Two different vibratory signals in Rhodnius prolixus (Hemiptera: reduviidae)

In this study the substrate-borne stridulatory vibrations produced by Rhodnius prolixus females were recorded and analysed in two different behavioural contexts. In the context of sexual communication females spontaneously stridulated to reject copulatory attempts performed by males. These male-deterring stridulations were fully effective: out of 61 attempts, no copulation occurred. These stridulations consisted of short series of repetitive syllables, each one composed by a single chirp. In the context of defensive behaviour, bugs stridulated if they were clasped or restrained. These disturbance stridulations consisted of long series of repetitive syllables, each one composed by a series of short chirps and a long one. Male-deterring and disturbance stridulations differed in their temporal pattern and frequency spectra, having a main carrier frequency of about 1500 and 2200 Hz, respectively. As no differences in the inter-ridge distances along the whole stridulatory organ were found, the differences in the frequency between both signals could be explained on the basis of a different velocity of rubbing of the proboscis against the prosternal stridulatory organ. It was found that R. prolixus and the related species Triatoma infestans rubbed only the central region of the stridulatory groove (around 1/3 of the total length) to produce disturbance stridulations. The results are discussed in relation to previous work on vibrational sensitivity in R. prolixus and are also compared with results reported for T. infestans.