STUDIES OP 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 surface 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. — Pupae of pink boll worm (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 tbe 
soil 
July 21 
1921 
2 
29 
2 
1 



7 
96 
Sept. 6 
28 
25 
1 
Oct. 18 _. 

29 
2 
Nov. 28 
2 
Total 
34 
136 
DEPTH TO WHICH LARVAE 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 larvae, pupae, and pupal cases found per square yard at different 
depths in the soil 
Date 
First 2 
inches 
Second 2 
inches 
Third 2 
inches 
Aug. 4._ 
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 
Percentage of total 
8.1 
Both larvae and pupae are 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 square yard taken as a sample was divided 
into two areas. The first area consisted of a strip immediately under 
the plants, 1 foot wide and 3 feet long, running lengthwise with the 
row, and the second, 2 strips of the same size as the first and on either 
side of it. The inner area was thus only half as large as the outer. 
Table 5 shows the results of these examinations, 67.1 per cent of the 
