Death-Feigning in Insects

Tonic immobility is an interesting behavior that occurs reflexively in various animals under physical restraint by predators. The physiological mechanism of thanatosis was extensively investigated during 1960-1980. Researchers have proposed hypotheses to explain the mechanism underlying tonic immobility in vertebrates; local inhibition of the central nervous system, acceleration of the limbic system, abnormal control of the autonomic nervous system. On the other hand, the peripheral and central mechanisms of tonic immobility were intensely investigated at a behavioral and a neuronal level in stick insects and crickets. In the 1970s, behavioral ecology has shed light on the aspect of an ultimate factor for tonic immobility. Ethologists and ecologists challenged this matter in the laboratory and natural habitats, and have collected evidence for its functional roles using mainly insects such as beetles, moths, locusts. More recently, studies of tonic immobility in humans are drawing attention, as clinicians are trying to explain the defencelessness of rape victims from the viewpoint of animal hypnosis.