A comparative study of ultrasound-triggered behaviour in tiger beetles (Cicindelidae)

This study examines the behavioural responses to ultrasound in 52 species f rom the family Cicindelidae using both tethered night and non-flight assays . Tethered flying tiger beetles respond to trains of bat-like ultrasonic pu lses with a short-latency, multi-component behaviour. There was no variatio n in the nature of the behavioural responses regardless of geographical dis tribution or phylogenetic position. Lowest mean behavioural thresholds lie predominantly between 30 and 45 kHz. Sensitivity, however, varies widely, a nd several species do not respond at all in these assays. The lowest thresh olds for responders are most often between 70 and 80 dB SPL. Almost all sub genera of North American tiger beetles in the genus Cicindela have at least some species with low-threshold acoustic behaviour. The single exception i s the large subgenus Cicindela ln where all species are completely unrespon sive or have very high thresholds. There was little relationship between ha bitat and responsiveness to ultrasound, but there is a strong correlation w ith seasonal activity - species with adults active in the spring and autumn tall in the subgenus Cicindela) do not show ultrasound-triggered behaviour whereas summer-active species generally do. Superimposing these data on a current phylogeny of the North American tiger beetles suggests that acousti c behaviour (and hearing) is a shared primitive trait among the taxa examin ed here and that there have been at least five independent losses of this c haracter.