FEEDING HABITS OF THE JAPANESE BEETLE. 6 
July 10 it was noted that the beetles were less abundant, although 
there was still plenty of foliage upon which they could feed. By 
July 12 only 6 beetles were left on this particular patch of smartweed; 
5 of these were males and 1 a female. Thereafter the infestation 
noted on these plants was as follows: July 13, 2 males; July 14, 7 
males; July 15, none; July 16, none; July 19, at 9 a. m., 3 males, 
at 3.30 p. m., 7 males; Jul}' 20, at 9.30 a. m., 3 females and 10 males, 
at 11.30 a. m., 12 females and 22 males, and by 2 p. m. the plants 
were heavily infested. One hundred and twenty beetles were col- 
lected at random from these plants, and of these 52 were females 
and 68 males. This patch of smartweed remained infested until 
after September 15. Similar instances were noted on sassafras and 
on Yellow Transparent apples. 
The beetles are strongly attracted to ripening fruit, and early 
apples and peaches may suffer severe injury from the depredations 
of the insects. So numerous do the beetles become at times that 
individual fruits, especially where they have ripened prematurely, 
will be completely covered by a swarming mass of the insects. It 
has also been noted that the foliage of those varieties which ripen 
early in the season is more severely injured than that of the so-called 
late varieties. It is possible that this may be due in a measure to 
the attraction of the beetles by the color of the fruit rather than to a 
preference for the foliage of the early varieties. This is indicated by 
the fact that the insects are gregarious and usually will alight on 
those plants where beetles are already present. No apples have been 
observed to be severely attacked early in the season and it is only 
after some of the fruits have partially ripened, either prematurely 
through disease or otherwise, that the heavy infestations of apples 
occur. Peaches affected with brown-rot, caused by Sclerotinia 
fructigena (Pers.) Schr., are particularly attractive to the beetles. 
It is probable that later experiments will show that these insects 
may cause serious losses through the dissemination of this fungus 
from diseased to healthy fruit. 
Throughout the season when the beetles are present they may be 
found at any time on a large number of plant species. In general, 
however, during the season of 1921 the beetles showed a tendency 
to be more abundant on weeds, sassafras, elder, sweet cherries, and 
grapes during the early part of the season. By midsummer fruit 
and shade trees were more heavily infested, while during August 
and September heavy infestations were confined to corn, beans, 
clover, and various plants in bloom at 'that time. The developing 
ears of corn were particularly attractive to the beetles and as many 
as 27 beetles were taken from a single ear. 
Moore and Cole have shown 4 that the beetles are positively photo- 
tropic and their results are borne out by the fact that on apples, 
cherries, grapes, and shade trees most of the feeding is done on the 
foliage which is exposed to the direct rays of the sun. The beetles 
rarely feed early in the season on the peach leaves borne on new wood. 
As the season progresses, however, they feed more or less generally 
on the mature foliage. It is of interest to note that on the majority 
of their food plants the beetles feed on the upper surface of the leaves, 
but on peaches they often feed from the under side. 
* Moore, A. R.,and Cole, W. H. The response otPopillia japonica to light and the Weber-Fechner law. 
In Jour. Gen. Physiology, v. 3, no. 3, p. 331-335, fig. 1. 1921. 
