14 THE IMPORTED ELM LEAF-BEETLE. 
Treatment with London Purple. — Already early in June the insect ap- 
pears plentiful. On June 7, 1882, it was at work on all the trees, and 
its clusters of eggs were numerous beneath the leaves. Some of the 
trees had half of the leaves considerably gnawed and perforated by 
larvje of all sizes, and by the adults. At this date fifteen trees, consti- 
tuting the south part of the grove, were treated. 
Preparation of the Poison. — London purple (one-half pound), flour (3 
quarts), and water (barrel, 40 gallons) were mixed, as follows : A large 
galvanized iron funnel of thirteen quarts capacity, and having a cross- 
septum of fine wire gauze such as is used for sieves, also having vertical 
sides and a rim to keep it from rocking on the barrel, was used. About 
three quarts of cheap flour were placed in the funnel and washed through 
the wire gauze by water poured in. The flour in passing through is 
finely divided, and will diifuse in the water without appearing in lumps. 
The flour is a suitable medium to make the poison adhesive. The Lon- 
don purple is then placed upon the gauze and washed in by the remain- 
der of the water, until the barrel is filled. In other tests the flour was 
mixed dry with the poison powder, and both were afterward washed 
through together, with good results. It is thought that by mixing in 
this waj less flour will suffice. Three-eighths of a pound of London 
purple to one barrel of water may be taken as a suitable percentage. 
Three-eighths of an ounce may be used as an equivalent in one bucket- 
ful of water. The amount of this poison was reduced to one-fourth of 
a pound to the barrel with good effect, but this seems to be the mini- 
mum quantity, and to be of value it must be applied in favorable 
weather and with unusual thoroughness. With one-half or three- 
fourths of a pound to the barrel about the maximum strength allow- 
able is attained, and this should be applied only as an extremely fine 
mist, without drenching the foliage. 
Effect* of the Mixture. — The flour seems to keep the poison from tak- 
ing effect on the leaf, preventing to some extent the corrosive injury 
which otherwise obtains when the poison is coarsely sprinkled or too 
strong. It also renders the poison more permanent. On the leaves, 
especially on the under surfaces, the London purple and flour can be 
seen for several weeks after it has been applied, and the insect is not 
only destroyed, but is prevented from reappearing, at least for a long- 
period. By poisoning again, a few weeks later, the insect is deterred 
with greater certainty for the entire season. By being careful to ad : 
minister the poison before the insect has worked, and, above all, to 
diffuse the spray finely but not in large drops, no harm worth mention- 
ing will accrue to the plant from the proportion of poison recommended. 
The new growth that developed after the first poisoning was protected 
by one-fourth of a pound to the barrel in 1882. From midsummer un- 
til autumn the unpoisoned half of the grove remained denuded of foli- 
age, while the poisoned half retained its verdure. The little damage 
then appearing in the protected part was mostly done before the first 
