Their bodies are often highly setose, and the pattern of setae is often taxonomically important.

The larvae of muscomorphs (in the sense the name is used here; see below) have reduced head capsules, and the pupae are formed inside the exoskeleton of the last larval instar.

Exit from this puparium is by a circular line of weakness, and this pupal type is called "cyclorrhaphous"; this feature gives this group of flies their traditional name, Cyclorrhapha.

The name Cyclorrhapha is used, in various modern classifications, to represent either a subgroup within the infraorder Muscomorpha, or simply a rankless group within the Brachycera.

In the Tree of Life Web Project, the name "Muscomorpha" refers to the Asilomorpha plus the Cyclorrhapha.