TRANSMISSION AND PERCEPTION OF ACOUSTIC-SIGNALS IN THE DESERT CLICKER, LIGUROTETTIX-COQUILLETTI (ORTHOPTERA, ACRIDIDAE)

Males of the desert clicker, Ligurotettix coquilletti (Acrididae: Orthoptera) defend a female-required resource, the creosote bush Larrea tridentata, in desert habitats of the southwestern United States. Males signal acoustically to each other as well as to searching females. The call is produced by tegminal/femoral stridulation where one or both legs are used for sound production. Sound pressure levels, measured laterally, are influenced by the intervening tegmen between the stridulating leg and the microphone. Differences in measured sound pressure levels between sides can vary up to 7 dB. When clicks are produced multiply, these multiple clicks may be 4 dB louder than single clicks. We examine the structure of the call and the effective broadcast area of single males by monitoring acoustic ascending neurons of the ventral nerve cord in the neck. By taking the neurophysiological preparation into the field, we were able to map the broadcast area of isolated males and also of males calling within aggregations. The distance over which the signal of isolated males could be detected was 8-14 m, whereas neural representation of the calls of males within aggregation were detectable within 4-6 m. The sound spectrum of the song, although having a major lower-frequency component around 10 kHz, has extensive power in the ultrasonic range. The tuning characteristics of the ascending auditory neuron matched the overall structure of the male call. The importance of the acoustic cue, as compared to visual cues, is discussed in relation to female attraction.