332 S. W. WILLISTON. 



ocelli ; by the loss of the pulvilli ; and the loss of the branch of 

 the third vein, save among some of the Ptychopterinae. The 

 Rhyphidae come next, but they have acquired holoptic eyes 

 in some forms. Of the other families, the Psychodidae and Culi- 

 cidae are perhaps the nearest allied to the original type, not- 

 withstanding the occasional occurrence of multiarticulate anten- 

 nae among the Cecidomyidae. The Culicidae evidently represent 

 an old type geologically, recrudescent in later times. Their fixed 

 venation and antennal structure could only have come from long 

 inheritance in a phylum which has not yet reached decadence. 

 The blood-sucking habit of the mosquitoes is doubtless a rather 

 recently acquired one, probably since the great development of 

 the warm-blooded animals, as is evidenced by the almost innumer- 

 able sexual modifications of the palpi, modifications seldom found 

 among the other families of Nemocera. The mosquitoes doubt- 

 less arose from the Corethrinae, now decidedly on the wane. 

 Every family, save the Tipulidae, is I believe, absolutely excluded 

 from immediate genetic relations with the Brachycera, because of 

 the venation and the antennae. I am, upon the whole, inclined 

 to the belief that Osten Sacken was right in insisting upon the 

 taxonomic importance of the Nemocera, as one of the chief phyla 

 of diptera. 



