104 



NORTH AMERICAN DIPTERA. 



never be accepted by dipterologists in general. And 

 secondary sexual characters should also be tabooed so 

 far as possible, since they represent merely evolutional 

 instability. 



The formation of so many genera from these slight 

 characters, is, however, no worse than the attempt to 

 classify and name genera and species purely from the 

 larval stage, which has been done to a degree never be- 

 fore attempted by scientific dipterologists. 



Upon the whole the characters made use of in the fol- 

 lowing table, verbally modified from Dyar and Knab, 

 come nearest to my own views of proper classificatory 

 characters for the family. I am not able to test the table 

 thoroughly, and cannot vouch for it, but I believe it to 

 be the best that has so far appeared. The student ma}' 

 also consult a recent table of the genera published by 

 D. W. Coquillett.* 



The habits of the immature stages of the Culicidse are 

 so familiar to all that little need be said here regarding 

 them. 



The eggs are laid by the females upon the surface of 

 stagnant or nearly stagnant water, in groups or singly, 

 whence the young larvae, hatching, descend into the 

 water to form those active little creatures of the rain- 

 barrel, commonly known as 'wigglers'. The pupal stage 

 is less active, passed in large part near the surface of the 

 water, hanging by the respiratory tubes. The adult in- 

 sect emerges from the pupal skin through a rent, using 

 its discarded shell as a temporary raft until its wings 

 are fully extricated. 



The following description of the larvae of the mosqui- 

 toes is paraphrased from Dyar and Knab : 



* Bull. U. S. Dept. Agric. Tech. Ser. No. 11 (1906). 



