On this day, St. Urho drove the grasshoppers out of Finland and by doing so saved the Finnish grape crop. More from SaintUrho.com and from the 1800+ fans of the St Urho page on Facebook.
Heinäsirkka, heinäsirkka, mene täältä hiiteen!
Traditionally: wear purple, celebrate by drinking wine.
As it turns out, Urho didn't complete his task, and a 2009 book Suomen heinäsirkat ja hepokatit ("The Grasshoppers and Crickets of Finland") describes the species of orthoptera found in Finland. The web site includes several sound samples, so if you always wanted your phone's ring tone to sound like a Finnish grasshopper, here's your chance.
More photos on Flickr: Grasshoppers and crickets, Finland, by Dr Sami Karjalainen.