5 



It should be remembered, however, that the percentage of green 

 bolls attacked is not the same thing as the number of boll worms per 

 100 bolls. When only ten per cent of the bolls are attacked most 

 or all of them will be attacked by a single worm only, but when more 

 than fifty per cent are attacked the majority of them will contain more 

 than one worm. For any given percentage of attacked bolls the 

 probable number of worms per 100 bolls can be calculated mathemat- 

 ically, and these calculated figures have been found to agree very 

 closely with actual fact. Thus in Table II figures actually found in 

 experiment by Mr. Ballou are compared with figures calculated by 

 Dr. Gough. The two sets show a remarkable similarity. 



TABLE II. 



If now we take Table I and replace the number of attacked bolla 

 by the probable number of boll worms per 100 bolls calculated as 

 explained above, we obtain the figures given in Table III. 



TABLE III. Wadi Tumilat. 



