INSECTS AFFECTING FIELD CROPS 499 



The beetles attack only cotton. Those issuing from their 

 winter hiding places early, feed on the foliage and lay their 

 eggs on the unopened buds, or "squares," as soon as they com- 

 mence to form. The larvae hatching from these eggs feed for 

 ten or twelve days, and usually cause the infested squares to 

 fall to the ground. There may be four or five generations 

 during the summer, the beetles attacking the older bolls as 

 soon as the squares are no longer available. The adults of the 

 last generation hibernate in old cotton plants or in rubbish in 

 or near the fields. When they are hunting for suitable places 

 in which to hibernate they may fly for considerable distances, 

 and thus the distribution of the species is provided for. 



The larvae in many of the infested squares that drop to the 

 ground will perish on the hot, unshaded soil. It is therefore 

 advisable to plant the rows as far apart as practicable and to 

 use varieties of cotton that produce little foliage in order 

 that the sun may shine on the fallen squares. As the damage 

 is usually worse on the late varieties the best of the early 

 varieties should be selected in regions where there is danger of 

 boll- weevil infestation. Any cultural methods that will 

 strengthen the plant and aid in the early maturing of the bolls 

 will materially increase the yield. As soon as the crop is 

 gathered all the cotton stalks and all the rubbish in the field 

 *should be burned. This will kill many of the insects, and 

 destroy the feeding and hibernating places of most of those 

 that are left. 



The Cotton Boll-worm, which is the same as the corn ear- 

 worm, has been discussed on page 486. It is best controlled 

 in the cotton field by plowing late in the fall, thus destroying 

 the over-wintering pupae. Early varieties of cotton should be 

 planted, as it is the later broods of moths that lay their eggs 

 on the cotton, the corn being preferred as long as it is young and 

 available. Late planted corn in or near the cotton fields will 

 sometimes keep the boll-worm away from the cotton. 



TOBACCO 



Tobacco-worms, or Horn- worms. The large greenish horn- 

 worms (larvae of sphinx- or hawk-moths) are probably the most 



