AGONISTIC COMMUNICATION BETWEEN MALES OF A ZAPROCHILINE KATYDID (ORTHOPTERA, TETTIGONIIDAE)

The calls produced by male katydids serve to attract females and repel rivals. Males generally exhibit overt aggressive responses to conspecifics that call within their territories, and intermale spacing is maintained by properties of the call. Here we examine the acoustic behavior of a zaprochiline katydid in which male aggressive behavior and even the ability to detect conspecifics appear greatly reduced. Despite reduced hearing sensitivity, males were shown to detect and respond to the calls of conspecifics using substrate-borne vibrations. During playback experiments males increased their calling rates by decreasing the interval between chirps. However, rather than exhibit overt aggression males would simply change their calling sites when the intensity of playback song was increased. These results were supported by observations of natural encounters between males in the field. The interval between chirps decreased as the distance between calling males decreased, and encounters were always terminated when one male moved away from the other. We suggest that the loss in auditory sensitivity and reduced aggressive behavior of this species may be a consequence of the necessity to aggregate around highly localized feeding sites.