Symbiosis again

Bit of a manic day today; overseeing packaging waste returns, reissuing and environmental aspect and impact register, trying to gee folks up for Earth Day 2012 (projects so far - cycle to work days, beehives and bees at sites, huuuge big litter-pick, waste-at-work day) and then to the gym where I ragged myself for an hour to fit in 20km of cycling up (virtual) hills and 2km of hard rowing (on level 10 natch).

Did not, therefore, have much blipportunity (heh!) time and this will have to suffice.

They grow on a Silver Birch just outside my office in Hereford. I can't work out whether the yellow/ green one is Xanthoria paretina or not. They grey one has had me stumped for a bit but I'm plumping for Hypogymnea phydodes. I'm hoping ceridwen might be able to help?