Who Knew?

This morning my roommates and I were talking about bugs, specifically which ones bother us the most/least. I mentioned that flies are least offensive to me, whereupon my roommates informed me that flies throw up every time they land on something. (And by "throw up," apparently that means "rub their legs together vigorously.")

First of all, eww. Second of all, am I the last person on earth to just find out about this? How come I am the only person in my apartment who did not know this fact? People, WHY DON'T YOU TELL ME THESE THINGS?!