12 ' BULLETIN" 1374, TJ. S. DEPARTMENT OF AGRICULTURE 
A very sudden decrease in tme number of living larvae after the end 
of January without a compensating increase in the number of dead 
larvae is noted in both Tables 8 and 9. Few pupal cases were found 
in any of the bolls, so this does not explain the disappearance of the 
larvae; neither was there any increase in numbers found in the soil. 
On January 30 the first rain, 0.34 inch, fell since the experiment was 
started. This may have caused many larvae to leave the bolls; 
but, owing to the condition of the soil" immediately after the rain, 
they did not enter the soil readily. Many of them were probably 
destroyed by birds or crawled beyond the area of soil that was 
examined. 
Tables 8 and 9 indicate that very few larvae left the bolls on the 
stalks to go to the soil. With the larvae in the bolls placed on the 
surface of the soil the proportion leaving the bolls was much greater. 
As shown in Table 8, most of this entrance of larvae from the bolls 
into the soil must have taken place shortly after the bolls were placed 
on the soil. The first examination, six days after the bolls were 
placed, showed as many larvae in the soil as the average for all the 
examinations. That this may have been due to the heat of the sun 
is indicated by the experiment about to be described. 
EFFECT OF EXPOSURE TO SUN ON ENTRANCE INTO SOIL 
On December 11, 1922, 100 bolls were placed on the surface of the 
soil in each of two boxes filled with soil. One of these boxes was 
kept in the shade and the other in the sun, both outdoors. Every 
week the soil was taken from each box and carefully examined for 
pink bollworms. Fresh soil was then put into the boxes and the 
same bolls replaced on the surface thereof. The results of this test 
are shown in Table 10. 
Table 10. — Number of larvse leaving 100 bolls on the surface of the soil in the shade 
and in sun, and entering the soil 
I Number of larvae in Xumber of larvse in 
the soil the soil 
Date examined 
Date examined 
In the 
In the 
In the 
In the 
shade 
sun 
shade 
sun 
Dec. 18 

2 
Feb. 26 

4 
25 , 

6 
Mar. 5 

1 
Jan. 1 

3 
12 


8 . 


19 


15 


26 


22 


Apr. 2 


29 

1 
9 


Feb. 5 

2 
12 

1 
Total 

21 
19 

1 
The total of 21 larvae found to have entered the soil from the bolls 
in the sun, with none from the bolls in the shade, shows clearly the 
effect of exposure to the sun. Below (Table 11) is given a record of 
the precipitation and the maximum daily temperature reached at the 
surface of the soil during the time these experiments were conducted, 
as well as the maximum daily air temperature. 
