October, '17] back and GROSSMAN: MISCIBLE OILS V. SOAP SPRAYS 455 



Table I. — Effect op Summer Showers upon the Effectiveness of Miscible Oil and Soap Sprats 



> Larvae in third and pupal stages, and therefore more resistant to this strength. 

 * Larvae in first and second stages. 



by showers, except when these fall almost immediately after applica- 

 tion. Detailed data show that summer showers falling after the oil 

 spray has once had an opportunity to dry on the foliage, have very 

 little effect upon the efficiency of the spray. Since the leaves gathered 

 for the examination of the Aleyrodids were picked promiscuously, one 

 must be prepared for slight unexpected variations in the percentages 

 of forms killed. The main point to be emphasized is the greater weak- 

 ening effect showers have upon the different strengths of soap spray 

 than upon those of the oil spray. Thus showers, falling about 30 

 minutes after the oil spray had been applied, had little effect upon the 

 percentage of forms killed, w^hile they had a very evident effect upon 

 that killed by the soap spray. The weaker strengths of fish oil soap 

 were much more influenced by showers than the weaker strengths of 

 the oil spray. 



Miscible oil sprays appear to have a second advantage over soap 

 sprays in that aside from being more resistant to showers, they are 

 operative over a longer period of time after application, even when 



