PINK BOLLWOEM OF COTTON IN MEXICO. 43 
and the mortality increased by breaking up and burying the bolls. 
On the other hand, the bolls float on water and the wind frequently 
blows them against the borders on one side of the field, where they are 
piled up several inches or more deep. This concentration keeps some 
of the bolls out of the water and affords more protection for the bolls 
in the interior of the pile against heat and cold. If the fields are not 
irrigated it means they will not be planted the following year and 
such fields are usually grazed by goats, cows, and burros, which eat 
many of the bolls. 
Whether or not the results obtained in these experiments during 
only one winter 5 hold true for what actually takes place in the Laguna 
it is impossible to say, but they indicate beneficial results from irriga- 
tion and burying the boils. That a very heavy mortality, probably 
more than 95 per cent, does take place in the fields is shown by field 
examinations of the bolls and the very light infestation in the early 
part of the season. There are such enormous numbers of larvae 
hibernating in the fields that the crop would be entirely destroyed 
if the mortality was not very high. 
Willcocks (7) in Egypt left bolls out of doors exposed to the sun on 
the surface of dry ground and ground that was watered periodically 
(three waterings). He found a very high mortality during April, 
May, and June, and all the larvae were dead on June 25. There was 
a slightly higher mortality among the larvae in the watered bolls and 
all the larvae were dead on April 8, while some survived in the dry 
bolls till May 3. His figures "most certainly show that the chance of 
resting-stage pink bollworms surviving in the bolls fully exposed to the 
sun on the surface of dry sheraki land in May, June, and July is a re- 
mote one." He buried another lot of bolls on November 24 in damp 
soil in boxes. Some of these were kept dry and others wet. Some 
were stored indoors and others outdoors, though none were in direct 
sunlight. There was less mortality in the buried bolls than in those 
left on the surface exposed to the sun, and he says, in speaking of wet 
conditions, "this does not seem to be materially disadvantageous to 
the pest. " In all of the buried bolls there was a decided emergence 
of theiarvae to the top of the soil, which began as soon as the bolls were 
buried (November 24) and continued intermittently in some cases 
where the bolls were kept dry till the following November. Water 
hastened this larval emergence when applied in the fall or the fol- 
lowing spring, but though the bolls were badly rotted the larvae were 
still able to remain in them, and spun up in their almost water-tight 
cocoons during March, April, and May. 
In our experiments in Mexico, larvae survived better in bolls on 
the top of the ground than when buried and better when left dry 
than when irrigated. In Mexico the temperature was never as high 
& These results were substantiated by experiments during the winter of 1919-20. 
