Diapause in the gypsy moth: a model of inhibition and development

We present here the first recorded age-specific estimates of the developmental response to temperature in diapausing gypsy moth, Lymantria dispar (L.). The effect of temperature on diapause development in gypsy moth eggs was examined by exposing individual eggs to temperature regimes of 5 degrees C interrupted by a single, brief exposure to an experimental temperature. Exposure to each of six experimental temperatures took place at six different times during diapause. The relative effect of the exposure on diapause development was estimated by comparing the duration of diapause in each of the treatments to the duration in a control treatment of constant 5 degrees C. The effect of each temperature did not remain constant throughout the diapause phase and the pattern of change was not uniform among the experimental temperatures. We propose a model of diapause where the developmental phase is controlled by two simultaneous temperature-dependent processes: a typical developmental response to temperature that is inhibited by a temperature-activated biochemical agent, and the temperature-dependent removal of the inhibiting agent. This simple model of two simultaneous and temperature-dependent processes explains 92% of the variability in diapause duration observed in the experimental regimes.