Mighty mites. Spider mites in the garden obliterate things every Spring.
The last 5 or 6 years before my retirement, my main building developed a large population of nesting swallows on the exterior walls, and along with them came a building wide infestation of avian mites, with many chewed/bitten ankles including mine. I didn't want to aggressively go after the adults, and chemical treatment of the building was out of the question (vertebrate and invertebrate animal research lab) but my daily morning routine included knocking down all the new nests; Monday's were tough - may have broken an egg or 2. Did manage to get the mites under control, though.