About two months ago I tackled a lice problem. I mixed (in a wheelbarrow) DE, Sevin, and Poultry dust. I dusted each bird (30) under wings, vent, breast, back. I repeated once a week for a month for a total of 4 dustings and cleaned the coop after every time except the last. I was determined to get rid of them. It seemed to work. Until today I picked up one of my roos and noticed he had them crawling on his face. I looked on his neck and back and didn't see any anywhere else. Dusted him with Sevin real quick and isolated him. Also picked up a hen but didn't see any on her. What's the deal?! I know we have a lot of wild birds (ring neck dove, sparrows etc.) and there isn't anything I can do about it as my chickens free range. It's so frustrating! Any tips?