wood lice in old firs

[park ranger]

A friend of mine here in western Washington has some big Douglas firs.  He asked me if I know what the wood lice in the bark of the firs would be hurting the trees.  They are all thru the bark on all the trees, just way more than you would expect.  These things are like flat potato bugs.  This is a very nice stand of old growth right on the salt water near Bremerton.  Any ideas?

[DRB]

Harmless they do not eat wood

http://en.wikipedia.org/wiki/Woodlouse