-2- 



The tests were made by the Campbell turntable method on laboratory- 

 reared adult house flies ( Musca domestica L.). Approximately 110 flies 

 averaging 2 to 3 days in age were used in each test. The m.ixed sprays 

 were replicated four times on the same day with the same population of 

 flies to avoid the danger of appreciable loss of acetone. The sprays con- 

 taining the adjuncts alone were replicated twice. Since it was necessary 

 to make the tests in several series, each with a different population of 

 flies, the allethrin standard sprays were included in each series. 



Since knock-down of flies is increased by the addition of acetone it 

 is not reported; for the sprays containing allethrin it would be complete, 

 or very nearly so, at the concentrations used without the presence of 

 acetone. Mortality only was determined for each spray. 



The adjuncts alone caused no or negligible mortality in 1 day at the 

 concentrations used. The mean mortalities obtained with the sprays are 

 given in table 1. 



To determine whether synergism existed in the toxic action of the 

 m.ixed sprays, the following procedure was used: In each series a 

 regression equation for the allethrin standard was determined from the 

 data by the method of probit analysis as described by FinneyA.' From 

 this equation the logarithm of the allethrin equivalent was calculated 

 for each of the four individual niortalities obtained with each spray. 

 From an analysis of variance of these log concentrations the relative 

 standard error of the mean allethrin equivalent was computed. The 

 error contributed by comparison with the allethrin standard was com- 

 puted. From a combination of the errors from, the two sources the 

 allethrin equivalent required to demonstrate synergism was determined, 

 and reported in table 1. 



The mean allethrin equivalents are given in table 1 and, since they 

 are to be compared with the actual amount of allethrin in the mixtures -- 

 50 mg. per deciliter- -they give, when divided by 50, expressions of 

 relative toxicity. 



Since the adjuncts were nontoxic at the concentrations used, any 

 significant increase in toxicity over that of the allethrin in each mixture 

 may be ascribed to synergistic action. Such an increase was clearly 

 demonstrated for 7 mixtures; of the remaining 20, the increase for 14 

 was on the borderline of significance. Synergism could perhaps be 

 demonstrated for the latter mixtures in more critical work. However, 

 this would be of no practical imiportance, for in these preliminary tests 

 the mixtures were less than 1.5 as toxic as allethrin. 



2/ Finney, D. J. Probit analysis. 318 pp. Cambridge. 1952. 



