I saw a butterfly get stuck to a web once. It immediately started hurling itself violently away, trying to shake itself free. The spider was not immediately in evidence.
I managed to take the web off it, but not without tearing off the part of the wing that made contact. I assume that in the butterfly's best-case scenario, that would have happened anyway. It was able to fly afterwards.
Ever wonder where those flies have been? Maybe on some nice smelly garbage, and then on your food or your dishes. Flies carry diseases, man.
> and get stuck to some fly paper
Glue traps are cruel.