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grain than that intended for seeding, since when used excessively it 
may injure the germ. It must always be remembered that the vapor 
is highly inflammable and explosive, and that no fire or lighted cigars, 
ete., Should be in the building during its use. If obtained in large 
quantities it should be kept in tightly closed vessels and away from 
fire, preferably in a small outbuilding. 
GENERAL CONSIDERATIONS ON THE CONTROL OF INSECTS. 
ADVANTAGE OF PROMPT TREATMENT. 
The importance of promptness in the treatment of plants attacked 
by insects can not be too strongly insisted upon. The remedy often 
becomes useless if long deferred, the injury having already been 
accomplished or gone beyond repair. If, by careful inspection of plants 
from time to time, the injury can be detected at the very outset, treat- 
ment is comparatively easy and the result much more satisfactory. 
Preventive work, therefore, should be done as much as possible, rather 
than waiting for the remedial treatment later; the effort being to fore- 
stall any serious injury rather than to patch up damage which neglect 
has allowed to become considerable. 
KILLING INSECTS AS A PROFESSION. 
It may often happen that the amount of work in a community is 
sufficient to induce one or more persons to undertake the treatment 
of plants at a given charge per tree or per gallon of the insecticide 
employed. Where this is the case, and the contracting parties are 
evidently experienced and capable, it is frequently more economical in 
the end to employ such experienced persons, especially when a guar- 
antee is given, rather than attempt to do the work one’s self with the 
attending difficulty of preparing insecticides and securing apparatus 
for work on a comparatively small scale. In California this is a com- 
mon practice, and also in some of our Eastern cities, and has worked 
excellently. 
THE DETERMINATION OF THE RESULT OF TREATMENT. 
It is often of importance to know when and how to determine the 
effect of any treatment applied directly to insects exposed on the 
surface of plants. In the case of scale insects, especially during the 
dormant condition in winter, the response to insecticides is very slow 
and gradual. The scale larve, or any young scales during the growing 
season, are killed in a few minutes, or a few hours at the furthest, just 
as any other soft-bodied insect, but the mature scale does not usually 
exhibit the effects of the wash for some time. Little can be judged, 
ordinarily, of the ultimate results before two weeks, and it ‘s often 
necessary to wait two months to get final conclusions. The slow, pro- 
gressive death of the scales is apparently due to the gradual penetra- 
