6 
BULLETIN 1429, IT. S. DEPARTMENT OF AGRICULTURE 
presumed that the activities of the parasite would be extended 
over a greater period of time. 
No further studies upon the species being possible that season, 
attention was turned to the finding of other natural enemies of 
Popillia japonica. Observations were renewed in 1921, and in that 
and the following year studies and collections were made both at 
Koiwai and at Sapporo immediately upon the appearance of the first 
beetles of the season. In 1923 final observations and collections 
were made at Sapporo only, since at this place conditions for the 
work were nearly ideal, the area infested by the beetle being of con- 
siderable extent, the parasites abundant, and collectors available in 
unlimited numbers (fig. 5). Although the parasite is usually found 
in most localities north of Morioka, the greater part of the work was 
conducted at Sapporo because of the favorable conditions prevailing 
there. 
Fig. 5.— Children engaged in collecting Popillia beetles parasitized by Centeter cinerea, Sapporo, 
Japan 
As is pointed out in the account of the life history of Popillia 
japonica in Japan, there is for the most part a pronounced two-year 
life cycle in Hokkaido, resulting in an abundance of beetles every 
second year (1921 and 1923), with a lesser number during the alter- 
nate years. At Koiwai, although some of the grubs carry over for 
two years, the number of beetles emerging each year is fairly constant. 
This point is elaborated in the discussion of the life history of the 
host. Such deviation from the normal one-year cycle has had a 
pronounced influence upon the parasite itself as will be shown later. 
FIELD OBSERVATIONS 
Centeter cinerea was under close observation during the years 1920 
to 1923, inclusive, and its behavior over this period has given a fair 
indication of its possibilities. Figure 6 shows the relative abundance 
of the beetle at Sapporo during the period mentioned, and the per- 
centage of parasitism effected by C. cinerea. In 1920 the beetles 
were relative!}' scarce; the parasitism of the females exceeded 90 
