These tiny white things crawled slowly around on a botrichid beetle
that came to my UV light. They looked different than the mites I often see on beetles, so I think they might be some other tiny arthropod. I have never seen white mites on a beetle before, nor have I seen any so oblong in shape.
One possibility I thought of was beetle lice. Some months back I chanced upon a paper online about the lice of Denmark I think. It listed page after page after page of louse species, many with specific hosts, including beetles! Two problems: I don't know what a beetle louse looks like, and even if I did, my lens is inadequate to show much anatomical detail. General shape, size, color, and host is about all we have to go on.