Shit- that would scare the crap out of me.

Wow that fly would scare the hell out of me if I saw one too...

I noticed some mentioned Cockroaches and couldn't help to think of Creepshow :D ah what a great classic that is, I need to revisit that one soon.

It's hard to choose something that hasn't already been done, I know one has even been done on Ticks but hey those things still scare the hell out of me. It would be tough to make a movie on them though as the cheesy film in the 90s (I believe) already proved.