2 BULLETIN 1429, U. S. DEPARTMENT OF AGRICULTURE 
Popillia japonica was first found in the United States near River- 
ton, N. J., in the summer of 1916. The beetles no doubt entered 
this country in soil surrounding the roots of Japanese nursery stock 
shipped into Burlington County, N. J., at a date shortly prior to 
1916. When first found the infestation covered an area of approxi- 
mately one-half square mile and the beetles were exceedingly scarce, 
only about a score having been taken at that time. The increase 
in the area infested has been so great that the pest now (1925) covers 
some 6,047 square miles. The beetle is an omnivorous feeder and 
in recent years has caused serious destruction to both cultivated and 
native plants within this area, and to fruit and shade trees. 
In the central portion of the infested area the numerical increase 
has been incredible, as is shown by the following statement from a 
recent publication by L. B. Smith, in charge of the Japanese beetle 
laboratory at Riverton: 
During July, 1923, in an orchard of one hundred fifty-six 10-year-old Red- 
bird peach trees, thirteen 16-gallon tubfuls of beetles were shaken from the 
trees and collected early one morning, in somewhat less than two hours. The 
next morning the beetles were apparently as numerous on these trees as before. 3 
Popillia japonica entered the United States apparently free from 
its natural enemies, and its increase has been due not only to this 
fact, but to an acceleration of development in a new and apparently 
ideal environment. Under these circumstances it has become one 
of the major insect pests of the sections in which it now occurs. 
American parasites and predators thus far seem to be a negligible 
factor in preying upon it, and mechanical and cultural control 
methods are so far not wholly effective. In view of these facts the 
necessity for an attempt at control by the biological method is evi- 
dent. 
THE FIELD OF INVESTIGATION 
The investigations in Japan were begun in 1920 at Nagasaki in 
the south (fig. 1) and extended northward as the season advanced. 
On account of existing agricultural conditions and methods in the 
southern half of the country and the absence of waste land, it was 
almost impossible to conduct extensive scouting for grubs in the soil. 
During the first 10 weeks of search only 76 grubs of Popillia japonica 
were found, even though beetles were later fairly common. With so 
small a number of grubs available, it was evident that the chance of 
finding parasites upon them would be very slight, and that extensive 
experimental tests with the various Scoliidae and other parasitic 
species collected as adults in the field would be impossible. It was 
only on the arrival of the writers at Koiwai, in northern Japan, on 
July 12 that beetles and grubs were found in sufficient numbers to 
give hope of success in the search for parasites. It was in these 
northern sections that the greater number of parasite species were 
eventually obtained. 
Although Popillia japonica itself was not found in Chosen, the 
presence of other species of the same genus gave promise of addi- 
tional parasites of value. The five species of the latter found there 
substantiated this conclusion, since it was determined that none of 
these species was specific in its choice of hosts, but would reproduce 
equally well upon P. japonica. 
• Smith, L. B. Service and "Regulatory Announcements, Federal Horticultural Board, U. S. Depart- 
ment of Agriculture, October-December, 1923, p. 150. 
