46 
BULLETIN 1429, U. S. DEPARTMENT OF AGRICULTURE 
climate is considerably colder than at the latter place, the growing 
season being confined to June, July, and August. Because of the 
grass and meadow lands here Popillia is more abundant than south- 
ward, although it is not an economic pest. The first beetles of the 
season appear about July 1, increasing rapidly to maximum numbers 
by July 24, after which the decline is gradual through August, and 
by September 10 only a few are left. Here approximately 25 to 30 
per cent of the beetles undergo a two-year cycle. This condition 
seems constant in northern Honshu. 
At Sapporo (lat. 43° N.), on the island of Hokkaido, and about 520 
miles north of Yokohama, Popillia is more abundant than elsewhere 
in Japan, perhaps because of the presence of extensive grass and 
meadow lands which afford undisturbed breeding grounds. It is 
said that at times the adults occur in such numbers as to cause damage 
to the foliage of the soybean, although in four years' observations by 
the writers no material damage to any economic crop was noted. 
JUNE- JULY- AUG -SEPT 
JUNE-JULY- AUG -SEPT 
JUNE-JULY- AUG -SEPT 
JUNE-JULY-AUG-SEPT 
too 
A 
"z 
Mk 
JOIN 
IX 
A 
" a 
4 
P 
4 
\ 
1 m* 
05 
23 
I9J20 
21 
19 
22 
19 
Fig. 31.— Diagrammatic calendar of the fluctuating biennial broods of Popillia japonka at Sapporo, 
Japan. Lines 1, 2, 3, and 4 represent, respectively, 25 per cent of the stages passed in the soil, 
eggs, larvae, and pupae. Solid black curves represent adults as they occur during the seasons. 
Winter months are omitted for convenience. The years 1920 and 1922 were seasons in which 
only 25 per cent of the larvae (No. 1) transformed to adults, larvae Nos. 2, 3, and 4, or 75 per cent, 
remaining in the soil to transform the following seasons. The years 1921 and 1923 were seasons 
in which practically all larvae transformed into adults. Curves for adults in 1920 and 1922 have 
their apices about July 20, or 10 days earlier than normal, because of the intensive parasitism by 
Centeter cinerea. Curves for adults in 1 921 and 1923 represent normal abundance with apices at 
the end of July, C. cinerea not being abundant enough to affect the decline as in the preceding 
years. This fluctuating condition seems to be constant for this region 
In this region Popillia has largely a two-year life cycle with about 
75 per cent of the adults emerging in alternate years (see fig. 31). 
Thus 1920 and 1922 were years of minimum emergence, comprising 
about 25 per cent of the beetle fauna. During these years the first 
adults appeared about July 5, the maximum numbers occurring 
about July 22, followed by a rapid decline and the disappearance of 
the beetles by the first week in August. This latter condition is 
due to the parasitism of the adults by Centeter cinerea and is discussed 
under that head. In the years of greatest abundance (1921 and 1923) 
the first beetles appeared about July 5 also, and reached the maximum 
by the end of the month. The decline was gradual through August 
and by early September all had disappeared. 
In the years of adult abundance virtually all larvse develop into 
adults, only a fraction of 1 per cent of the total number remaining 
in the larval stage by the end of July. These doubtless comprise 
two-year cycle grubs which originated from the 25 per cent of one- 
year beetles. It is also presumed that a fraction of the progeny of 
the two-year beetles may revert to the one-year cycle. During the 
