For butterflies and skippers, surviving winter demands a period of dormancy known as hibernal diapause. This multi-step process suspends development or reproduction at the onset of cold weather, and is initiated by a hormonal response to changing environmental conditions, particularly the length of day and temperature. These same conditions trigger the end of diapause the following spring, as daylight lengthens and warmer temperatures return. At such time, development and reproductive processes return to normal.
