Rethinking diapause timing thresholds in a warming world

Diapause lets insects synchronize their life cycles with seasonal environments, but climate change challenges its effectiveness by reshaping thermal regimes and obscuring seasonal cues. Diapause responses are often described using coarse thresholds such as critical daylength for diapause induction or chilling requirements for diapause termination, but these simplifications overlook the continuous nature of the underlying processes. Even though individual diapause decisions are binary, population-level probabilities of entering diapause follow smooth distributions. Similarly, the rate of diapause termination is likely to be - at least partly - governed by a continuous thermal performance curve. Our perspective provides a parsimonious framework for understanding partial voltinism, rapid evolutionary shifts in seasonal timing, and phenological buffering across time and space. Treating diapause timing as a continuum reveals mechanisms enhancing resilience to climate change, and we argue that incorporating these mechanisms will improve the realism of predictive models for insect phenology, voltinism, and geographical distributions.