TWELVE] OUR RIVALS—THE INSECTS 
I have not given space to a discussion of the oil 
remedy, because there is so much danger of serious 
damage being done by amateur workmen. If, 
however, you care to experiment with crude petro- 
leum to destroy scale insects or aphides, I advise you 
not to use a stronger than twenty-five per cent. mix- 
ture. In peach orchards I should use it with still 
greater caution. Pure crude petroleum was for a 
while recommended to be used in very fine spray, 
but a vast amount of damage was done. 
I shall not pass away from this discussion of in- 
secticides, involving a free use of arsenical mixtures, 
without warning you that these poisons cannot 
be used without more or less danger. Some of 
us cannot handle or come in contact at all with 
these spraying materials without serious injury. 
A great deal too much arsenic is used in potato 
fields, and elsewhere. The storing of it is often 
very careless. Arsenic, even when used in the 
form of spray, and blown about by the wind, is not 
inhaled by the lungs with impunity. I give you, 
therefore, a word of sharp caution in the handling 
of this poison and its application. 
A large number of insects are very migratory in 
their habits. They are always coming and they 
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