MEASURES FOR INSECT CONTROL 315 



weevils are reckoned invariably as plant feeders, almost 

 entirely confined to fruit or seeds, while CardbidcB, though 

 largely carnivorous, show too much variation in food and 

 too many herbivorous species to make it safe to draw con- 

 clusions without the study of each species. In the applica- 

 tion of this principle, therefore, it becomes necessary to 

 consider the nature of the group as a whole, not merely 

 the habits of certain ones. 



MEASURES FOR INSECT CONTROL. 



There have been a great many different remedies and 

 plans of treatment for the control of injurious insects and it 

 would be impossible to discuss them all, even those which 

 have general application, in a short course. The attempt 

 will be to select some of the most universal and useful and 

 give them with such rules as to make it possible to apply 

 them without further instruction. 



In general the methods of control for insects may be 

 separated into those which are direct and have in view the 

 destruction of the insect with some destructive agent or 

 mechanical application, and those methods that depend upon 

 some plan of cultivation or sequence of crops to prevent or 

 modify the insect attack. 



Direct Methods. Insecticides. — Substances used in such 

 manner as to kill directly are termed insecticides, and insec- 

 ticides may be classed broadly into two large groups: (1) 

 those which are poisonous in character and depend for their 

 effect upon the insects swallowing them with their food and 

 (2) those which affect the insects by contact or penetration, 

 such as the oils and fumigants. 



Of the poisonous materials some preparations that are 

 among the most important may be mentioned. 



Paris Green.— Paris green is a bright green arsenical 

 powder which should contain at least 50 per cent, arsenious 

 oxide and not over 3.5 per cent, soluble arsenic. The for- 

 mula^ for its use are as follows: 



Paris green 5 ounces 



Lump lime 1 pound 



Water 50 gallons 



