38 BULLETIN 918, U. S. DEPARTMENT OF AGRICULTURE. 
In general, it may be said that larva? will live in bolls submerged 
in water or floating on the surface of the water till the bolls them- 
selves are thoroughly rotten. This may be a week or more, depend- 
ing upon the condition of the bolls. The old dried bolls and larvae 
webbed up in bits of rubbish are particularly likely to carry an infes- 
tation a long distance, for they float more readily than green bolls. 
One of the large plantations was considering dividing their property 
into zones which would be planted in cotton only every third or 
fourth year in order to reduce the damage by the pink bollworm, but 
the danger of reinf estation by irrigation water was considered so great 
that it was not adopted. 
NATURAL CONTROL. 
From the data collected in 1918 and 1919, it is concluded that the 
maximum infestation and the maximum damage to the cotton of 
the Laguna have been reached by this time, except for slight yearly 
variations due to climatic conditions which may have some effect 
on the development of the pink bollworm and its attack on the 
cotton. It is the belief of the plantation owners that the damage 
or loss to the crop has remained about the same since 1916, or that 
the maximum had been reached at the end of five years from the time 
of introduction. 
MORTALITY OF NEWLY-HATCHED LARV,£. 
It has been shown in Table III that 47.1 per cent of the pink 
bollworm eggs are not deposited on the squares or bolls. The larva? 
from these eggs must crawl some distance before reaching food. In 
this migration they are readily attacked by insect enemies, are ex- 
posed to the hot sun, become weakened and exhausted, and event- 
ually may succumb to starvation. It is thought that very few or 
possibly none of the larva? from this 47.1 per cent of the eggs ever 
enter the squares or bolls. Many of the larva? from the remaining 
52.9 per cent of the eggs deposited on suitable parts of the plant 
never succeed in entering the bolls or squares either. To determine 
what percentage of the larva? hatching from eggs deposited on the 
plants fail to enter the bolls or squares, five plants were examined. 
These records were carefully made. Every part of the plant was 
closely examined with a hand lens for eggs and eggshells. The larva?, 
pupa?, and exit holes were also carefully counted and the mortality 
rate calculated from the number of eggshells found on the plants 
and the total infestation of the plants. The results are given in 
Table XIX. 
