Have you ever noticed these little skin-colored (I mean light colored :) ) lice in your house/apartment?
They like to walk on mopboards where there is a layer of dust. I first noticed them in my previous apartment, it was in a very old house and it was very humid (50-70% rH).
They seem to have managed to get into my new apartment during the relocation. Although the humidy is much lower here (30-50% rH).
I always thought they eat the dust but on Wiki it says: "They feed primarily on fungi, algae, lichen, and organic detritus in nature" (Psocoptera article).