CONTACT INSECTICIDES 53 



Pjrrethnim, Insect Powder or Buhach. — This is made by grinding 

 up the blossoms of certain plants, which contain an essential (and volatile) 

 oil effective against insects but not injurious to man. Its use is mainly 

 limited to small areas, and best, those which can be tightly closed. 



Various other materials will be considered in connection with the 

 particular insects, for the control of which they are used. 



