62 



CIRCULAR 9 7 7, IX. S. DEPARTMENT OF AGRICULTURE 



The residual action of the MYL powder was much shorter than 

 that of DDT, but it did give complete control of lice for 1 week and 

 a high degree for 3 or 4 days longer. Although this length of time 

 took care of most of the nymphs that emerged from eggs present at 

 the time of treatment, the inclusion of the ovicide was thought desir- 

 able. However, it was difficult to reach all the eggs with the pow- 

 der, and for safety two treatments a week apart are recommended. 



% IPiS 



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Figure 25. — Ai 



clothing with a plunger-type hand dust 



