Hi I find that *looking* at bees is a very poor way of finding mites. Colonies with high mite loads *appear* to have very few on their backs. That is why I prefer to ether roll them. I can only assume the mites are hided on the bees, like you say. This summer, however, I saw a hive that was so heavily infested there were a couple of mites clearly visible on the back of the queen. pb