430 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 14 



table of results is a count from egg rn.asses collected from an orchard 

 sprayed in January 1919 with Miscible Oil No. 1, m.anufactured by Bal- 

 four Guthrie & Com.pany. In regard to this latter test, however, the 

 writer desires to explain that he cannot \'Ouch for the quality of the work 

 as it was purely a commercial job and was in no way under his direction 

 nor was he present to witness any of the operation of spraying. 



The writer's experiments, which for the most part were similar to those 

 conducted by other workers along these lines, included the dipping of 

 egg m-asses in various emulsions as well as the actual spraying in the field. 



By referring to the accompaning tables the data obtained in counting 

 the egg masses may be noted. The (a) figures represent the results of 

 the kill obtained by dipping egg masses in emulsions and then incubating 

 the eggs at about 27°C. Before placing the eggs in the incubator they 

 were left exposed to the air for a period of fourteen days. The reason for 

 dipping egg masses in the emulsions was to obtain thorough contact 

 between the m.ass and the liquid, a factor which cannot be entirely con- 

 trolled in actual spraying. Dipping also affords a simplified m.ethod of 

 indicating, to a limited extent, the effects of the various strengths of the 

 oils used. 



The (b) figures represent the egg counts from, the sprayed plots. 



All of the em.ulsions prepared for the experiments contained 2.5% of 

 cresol soap as the em.ulsifying agent, with the exception of one sample of 

 the Pennsylvania crude oil which was emulsified by the California Spray 

 Chemical Company using the sam.e method that is employed in preparing 

 the regular Ortho Crude Oil Emulsion. The cresol soap was prepared 

 according to the following formula : creselic acid 5 pounds, fatty acid 5 

 pounds, sodium, hydroxide 1.7 pounds. 



The figures obtained from the Western Shell distillate plot serve very 

 well for a check as the count from the actual check plot varied but little 

 from, these figures. In obtaining the counts from the eggs on the trees 

 the m.ethod followed was to tag a number of egg rn.asses on the trees of 

 each plot just after spraying and to refer to these masses for the count 

 when the hatch for the district was complete. This tagging prevented 

 including egg m.asses that m.ay have remained on the trees from the years 

 previous. In each case when one or m.ore eggs hatched in the mass it was 

 considered as a hatch for the mass. 



In arriving at the percentage of kill for the various oils a m.ore accurate 

 figure would obviously have been obtained if a greater number of egg 

 masses had been used for the counts. However, in order to facilitate the 

 work, this higher degree of accuracy was sacrificed for the reason that 

 the total number of eggm.asses in any infestation in this district is relative- 



