Adaptive developmental plasticity in a butterfly: mechanisms for size and time at pupation differ between diapause and direct development

Diapause (overwintering) and direct development are alternative developmental pathways in temperate insects. Diapause necessitates physiological preparations for dormancy, while direct development is associated with strong time constraints, resulting in selection for fast development under the direct development pathway. Physiological and behavioural preparations for pupation contribute to development time, so divergent selection in them is expected between the alternative developmental pathways. Critical mass for pupation induction is a central physiological parameter for the pupation process. Here, we compare the critical masses and the characteristics of the wandering stage – wandering taking place after the cessation of growth and before pupation – between diapausing and directly developing larvae in the butterfly Pieris napi. Critical mass estimation succeeded only for diapausing individuals, among which it was lower in females than in males, indicating an inter-pathway difference ...