No. 64] DIPTERA OF COXNECTICUT : MORPHOLOGY 117 



A second section, the TherevoTnorph-a, centering about the Therev- 

 iclae at the base of the stem, includes four principal superfamilies 

 (and possibly a fifth, whose closest affinites are uncertain). The 

 first of tliese superfamilies, the Therevoidea, includes the Therevidae 

 and the Scenopinidae or "Omphralidae''. The second superfamily, 

 the Asiloidea (in the restricted sense), includes the Mydaidae, the 

 Apioceratidae and the Asilidae. The third superfamily, the Empidi- 

 doidea, includes the Enipididae and the Dolichopodidae. The fourth 

 superfamily, the Bombyloidea (in tlie restricted sense), includes the 

 Nemistrinidae, the Bombyliidae and the Gyrtidae or "Acroceratidae", 

 with the Bombyliidae as the, forms loadino- to the pipunculid-syrphid 

 group at the base of the cj^clorrhaphan stem. A fifth superfamily, 

 the Phoroidea, includes the Phoridae (in the broad sense — i. e., includ- 

 ing the Thaumatoxenidae, etc.) and the Lonchopteridae or "Musi- 

 doridae'', although the latter family is not very closely related to the 

 Phoridae, and may belong elsewhere. The exact location of the Phor- 

 oidea in the phylogenetic scheme is not clear, and the group may 

 belong within the next subclass. At any rate it represents an isolated 

 border-line group, of little phylogenetic interest since it does not 

 appear to lead to any of the other groups next to be considered. 



The cyclorrhaphous Brachycera, or Cyclorrhapha, may be divid- 

 ed into the more familiar groups Acalypteratae and Calypteratae, 

 merely for the sake of convenience, although the presence (or absence) 

 of the calypteres in the members of these groups is not a decisive 

 feature; and the designation "Muscoidea'' is here applied in a much 

 more restricted sense than that in which it is sometimes employed for 

 the cyclorrhaphous families. From the phylogenetic standpoint, the 

 family 8yr])hidae (with the Pipunculidae) is the "key"' group for the 

 evolution of the Acalypteratae, and the family Anthomyidae is the 

 "key" group for the evolution of the Calypteratae. 



The families clustering about the Syrphidae as a center may be 

 grouped in the section Syrphomorpha, which contains several super- 

 families (some of which are not mentioned here). The first, and 

 phylogenetically the most important of these, is the superfamily Syr- 

 phoidea, containing the Syrphidae and the Pipunculidae or "Dori- 

 laidae", with which the somewhat more distantly related Platypezidae 

 may also be included, although the Conopidae, which are usually 

 placed near these families, may belong elsewhere. A second super- 

 family, the ()]-taloidea, containing the Pyrgotidae, the Ortalidae, the 

 Trypetidae or "Trypaneidae", the Richardiidae, and several other 

 families, is practically a direct continuation of the syrphoid stem; 

 and the coiled aedeagus occurring in the males of many of these forms 

 was apparently inherited from certain pipunculid forebears, although 

 the suppression of the sixth abdominal tergite and tlie linking up of 

 the displaced sixth, seventh and eighth abdominal sternites in the 

 males of these insects is perhaps more of a syrphid than a pipunculid 

 feature. 



It is not certain which line of development leads from the ances- 

 tral syrphoid stem group to the families at the base of the calypter- 



