Whether the flies leave the station to die or die inside all depends on what kind of bait you place inside it. We recommend the Maxforce Granular Fly Bait
which will kill a fly within 60 seconds of landing on it. This means that some flies will die in the station on the bait and some will fly out before they die. If you do have a lot of fly activity, then you would probably want to clean them out of the station every few days until activity was under control. However it is very easy to clean the flies out if you have to do this. The flies are much larger than the bait and will be sitting on top of it. You can take a stick or a plastic knife and just push them out of the station onto the ground or in the trash.