Negative relationship between ambient temperature and death-feigning intensity in adult Callosobruchus maculatus and Callosobruchus chinensis

Although the effects of temperature on insect behaviours are studied frequently, few studies report on the relationship between temperature and anti-predator behaviours. A negative relationship between ambient temperature and the intensity of death-feigning is found in adults of two seed beetle species, Callosobruchus maculatus (F.) and C. chinensis (L.) (Coleoptera: Bruchidae). Two traits representing the intensity of immobility, the frequency and the duration of death-feigning, are measured at different temperatures. Almost all adults feign death at 15 degrees C, but the frequency of death-feigning decreases at higher temperatures in C. maculatus, whereas all C. chinensis adults show this behaviour at 15 and 20 degrees C and almost all show it at 25 degrees C, but the frequency of death-feigning decreases at 30 and 35 degrees C. The difference between the two species might be due to the specific strain of each species used in the experiment. The duration of death-feigning is correlated negatively with the increase in ambient temperature in both species. The frequency at which adults feigned death is higher in females than in males in both species, but the duration of death-feigning is higher in females than in males only in C. maculatus. The relationships between temperature and death-feigning behaviours are discussed from physiological and ecological viewpoints.