This butterfly can be encountered in almost any month of the year in both North America and Europe. In Britain it is a rare migrant and it is known as the Camberwell Beauty. According to the eighteenth century lepidopterist Moses Harris, who also called it the Grand Surprize, "This is one of the scarcest Flies of any known in England." Here on Vancouver Island its numbers are quite variable, though it is not often common, and it is most often seen in April or May after spending the winter in hibernation as an adult. The highly gregarious caterpillars feed on willow and elm.