112 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 10 



The emulsion was made by using f lb. of caustic soda, 98 per cent 

 pure, dissolved in a known quantity of water, for every gallon of pine 

 tar creosote to be emulsified, and the subsequent dilution with cold 

 water to the desired strength. This emulsion is very stable and 

 slightly alkaline.^ 



In the preliminary tests, the herd was divided into two equal lots; 

 one being sprayed with 1 per cent emulsion, and the other lot, with 



2 per cent emulsion. 



The herd was sprayed each afternoon just prior to milking (about 



3 p. m.), and notes made of the effect on fly prevalence, the effect of 

 the spray on flies actually hit, and the effect on the hide and exposed 

 mucous membrane. 



This test ran for three days and then 3 per cent and 5 per cent 

 emulsions were substituted for a test of three days' duration. 



Immediately after the application, all flies left the cattle or fell to 

 the floor. Some few returned to parts of the animals that were not 

 touched by the spray, through careless work. However, for the time, 

 the cattle were approximately fly-free, and remained so until they 

 were again turned out to pasture. 



The best indication of the effect of the spray was in the cessation 

 of the switching of tails, which, previous to the spraying, were in 

 constant motion. 



The flies that were hit, fell to the ground in a more or less bedraggled 

 condition. Some recovered after 10 to 12 hours, confined in a wire 

 cage, though most of those that fell to the floor were killed by all the 

 strengths of the emulsion. The 3 and 5 per cent emulsions killed all 

 flies that were thoroughly wetted. 



Throughout the duration of the experiments, very careful daily 

 examinations failed to reveal the slightest damage to hair or skin or 

 to the exposed mucous membranes of the eyes or nostrils. 



At first the cows were afraid of the spray when directed at their 

 faces, but, later, many became used to the spray and hardly moved 

 during the application. 



The preliminary tests showed 3 per cent emulsion to be the most 

 effective minimum strength, and this was adopted in the subsequent 

 tests. 



Using 3 per cent emulsion, one third of the herd was sprayed every 

 day; one third, every other day; and the balance, every third day, to 

 ascertain the lasting quality of the emulsion. 



It was found that the mixture was fully effective only one day. 



1 This formula was supplied by Mr. C. D. Vreeland, then of the Vreeland Chemical 

 Company. The pine tar creosote has since been obtained for us by the same gentle- 

 man through the Kilton Chemical Company. 



