Fly is a type of insect from the Diptera order that comes from the Greek "di" means two and "ptera" means wing. The most obvious difference between flies and other insect orders is that flies have a pair of flying wings and a pair of halter, coming from the rear wing, on metastax (except for some fly species that can not fly). The only other insect order that has two wings that actually function and has a dumbbell is Strepsiptera. However, unlike flies, the Strepsitera dumbbell is in mesotoraks and wings in the metastax.
Thanks 
