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JOURNAL OF ECONOMIC ENTOMOLOGY 
[Vol. 11 
every distillation. Hence volatility as a factor in the toxicity of the 
oils enters into consideration because it serves as a measure of the 
amount of gaseous material given off in a given time and because the 
more toxic chemical constituents seem to be contained in the volatile 
fractions of an oil. 
Although in all the petroleum oils having a boiling point below 250° 
C. the volatile constituents of the oil produce the lethal effects, those 
with the higher volatility producing the most marked and rapid results, 
in the oils having a boiling point higher than 250° C., the effects of the 
volatile constituents which are practically negligible in quantity may 
be overtaken by the effects of stoppage, actual contact, and even 
suffocation. 
Moore (1917) working with terrestrial insects states that in volatile 
organic compounds the toxicity is correlated closely with the volatility 
but that a decreasing volatility is accompanied by an increased toxicity. 
This would seem to be in direct contradiction to the results of our 
experiments but closer consideration of his findings suggests that the 
apparent discrepancy may be explained upon a difference in interpre¬ 
tation of the word “toxicity.” From his point of view, a laboratory 
measurement of the total content of toxic elements was desired and 
possibly in no case was a saturated atmosphere of the chemical ob¬ 
tained. On the other hand, we were working to determine the toxicity 
of the oils under field conditions and in all our experiments we used a 
saturated atmosphere. In short, our object was to determine the oil 
which would give off the largest quantity of toxic material in the 
shortest length of time, while the experiments of Moore were designed 
to show the toxicity of definite amounts of the different chemicals 
exposed for a given period and confined in a given volume. Thus our 
standards of comparison were based on an entirely different viewpoint. 
Again his results with petroleum oils seem hardly justifiable for his 
results are tabulated and his curves plotted in gram-molecules, i. e ., 
the molecular weights expressed in grams. Owing to the present im¬ 
possibility of establishing the molecular weight of the petroleum oils it 
is difficult to conceive of an accurate measurement of these oils in 
gram-molecules. 
In a later publication (1918) Moore tests out the toxicity of kero¬ 
sene, again with terrestrial insects; but in some cases at least, using 
saturated atmospheres and concludes that “low boiling point fractions 
(highly volatile) are more toxic to insects in the form of vapor than 
high boiling point fractions due to the slight volatility of the higher 
fractions.” He adds to this statement that “high boiling point com¬ 
pounds are more toxic than low boiling point compounds when used 
as contact insecticides in the form of an emulsion.” 
