...or book lice, if you wish to call them that. I've been doing a lot of research on these guys since I ended up with them too.
They are little teeny spider/mites that live all over the world, in everyone's houses. They eat paper, bug carcases, etc...They're one of the clean-up crew. LOL! The point is, that there is no way to be completely rid of them, but you can do a few things to reduce their numbers (back to the point where you just don't see them anymore).
They move into our mealworm colonies because we provide a great breeding ground for them...Since we give them mealworm sheddings and adequate moisture, they reproduce so fast, we don't see what hit us.
What you will need to do is put a slices of potato in there and change them out several times a day. The mites will climb on the potato every time you put in a new potato slice, you can remove that many more. Each time you remove a mite covered potato slice, tie it in a plastic bag and throw away outside. Within a few days, you'll see a drastic reduction in these critters. Once you've brought down their numbers, make sure the mealworm colony stays dry-ish. The mealies do not need very much moisture all all.