Proceedings of Eighth Annual Meeting 123, 



over the surface of the water, into hoof-prints, etc., and will float in among 

 plants or other obstructions, provided such obstructions do not form a com- 

 plete canopy. A remarkably small amount of this material will kill anopheles 

 larvae if properly applied. Apparently a film of creosote is not essential, as 

 the lethal action is not brought about by suffocation, so much as by poisoning 

 and the fine mist over the surface of the water suffices for this purpose. For 

 treatment of small puddles, edges of streams, ponds, etc., and for handling 

 a large territory where bodies of water are scattered and transportation is 

 difficult, this method holds considerable promise. 



Since creosote is poisonous to fish and other animals, it must be used with 

 caution on water containing fish and on water used by stock. If a pond or 

 stream is more than a few feet wide, fish are not affected by treatment of the 

 edges. In small ditches with good current, fish do not seem to be affected 

 unless a large amount of oil is applied, but in small puddles even a slight 

 application is very apt to kill them. Owing to the irritating qualities of 

 creosote, it is improbable that stock will drink water containing enough to do 

 harm, but its use is not recommended in such cases except after careful 

 trial. 



The irritating effects of creosote are also felt by those who apply it if much 

 is allowed to come in contact with the skin. For this reason, as well as to 

 facilitate spreading the mist over the water, it is best, where possible, to apply 

 it from the windward side." 



The advantages of creosote as a larvicide are : 



It readily kills larvae. 



It is lethal without forming a complete film. 

 Reduces larval fool supply. 



One gallon will do the work of 5 to 6 gallons of oil. 



The disadvantages of creosote are : 



It is poisonous to fish and stock. 



It is very irritating to the human skin. 



It is costly. 



Its use on salt pools is questionable at least my personal experiments were, 

 not conclusive. 



In conclusion, petroleum as a larvicide is not entirely satisfac- 

 tory, but in the absence of a more acceptable larvicide, it is the 

 most practicable medium for larval destruction. 



The destruction of larvae, as previously stated, is brought about 

 by sufifocation, due to the mechanical action of oil resting on the 

 surface of the wattr in an even layer, but only v^here the oil com- 

 pletely and continuously covers the v^ater surface. 



The destruction of larvae on salt marshes, with their excessive 

 vegetation, which interferes v^ith the spread of oil, is a hit or miss 

 process, resulting in little or no destruction, and a great waste of 

 oil. To control salt marsh breeding, attention should be centered 

 on the improvement of the drainage system, removing all standing 

 water which makes oiling necessary. Ditching won't do it, BUT 

 DRAINAGE WILL. 



