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 212 



Nature-Study Agriculture 



Mollusks 



U. S. D. A. 



FIG. 165. A common garden slug. Several troublesome kinds of slugs have 

 been brought to this country from Europe. 



stalks in the fall. If the cotton stalks are burned 

 by the middle of October, a very large percentage 

 of the eggs, larvae, and full-grown weevils will be de- 

 stroyed. Plowing the stalks under serves the purpose 

 about as well, and this is better for the soil, but it is 

 difficult to do when the cotton is large. The earlier 

 cotton can be brought to maturity the safer it is, for 

 the boll weevils increase in number as the season ad- 

 vances (Fig. 164). 



Snails and slugs (Fig. 165), though not insects, eat 



