June, ’18] FREEBORN AND ATSATT: PETROLEUM AND MOSQUITO LARVAE 307 
Inasmuch as we are confident that the oil vapors are the primary- 
cause of death in the larvae we feel that despite Dr. Moore’s previous 
apparent disagreement with our findings this later publication seems 
to be in perfect accord with our results. 
Conclusions 
(1) The toxicity of the petroleum oils as mosquito larvicides inr 
creases with an increase in volatility, the more volatile oils producing 
the more marked lethal effects. 
(2) The volatile constituents of the oils contain the principles that 
produce the primary lethal effects. 
(3) The lethal effects are produced by the penetration of the tracheal 
tissue by the volatile gases of the oils. 
(4) In the heaviest and least volatile oils (those having a boiling 
point greater than 250° C.) this action may be supplemented or ap¬ 
parently secondary to the effect of actual contact of the oil with the 
body tissue or perhaps to mechanical means such as suffocation or 
plugging of the tracheae. 
Bibliography 
Celli, A. 1904. Malaria (Translated by Eyre). 
Howard, L. O. 1892. Insect Life, vol. V., No. 1, pp. 12-14. 
McFie, J. W. 1917. Limitations of Kerosene as a Larvicide. Bull. Ent. Re¬ 
search, vol. VII., No. 3. 
Moore, W. 1917. Volatility of Organic Comps, as an Index of the Toxicity of 
their Vapors to Insects. Journ. of Agr. Research, vol. X., No. 7, p. 365. 
Moore, W., and Graham, S. A. 1918. A Study of the Toxicity of Kerosene. 
Journ. of Economic Entomology, vol. II., No. 1, February, 1918. 
Ross, R. 1902. Mosquito Brigades, p. 34. 
1911. Prevention of Malaria, p. 270. 
Schafer, G. D. 1911. How Insecticides Kill. Tech. Bull. No. 11, Mich. Agr. 
Ex. Station. 
Sen, S. K. 1914. Observations on Respiration of Culicidae. Ind. Journ. of Med. 
Research, vol. II., p. 696. 
President G. P. Weldon: Discussion of Mr. Freeborn’s paper is 
now in order. 
R. W. Doane: Do you find that the action of the valves of the anal 
siphons have any effect upon the manner by which the oil enters the 
tracheae? 
S. B. Freeborn: We have noticed repeatedly, when using stained 
oils, that the oil seems to pass into the anal siphon around the valves 
even though they be apparently tightly closed. 
R. S. Woglum: Did you determine how long the oil of the different 
grades would remain on the water? , 
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