Sound production in the cockroach, Gromphadorhina portentosa: evidence for communication by hissing

Summary

• 1. Sound production of the giant Madagascar cockroach, Gromphadorhina portentosa, was examined by behavioral and acoustical methods in order to determine the functions of the hisses produced by this species.

• 2. Gromphadorhina is able to produce audible hisses from a pair of modified spiracles. Adult males hiss in three social contexts: during aggressive encounters, during courtship (when two types of hisses are discernable), and during copulation. Adults and nymphs of both sexes also hiss when disturbed (Figs 2 and 3).

• 3. There are reliable differences among hisses emitted in these social contexts which depend on several features: the shape of the amplitude envelope (Fig. 4), the relative loudness (Table 1), and the temporal characteristics both of single hisses and of hiss trains (Table 1 and Fig. 4).

• 4. In both courtship and aggression, hissing accompanies characteristic, stereotyped behavior patterns (Figs. 5 and 7); during aggressive encounters between males, hissing is predictive of winning (Fig. 6).

• 5. Males which have been silenced by occlusion of the specialized spiracles carry on apparently normal courtship, but they are unsuccessful in copulating due to a lack of receptive behavior by the female (Fig. 8).

• 6. Playback of recorded courtship hisses during courtship of females by silenced males leads to receptive behavior by females, and to normal rates of copulation (Fig. 8).

• 7. Our evidence supports the hypothesis that G. portentosa has evolved a system of communication in which hisses serve as auditory social signals.