Photoperiodic induction and termination of diapause in an insect: response to changing day lengths.

Chrysopa carnea diapaused after experiencing a decrease in day length above the critical photoperiod. Animals experiencing increasing day lengths less than the critical photoperiod did not diapause, and those in diapause began to reproduce. These experiments are the first to demonstrate that insects respond to the direction of change in photoperiods (both increasing and decreasing) which do not encroach on the critical photoperiod.