We dust the hens and hen house and nests when the hens seem to scratch a lot and that puts an end to it. I figure they probably have mites but I don't see well, and I don't care to stick my nose down among the feathers to determine whether it's fleas or mites or lice or what! DE is great stuff! I had some kind of bugs in the basement several years ago and put DE around all the walls and haven't seen any bugs since. Don't ask me what kind of bugs, I was new to the area so I don't know. The only critters I tolerate in the house is rabid wolf spiders, they eat everything else, including black widows and brown recluse spiders.