BOLL WEEVIL. 9 



business, -which is principally that of reproduction. The entire 

 time from the laying of the egg until the emergence of the fullgrown 

 ■weevil varies with temperature and humidity, but is usually three or 

 four weeks or longer. 



During the early growing season the weevils move about from 

 plant to plant, but no general flight takes place until late in the sea- 

 son, probably not earlier than the middle of August. The weevils 

 then sometimes move as far as 40 miles in short successive flights. 

 As soon as the weather begins to get cold all adult weevils begin 

 to seek shelter, so as to pass the winter in safety. Many of the eggs 

 laid in the squares continue their development if sufficiently pro- 

 tected from the cold. The weevils thus produced hibernate during 

 the winter and are ready to join their parents in the campaign 

 against the farmers the following spring. 



SPREAD OF WEEVIL. 



The boll weevil's first invasion of the United States was in 1892 

 in the vicinity of Brownsville, Tex. Since that time it has advanced 

 from year to year in practically concentric curves. There have been 

 some interruptions clue to climatic conditions, but an annual average 

 advance of more than 50 miles per year has been made. 



Tlie pest crossed the Savannah River in November, 1917, and hy 

 spreading over additional territory in succeeding seasons it had cov- 

 ered the entire cotton-producing area of this State in the fall of 1920. 



Comparison of Sotjth Carolina and Louisiana. 



Many people maintained that the conditions in this State were 

 different from those in the other States where the greatest damage 

 was done hy the weevil. However, a careful comparative study of 

 conditions as well as the evidence of destructiveness already ex- 

 hibited in the lower counties during 1920 and 1921 have shown that 

 this is. not the case. 



Careful study would indicate that such is not the case. There 

 may be less damage in the Piedmont sections on account of the ele- 

 vation and the lower. winter temperatures, but over against these 

 advantages must be put the disadvantage of the heavy soil type and 

 the large amount of hibernating shelter furnished by terraces and 



woodland. . . . „ 



Except in the upper Piedmont section, the situation m South 

 Carolina approaches very closely to that of central and northern 

 Louisiana, Avhere the recent investigation of boll-weevil conditions 

 shows the most disastrous results. 



CHIEF CONTROLLING FACTORS. 



The two most important climatic factors which affect the boll 

 weevil are minimum winter temperature and maximum summer rain- 

 fall. Winter temperatures have the effect of controlling the number 

 of weevils which pass through the winter. Summer rainfall has an 

 important effect upon' the reproduction of the weevils. A heavy 

 summer rainfall is most favorable to a large hatch of the weevil eggs 

 laid in the squares. A hot dry summer has the opposite effect. In 



S. Doc. 76, 67-1-^2 



