Overwintering in the Cabbage Root Fly Delia radicum: A Dynamic Model of Temperature-Dependent Dormancy and Post-Dormancy Development

1. Emergence data on adult Delia radicum from overwintering dormant pupae were used to develop a temperature-driven stage dynamics model to analyse development during winter in this species. 2. The model suggests that overwintering has three phases: two in which no morphological development occurs, followed by a third phase or metamorphosis of the pupae to the adult stage (i.e. post-dormancy) culminating in the emergence of the adult. It is proposed that each phase has a different response to temperature and different optima. 3. The biology of the model is in accord with the empirical knowledge about overwintering in this species, and predicted well the patterns of emergence of adults from six cohorts of dormant pupae reared under different temperature regimes.