Not so difficult to spot this camouflated barklouse (Psocoptera) among the lichen, is it? It might even sound dumb to be calling this one invisible:
Camouflated Psocoptera at 2:1
Canon Xsi, ISO 200 | f/11 | 1/200 on a 28mm reversed, stack of 2 shots.
Except… how about now, without the help of magnification? The natural view to the naked eye:
Canon Xsi, ISO 200 | f/18 | 1/200 @35mm on a 18-55 5.6 IS