Yay, first butterflies of the year! The European Peacock butterfly (Aglais io) usually spend the winters in buildings or trees, and therefore often appear quite early in the spring. Before it goes into hibernation, it convert some of their blood sugar into glycerol which works as a kind of “anti-freeze” during the cold winter. Clever, eh! After hibernation (March or April), it will lay its eggs, often in batches of 500 (!) at a time and several layers deep to increase the chance that some will be protected from desiccation and birds. In the next coming weeks, the adults have lived for almost a year and they die of old age. Around the same time, the caterpillars of the next generation hatch and in July they form chrysalides, in August they emerge as adults, and in September they go into hibernation. And so the cycle goes on!
Note: It shouldn’t be confused with the American Peacock butterfly (Anartia), they’re not closely related.
More interesting information and pictures can be found on this excellent learning site here