8 MISC. PUBLICATION 181, U. S. DEPT. OF AGRICULTURE 



At a certain period in the summer, usually July or August, the 

 weevils become restless and seem to want to leave the cotton fields 

 where they have been living and go to other fields, where they can 

 live more easily. As long as there are fields of cotton free from 

 weevils anywhere nearby, the weevils are sure to fly in that direction. 



The only thing that will stop the progress of the weevils across the 

 country is a lack of fresh cotton fields or a very dry climate. Weevils 

 do not breed fast when it is dry and hot and do very little damage at 

 that time; they need a warm, moist climate. Thus in eastern Texas, 

 where the summers are cool and moist, they infest all the cotton terri- 

 tory, but in western Texas they have done very little damage because 

 there the summers are very hot and very dry. The boll weevil is to 

 be found in nearly every part of the cotton-producing area except the 

 Southwest. It is also found in Mexico, Central America, Cuba, and 

 Haiti. The map in figure 5 shows where cotton is grown in the United 

 States and where weevils are found. 



HOW NATURE HELPS TO CONTROL THE BOLL WEEVIL 



When one begins to study how to get rid of boll weevils, he finds 

 that nature helps to destroy them. It has been estimated that the 

 possible children, grandchildren, great-grandchildren, and great-great- 

 grandchildren of a single pair of weevils born in one season could 

 amount to several million weevils if nothing happened to them. But 

 something does happen to a great many of them. If this something 

 did not happen to them in a natural way, and if every one of them 

 grew, it would be impossible for farmers to raise a bale of cotton no 

 matter what they did to control these pests. 



Some kinds of climate will kill off the weevils very fast. Often 

 squares with the young weevils in them fall to the ground and become 

 so heated by the direct rays of the sun that the little creatures inside 

 die in a short time. Too much dry heat is bad for the young weevil, 

 and this is the reason a cotton farmer likes a hot, dry summer; it 

 gives his cotton a chance to grow. 



There are certain insects whose young like to eat the soft weevil 

 grubs. These tiny wasplike insects lay their eggs in the bodies of the 

 boll weevil grubs. The eggs hatch into very small grubs, which feed 

 on the boll weevils and kill them. Sometimes as many as half the 

 young boll weevils in a cotton field are killed in this way, while in 

 other fields very few or none seem to be killed. 



Then there are other insects that cut their way into the infested 

 squares and eat up the soft-bodied little weevils found there. The 

 most important of the insects that eat the boll weevils are certain 

 kinds of ants. These ants seek out the infested squares and gnaw 

 through the wall to feast upon the juicy grub inside. Often a large 

 number of the weevil grubs and pupae in a cotton field are destroyed 

 in this way. 



The most effective way, however, that nature helps man to control 

 the boll weevil is by means of heat and cold. Very hot weather and 

 very cold weather are even more distressing to a weevil than they are 

 to man. A very cold winter, followed by a bright, hot summer will 

 generally stop the weevils from increasing to numbers large enough 

 to do serious damage to the cotton crop. On the other hand, if the 

 winter is mild and the following summer is wet and cloudy, large 

 numbers of weevils and much damage may be expected. 



