Don't those annoying flies drive you nuts? Makes you want to strangle them! Come to think of it, is it possible to choke a fly?
Here are the facts:
First off, insects breathe quite differently from us. They don't have a central area like our lungs where they gather oxygen; nor do they have a transport system like our heart, which uses blood to deliver oxygen to all of our cells.
Flies, like all insects, breathe through many tiny openings called spiracles. These openings are part of tubes called trachea. Each tube leads to a fluid-filled tracheole, where the oxygen dissolves and then diffuses across the wall of the tracheole and into several of the insect's cells. So there is no central breathing area to block off so that you might strangle a fly.
However, if you wanted to drown a fly, that's another story. The spiracles of most insects can close to keep things like dust out. Therefore, they can hold their breath, so to speak. But if an insect is trapped in water for too long, it will run out of oxygen and eventually drown.