If you're wondering where fruit flies come from, you're probably not going to love this answer. But getting rid of them is easy. If you have been seeing small flies or gnats in your kitchen, they're probably fruit flies. Fruit flies can be a problem year round, but are especially common during. Fruit Fly Feeding. The common fruit fly (Drosophila melanogaster) measures 3 to 4 mm in length and is tan or light brown in color. Fruit flies have protruding eyes.