Why do flies die when left if the house overnight?

Question

I have done this few times in my life, I find a huge fly I lock it in a room and the next day is death on the middle of the room...why? why they die? of hunger? why they die just like that? do you have any idea?

Answer 1

A flies life span in only 48 hours.  It was just their time.

*bows head in reverence