8 
BULLETIN 1429, U. S. DEPARTMENT OF AGRICULTURE 
This is given in Table 1. At Koiwai the beetles were present in 
about equal numbers each year, and consequently conditions in this 
respect more nearly approach those found in New Jersey and Penn- 
sylvania. Few actual counts were made' in 1920, and none in 1923, 
so that data for only two years are available. It is known, however, 
that the general parasitism in 1920 approximated that of the follow- 
ing two years. It may be explained that in taking these data mating 
pairs were collected in the field and the number of eggs borne by 
each sex recorded. In this way a representative series of each sex 
was secured, and the figures are felt to be a fairly accurate represen- 
tation of field conditions 'at the time the observations were made. 
The general averages cover the period from the appearance of the 
beetles in numbers to the cessation of oviposition by the parasite. 
Reference to the tabulated data for Koiwai shows that in 1921 
(Table 1) 42.1 per cent of the female beetles observed bore Centeter 
cinerea eggs, with an average of 1.4 per parasitized female. The 
males, on the contrary, were attacked only to the extent of 1.1 per 
cent. Of all eggs, 95.9 per cent were deposited upon female beetles. 
An explanation of this will be given later in the discussion of the 
manner of oviposition of the parasite. During 1922 the parasitism 
was somewhat higher than in the preceding year, the percentage 
being 58.4 for the females and 16.2 for the males, and the proportion 
of the egg total on the former 85.9 per cent. 
Table 1- 
-Field 'parasitism by Centeter cinerea at Sapporo and Koiwai, Japan, 
1921-1923 
Total number of beetles exam- 
ined 
Total number bearing C. cinerea 
Total number of eggs present 
Proportion on each sex 
Maximum parasitism 
Maximum number of eggs on one 
beetle 
Average per parasitized beetle 
1922 
Sapporo 
Females 
812 
158 
190 
\Per cent 
4 
1.2 
Total number of beetles exam 
ined... 1, 292 
Total number bearing C. cinerea 
eggs 1, 135 
Total Rumber of eggs present 4, 507 
Proportion on each sex... 
Maximum parasitism 
Maximum number of eggs on one 
beetle 14 
Average per parasitized beetle 4. 
1923 
Total number of beetles exam- 
ined 
Total number bearing C cinerea 
eggs 
Total number of eggs present 
Proportion on each sex ...... 
Maximum parasitism 
Maximum number of eggs on one 
beetle 
Average per parasitized beetle 
2,122 
401 
475 
4 
1.2 
Males 
Per cent 
812 
19.5 
~~~85.~6~ 
22.6 
32 
32 
1 
1.0 
1,292 
87.8 
"loT 
100.0 
670 
1,096 
6 
1.(5 
2,071 
18.9 
""9576" 
30.5 
22 
22 
1 
1.0 
4.4 
1.5 
Koiwai 
Females 
1,584 
3.9 
~~~14~4~ 
667 
934 
4.7 
5 
1.4 
500 
51.9 
84.3 
292 
614 
6 
2.1 
Per cent 
42.1 
95.9 
53.2 
85.9 
62.0 
Males 
1,985 
Per cent 
36 
40 
1.8 
--- 
6.3 
2 
1.1 
500 
81 
101 
16.2 
14:71 
25.0 
2 
1.2 
