For many organisms, temperature has a significant influence on phenology— the timing of important life events in the natural world (e.g. bird migrations, trees budding, and juvenile insects reaching adulthood). Phenological shifts— interannual changes in the timing of phenological events— have been among the most apparent signatures of climate change. Many phenological events such as the emergence of plants and insects depend on how fast they develop. For example, seeds often require spring temperatures to reach a certain threshold to sprout and begin growing. The plant will develop more rapidly when temperatures exceed the threshold for longer durations and by more degrees, so warm springs accelerate phenology. Insect herbivores often have different developmental constraints than the plants they feed on, so warm seasons can differentially accelerate the phenology of the plants and insects resulting in a phenological mismatch that changes the strength of their interaction. Using insect developmental constraints to predict phenology can inform management decisions such as when to plant crops and when to deploy herbivore or pest control strategies.
The activity and life cycle of insects is highly dependent on temperature. Many insect eggs are laid in the summer and they begin to develop. The insects often spend the winter as eggs or juvenile stages in a state of dormancy termed diapause. Diapause ends and development resumes once spring temperatures exceed their lower developmental threshold (T0,°C).