Thanks a lot. Pictures look identical. So, It is Agelastica alni? [Chrysomelidae]. That time and that region it was very abundant with several larvae on each leaf.
Igor.
I haven' got it confirmed. I put the question on a swedish coleoptera forum, but no reply there. There were as you say several larvae on each leaf. The name fits (alnus=alni), but there might be other species that looks similar. There aren't many photos depicting the coleoptera larvae to compare with either. As you see on the other thread I have put a link to the german site with a photo of the Agelastica alni larvae.
Tried to attach an image to a forum post. jpg, 32kB, 72dpi, no blanks, ... File name is correctly displayed, but when I click "Preview Thread" it just vanishes. Help!