Vibrational cues in the host location of Bethylidae (Hymenoptera Aculeata)

Substrate-borne vibrational communication is widespread in insects and spiders, yet its role in host location by bethylid ectoparasitoids remains largely unexplored. In this study, we investigated the responses of Sclerodermus domesticus Klug and Sclerodermus cereicollis Kieffer to vibrations produced by the feeding activity of their natural hosts, the longhorn beetles Hylotrupes bajulus (L.) and Trichoferus holosericeus (Rossi). Vibrations were recorded using a laser Doppler vibrometer and characterised in terms of biting frequency, damping, and spectral composition, revealing two distinct bite types with species-specific frequency profiles. A new tool, vibrational Y-shaped arena, was developed to replicate and deliver vibrations, allowing the testing of parasitoids behaviour. Choice tests demonstrated that S. domesticus was attracted to vibrations from H. bajulus, whereas S. cereicollis preferred vibrations from T. holosericeus. Behavioural observations revealed increased antennal drumming and leg rubbing in the presence of host-produced vibrations, suggesting that these behaviours are associated with vibrational detection. Our results provide the first evidence that bethylid parasitoids can detect and respond to host-emitted vibrations, highlighting the importance of substrate-borne cues in host location. These findings advance our understanding of bethylid sensory ecology and may inform novel strategies for the biological control of xylophagous pests.