Male recognition mechanism for female responses implies a dilemma for their localisation in a phaneropterine bushcricket

The phonotactic behaviour of the duetting bushcricket Poecilimon ornatus wa s investigated on a walking compensator when two females responded to the m ale's call. Whenever two female clicks from different directions were prese nted within the time window, males tracked an intermediate course even when the two clicks were separated by up to 60 ms and differed widely in intens ity. Thus, any signal arriving within that inter val contributes to the loc alization of the female response. The inability of male P. ornatus to selec tively track one of two females is in contrast to previous results found in other bushcricket species which track the leading of two singing animals. We suggest that the intermediate walking is a consequence of the basic ensi feran neuronal processing of song recognition and localization. Choice expe riments in the natural habitat show that - earlier or later during the phon otactic path - the male tracks that female which is favoured by the unpredi ctable acoustic conditions in dense vegetation.