Flies are a type of insect from the Diptera order (derived from the Greek word means two and ptera means wings). The most obvious difference between flies and other insect orders is that the fly has a pair of flying wings and a pair of halter, coming from the rear wing, on the metatorax (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.