Acalyptratae is a subsection of Schizophora, commonly referred to as the acalyptrate muscoids (or simply acalpytrates). It is a very large assemblage, exhibiting very diverse habits. The name refers to the lack of calypters in the members of this group of flies.
Links: Diptera classification
The first stage in taxonomy, viz. the descriptive stage which is concerned with the characterisation and naming of species. An example of a taxonomic exercise at the alpha level is:
Hines, J.S., 1911. New species of Diptera of the genus Erax. - The Ohio Naturalist 11(6): 307-311.
The next two stages in taxonomy are systematising (beta taxonomy) and evolutionary studies (gamma taxonomy).
Located in the direction of the head when considering a position along the longitudinal axis. Even a structure near the apex of the abdomen has a side that is directed towards the head end and another that is directed towards the apex of the abdomen. Likewise, every structure perpendicular to the longitudinal axis of the body (leg, wing) has a side that is directed towards the head.
Originating from the activity of humans.
Example 1: The most serious historic anthropogenic stress on robber fly (Asilidae) populations has been the destruction of grassland habitat.' Robert A. Cannings Analysis of trends in species occurrence and abundance.
Example 2: 'Musca domestica has an anthropogenic distribution', meaning it has a distibution that is mainly determined by the spreading of the species by man.