Portrait of a fly, made with magnification 6 and f/11 using a Canon 7D, a Canon macrolens MP-E 65mm/f2.8 and a Canon 2x teleconverter. The fly was alive and busy in the garden.
True flies are insects of the order Diptera (from the Greek di = two, and ptera = wings). They possess a pair of wings on the mesothorax and a pair of halteres, derived from the hind wings, on the metathorax.
Diptera is a large order, containing an estimated 240,000 species of mosquitoes, gnats, midges and others, although under half of these (about 120,000 species) have been described. It is one of the major insect orders both in terms of ecological and human (medical and economic) importance (source: Wikipedia).