Addendum dated July 14, 1922. 



Since writing the foregoing, the author has received a copy of 

 U.S. Bulletin No. 918, " Report on Investigation of the Pink Boll 

 Worm of Cotton in Mexico," by Messrs. LOFTIN, McKiNNEY and 

 HANSON. 



Some figures given by them allow comparison to be made between 

 Mexican and Egyptian crop-loss. 



On page 31 they put the fallen and unpickable bolls as 20 per 

 cent of the possible crop. 



The pickable crop is divided into three picks, the first giving 

 40 per cent, the second 40 per cent, and the third 20 per cent of the 

 crop (page 29). 



It appears to the present writer that it ought to be quoted, 

 first pick 32 per cent, second pick 32 per cent, third pick 16 percent, 

 unpickable 20 per cent. 



The loss found was 3-1 per cent of the first picking, 4-6 per cent 

 of the second, and 19-1, per cent of the third. This would give 1 per 

 cent of the total crop lost in the first, 2 per cent in the second, and 

 3 per cent in the third picking, plus 20 per cent unpickable, totalling 

 26 per cent ; not 0-9 per cent as calculated by the authors. 



It is noticeable that the third picking contains 52 per cent 

 damaged seed ; and that it is smaller than the lost part of the crop. 



Unfortunately the authors do not give any information as to the 

 numbers of bolls used, neither do they state the variety of cotton 

 the observations refer to. But it is probable that the size of the 

 loss observed by them was of the same magnitude as occurs in Egypt. 

 There can have been very little unpickable cotton in their first and second 

 pickings, the lost bolls consequently nearly all belonged to the third, 

 The apparent percentage of attack at the time of the third picking 

 must have been very high to produce over 50 per cent seeds damaged, 

 and the lost bolls outnumber the third picking bolls. For the select 

 population comprising the third picking pluu lost bolls the damage 

 must have been about 58 per cent. It is also obviou' that the standard 

 of pickable cotton used in Mexico was lower than the Egyptian. 

 Here samples of pickable cotton would hardly contain such a percen- 

 tage damaged seed. With a higher standard for pickable cotton, 

 the total loss figures would also be greater. 



