Review of the Classification of the Schizophora

Abstract

The classification of the Schizophora has long been recognized as presenting formidable difficulties, not the least of which is the sheer number and diversity of the species and species-groups included. Conventionally the group has been divided into two ‘sections’, the Acalyptratae and Calyptratae. The current delimitation of these ‘sections’ was worked out by Girschner (1893), whose work was a major advance in the field of classification. However, only the Calyptratae in Girschner’s revised sense constitutes a probable monophyletic group. The ‘Acalyptratae’ are a residual group (paraphyletic in Hennig’s sense) which contains all Schizophora excluded from the Calyptratae. Such groups do not belong to the phylogenetic system. I doubt whether even adherents of other principles of classification would find the group ‘Acalyptratae’ satisfactory, if they examined it critically. It seems of little value for purposes of identification, since I have not yet seen a key in which members of all groups of Schizophora are likely to be taken under the appropriate alternative in the couplet where the ‘Acalyptratae’ and Calyptratae are separated. One of the consequences of my rejecting the group ‘Acalyptratae’ is that the group Calyptratae loses relative rank because of subordination to a wider group (Muscoidea in the new sense proposed below). This does not necessitate a change of name, since the name Calyptratae carried no connotation of rank. This relative downgrading of the Calyptratae was already implied in Hennig’s (1958) treatment.