what are the use of flies?

Answer 1

To keep the front of your pants closed.
Flies are the bottom of the food chain they feed birds, frogs,other insects and so on, also there larva help in decomposition of rotting organic matter.
The number one reason is to pester us.

Answer 2

If you're talking about flies as in fly fishing, they are used to simulate insects to catch fish. They are tied to the end of a "tippet" which in turn is tied to a "leader" and then to the fly line itself. When casting in fly fishing the fly isn't actually being cast as it has virtually no weight. Rather, the line is being cast.
The fly may either float or sink. The floating fly is referred to as a "dry" fly and the sinking fly is a "wet" fly. the wet fly will imitate the caddis, pupae, or emerger stage of insect development. The dry fly imitates the dun or spinner stage. Approximately 95% of a fishes food come from beneath the water in the form of insects, minnows, or crustaceans.

Answer 3

The use of flies is to annoy you and to feed all the horrible spiders

Answer 4

Information about the use of flies here
http://en.wikipedia.org/wiki/Fly#Use_in_medicine

Answer 5

Kind of like natures little garbage men, they eat dead rotten stuff along with the other things they eat. Now this is kind of gross but in certain medical conditions they have used fly maggots in wounds to disinfect them as they will only eat rotten flesh and leave the healthy stuff alone. Hey I said it was gross.