Temperature dependence of cicada songs (Homoptera, Cicadoidea)

The songs of male Portuguese cicadas Tettigetta argentata, T. josei and Tympanistalna gastrica were recorded at five to seven temperatures within the range 24-38.5 degrees C. To investigate the temperature dependence of the neuromuscular apparatus involved in song production, different temporal elements of the calling songs were measured. We report a strong temperature dependence for the syllable and the echeme rates in T. josei and Ty. gastrica. This suggests that in these species the neuromuscular structures involved in the timbal cycle and in generating the echeme succession of the song are strongly temperature dependent. In T. argentata, the syllable rate was again significantly temperature dependent; the echeme rate, however, increased between 25.5 degrees C and 33.5 degrees C but decreased with the highest temperature. This indicates that at least in T. argentata two separate neuronal networks control both song parameters. Other temporal elements of the song with potential behavioural significance were also measured and found to be temperature dependent (e.g. echeme duration and interval). The possible implications for intraspecific communication are discussed. We also demonstrate that the temperature of these small cicadas is not significantly influenced by the muscle activity involved in song production. On the other hand, exposure to sunlight can be used by these cicadas to elevate their body temperature by more than 10 degrees C.