Order consisting of the two-winged 'true' flies. The order contains some 75,000 species arranged in approximately 100 families.

Diptera is divided into three suborders.

Suborder Nematocera
The adults are usually long-legged delicate flies. Their long filamentous antennae have many segments. The larvae usually have a well-defined chitinous head. The pupae are usually free and active. This suborder includes: midges, mosquitoes, gnats, and craneflies

Suborder Brachycera
These are more robust flies than the nematocerans, with various types of antennae, usually made up of various, dissimilar segments. The larva has a less heavily chitinized head which is retractile. The pupa is usually free. This suborder includes: assassin flies, bee flies, and horse flies.

Suborder Cyclorrhapha
The antennae are usually of two small segments with a larger, pendulous third segment; an arista (bristlelike extension) is usually present. The palps usually consist of one segment. The larva is a maggot without a head capsule. The pupa usually has a puparium which is formed from the last-stage larval skin. This suborder includes: house flies, blowflies, botflies, tsetse flies, and fruit flies.

Classification
Diptera is in the subclass Pterygota, class Insecta, phylum Arthropoda.