PLANTS AND ANIMAL PARASITES 157 



better than paris green and has therefore largely replaced 

 it as a poisonous insecticide. It may be prepared at 

 home, but this is a rather unsatisfactory method and as it 

 can be readily secured upon the market, home preparation 

 is not recommended. 



Commercially it can be secured either as a powder or 

 as paste. The powdered form has more recently come 

 upon the market and is preferred by many users of this 

 insecticide. The amounts to use vary somewhat with 

 the insect which is to be controlled. Ordinary appli- 

 cations are one and one-half pounds of powdered arse- 

 nate or three pounds of paste arsenate to fifty gallons of 

 water. 



It is also offered upon the market under different 

 trade names but as these are no better than the common 

 forms and usually cost more, their use is not recommended. 



287. Other arsenites. — London purple (arsenite of 

 lime, with certain impurities) was gne of the first arsenical 

 poisons used. It was cheaper than paris green, which ac- 

 counted largely for the extent to which it was used. It 

 was variable in its chemical qualities, often containing 

 considerable soluble arsenic, which caused injury to the 

 foliage. For these reasons it has practically passed out 

 of use. Arsenite of zinc has recently been placed upon 

 the market as an insecticide for use with certain plants. 

 It is largely in the experimental stage at the present time 

 and therefore should be used with considerable caution. 



288. Poisons. — Compounds of arsenic are deadly 

 poisons and should always be handled with the greatest 

 care. 



289. Hellebore powder, the ground root of white 

 hellebore, is a far less virulent poison than the arsenic 

 compounds. Some persons do not like to use arsenic 



