Daily Eclosion Patterns in Nymphalid Butterflies (Lepidoptera: Nymphalidae): Interspecific and Intraspecific Variation

Abstract

Eclosion, the molt from pupae to adult stage, occurs at specific times of the day in many holometabolous insects. In this study, we explored the daily pattern of eclosion and the extent to which it varies both within and among six species of nymphalid butterflies. Our broad goal was not only to document the variation in eclosion times, but also to evaluate, through comparative analysis, predictions from several potential adaptive explanations for when during the day eclosions occur. For all species, we reared individuals to pupation, and, at the beginning of the pupal stage, placed the pupae in a greenhouse and recorded their eclosions with a video camera. From these recordings, we obtained for each pupa the time of day at which eclosion occurred. All six species exhibited eclosion distributions that were significantly clustered in the hours around and immediately after sunrise. Only females of the Monarch butterfly showed a non-clustered pattern of eclosion times. There were no sexual differences in eclosion times for any species. The data on interspecific differences in the daily pattern of eclosion do not fit predictions from the known interspecific differences in the daily timing of mating. The data do not fit the prediction that elevated avian predation in the morning will favor eclosion at other times during the day.