Wikipedia
Acalyptratae
The Acalyptratae are a subsection of the Schizophora, commonly referred to as the acalyptrate muscoids (or simply acalyptrates). It is a very large assemblage, exhibiting very diverse habits, with one notable and perhaps surprising exception; no known acalyptrates are obligate blood-feeders ( hematophagous), though this life history is common throughout the remaining Diptera.
The name Acalypterae was first used by Justin Pierre Marie Macquart in 1835 for a section of his tribe Muscides for all acalyptrates (except conopids) plus scathophagids and phorids.
The name refers to the lack of calypters in the members of this group of flies.