12 LEAFHOPPERS AFFECTING CEREALS, ETC. 
This is especially true because the means of control for these insects 
are for the most part to be based on entirely different grounds than for 
the Hessian fly, green bug, or other insects to which their injury is 
likely to be referred. 
This question has seemed of importance to me for many years. 
In 1890, in a report to the Division of Entomology, 1 a number of 
species were treated for the central part of Iowa, and in several 
other papers issued while I was connected with the Iowa Exper- 
iment Station will be found discussions of the Iowa species with 
reports of some experimental studies in control. However, so many 
points remained undetermined and there seemed so much need of a 
general survey of the conditions for the country at large that it was 
a special gratification to have the matter taken up by the Bureau of 
Entomology and to be given the opportunity of devoting some time 
to the study. Coming at a time when the Ohio State University 
authorities had generously offered a year's freedom from teaching, it 
has been possible for me to visit many different States and to exam- 
ine field conditions, collections, etc., and in this way to obtain a 
comprehensive view of the situation that would have been entirely 
impossible under other conditions, and which has brought to light 
some measures of control that it is hoped will be of distinct service. 
This field survey has included, in the summer and autumn of 1909, 
trips through the northwestern wheat-growing and grazing sections of 
Minnesota, the Dakotas, Montana, Wyoming, Idaho, and Washing- 
ton; parts of Ohio, Indiana, and Illinois; and Iowa, New York, 
Pennsylvania, Delaware, Maryland, Virginia, North Carolina, South 
Carolina, Georgia, Tennessee, and Kentucky; and in 1910, Missis- 
sippi, Texas, Arizona, southern California, Utah, Colorado, Kansas, 
Iowa, Ohio, and Michigan, particularly the vicinity of Sault Ste. 
Marie. 
SCOPE OF THE PRESENT INVESTIGATION. 
The effort in this present work is to determine so far as possible the 
actual nature and extent of injuries to these crops by leaf hoppers and 
the extent to which they form an economic factor, and to determine 
the conditions which affect their increase and destructiveness, the 
natural agencies which serve to keep them in check, and the possible 
basis for control by management of crops or application of direct 
remedies. The plan has been to make careful examinations of fields 
in the different regions visited, securing data so far as possible con- 
cerning previous history of fields or relation to preceding crops and 
to crops on adjacent fields, and to make extensive collections of 
specimens to determine the actual species present and the relative 
importance of these species to the crops concerned. 
> Bui. 22, o. s., Div. Ent., U. S. Dept. Agr., pp. 26-32, 1890. 
