PINK BOLL WORM OF COTTON" IN MEXICO. 17 
is cut just prior to pupation and not when the seeds are first webbed 
together. Often the end of the pupal shell is seen protruding from 
the seeds through this opening. 
When pupation occurs in old bolls of cotton a favorite method is 
to make a slight depression in the lint and pupate between the cot- 
ton and boll. Where hibernation has been in the fields larvae may 
leave the bolls and pupate in the ground. On March 14, 1919, 1^ 
square yards of soil in the corral at Lerdo, where many bolls were 
lying around, were examined. Four live larvae and one dead one, 
together with one live pupa and several empty pupal cases, were 
found. All were near the surface, one larva being under a piece 
of trash and the others an inch or so down. All the larvae and 
the live pupa had light cocoons and seemed to have gone into the 
soil for pupation rather than hibernation. In the case of the old 
pupal skins it could not be determined whether they came from 
hibernating larvae or were left over from the previous summer. 
The duration of the pupal stage from 250 resting larvae ranged 
from 8 to 26 days, with an average of 10.3 days. This is an average 
of 1 day more than for the summer larvae, due to the fact that pup- 
ation took place during the colder months. There is considerable 
individual variation in the length of pupae formed at the same time, 
but this occurs in pupae from summer larvae as well as from resting 
larvae. The pupae from which male moths emerged required an 
average of one-half day more than those from which females emerged, 
the males requiring 10.5 days and the females 10 days. 
Time of Emergence from Resting Larvae. 
A few moths may emerge throughout the year in the Laguna. 
When work was first begun in the early part of February, 1918, 
freshly formed pupae were found among seed at the seed warehouses. 
During the month of March, 1918, there emerged 23.5 per cent of all 
the moths which emerged during the year from larvae collected in 
seed in February and removed to the laboratory. Emergence con- 
tinued till August, when all of the larvae had died or emerged, the 
maximum being reached in May. Pupae were formed from larvae 
collected in the summer and fall of 1918 throughout the fall and 
into January, 1919, thus completing the cycle of pupation for every 
month in the year. The pupal period is greatly retarded during the 
cold months, but this does not prevent emergence on warm days. 
Table VII shows the monthly emergence of moths from resting 
larvae for 1918 and 1919. 
11696°— 21— Bull. 918 3 
