Temporal structure of two call types produced by competing male cicadas.

Male cicadas emit sounds to attract females. The acoustic traits of calls vary among species and show unique patterns that dynamically change, even in the same bout. While the calling behavior of a single cicada has been quantified for many species, the acoustic interaction between two or more cicadas has been examined in only a very few species. In this study, we investigated the acoustic interaction between male cicadas (Meimuna opalifera) that utilize two types of calls. First, we caught cicadas and recorded their calls in the laboratory. Second, we detected the calls of each cicada and classified them into two types based on previous studies: type I calls with short duration and high repetition rate and type II calls with longer duration and low repetition rate. The analysis of the chorus structure demonstrated that: (1) cicadas emitted a type II call soon after another cicada emitted a type I call and (2) they sometimes switched call types with each other. Furthermore, we tested the hypothesis that such a timing strategy allowed the cicadas to effectively make call overlap with the signals of competitors compared with the random production of type II calls. Our analysis combining empirical data and simulation did not support the hypothesis (i.e. good overlapping performance was significant for only two of 23 males). While this study revealed a new type of the well-organized chorus structure in M. opalifera, its function, including a possible masking effect, needs to be further examined.