FIELD CROP INSECTS 



255 



the soil for two to five inches and after making an upward 

 burrow nearly to the surface for the escape of the moth, 

 changes to a pupa at the bottom of the burrow. During 

 the summer the moths emerge in about two weeks, but the 

 last generation in the fall passes the winter in the pupal 

 stage. The second generation of moths appears about mid- 

 summer in the lati- 

 tude of Delaware and 

 Kansas. The cater- 

 pillars of the second 

 generation in the 

 South and of the 

 third farther north 

 prefer to lay their 

 eggs on corn silk and 

 tassels and do seri- 

 ous injury by eating 

 outthetipsoftheears. 

 From 2 to 3 per cent 

 of the corn crop of 

 the country, valued 

 at from $30,000,000 

 to $50,000,000, is 

 thus destroyed an- FlG - 179.-Bollworm at work on cotton 



bolls, boring into grown boll slightly 



nually, and the an- re duced. (After Quaintance and Brues, 

 nual damage to cot- u. S. Dept. Agr.) 

 ton is estimated at 



$20,000,000. In the Gulf States there are four or five gener- 

 ations, the larvae of the third and fourth generations being 

 the most injurious to cotton in August and September. This 

 is also the season when tobacco is worst injured. 



Inasmuch as the pupae pass the winter in the soil, the 

 most practical means of control is to plow infested land in 



