What I can't figure out is how they are getting in. I had the same problem last year and their dead bodies are all in the same location on the floor. I'm thinking they're coming in thru the dryer vent where I've sprayed and then dying soon after.
Are you getting a lot? Or just one or two every now and again? If it’s several dead after you spray, might be a nest somewhere. Stand outside and see if you notice where theynare going in. You can use foam sealer to seal it off if you find it. Sounds like the spray is working though.