180 FRIENDS AND ENEMIES OF PLANTS 



Groups of Insects. So far as the insect pests of agriculture are 

 concerned we may make two general groups: (1) biting and chew- 

 ing insects, (2) sucking insects. 



Biting Insects. This group includes all insects in which their 

 mouth parts are formed for biting and chewing. They bite off, 

 chew, and swallow the leaves or other portions of the plant upon 

 which they happen to feed. Common examples of this class are 

 to be found in caterpillars, grasshoppers, beetles, cotton boll 

 weevil, etc. On account of the manner in which these insects 

 secure their food they may be killed by spraying the plants with 

 poisonous solutions. 



An effective spray may be made as follows: 



Scheele's Green . . . . 1 Ib. 

 Quicklime . . . . . 1 Ib. 

 Water 100-300 gal. 



In applying this solution it must be kept well stirred. Paris green 

 may be substituted for Scheele's green, but it is more costly and 

 often burns the foliage of plants. 



Another good spraying solution is prepared in this way: 



Arsenate of soda . . . 4 oz. 



Acetate of lead . . . . 11 oz. 



Glucose 2 qt. 



Water . . . . . 25-100 gal. 



Dissolve the acetate of lead in a bucket of warm water and mix it 

 with the arsenate of soda, which has been previously dissolved in 

 another bucket of warm water. Use wooden buckets because these 

 chemicals will corrode vessels made of tin or other metal. 



Sucking Insects. This group includes all insects in which the 

 mouth parts are adapted for sucking rather than for biting. Since 

 these insects secure their food from the juices of the plant and not 

 from the surface, it is evident that spraying the plant with poison 

 would do no good. In this group are the squash bug, chinch bug, 

 green bug, plant lice, mosquitoes, flies, San Jose scale, and other 

 scale insects. 



The only sprays that are effective with this class of insects are 

 those that corrode the body of the insect, and those that penetrate 

 the breathing pores of the insect and produce suffocation. 



