by 'fly strips', I hope you mean the 'No-Pest Strips', and not the sticky, gooey fly strips ... if the No-Pest strips don't kill them , you might consider FIRE !! :jumphappy: ... just kidding, don't use fire ... I've used the No-Pest strips for many years, and never had an insect in the room, (but I never had to use them to get rid of insects already present), maybe they don't work that way ... ?? ... good luck, let us know what works :jointsmile: