Why do flies rub their hands / legs together?

Mood:

I'm cleeeeeaaannn! -_-'

For sole purpose of grooming their taste receptors. It's apparently on their little hairs. Wonder how it is when you always taste something when you land? ^_^

Fun fact:

Did you know that flies can't eat anything solid? They don't have teeth or any other organs that allow them to do so. They can only get intakes of liquid food. :-O