Vibration-Induced Immobility in Coleopteran Insects

Abstract

Many insects demonstrate immobility, such as death feigning (tonic immobility) and freeze responses in the context of interactions within and between species. Immobility is induced by environmental information, including substrate vibrations generated by predators or conspecifics. In this chapter, we review immobility induced by vibrations in the order Coleoptera. Tonic immobility and freeze responses are observed in 18 coleopteran families, particularly in characteristic postures during tonic immobility with extended or flexed legs. Chordotonal sensory organs located in the legs play important roles for detecting vibrations and triggering tonic immobility. Vibration-induced immobility has various functions, e.g., defense from predators, and interactions within the species. As individual case studies, behavioral mechanisms for immobility related to vibrations have been described in the orders Cerambycidae, Nitidulidae, and Scarabaeidae. Adults of a longicorn beetle Monochamus alternatus (Cerambycidae) detect vibrations on their host plant via leg chordotonal organs. They show freeze or startle responses to vibrations, presumably for conspecific and predator recognition. Larvae of a group living beetle Trypoxylus dichotomus (Scarabaeidae) show freeze responses to vibrations produced by both conspecific pupae and mole predators in the soil. Vibrational interactions and freeze responses among larvae and predators in Scarabaeidae also shed light on the evolution of deceptive communication in T. dichotomus.