SEASONAL HISTORY. 



83 



season with no actual gain in the yield of the current season. Plants 

 standing until frosts kill them are often allowed to remain throughout 

 the remainder of the winter and easily furnish an abundance of favor- 

 able hibernating places for the weevils. The consequence of this 

 practice is that so many weevils are carried through the winter alive 

 that the yield of the next year is much less than it might have been 

 but for the farmer's indulgence of the forlorn hope of a top crop. It 

 is far wiser to abandon the uncertain prospects of a top crop and 

 destroy the stalks in order to insure a better crop the following year. 



Fig. 19.— Status of the boll weevil in Texas in August, 1911; percentage of infestation of all forms. 



(Original.) 



VARIATIONS IX ABUNDANCE OF THE WEEVIL FROM YEAR TO YEAR. 



The decrease in damage by the weevil in Texas in the last few years 

 has led some observers to believe that the insect will finally disappear 

 altogether. Investigation shows that this belief is erroneous. In 

 1897 the French entomologist, Dr. Paul Marchal, published a paper 

 which set forth some of the essential factors governing insect abun- 

 dance from year to year. This author called attention to the more 

 or less regular periodicity in the abundance of certain well-known 

 injurious insects. In this country the cotton leaf worm, Alabama 

 argillacea Hiibner, is an example of such periodical abundance. The 



