124 N. J. Mosquito ExTERMI^fATION Association 



On water surfaces that can be completely and continuously 

 covered with a film of oil, some chemical, if found, which is readily 

 miscible with oil, that will prevent evaporation and loss of surface 

 tension, will in my opinion, solve the problem of destroying larvae 

 by the mechanical action of suffocation. 



My brief consideration of larvicides clearly visualises one fact — 

 that the ideal larvicide does not exist. Nearly all the larvicides on 

 the market at present have a limited use or obvious disadvantages, 

 which make their use impracticable from the standpoint of economy 

 and efficiency. 



Mosquitoes, by natural choice, oviposit their eggs on the surface of 

 water in which organic matter is always present in some form or oth- 

 er. Unfortunately nearly all commercial larvicides lose their toxicity 

 in the presence of organic matter and unless they kill in a reasonable 

 length of time, soon become ineffective and practically worthless for 

 such destruction. This disadvantage, together with the fact that most 

 larvicides do not readily mix with salt water, is the chief draw-back 

 to larvicides in general. 



The ideal larvicide should have the following characteristics : 



It should readily affect and destroy larvae, preferably in from ten to 

 twenty minutes. 



It should be uniform and high in toxic power and non-toxic to man 

 and stock. 



It should readily mix with salt water. 

 It should reduce or destroy algae. 



It should remain affective for a month or more, be convenient to handle 

 and be inexpensive. 



Finally, the ideal larvicide will result only after extensive study 

 and research. It is to be remembered, that the physiological activity 

 of the larvae and the effect upon the latter of such factors as habitat, 

 temperature, light and food supply, are recognized variables for 

 study and experiment. 



References 



The Mosquitoes of North and Central America and the West Indies, Vol. i. 



LePrince & Orenstein — Mosquito Control in Panama. 



Deriveaux— U. S. Public Health Bulletin No. 88. 



Tarbett— U. S. Public Health Bulletin No. 104. 



LePrince — U. S. Public Health Reprint No. 260. 



Metz— U. S. Public Health Reprint No. 500. 



Headlee — New Jersey Experimental Station Bulletins, 



