Photoperiodic determination of insect development and diapause

Summary The hypothesis advanced by James W. Truman to explain the photoperiodically regulated circadian rhythm of adult eclosion in a Saturniid moth has been modified and extended to form the basis of a proposed Developmental Determination Model. This model postulates the synthesis of a hypothetical substance (S) and the kinetics of its metabolism in the presence or absence of light energy. The relationship of scotophase duration to the temporal occurrence of postulated determination response thresholds was estimated in the terms of the hypothetical model. The temporal position of a postulated Determination Gate was also approximated in terms of the model system. The characteristics of the proposed model were designed to be consistent with the observed effects of different 24-hour photoperiods on the incidence of diapause among larvae of the European corn borer,Ostrinia nubilalis. The proposed Determination Model was shown to be capable of generating all four types of photoperiodic diapause reponse curves reported in existing literature.Research supported by the College of Agriculture and Life Sciences, University of Wisconsin, and by a research grant (GM 07557) from the National Institutes of Health.