THE PARASITES OF POPILLIA JAPOKICA 
9 
At Sapporo, with its biennial periodicity in beetle abundance, in 
1921 there was an average parasitism in the females of 19.5 per cent, 
of the males 3.9 per cent, with 85.6 per cent of the egg total on female 
beetles. The following year revealed a parasitism of female 
beetles to the extent of 87.8 per cent, of the males 51.9 per cent, and 
the proportion of eggs on female beetles was 80.4 per cent. The 
third year, 1923, revealed 18.9 per cent of female beetles bearing 
parasite eggs, 1.1 per cent of the males, and 95.6 per cent of the egg 
total on the former. It is thus seen that conditions in 1921 and 1923 
were practically identical and, though lacking exact figures for 1920, 
it is known that the parasitism for that year was approximately equal 
to that for 1922. These four years may therefore be taken as illustrat- 
ing the normal cycle of Centeter cinerea at Sapporo. 
/00 
$0 
iSt//.r 
**6/&&&7- 
' /7 /& /& 20 2/ 22 23 2* 2J~ 2S 27 2S 2? 30 &/*'/ 2 3 + f <? 7 & & /0 // 72 73^ 
"*\ 
—<0 
... 
>— 
... 
•♦, 
k 70 
X- 
^ 30 
£0 
/0 

/00 
00 
S0 
\*» 
\30 
... 
N 
m ,. 
c 
"• 
»*" 
.... 
... 
N 
k * 
"••« 
\ 
»-* 
*>. 
"■" ■ 
"•^ 
L «>. 
«* 
^ 
"•s 
/& 
22 
s 
%, 
"~* 
^ 
r' 
f&* 
9 
d. 
<+ 
/0 
Fig. 7.— Curves showing the percentage of parasitism of Popillia japonica by Centeter cinerea at 
Sapporo, Japan, in 1922 and 1923: A, parasitism of female beetles; B, parasitism of male 
beetles; C, proportion of eggs laid upon female beetles 
In Figures 7 and 8 are given in graphic form the data on parasitism 
at Sapporo in 1922 and 1923, and for 1921 at Koiwai, these being the 
years when most extensive data at these places were obtained. The 
most striking difference in the graphs for Sapporo is that for the 
parasitism of the males, which in 1923 never exceeded 1.5 per cent, 
and therefore was too low to be represented on the chart, in 1922 
attained a maximum of 84.3 per cent. In both years the graphs 
representing the proportion of eggs on female beetles remained ap- 
proximately constant throughout the season, as it did also at Koiwai. 
The full effectiveness of this parasite is not indicated by the figures 
previously given, but is in reality somewhat greater. Life-history 
studies have shown that the beetles are killed within a period of six 
days after the parasite eggs are deposited; consequently practically 
all beetles bearing eggs on any given date are dead within six days 
thereafter, and the parasitized beetles in the field at the latter date 
98689—27 2 
