Do they move? If so, you have mites or springtails. If not, you have some sort of fungus.

If mites, springtails or fungus they too are helping to decompose items in the bin and get them ready for the worms. To not see them you might want to put some shredded newspaper over the top of them to both dry it out and cover them up. Or you can just watch the free show.

So, no matter what they are, they aren't a cause for worry or a need for a bin adjustment?

Only if they take over.

Just a follow up--they do move. Not fast, and it isn't barely noticeable but my husband and I were STARING at them and they move. What is a springtail?