184 AGRICULTURE ON THE PACIFIC SLOPE 



leaves. For this we use a spray ofjsoap and kerosene, 

 or some other substance which does not need to be 

 eaten in order to kill them, but kills them merely by 

 getting on the outside of their bodies. The spray 

 should be applied with considerable force. 



Much time and money have been wasted year after 

 year in sprayingjead arsenate (and Paris green) upon 

 sucking insects such as plant lice and soale insects. 



Some insects feed on the roots. They may be starved 

 by keeping the land bare of crops for a time, or by grow- 

 ing a crop which they cannot eat. In some cases they 

 may be killed by leaving poisoned food on the ground 

 where they can easily find it. 



Some bore into the wood and bark. For these there 

 is no good remedy. They are sometimes dug out by 

 hand, and sometimes killed by carbon bisulphid. 



poisonous gases bre used to kill all sorts of insects, 

 either out of doors with the aid of a tent placed over 

 the tree, or indoors in a closed box. Most states have a 

 quarantine station through which plants coming from 

 outside must pass. There the plants are usually ex- 

 posed for a short time to poisonous gases to kill any in- 

 sects which may be on them. This is called fumigation^ 



Household plants are often attacked by insects. 

 The best way to treat them is to brush the leaves and 

 stems carefully with a toothbrush dipped in soapsuds. 



Insects form one of the most interesting parts 

 of nature study. " The life stories of many insects, 



