Injurious Insects and How to Control Them. 61 



set out, but for the crops ten to twenty-five years later; conse- 

 quently it should always be some distance from the boundary 

 lines, so that the owner may never be obliged to suffer thron-iQ 

 the carelessness or indifference of a neighbor. All trees and 

 plants brought on a farm should be closely scrutinized and it 

 would be a wise precaution to fumigate all such with hydrocyanic 

 acid gas (as recommended on a following page) or else to buy only 

 stock which has been so treated. If these precautions are taken, 

 a man may reasonably expect to reap nearly full benefit from his 

 efforts to keep his orchards free from injurious insects. 



Number of injurious insects. — The number of injurious insects is 

 so great that it is impossible to tre&t of all those worthy of notice. 

 For example, 378 different species have already been listed as 

 preying in some manner or other on the apple tree or its fruit, and 

 while the majority of these can hardly be regarded injurious, as a 

 rule, yet under unusually favorable circumstances almost any 

 one of them might cause considerable damage. Before passing to 

 the consideration of individual species, there are a few funda- 

 mental facts which should be emphasized. 



Biting and sucking insects. — In a practical way we must dis- 

 tinguish between those insects which bite off and devour por- 

 tions of their food and others which obtain their sustenance by 

 sucking fluids from the underlying tissues. The work of the 

 former class may easily be recognized by portions of a plant being 

 eaten away. As a general rule such insects can be controlled by 

 spraying with an arsenical preparation, provided the poison is 

 placed where the insect must eat it or go hungry, and the suc- 

 cess of the operation will be proportional to the plant surface 

 covered. In short, when spraying with arsenical poisons aim to 

 have the insecticide hit every portion of the plant liable to attack. 

 The necessity of this is shown by the following: Last spring 

 maple leaves were sprayed with several arsenical preparations. 

 The variously treated leaves (after the spray had dried and the 

 poison was therefore nearly invisible,) and some untreated ones 

 were placed in separate jars and forest tent caterpillars placed 



