This cicada i cannot figure out. Observed in July in Norway. The only bluish species i know of is c. viridis, but that one has a yellow head. Any clues?
This looks like Sonronius dahlbomi - by coincidence I was updating this page earlier today:
http://www.britishbugs.org.uk/homoptera/Cicadellidae/Sonronius_dahlbomi.html