748 
Journal of Agricultural Research 
Vol. XXXI, No. 8 
The susceptibility of various species of insects to chloropicrin is 
different. The results of Moore (16), Bertrand (6), and others 
agree with those of this present work in showing that the confused 
flour beetle, Tribolium confusum (Duval) is more resistant than the 
weevils worked with, from 30 to 50 per cent greater dosage being 
required to kill it. 
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FiG. 1.—Time and temperature curves for toxicity of chloropicrin to Calendra granaria L. (used 
by these writers in this work) and Calendra oryza L. (used by Bertrand (3)). Dots represent 
results of the present work, and crosses those of Bertrand 
EXPERIMENTS IN PRACTICAL APPLICATION 
The experiments with the practical application of the chloropicrin 
have had to do very largely with the technique of application. In 
general, it has been found that the material gives a quicker and more 
uniform action when it is 
360 
300 
240 * 
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60 
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atomized. A pressure 
sprayer which would throw 
a fine mist has been con¬ 
sidered the most satisfactory 
means of application. 
No satisfactory method 
of measuring the rate of 
E enetration of chloropicrin 
as been found. However, 
chloropicrin has been ob¬ 
served to have unusual 
powers of penetration. The 
confused flour beetle has 
been killed in the center of 
a 98 pound sack of flour in 
Fig. 2—Time and concentration curves for toxicity of Ipao than 94 Vimir «5 with ft 
chloropicrin to Calendra oryza L. and Calendra granaria L. “ 
concentration of about 32 
gms. per cubic meter in a wooden box. This same propertv, however, 
makes it possible for the chloropicrin to escape through the walls of 
the fumigation chamber more readily than other fumigants do. 
After experiments in 1920^Burkhardt (10) concluded that chloro¬ 
picrin was unsatisfactory for fumigation on a large scale, but he 
used only 10 gms. per cubic meter, a lower concentration than that 
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40 
