Acalyptratae

Acalyptratae is a traditional grouping within the order Diptera, specifically among the Cyclorrhapha, that brings together a large and diverse set of flies that lack calypters. Calypters are small membranous lobes at the base of the wings that cover the wing bases in many related flies, and the name Acalyptratae reflects their absence of these structures. The term has historically served as a practical counterpart to Calyptratae, which possess calypters.

The composition of Acalyptratae has varied with classification schemes, but it includes numerous families across several superfamilies. Some representative groups often cited within Acalyptratae are Drosophilidae (fruit flies), Agromyzidae (leaf miners), Chloropidae (grass flies), Ephydridae (shore flies), and Tephritidae (true fruit flies). The group is highly diverse, spanning many ecological niches and life histories, and its exact membership depends on the taxonomic system in use.

Phylogeny and classification: Modern molecular and morphological studies have shown that Acalyptratae is not a strict, monophyletic clade. It tends to be treated as a broad, often paraphyletic assemblage within Cyclorrhapha, with boundaries to Calyptratae and other lineages not consistently resolved. As a result, some authorities emphasize the historical nature of the term and prefer revised classifications that reflect phylogenetic relationships more accurately, while others continue to use Acalyptratae as a convenient descriptive label with caveats about its non-monophyly.