I couldn't be completely sure as to the proper name for these fly catching devices, though I've heard several variations on the name including (but not limited to): fly tapes, fly stickers, hanging fly traps.

I can be sure about one thing, these things are terribly cruel and awful. They're effective of course, but how anyone can use these and not feel like a sadistic evil little human?

The catchers generally come in a little tube from which you pull a long sticky strip, and it hangs from the ceiling or wherever you might choose to place it. The flies are attracted to it, I believe, and when they land on it, they're stuck. Of course it doesn't kill them instantly, they struggle and get stuck worse and worse until they can't move at all, sometimes by the wings, the legs, whole body. Then they die slowly and painfully.

This reminds me of those evil children who pull the legs and/or wings off of insects. (It also makes me chuckle, because one day they'll try to pull the wings off of a bee, or a poisonous spider.. bwahhaha. Oh, there is my sadistic side shining through.)