INTRODUCTION. 



In the preparation of this paper it was intended to bring together 

 all obtainable information concerning the known species of the gen- 

 era treated, and to give this information in such form as to be of 

 service to the genera] entomologist as well as to the specialist. 



For the purpose of securing for study as large an amount of 

 material as possible, Professor Fernald prepared and sent out a 

 circular letter to a large number of entomologists both in this country 

 and abroad, and we also sent personal letters to all who were 

 especially interested in the Coccidae, asking for specimens. The 

 results have been most gratifying, for a large amount of material has 

 been received from nearly every correspondent. I also spent some 

 time in Washington studying the unrivaled collection of Coccids in 

 the Department of Agriculture where every facility for this work was 

 granted by Dr. L. O. Howard and his assistants. 



It became evident in the course of my work that the genus Chion- 

 aspis in the sense in which it was first established was an unnatural 

 group and must be broken up into several genera. Chionaspis in a 

 restricted sense and Hemichionaspis have been treated of in this 

 paper and it is my intention at some future time to publish the others. 



The generic name Chionaspis has been retained for that division 

 which includes salicis L. and this species should be regarded as Sig- 

 noret's type of the genus, as is shown later in this work, as well as 

 for the genus in its more restricted sense. It may be well to state 

 that the old genus Chionaspis now contains over one hundred species, 

 and that not only in my own collection, but also in that of the Mas- 

 sachusetts Agricultural College are authentic specimens of nearly all 

 of these, as well as a very large number of species in other genera 

 of the Coccidae. 



I take this opportunity to express my sincere thanks to all who 

 have kindly aided me, either with specimens or otherwise, and espec- 

 ially to Mr. Alexander Craw of San Francisco, Cal. for specimens 

 of very choice species ; to Mr. A. H. Kirkland of Maiden, Mass, 

 for numerous specimens collected by himself, and to Mr. C. P. 

 Lounsbury, Government Entomologist at Cape Town, South Africa, 



