PHYLOGEXY OF THE NEMOCERA. 26 1 



principle. An arrangement which collocates those families 

 possessing the most archaic characters would seem to be more 

 proper. I would arrange Williston's groups I and 2 at the head 

 of the Nemocera as follows: 



1. Rhyphidae. 



2. Simulidae. 



3. Cecidomyidae. 



4. Mycetophilidae. 



5. Orphnephilidae. 



6. Psychodidae. 



7. Tipulidae. 



8. Dixidae. 



9. Culicidae. 



10. Blepharoceridae. 

 n. Chironomidae. 

 12. Bibionidae. 



I would place the Rhyphidae first, since the venation is archaic, 

 complete ocelli are present, the size is small and the pubescence 

 and leg bristles are primitive. Add to these the structure of the 

 mouthparts which appear to have their prototype in the Myria- 

 poda, and it appears to me that the evidence is overwhelming 

 that the family represents the most archaic type of Diptera; but 

 I shall have more to say on this subject later. 



The Simulidae follow, as they also possess the peculiar structure 

 of the palpi and have a nearly complete mouth-armature and 

 are small in size. The Cecidomyidae come next on account of 

 the many-jointed antennae and the archaic type of eye structure, 

 but I admit that their place in the scheme is tentative. The 

 Mycetophilidae are difficult to separate from the Cecidomyidae, 

 but their eye structure, mouth, tibial bristles and the variable 

 condition of the venation all justify their position here. The 

 Orphnephilidse are usually placed next to the Psychodidae, which 

 is a very old type retaining many archaic characters in eyes, 

 mouth and wings. 



The Tipulidae follow as preserving the oldest type of venation, 

 of leg pubescence and bristle-structure, together with the old 

 types of eye structure, mouth and genitalia. The Dixidae 

 follow as the first family of Williston's second phylum. It is 



