Tortoiseshell Butterfly. According to info
The adult butterflies can be seen at any time of the year, even on the last days of December or first days of January if the temperature is high enough to wake them from hibernation. However, adults normally emerge from hibernation at the end of March and start of April.
It doesn't say what happens if the weather changes to cold. It might be ok if it can find some food.
...and those who were seen dancing were thought to be insane by those who could not hear the music.FN