Make your penis hard and put jam or jelly on your stomach.
When a fly lands on your stomach to eat the jam, pull your penis back and let it go so it springs back, smacking into your stomach, and thus killing the fly.
Yes, it is completely wrong in every sense of the word!
I was a little surprised when Janet asked me if I've ever encountered a flytrapping experience and when I said no, she surprised me with one. I had no idea what I was in for!