As the name, Diptera indicates, most true flies have just one pair of functional wings. A pair of modified wings called halteres replace the hindwings. The halteres connect to a nerve-filled socket and work much like a gyroscope to keep the fly on the course and stabilize its flight.

The order Diptera includes all true flies. These insects are distinctive because their hind wings are reduced to small, club-shaped structures called halteres – only the membranous front wings serve as aerodynamic surfaces. The halteres vibrate during flight and work much like a gyroscope to help the insect maintain balance.

Although some families, species, and sometimes members of one sex of flies are apterous (possess no wings), Diptera as a whole can be characterized for possessing only two functional front wings, and a pair of vestigial knob (named halters) behind the wings, that function as organs of equilibrium, helping the flies to remain stable during flight (Figure 1).

The Diptera -- < General Characteristics > < Juv e niles > -- have only one pair of functional wings, hence their name meaning "Two-wing". The hind pair of wings is reduced in size to highly sensory stumps or halteres. The mouthparts are usually suctorial but sometimes piercing or biting, and elongated to form a proboscis.

dipteran, Any member of the more than 120,000 species in the insect order Diptera (the two-winged, or “true,” flies), characterized by the use of only one pair of wings for flight and the reduction of the second pair of wings to knobs used for balance.