Four families are often placed here: (Note that the Mystacinobiidae, while also a bat fly, belongs to the superfamily Oestroidea).

[2] The family Glossinidae, monotypic as to genus, contains the tsetse flies, economically important as the vectors of trypanosomiasis.

The enigmatic Mormotomyiidae are believed to belong to the Ephydroidea and not to Hippoboscoidea as previously construed.

[3] In older literature, this group is often referred to as the Pupipara ("pupa-bearers"), because, unlike virtually all other insects, most of the larval development takes place inside the mother's body, and pupation occurs almost immediately after "birth" – in essence, instead of laying eggs, a female lays full-sized pupae one at a time.

Instead, the larvae hatch in utero, are fed internally by "milk glands," and pass through three morphological stages before being deposited to pupate.