I tried looking on Google if anything preys on demodex – those mites that live in your eyelashes, etc – but didn’t find an answer. My instinct says “no” because not only would someone have likely mentioned it but also I’m sure there’s a very low upper limit to how large an organism can be and still scamper about on your skin without attracting negative attention.
However, we’re not the only lucky species to house freeloading mites and not every animal has access to lice shampoo so I expand my title question: Are there examples of predator-prey relationships that occur completely within the “ecosystem” of a single larger animal? I’m really looking for a few resident bugs playing fox & rabbit in the shaggy forests of some host animal’s pelt. Not so much animals that travel from host to host (tick-eating birds on elephants) or fungi/viruses and the like.