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310 Report oF THE ENTOMOLOGISTS OF THE 
looked for and destroyed. If the orchard has been badly infested 
it will pay to make a special search for them. 
Destroying the caterpillars— Many methods have been sug- 
gested for destroying the caterpillars but there are three especially 
feasible ones, which, if carefully carried out, will usually prove 
effectual. 
First, spraying with an arsenical compound.—Any good arseni- 
cal will answer the purpose if applied before the caterpillars are 
half-grown. Some of the principal arsenical insecticides are 
Paris green, green arsenite and arsenite of lime. For a discussion 
of green arsenite and arsenite of lime see Bulletins 143 and 152 
of this Station. A third arsenical, arsenate of lead, has been found 
by the Gypsy Moth Commission of Massachusetts to be especially 
effectual against the gypsy moth and to be almost harmless to 
foliage. The formula is as follows: 11 ounces acetate of lead,.4 
ounces arsenate of soda, 150 gallons of water. The directions for 
making arsenate of lead as given by Professor C. H. Fernald® are 
as follows: “Arsenate of lead is easily prepared by putting 11 
ounces acetate of lead in 4 quarts of water, in a wooden (not 
metal) pail, and 4 ounces of arsenate of soda (50 per ct.) in 2 
quarts of water in another wooden pail, and when entirely dis- 
solved mixing them in a hogshead containing 150 gallons of water, 
when a chemical reaction will take place forming arsenate of lead 
in a fine white powder in suspension of water. If cold water be 
used in the wooden pails, the solution of the acetate of lead will 
require a little time, but, however, if the water be hot, it will dis- 
solve very quickly. It is customary to add from 2 to 4 quarts of 
glucose to the above amount of water. If it is desired to use larger 
proportions of the arsenate of lead, it is only necessary to use more 
acetate of lead and arsenate of soda, but always in the proportions 
given above.” ‘To ensure success in spraying two points should be 
kept in mind, namely, promptness and thoroughness. The poison 
will be much more effective if applied before the caterpillars are 
32 Ann. Rept. Mass. Bd. Agr. 1897. 
