Most butterflies spend the vast majority of their lives from caterpillar through to a fully grown adult butterfly in quite a small geographic area, and generally they don't move more than a few hundred yards during this time.  Some butterflies that do move to a new area, often move as the direct result of human intervention. For example it is thought that the rise in Essex Skipper colonies across central England is because their eggs have been moved from one area to another with the transportation of Hay.

But there are two butterfly species that migrate North to our shores on a regular basis, and these are, Clouded Yellow, and Painted Lady.

The numbers of migrating butterflies each summer varies considerably from year to year, but in some years the numbers involved are truly massive.  Each year, Painted Lady butterflies originate from the High Atlas Mountains in Morocco and then fly North during the summer.  They pass through mainland Europe and each year some will end up visiting Britain.

In the spring of 2009 there were a incredible number of Painted Lady butterflies reaching our shores, the numbers involved were many many millions.  Indeed it was said that at some coastal sites the numbers arriving were over 50 per minute.

I certainly recall several days at different locations where there was a large stream of Painted Lady butterflies passing through all going in the same direction.  Not quite the same sight as the great migrations in the Serengetti, but it was a great sight actually seeing a natural migration from the windows of your own home.

Being such a spectacle, and with the numbers involved, the 2009 Painted lady invasion became newsworthy  and was widely reported in the press.  Internet information and press reports at the time suggest that over a billion butterflies entered Britain during the summer of 2009.