April, ’20] 
DAVIS: GREEN JAPANESE BEETLE 
189 
There is a possibility that beetles have been carried out and become 
established outside of the known infested area, but the limits of the 
infested area are as nearly accurately known as the most careful study 
by competent men can make them. This conclusion is reached be¬ 
cause: (1) Throughout the season of beetle flight experienced men were 
kept continuously scouting the outskirts of the known infestation and 
constantly making beetle collection excursions into the outlying terri¬ 
tory; 1 (2) Every report of supposed Japanese beetle occurrence outside 
of the area, both in New Jersey and Pennsylvania, was traced out but 
with negative results in every case; (3) Areas of favorite food plants 
on the west side of the Delaware river in Pennsylvania were carefully 
scouted for the presence of the beetle just after the close of the period 
of maximum spread without finding the beetle; (4) This imported 
beetle has been well advertised by the distribution of colored poster 
charts, newspaper articles and specimens themselves in all sections of 
the United States and Canada and regardless of this publicity we have 
received no report of the occurrence of the beetle outside of the reported 
findings in New Jersey and Pennsylvania, all of which were investigated 
as already noted. 
The area known to be infested is now about 15,000 acres as compared 
with 4,000 acres or more in 1918 and the rate of spread during the past 
season has averaged about one mile with a maximum spread of three 
miles in any one direction. The beetles began to issue the last of June 
and reached their maximum abundance early in August and although 
they were present until the last of October this past year the date of 
maximum spread was August 30. 
Object and Plans 
Owing to lack of the necessary funds and for other reasons already 
noted plans for eradicating the green Japanese beetle have been laid 
aside. Our project is now to control the bettle and to prevent, so far 
as possible, the further spread of the insect and at the same time to 
discover practical control measures and introduce the natural enemies 
from Japan. 
Methods of Accomplishing These Objects 
1. The Introduction of Native Natural Enemies is a logical 
undertaking and plans are being made to send a thoroughly equipped 
entomologist to Japan to spend not less than a year in that country 
studying the conditions in relation to the beetle, the parasites attacking 
1 Accurate records of beetle occurrence were kept by using maps printed on cross- 
section paper, the perpendicular lines lettered and the vertical lines numbered; thus 
in the notes a record at A25 shows that the beetle was found within an area of 264 
feet of where vertical line 25 crosses perpendicular line A. 
