﻿STUDIES OF THE PINK BOLLWOEM IN MEXICO 



13 



Table 11. — Precipitation and maximum daily temperatures of the air and the sur- 

 face of the soil. 





Maximum 



daily 



temperatures 



Precipi- 

 tation 



Date 



Maximum 



daily 



temperatures 



Precipi- 



Date 



Air 



Surface 



of the 



soil 



Air 



Surface 



of the 



soil 



tation 



1922 

 Dec. 11 



"F. 

 80 

 80 

 81 

 84 

 81 

 81 

 78 

 79 

 79 



°F. 

 116 

 119 

 116 

 124 

 120 



Inches 

 

 

 

 

 

 

 

 

 



1923 

 Jan. 1 to 7 



°F. 

 82 

 82 

 83 

 86 

 86 

 85 

 87 

 80 

 86 

 96 



120 

 123 

 122 

 128 

 127 

 125 

 130 



Inches 

 



12 



8 to 14 .. 







13 



15 to 21 







14 



22 to 28 --- 







15 



16 



29 to Feb. 4 



Feb. 5 to 11 



0.34 

 



17.. 





12 to 18... 



0.21 



18 to 24. . 





19 to 25.- 







25 to 31. -- - 





26 to Mar. 4 



Mar. 5 to 11 





0.15 





















THE PRACTICAL IMPORTANCE OF HIBERNATION IN THE SOIL 



In a series of experiments reported in Department Bulletin 918,® 

 it was found that tne survival of the larvae in the soil is greatly de- 

 creased as the amount of moisture increases. In nonirrigated plots 

 it was found that 12.8 per cent of the larvse were alive or had emerged 

 as moths during May and June, whereas in several irrigated plots 

 no larvae whatever survived the winter. It was also found that in 

 Mexico the infestation of the season generally starts from material, 

 such as old bolls, left on the surface of the ground. These facts show 

 the reason for the effectiveness of the clean-up measures followed in 

 the United States, where all of the possibly infested material on the 

 surface of the soil is removed and burned and such infestation as 

 remains in the soil dies out on account of the heavy winter rains. 



LONGEVITY OF RESTING LARV^ 



Studies to determine the longevity of the resting larvae were 

 carried on during 1921 and 1922. On March 8, 1921, several thousand 

 heavily infested, open bolls were gathered from standing stalks of 

 the 1920 crop. These bolls were stored in a box in the laboratory, 

 and monthly examinations were made to determine the mortality 

 of the larvaa. In the latter part of the same month several thousand 

 double seed were collected from a large quantity of 1920 seed stored 

 in an oil mill at Gomez Palacio, Durango. These were placed in a 

 cloth bag and stored with a quantity of other seed in a sack in the 

 laboratory. Monthly examinations were also made of these seed. 



The results of these studies arc given in Table 12. 



» U. C. Loftln, K. B. McKinney, and W. K. Hanson. Op. clt. 



