Evolution
Diptera derive from Mecoptera or a strictly related group. The first true dipterans known are from the Middle Triassic, and they became widespread during the Middle and Late Triassic .
The basal clades in the Diptera are the Deuterophlebiidae and Nymphomyiidae. The Bibionomorpha are a sister clade to Brachycera. The branching order of the remaining clades of the lower Diptera - infraorders Culicomorpha, Psychodomorpha and Tipulomorpha - has yet to be resolved.
Within the Brachycera, several progressively nested groups exist: Eremoneura (three larval instars), Cyclorrhapha (pupation occurs within a puparium), Schizophora (flies that escape from their puparium using the ptilinal sac, an evertable frontal pouch) and Calyptratae (larger flies with wings that have the calypter, an enlarged basal lobe).
The Schizophora include most of the family-level diversity in Diptera (∼85 families) and more than 50,000 species. The Calyptratae form a monophyletic superfamily. Other monophyletic superfamilies include the Ephydroidea, Lauxanioidea, Nerioidea, Sciomyzoidea and Tephritoidea. The relationships between the remaining families have yet to be clarified.
Sister groups to the Drosophilidae consist of two families, Braulidae and Cryptochetidae.
There were three episodes of rapid evolution in the lower Diptera (~220 million years ago), lower Brachycera (180 million years ago) and Schizophora (65 million years ago).
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