54 BULLETIN 1429, U. S. DEPARTMENT OF AGRICULTURE 
POPILLIA MUTANS Newm. 
This third Chosen Popillia is much less abundant than the preceding 
two. The adults are robust beetles from 11 to 13 mm. in length, 
entirely deep indigo blue in color, and resembling somewhat the blue 
forms of P. atrocoerulea, but distinguishable from them by the ab- 
sence of the abdominal tufts of white hair. 
This is a late-appearing species, being found from mid-August 
to mid-September, and at no time is it abundant. Larvae are found 
feeding on the roots of grasses. Only a few individuals have been 
reared through the life cycle, and these hibernated in the second 
larval instar. 
The adults are flower feeders, confining their attention almost 
exclusively to the flowers of bush clover (Lespedeza bicolor), though 
they occasionally feed on flowers of other clovers. 
SUMMARY 
Nine species of parasites and one predator of the Japanese beetle 
(Popillia japonica) have been found and studied in Japan and Chosen. 
These represent three species of tachinids, two dexiids, four scoliids, 
and one carabid. 
Among the tachinids Centeter cinerea is the most promising species, 
for in its native habitat it is very abundant and exerts a marked 
control upon Popillia japonica. In Hokkaido the largely two-year 
life cycle of the nost interferes with its rate of increase, so that in 
successive years the percentage of parasitism fluctuates from ap- 
proximately 20 to 90, respectively. At Koiwai in northern Honshu, 
where the number of beetles is fairly constant each year, the para- 
sitism averages somewhat above 50 per cent. The climatic condi- 
tions under which this species lives correspond fairly closely to those 
of the infested locality in America. 
Ochromeigenia ormioides is more common in the warmer regions 
of Japan, though it ranges into Chosen and northern China, which 
would indicate that it is not limited to mild climatic conditions. 
This parasite is extremely sporadic in its attacks upon P. japonica. 
In some seasons parasitism reaches 35 per cent in a given locality, 
but in the following seasons it may fall below 2 per cent. A secondary 
host is necessary for the overwintering brood. The establishment 
of the species therefore depends upon its ability to become adapted 
to a new alternate host in America, if such is available. 
Eutrixopsis javana has been obtained only from Hokkaido, and 
in that locality is of very minor importance as compared with C. 
cinerea. 
Of the Dexiidae two species have been found to parasitize Popillia 
larvae. Prosena siberita occurs abundantly in northern Japan and 
Dexia ventralis in Chosen. Living larvae are deposited on the soil 
and these burrow about in search of host grubs, into which they 
penetrate and upon which they feed. P. siberita has but a single 
brood each year and is well adapted to its host as regards the time 
of appearance. It effects a field parasitism in Japan of approxi- 
mately 10 per cent. D. ventralis has three broods per year and 
apparently requires a different host for each one. The establish- 
ment of this parasite in America depends upon the presence of addi- 
tional hosts which pupate at a time favorable to the brood of Dexia., 
