5^4 



BIOLOGY AND HUMAN LIFE 



Fig. 231. Cotton-boll weevil {Aiithononnis grandis) . (Greatly enlarged) 



This animal feeds only upon the cotton plant and could probably be completely ex- 

 terminated if the planting of cotton were suspended for a year or two. This was the 

 advice of the government experts to the growers of Texas about twenty years ago ; 

 but it was unheeded, with the result that millions of dollars' worth of cotton have 

 been destroyed each year since. Rotation of crops was finally forced upon many of 

 the farmers, with beneficial results, a, larva ; b, larva in mature boll ; c, pupa ; 



d, pupa in boll ; e, adult 



dollars every year. To this must 

 be added the injury to forests 

 and forest products, and the in- 

 jury to animals. 



The locusts and many other 

 species of insects will eat almost 

 every kind of plant ; but many 

 insects confine their attention to 

 one or a limited number of food 

 plants. The damage done by 

 such insects is accordingly con- 

 fined to special kinds of crops. 



The Colorado potato beetle is 

 perhaps the best known of the 

 special-crop insects (Fig. 235). 

 It is kept in check by the use 

 of poisonous sprays or powders 

 applied to the growing plants. 



The cotton-boll weevil has spread over a large part of our 

 cotton area in recent years and has ruined many a crop 



Fig. 232. Meal-worm 



Adult and larva of the miller beetle 

 {Tenebrio molitor) . (X 3) 



