A Painted Lady butterfly relaxing on a wall in the sunshine. This year Britain saw a huge migration of millions of these butterflies arriving in May and June from the Atlas Mountains of Morocco where apparently the heavy rains had led to the growth of the correct food for the caterpillars. The painted lady has a one month metamorphosis period, that's from being an egg to a caterpillar to a butterfly. Consequently there have been sightings of these butterflies all summer as the eggs of the May/June arrivals are now hatching. In the autumn they will all depart for warmer climes in Morocco and Africa.