LEAVES 



117 



comes infested with a very small mite called red 

 spider because it spins a web. These mites injure 

 the leaf by sucking sap from it. They can be kept 

 in check by frequent spraying for they do not like 

 water. If, then, we are careful to frequently spray 

 the leaves of our house plants we will have very 

 little trouble from aphis, red spider or over trans- 

 piration. The aphis, or plant louse, is often very 

 numerous on out-door plants, for instance, the rose, 

 chrysanthemum, cabbage, and fruit trees. They 

 vary in color from green to dark brown or black. 

 They are treated in the same way as those on the 

 house plants. Some familiar out-door insects which 

 interfere with leaf work are the common potato 

 bug, the green cabbage worm, the rose slug, the 

 elm tree leaf beetle, the canker worm, the tomato 

 worm. These insects and many others eat the 

 leaves (Fig. 67). They chew and swallow their 

 food and are called chewing insects. All insects 

 which chew the leaves of plants can be destroyed 

 by putting poison on their food. The common pois- 

 ons used for this purpose are Paris green and Lon- 

 don purple, which contain arsenic, and are used at 

 the rate of one teaspoonful to a pail of water or 

 one-fourth pound to a barrel of water. This is 

 sprinkled or sprayed on the leaves of the plants. 

 Another poison used is white hellebore. This loses 

 its poisoning qualities when exposed to the air for 

 a time. Therefore it is safer to use about the flower 

 garden and on plants which are soon to be used as 

 food or whose fruit is to be used soon, like cab- 



