40 
BULLETIN 1374, U. S. DEPARTMENT OF AGRICULTURE 
These cylinders were kept under observation throughout the 
summer and in October the soil was removed from them and carefully 
examined. Table 30 shows the results of this experiment. 
Table 30. — Emergences of moths and larvae buried at different depths in soil in 
cylinders 
Larvae buried 
Emerged during summer 
Found in soil (dead) 
Depth 
Number 
Larvae 
Pupae 
Moths 
Larvae 
Pupae 
Pupal 
cases 
Inches 
4 
8 
12 
16 
20 
74 
2 
1 
17 
15 
6 
3 
2 
4 
3 
1 
4 
6 
74 
74 
74 
73 
4 
1 
1 
8 
15 
1 
1 
The larvae recorded under " Emerged during summer" were found 
in the traps, evidently having issued from the soil and entered the 
screen- wire traps in searching for a place to pupate or trying to escape 
from the cylinders. This also accounts for the one that entered and 
later pupated. These larvae and the pupa were all dead when 
found, having evidently been killed in the traps by the heat of the 
sun. The adult taken from the cylinder in which the larvae were 
buried at the depth of 4 inches was alive and perfectly devel- 
oped. The other adult was imperfectly developed and had been 
partly eaten by ants when found. 
Considering the number of larvae that were found to have issued 
from|the soil, the most reasonable explanation of the emergence of 
the moths is that the larvae first came to the surface, or near the sur- 
face, and then pupated. This explanation is much more reasonable 
than that a moth could issue from any great depth of soil unless it 
were of such nature that the moth would not have to burrow its way 
out. The experiment plainly shows that the pink bollworm, at least 
in the larva stage, can escape even if buried to a considerable depth 
by cultivation. 
SUMMER CULTIVATION 
It was shown in Tables 25 and 26 that during the summer the 
natural mortality of the pink bollworm in the soil is greater for in- 
dividuals found between the rows than for those found immediately 
under the plants and that the mortality decreases with depth. This 
suggested that the heat of the sun might be responsible for the in- 
creased mortality, since larvae between the rows, particularly near 
the surface, are more exposed to this heat. A few experiments were 
conducted to determine whether this is true. 
Temperature readings were taken on several days in September, 
1921, on the surface of the soil and 1 and 2 inches below the surface 
during the hottest part of the day. These readings are recorded in 
Table 31. 
