Butterflies that overwinter as pupae can be brought out of the cold roughly 90-150 days after the initiation of the cold weather treatment--depending upon the species and habitat. For butterfly species that have pupae that diapause, they do NOT necessarily need a long summer and then a long winter before emerging. These butterflies tend to not monitor time during the summer. In other words, if someone wanted to shorten the time period between pupation and emerged adults, they could easily expose diapausing pupae to 1 month of summer, and then place the pupae in the refrigerator for approximately 4 months; and then bring them out for emergence.

Another consideration is if you are overwintering pupae with the intent of releasing butterflies back into the wild at the right time, I would first identify when the first generation of your butterfly typically flies in the spring or summer. (Keep in mind that flights can be early or late depending upon precipitation, the timing of spring, and/or the prolonging of winter, etc.) Then, I would keep pupae in their cold cycle until roughly two weeks before the mid-flight of that generation so that you will release adults right when your local populations are in mid flight.