141 



The probability, log dose, upper and lower fiducial limits, and 

 probits are shown in Table 29. The probit curve with the LC S0 of 

 0.45 ppm is shown in Figure 29. The slope of the probit curve indicates 

 relative heterogeneity in the susceptibility of the laboratory house 

 fly population to CGA 72662 (Hoskins and Gordon, 1956). 



Comparison of the efficacies of CGA 72662 and commercially used 



organophosphorus larvicides. CGA 72662 and three commercially used 



organophosphorus larvicides were applied to manure in one house at the 



tilling site. Sectioning of the manure collection area, assignment of 



treatments, and the application rates of the compounds are shown in 



Table 30. Treatment blocks measured 7.6 m along the walk by 1.2 m wide. 



The procedures for mixing the test concentrations are given in Table 31. 



Time interval for the collection of samples was as follows: 



Sample Time 



No. Interval 



1 pretreatment . but on treatment day 



2 4 days post-treatment 



3 7 days post-treatment 



4 1 1 days post-treatment 



5 14 days post-treatment 



6 28 days post-treatment 



7 35 days post-treatment 



Sampling ceased after the larval population mean of a treatment block 

 exceeded that of the control block. All sampling ceased 35 days post- 

 treatment because manure in the control block became too dry to support 

 fly populations. 



Results. The larval population means for all treatments during 

 each sampling period are shown in Table 32 and Figure 30. The active 

 period for the larvicides is shown in Table 33. 



