Auditory-based defence against gleaning bats in neotropical katydids (Orthoptera: Tettigoniidae)

Neotropical katydids (Orthoptera: Tettigoniidae) are preyed on by gleaning bats, which are known to use male calling songs to locate them. At least one katydid species has been reported to stop singing in response to bat echolocation calls. To investigate the relationship between this behavioural defence and ecological and sensory factors, we surveyed calling song characteristics, song cessation in response to the echolocation calls of a sympatric gleaning bat (Trachops cirrhosus), and T-cell responses (an auditory interneuron sensitive to ultrasound) in five katydid species from Panama. The two katydid species that stopped singing in response to bat calls (Balboa tibialis and Ischnomela gracilis, Pseudophyllinae) also had the highest T-cell spike number and rate in response to these stimuli. The third pseudophylline species (Docidocercus gigliotosi) did not reliably cease singing and had low T-cell spiking activity. Neoconocephalus affinis (Copiphorinae) produced continuous calling song, possibly preventing males from hearing the bat during singing, and did not show a behavioural response despite high T-cell activity in response to bat calls. Steirodon rufolineatum (Phaneropterinae) did not cease singing and differed in T-cell activity compared to the other species. T-cell function might not be conserved in katydids, and evidence for this idea is discussed.