Temporal patterns of intra- and interspecific acoustic signals differ in two closely related species of Acanthoplus (Orthoptera: Tettigoniidae: Hetrodinae)

Males of the closely related African tettigoniids Acanthoplus discoidales and Acanthoplus longipes produce a long-lasting calling song and a short disturbance sound. The temporal patterns of the sounds were analysed in respect to species differences and song type differences. The calling songs of both species consist of impulses which are separated into verses of two syllables, with fewer impulses in the first syllable. A. longipes produces more impulses in each syllable than A. discoidales and has longer verse durations, verse intervals and syllable intervals. Also, the disturbance sounds, produced after mechanical stimulation, contain distinct verses of impulses. The disturbance sound of A. longipes has a higher number of impulses per verse than that of A. discoidales. The frequency spectra of the songs in both species have similar peak frequencies (around 12.5 kHz) and both species have their greatest hearing sensitivity in the range between 5 and 10 kHz. Females of A. longipes perform phonotaxis only to songs with a species-specific temporal pattern. By contrast, females of A. discoidales react positively to calling songs of both species.