308 THE ESSENTIALS OF AGRICULTURE 



397. Methods of controlling the cotton-boll weevil. The 

 most important means of control is a thorough cleaning of the 

 cotton fields as soon as the cotton is picked. This should in- 

 clude the destruction of all stalks, dead bolls, and crop rem- 

 nants. In this way the great bulk of the adult beetles and 

 the immature stages in the squares and bolls are destroyed. 

 This method, when supplemented by a thorough cleaning of 

 the hedges, fence rows, and other waste places, results in the 

 death of a large proportion of the weevils. 



Another means of control, especially in localities where cheap 

 labor may be had, is by gathering the fallen squares. However, 

 since many of the larvae in these squares are parasitized, these 

 gathered squares should not be burned but be placed in wire 

 cages so that the parasites may escape. The wire on the cages 

 should be tight enough to retain the weevils but not tight enough 

 to prevent the escape of the parasites. If the squares are burned 

 the enemies of the weevil are destroyed. 



Any practice that will help to get the cotton planted and 

 matured early will help to avoid serious injury, because the 

 cotton will be well along before the weevils have become abun- 

 dant. Winter plowing, early spring planting, providing for 

 plenty of space between the rows, the use of early-maturing 

 varieties, and frequent cultivation in the growing season are 

 advisable. 



398. Helpful insects. A study of insects, such as can be 

 made with simple apparatus (Fig. 155), will show that many are 

 useful and many harmful. The honeybees are useful because 

 they supply food. Others, as the silkworm, supply materials 

 for clothing. The predacious insects are those which attack 

 other insects, devouring them bodily, tearing them to pieces, or 

 sucking their life blood. Good examples of these are ladybirds, 

 dragon flies, ground beetles, robber flies, lacewings, and tiger 

 beetles. 



The parasitic insects differ from predacious ones in that they 

 spend all or a large part of their life cycle within the bodies of 

 their victims, and thus destroy them. These are the ichneumon 



