive during flight. One interneuron (TN-1) is probably involved in filtering the minimum interval duration. As this n euron is also the most likely candidate for transmitting bat calls during f light, it is suggested that the selectivity differences between walking and flying might be due to the need for detecting predator signals during flig ht, when TN-1 would be occupied listening for bats. With TN-1 unavailable f or song processing during flight, temporal selectivity for the minimum inte rval duration should be reduced, as was found here.