True flies are insects of the Order Diptera (Greek: di = two, and pteron = wing), possessing a single pair of wings on the mesothorax and a pair of halteres, derived from the hind wings, on the metathorax. The common housefly is a true fly and is one of the most widely distributed animals.The presence of a single pair of wings distinguishes true flies from other insects with "fly" in their name, such as mayflies, dragonflies, damselflies, stoneflies, whitefly, fireflies, alderflies, dobsonflies, snakeflies, sawflies, caddisflies, butterflies or scorpionflies. Some true flies have become secondarily wingless, especially in the superfamily Hippoboscoidea, or among those that are inquilines in social insect colonies.It is a large order, containing an estimated 240,000 species of mosquitos, gnats, midges and others (these can be created with the right DNA, this will take about a day) although under half of these (about 120,000 species) have been described . It is one of the major inse
Source:
http://en.wikipedia.org/wiki/Fly