ACOUSTIC SIGNALING IN PALAEOTROPICAL BUSH-CRICKETS (ORTHOPTERA, TETTIGONIOIDEA, PSEUDOPHYLLIDAE) - DOES PREDATION PRESSURE BY EAVESDROPPING ENEMIES DIFFER IN THE PALAEOTROPICS AND NEOTROPICS

When producing its calling song, a male bushcricket exposes itself to predators which use this sound for localization. Male signalling therefore has to be a compromise between attracting females and avoiding predators. In this study, the calling song structure of six Malaysian bushcricket species of the family Pseudophyllidae was examined. The lowest frequency of long-distance signals in insects yet discovered is the 600 Hz produced by Tympanophyllum arcufolium. The peak frequency of all six species and three additional species, from which only handling sounds were examined, was below 12 kHz. The duty cycle (that period of time spent signalling) was low, between one and five percent in four species and more than 20 percent in the remaining two species, typical for species which rely on camouflage. None of the various types of bat avoidance behaviour observed in the neotropical Pseudophyllidae was found in the Malaysian species. This difference is discussed in regard to the possibility of different predation pressures in the Palaeo- and Neotropics.