August, ’23] 
HADLEY: JAPANESE BEETLE SPREAD 
349 
SPREAD OF THE JAPANESE BEETLE, POPILLIA 
JAPONICA NEWM. 
By C. H. Hadley, Entomologist and L. B. Smith, Entomologist, U. S. Department 
of Agriculture 
Abstract 
The area of infestation by the Japanese beetle has increased from less than one 
square mile in 1916, when it was first discovered in Burlington County, New Jersey, 
to 773 square miles at the end of the 1922 season, comprising adjacent portions 
of Pennsylvania and New Jersey. 
It is believed that the spread to date is largely a natural spread on the part of the 
insect, by means of flight in search of food and suitable breeding grounds. Winds, 
storms, and waterways are also factors of some importance in the natural spread of the 
insect. 
Artificial agencies are important factors affecting the dispersion of the insect, 
especially the movement from infested areas of farm products, particularly sweet 
sugar corn; vehicles of all kinds, and pedestrians traveling through heavily infested 
districts are also important means of at least local dispersion. 
The shipment of infested nursery stock originating in heavily infested portions of 
the territory is probably the most important means of long distance dispersion of the 
insect, and this is being guarded against by stringent quarantine regulations. 
The Japanese beetle, (Popillia japonica Newm.), was first found near 
Riverton, in Burlington County, New Jersey, in the summer of 1916. 
Previous published accounts 1 have described the development of the 
insect from that time, and the work being carried on at the Japanese 
beetle laboratory. Seven years have elapsed since the original finding 
of the insect in this country and the data now at hand are sufficient to 
allow the drawing of certain conclusions as to the spread of an imported 
insect in a new environment, under the conditions obtaining in the 
present case. It is the object of this paper to indicate the spread of the 
insect during the period mentioned, and to discuss briefly some of the 
factors primarily responsible for the dispersion which has taken place. 
The data are drawn from the scouting records compiled each year at the 
Japanese beetle laboratory, and from the personal observation of the 
writers and other members of the laboratory force. 
Yearly Spread 
In 1916, the area found to be infested was very small, estimated to be 
less than 1 square mile in extent. At this time, the beetles were first 
found feeding on the tips of Crataegus. It was assumed to be a Southern 
species and no particular efforts were made to determine the limits of 
the area infested. However, the fact that comparatively few beetles 
were found, would indicate that the area infested was relatively small, 
certainly not over the figure given above. 
In 1917 a considerable area was scouted and the infestation found 
^avis, J. J. N. J. Dept. Agric. Circ. 30, 1920. 
Hadley, C. H., N. J. Dept. Agric. Circ. 46-1922. 
