And then felt bad about it…
Damn. I knew I was a pacifist but I didn’t think I was that pacifist!
It was one of those flys with long legs and big wings. Too small to be a daddy long legs, too not-fly-shaped to be a bluebottle. I flicked it out of the air and then watched it struggle to stand up with broken legs. This is where the bad feeling came.
Then I picked it up and helped it stand. And it flew away… :rolleyes: 
Can something so small feel pain??
A cranefly? Looks like a giant mosquito?
I’m not a pacifist, but whenever I kill bugs, I try to do it as quickly and painlessly as possible. It just seems more humane to always kill in the best way possible, regardless of the creature. I’d feel bad, too, if I’d broken its legs. But I doubt it’s able to feel pain, if that helps a little. It probably doesn’t have room in its “brain” for pain sensors.
“Do flies feel pain?” happens to be a classic Philosophy 101 kind of question, ie: there’s a limit to how much we can know, given that you can’t really ask Mr. Fly to press a red button or raise his little suction cup hand when it hurts.
Flies’ brains are mostly dedicated to visual processing, so there’s not much left over for neural activity. But one study claimed flies learned to associate certain smells with electric shocks. Whether this meant they experienced the shock as “pain” was merely assumed.