XXX INTRODUCTION. 



Group 2. Heterodact3'la. 



Superfaiiiily 1. Procephala. Families Mydaiilfe, Asilidaa, 

 Bombyliidae. 

 Tribe 6. Orthogenya. Families Enjpidida?, Dolichopodidas. 



SUBORDER CYCLORRHAPHA. 

 Section I. Aschiza. 



Tribe 1. Syrpliidas. Families Syrphidaj, Pipunculida;. 

 Tribe 2. Hypocera. Families Phoridaj, Platypezidaj. 

 Section II. Schizopliora. 



Tribe 3. Eumyidte. Muscidea of the present work'. 



Superfamily Schizometopa. Calyptrataj of the present work. 

 Superfamily Holometopa. Acalyptrata> of the present work. 

 Tribe 4. Pupipara. Pupipara of authors. 



Osten Sacken, however, objects to this chissifieation and 

 offers valid reason to sustain his objections, at least so far as 

 the Orthorrhapha are concerned. He insists that the Nemato- 

 cera and Brachycera are natural divisions and bases their 

 distinction ultimately upon the palpal characters. He says 

 that for some unexplained reason later authors have neglected 

 these characters and have concentrated their attention upon 

 the antennae. In this statement, however, I think that Osten 

 Sacken is somewhat unjust. The characters of the palpi 

 have been used by both Schiner and Brauer, as well as in my 

 own classification, and stress has been placed upon them. 

 Schiner states explicitly that Nemistrina Ivas three-jointed pal- 

 pi, and it is known that Aedes, as well as some genera of Ce- 

 cidomyidae, have but a single palpal joint. This being the case, 

 it is seen that the character of the palpi is not the ultimate 

 distinction between the two groups. As I have already said, 

 there are never more than four articitlated joints among the 

 diptera in the palpj, and tlie great majority of the Cyclorrha- 

 pha have none, the basal process or projection being all that 

 is present, and this will usually if not always be found, albeit 

 often in a rudiment condition, among all forms of the order. 



I give Osten Sacken's classification at length, as follows : 



