Sasakia charonda Japanese emperor, Great purple emperor.
This stamp was issued by Japan in 1956 and depicts the National Butterfly of Japan.
I know this butterfly does not flutter around in Mediterranean gardens but I did so want to recommend the article written by Melissa Hamilton, GOING NATIVE, where she explains how to make the garden into a retreat for local wildlife, butterflies, insects, bees, birds and bats to name a few.
THE MEDITERRANEAN GARDEN number 83, January 2016
This article, illustrated with photos, can also be found on the MGS website