﻿STUDIES OF THE PINK BOLLWOEM IN MEXICO 



particles of plant material and other coarse matter, which was 

 allowed to dry and was then examined. In examinations where 

 forms on the plants and on the sm-face of the soil were considered, 

 only those forms on the same square yard as that in which the soil 

 sample was taken were included. 



Table 3 gives a record of the number of pupae found in and attached 

 to forms on the surface of the soil, and in the soil. The totals, 34 

 and 136, show that the larva prefers to enter the soil for pupation. 



Table 3. — Pupse. of pink bollworm (live and dead) found per square yard informs 

 and plant material on the surface of the soil and in the soil 



Date 



On the 

 surface 



In the 

 SOU 



July 21 



1921 



2 

 29 

 2 

 1 

 

 

 



7 



Aug. 4 - - - 



96 



Sept. 6 



28 



25 - - - --- 



1 



Oct. 18 . . 







29 



2 



Nov. 28. 



2 









Total .. 



34 



136 







DEPTH TO WHICH LARViE ENTER SOIL 



Larvae often enter the soil to a depth of 6 inches, but the majority 

 are found within the first 2 inches. In a number of soil examinations 

 made in 1921 cotton fields, the soil was taken up in three 2-inch layers. 

 A record of these examinations is given in Table 4. As will be noted, 

 70.6 per cent of all stages are found in the first 2 inches, 21.3 per cent 

 in the second 2 inches, and 8.1 per cent in the third 2 inches. 



Table 4. — Total larvse, pupse, and pupal cases found per square yard at different 



depths in the soil 



Date 



First 2 

 inches 



Second 2 

 inches 



Third 2 

 inches 





1921 



101 

 65 

 50 

 41 

 15 

 19 



25 

 16 



7 



23 

 33 

 20 

 2 

 4 

 9 



3 







8 



3 



19 



17 



Sept. 6-- --- - - --- 



10 



Oct. 18 







29 . 







Dec. 16 







Jan. 3 



1922 



3 



20 . - --- 



5 



Feb.' 28 



1 









Total .. 



339 

 70.6 



102 

 21.3 



39 





8.1 







Both larvae and pupa3 arc found more abundantly in the soil im- 

 mediately under the plants than in that between the rows. This is 

 shown by the results of some of the soil examinations made in 1921 

 cotton fields, in which each squares yard taken as a sample was divided 

 into two areas. The first ansa consisted of a strip immediately under 

 the plants, 1 foot wide and 3 fer^t long, running lengthwise with the 

 row, and the second, 2 strips of th<! same size as the first and on either 

 side of it. The inrnw area was thus only half as largo as the outer. 

 Table 5 shows the results of tlicsc examinations, 67.1 per cent of the 



