My parent's home has a problem with them. They seem to appear in waves. They might leave the house in the morning and come back in the afternoon to find 10 of them. We have no idea where they are coming from. Has anybody else experienced this? They are slower than the flies that enter a house when you leave a door open -- so they are easier to catch. Makes me think they are breeding somewhere inside the house and since they were born indoors they are slow and retarded or something. It's really annoying.