vi Preface. 



factorily by his classification of 1910. I have therefore worked out 

 a systematic key to the genera and higher groups represented in our 

 fauna which has recently been published, with my reasons for the 

 changes introduced. In the Homoptera there has been no such complete 

 system of classification as Dr. Renter has given us for the Heterop- 

 tera. Hansen and Kirkaldy have published some fragmentary studies 

 and these have been followed to some extent but I have been unable to 

 accept Kirkaldy's arrangement of the Fulgoridje. There is no ques- 

 tion but he was right in considering this group as of superfamily 

 value but his subdivisions are hardly satisfactory and it has seemed 

 best to follow the old arrangement until something more philosoph- 

 ical has been produced. 



The sequence of the families of the Homoptera here followed is 

 merely tentative but in a general way I have tried to follow that used 

 in the Oshanin Katalog. The placing of the highly specialized Ful- 

 goridae near the bottom of the series seems unnatural, but on the other 

 hand, there is such an obvious advantage in having this List corre- 

 spond as nearly as possible with the latest and best list of the palae- 

 arctic Hemiptera that it has seemed best to waive all personal views. 



Within the genera I have tried to arrange the species so as to in- 

 dicate so far as possible their natural relationships but in some of the 

 larger unorganized homopterous genera the best I could do was to 

 place them roughly into groups. In the heteropterous genus Arcto- 

 corixa even this has been impracticable and there an alphabetical ar- 

 rangement was adopted. In the Chermidse (Psyllidse) I have fol- 

 lowed Crawford's recent monograph, merely changing the nomen- 

 clature in a few points to bring it into line with that used in the other 

 families. 



Nomenclature. 



The rule of priority has been strictly followed throughout this list 

 for all names up to and including those of the superfamilies, or such 

 has been my intention. So far as I know this is the first list in which 

 this plan has been adopted for families and other groups higher than 

 genera and it will serve in a measure to show how the rule will work 

 in the case of family names. It was my intention to follow Dr. Hor- 

 vath's scheme in all its details but as the work advanced it was found 

 necessary to abandon his plan to discard all names not strictly in latin 



