8 INJURIOUS INSECTS OF KANSAS. 



as to machines, page 10), the Paris green should be mixed (it is 

 insoluble, and only a mechanical mixture is obtained ) with water, 

 in the proportion of one pound to 150 to 200 gallons of water. 

 The proportion, however, must vary with varying conditions of 

 spraying. If the poison is applied too strong to the foliage of 

 plants it is very destructive. The susceptibility to the influence 

 of the poison varies in different plants. The foliage of peach 

 trees is very easily injured, and the proportion of Paris green to 

 water should not exceed one pound to 300 gallons. For apple, 

 plum, and cherry, one pound to 200 gallons is safe, and yet ef- 

 fective in killing the insects. The corrosive power of the poisons 

 may be much lessened if a quart of common flour for every 12 

 gallons of water is introduced into the mixture (Riley). In 

 spraying the same trees several times during a season, the later 

 applications should not be as strong as the earlier ones (Fletcher). 

 In making the poisonous mixture, the Paris green should be mixed 

 up with a small amount of water, as a paste, and the bulk of the 

 water then added. The mixing must be effectively done ; a thor- 

 ough churning, by use of a force-pump, does it well ; and during 

 the spraying the mixture should be kept well stirred. The Paris 

 green is rather heavy, and soon sinks to the bottom if left long 

 undisturbed. 



LONDON PURPLE, a by-product obtained in the manufacture of 

 aniline dyes, containing a large percentage of arsenite of lime, and, 

 in addition, some soluble arsenious acid. The total arsenic per- 

 centage is about the same as in Paris green. London purple is 

 lighter and more finely divided than Paris green, and hence re- 

 mains in suspension better in the water. The soluble arsenic, 

 however, renders the danger of scorching the foliage more real ; 

 but the addition of lime will prevent almost all injury to foliage 

 (Gillette). One pound of London purple to 200 gallons of water, 

 with a pail or two of milk of lime, is recommended as the most 

 approved formula ( Smith). London purple costs less than Paris 

 green, retailing at drug stores at about 15 cents a pound. 



Either Paris green or London purple may be used dry. The 

 poison should be mixed with 100 times its weight of perfectly dry 

 land-plaster, air-slaked lime, flour, or sifted wood ashes, and dusted 

 on the foliage ( Fletcher). 



The most important external irritant is a 



