Hi everyone!

We have some really beautiful birch trees near by our house here in Lulea, Northern Sweden. Unfortunately the trees are under attack by malicious intruders! Following links show what it looks like:

http://webnews.textalk.com/upload/banner/document/3301-tb_ohyra1.jpg
http://webnews.textalk.com/upload/banner/document/3302-tb_ohyra3.jpg

Any idea what this is, if it really damages the trees badly (some leaves seem to be riddled with holes..) - and how to get rid of these buggers?

Many thanks in advance!
/Niilo in Lulea, Sweden
/E-mail: niilo@yahoo.com