STUDIES OF THE PINK BOLLWOBM 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 
°F. 
120 
123 
122 
128 
127 
125 
130 
Inches 

12 . 
8 to 14 

13 
15 to 21 

14 . 
22 to 28 

15 
29 to Feb. 4 
Feb. 5 to 11 
0.34 
16 . 

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, 8 
it was found that the 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 larvae 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 LARVAE 
Studies to determine the longevity of the resting larvse 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 larvae. 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 are given in Table 12. 
s U. C. Loftin, K. B. McKinney, and W. K. Hanson. Op. cit. 
