Stridulatory sound production and acoustic signals of the longhorn beetle Batocera lineolata (Coleoptera: Cerambycidae)

Insects have evolved different structures and ways to produce sounds which play a crucial role in many aspects of insect biology, such as reproduction and predator–prey interactions. Among acoustic insects, although a variety of stridulatory organs have been reported in beetles, acoustic behaviour of these insects has received little attention. Here, stridulatory organs, sound-producing behaviour and acoustic signals in males of the longhorn beetle Batocera lineolata were investigated for the first time. The detailed morphology of the file and scraper of the stridulatory organ are presented. Behavioural observations showed that sound production was associated with the rapid forward and backward movements of the pronotum. The forward and backward movements of the pronotum can both cause interactions between the file and scraper, and produce forward chirps and backward chirps, respectively. Oscillogram and frequency spectrum comparisons of the upward and backward chirps revealed that the two types of chirps exhibited significant differences in temporal and amplitude features, but had similar spectral characteristics. Acoustic studies on most longhorn beetles are strongly needed, which may make significant contributions in many areas, such as the evolution and diversity of the acoustic behaviour and the possibility of use of sounds in taxonomy of longhorn beetles.