THE PARASITES OF POPILLIA JAPONICA 47 
periods of larval scarcity it is impossible to obtain sufficient numbers 
for experimental purposes. 
As contrasted with the life cycle of Popiilia at Sapporo and Koiwai, 
Japan, that in the United States in the infested area of New Jersey is 
as far as known entirely of one year, corresponding in this respect to 
the condition existing at Yokohama. At Riverton the first beetles 
issue in numbers in mid-June, and the maximum emergence is reached 
from July 10 to 20. From the end of July or mid-August, according 
[to the season, the decline in numbers takes place, coming to a close in 
raid-September. 
FOOD PLANTS OF POPILLIA IN JAPAN 
During four years' study of Popiilia in Japan, the writers have not 
observed it as a serious pest, although Japanese entomologists have 
recorded it as at times doing considerable damage to soybean plants. 
jAs regards this particular food plant, we may cite the condition 
existing during the summer of 1921 at Koiwai, where feeding by the 
beetle was largely upon Polygonum reynoutria growing along the 
roadside bordering the breeding grounds, and immediately adjoining 
it was a large field of soybeans. Although the Polygonum foliage 
was almost skeletonized, hardly a single individual was found in 
the adjoining soybean field. At Koiwai also, where considerable 
corn is grown, there is no damage to the silks or to green corn. How- 
ever, at Riverton corn silk and green corn are favorite foods. Like- 
wise wistaria at Yokohama is much fed upon by Popiilia, yet wistaria 
at Sapporo is rarely touched. These points illustrate a common 
feeding habit, namely, that the favorite food plants of one district, 
although present in another, are often not fed upon by the beetles. 
The favorite food plants in the three localities in which observa- 
tions were most extensive are listed in Table 4. 
Table 4. — Favorite food plants of Popiilia japonica at Tokyo, Koiwai, and Sapporo 
Locality and botanical name Common name Parts of plant eaten 
Tokyo, Yokohama region: 
Cissus japonica. Blind grape Leaf and flowers. 
Wistaria floribunda Wistaria Leaf. 
Vitis sp Cultivated grape Leaf and flowers. 
Castaneasp Chestnut : Flowers. 
Koiwai: 
Polygonum reynoutria Itadori Leaf and flowers. 
Rumex sp Dock Do. 
Populus nigra Italian poplar Do. 
Pteridium aqualinum Fern ' Do. 
Sapporo: 
Polygonum reynoutria Itadori . Do. 
Prunus japonica .. Hedge plum Leaf. 
Populus nigra Italian poplar Do. 
Vitis sp Cultivated and wild grapes Leaf and flowers. 
Table 5 gives a more complete list of the food plants of Popiilia 
japonica. The list includes a few foreign plants commonly grown in 
Japan. 
