PREFACE 
The present paper is designed to include the general discussion of 
the group of leafhoppers, with such matter as pertains to the group 
as a whole and with the consideration of the species which have been 
recognized as of the greatest economic importance. It deals on this 
account particularly with those species affecting the cultivated crops, 
although there are many species which live upon wild grasses and 
forage plants of the western ranges that undoubtedly have an impor- 
tant relation to the extent of the pasturage they may supply. 
A second paper which is in preparation will deal more especially 
with the more technical aspects of the group, with a discussion of 
those species which are less noticeable as injurious species or which 
so far as at present known are confined to wild plants or to those of 
little cultural value. A knowledge of these is, however, important to 
economic entomologists, both for the sake of ascertaining their 
economic relations and as a basis for study in case they transfer their 
attacks to cultivated crops. 
In the collection of material for these papers I have had the hearty 
interest and assistance of so many different individuals that I hesitate 
to attempt an enumeration of them, knowing that some must almost 
certainly be omitted. As stated elsewhere, the work was made pos- 
sible by the interest of the officials of the Bureau of Entomology at 
a time when I had an opportunity to leave university duties, and for 
this interest and constant encouragement I am deeply grateful. At 
many localities and institutions where I worked I was given not 
only free access to collections and records, but the direct help of 
information as to available fields for observation and collection and 
often the advantage of personal direction and use of conveyances. 
In this way I am especially indebted to Mr. J. S. McGavren, of Missouri 
Valley, Iowa; the University of South Dakota; Prof. James Wilson, 
Brookings, S. Dak.; Prof. J. Ii. Sheppard, of the North Dakota 
Experiment Station; Prof. R. A. Cooley, of Bozeman, Mont.; Mr. 
George I. Reeves, of the Bureau of Entomology laboratory at Pull- 
man, Wash.; Mr. W. J. Phillips, of the laboratory at Lafayette, Ind.; 
Prof. S. A. Forbes and Mr. C. A. Hart, of the University of Illinois; 
the Carnegie Museum, Pittsburgh, Pa.; Prof. H. A. Surface and Mr. 
V.A.E.Da3cke,Harrisburg,Pa.; Prof. Mel. T.Cook, Newark, Del.; Prof. 
Franklin Sherman and Mr. Z. P. Metcalf, Raleigh, N. C; Prof. A. F. 
Conradi, Clemson College, S. C; Mr. E. C. Cotton, Knoxville, Tenn.; 
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