Diurnal periodicity of death-feigning in Cylas formicarius (Coleoptera: Brentidae)

Diurnal periodicity of death-feigning behavior, or thanatosis, was found in adults of the sweet potato weevil, Cylas formicarius (Fabricius) (Coleoptera: Brentidae). The proportion of death-feigned weevils was significantly lower at night than in the daytime only in males. The duration of death-feint was shorter at night than in the daytime in both sexes. The influences of a weevil's behavior prior to being startled (prestimulus behavior) on the proportion of adults feigning death and on the duration of the death-feint were examined. Resting weevils feigned death more frequently and took a longer duration to recover compared to walking ones. The results suggest that, in general, death-feigning is less frequent in active weevils compared to inactive ones. A cost-benefit relationship of death-feigning behavior is discussed in relation to survival and reproduction of C. formicarius.