Variability in Calling Signals of the Planthopper Javesella Pellucida (F.) (Homoptera: Delphacidae) in Relation to Temperature, and Consequences for Species Recognition During Distant Communication
Substrate transmitted calling-signals of the planthopper Javesella pellucida were record- ed at different ambient temperatures. Analysis of temporal patterns showed that most time-related parameters, such as durations and rates, were clearly temperature dependent, whereas the basic structure of the signals remained unaffected. Spectral composition and vibration patterns of single sound elements were found to be ex- tremely variable. The results are discussed with respect to some factors that may con- tribute to the variation in acoustic signals recorded from planthoppers: behavioural motivation, signal modification during substrate transmission, environmental con- ditions. An experimental procedure was developed to test the hypothesis, that an effective system of mate recognition in planthoppers would require that distant communication is at least to some extent insusceptible to spatially varying temperature. Females were found to respond remarkably well to play-back of male calling-signals, at temperatures differing by 5°C from the male calling temperature. Temperature dif- ferences of 10°C reduced female responsivity by more than fifty per cent. It is con- cluded that the relevance of temperature dependent parameters to mate recognition in planthoppers is rather limited. Therefore, such parameters, which are often used in describing acoustic differentiation between populations, may not form a proper basis for conclusions on possible acoustic isolation between the populations con- cerned.