There are two species of butterfly which we see at this time of year which have a completely differently life cycle from our other butterflies. These are the Red Admiral and the Painted Lady. These two species are powerful fliers and just like migrant birds they migrate to Britain each spring from their wintering grounds in the Mediterranean region.
They usually arrive in May and June but the numbers arriving vary considerably from year to year. In some years their numbers can be in the millions whilst in others very few arrive. Last year, 2019, the Painted Lady was very numerous and it was one of the best years ever for the species.
On arrival they lay eggs on thistles in the case of the Painted Lady and on nettles for the Red Admiral. These develop through the summer and a new generation of adult butterflies emerges in August, sometimes in spectacular numbers. Both species are large and colourful and will be familiar to people with gardens. The Painted Lady is salmon pink with black and white patches at the tips of the forewings. The Red Admiral is predominantly black with conspicuous red stripes and white blotches toward the wing tips.
These two butterflies are frequently seen in gardens, even in urban centres, and are especially attracted to Buddleia and other nectar rich flowers. Later in the summer this provides them with the energy to make the return migration to their winter quarters around the Mediterranean. Each autumn both the Painted Lady and Red Admiral must fly south again. This is because these two butterflies cannot survive the cold of a British winter and would die if they remained here. So they must go to warmer regions in the winter to survive, in many ways just like the birds which are summer visitors from the south.