64 
THE GEAPE ROOT-WORM. 
the beneficial effects of poison sprays are due rather to a distaste on 
the part of the beetles for poisoned foliage, and their consequent 
abandonment of sprayed foliage and migration to unsprayed areas, 
than to the direct killing effect of the poison. This view is supported 
to some extent by cage experiments which showed that in many 
cases when confined in cages the beetles fed but slightly upon sprayed 
foliage and the death rate was not as rapid as might be wished. In 
addition to this, beetles thus confined with poisoned vines have in 
feeding indicated a preference lor unsprayed areas, all of which left 
reasonable cause for doubt as to the direct efficiency of arsenicals as 
a killing agent. 
During our investigation of this pest, covering the seasons of 1907, 
1908, and 1909, we have observed this tendency of the beetles to feed 
more freely upon the unpoisoned than upon poisoned foliage, both 
in the open vineyard and in cages, yet we have no direct evidence of 
wholesale migration of the beetles from sprayed areas. 
CAGE EXPERIMENTS WITH POISON SPRAYS AGAINST THE 
BEETLES. 
On July 13, 1907, 100 beetles recently emerged from the soil were 
divided into two lots of 50 each and placed in cages; one cage con- 
tained sprayed foliage collected from a vineyard recently sprayed, the 
other unsprayed foliage. The beetles in the cage containing the 
unsprayed foliage fed freely upon the leaves soon after they were 
placed in the cage, whereas those placed in the cage containing the 
sprayed foliage did but little feeding during the first 3 days. During 
the next 3 days there was evidence of an increased amount of feeding. 
At the end of the 6 days, 25 of the beetles feeding on the sprayed 
foliage had died as against 6 dead beetles out of the 50 feeding on the 
unsprayed foliage. At this date (July 19) the experiment terminated 
on account of the withering of the sprayed foliage, and the impossi- 
bility of obtaining additional recently sprayed foliage. 
Another cage experiment to observe the feeding of beetles upon 
poisoned and unpoisoned foliage was undertaken during the summer of 
1909. This experiment was made upon young grapevines growing in 
large flower pots and covered with a wire screen (see fig. 22). Thus 
the freshness of foliage was assured throughout the experiment and 
the limited area of the plant permitted close observation of what took 
place. Three plants growing in pots were used in this experiment. 
The plants in two of the pots were sprayed very thoroughly, care being 
taken to cover the entire upper surface of all of the leaves with a poi- 
soned spray, which consisted of Bordeaux mixture with 3 pounds 
arsenate of lead to 50 gallons of the mixture, the proportions used in 
field experiments. The plant in the third pot was unsprayed. An 
