PINK BOLLWORM OF COTTON IN MEXICO. 
51 
Table XXVII is a summary of the experiments with the use of 
hydrocyanic-acid gas. From these experiments it is seen that it is 
not practicable to use hydrocyanic-acid gas when the seeds are over 
4 inches deep. It could not be recommended even when seed is in 
ordinary bags, for the center of a bag of cotton seed is more than 
4 inches from the surface of the sack exposed. 
Table XXVII. — Fumigation of cotton seed with hydrocyanic-acid gas. 
Experi- 
ment 
No. 
Position of generator. 
Dosage 
per 100 
cubic 
feet. 
Expo- 
sure. 
Per cent 
of larvse 
killed. 
Remarks. 
17 
Inside 
2-2-4 
4-4-8 
2-2-4 
2-2-4 
4-4-8 
4-4-8 
2-2-4 
2-2-4 
Hours. 
2 
3 
2| 
2" 
24 
24 
24 
48 
100.0 
70.0 
62.5 
60.0 
47.0 
34.0 
10.0 
.6 
Seed in bulk, 4 inches deep. 
24 
do.... 
Seed in bulk, 6 inches deep. 
Do. 
18 
do 
25 
do 
Do. 
16 
do 
Seed in bulk, 5 feet deep; all not killed 
15 
Outside 
6 inches deep. 
Seed in bulk, 5 feet deep; none killed 
14 
12 
do 
Inside 
2£ inches deep. 
Seed in bulk, ih feet deep; all not 
killed 1 foot from floor. 
Seed in bulk, 5 feet deep. 
POISONING EXPERIMENTS. 
As a possible means of controlling the pink bollworm in the field, 
poison experiments were conducted in the laboratory with both 
adults and larvse. Moths readily drink water in captivity when it 
is sprayed on the leaves or blotting paper in the breeding jars, and 
it was thought they might be killed by poisoning the drinking water 
with an arsenical solution. Repeated trials were made by using a 
solution of calcium arsenate for the moths to drink. The longevity 
of these moths was the same as that of those in the check, where 
pure water was used. 
While the laboratory experiments in poisoning the adults were 
not encouraging, it was thought advisable to try it under field con- 
ditions. From the habit of the newly hatched larvae of crawling 
over the plants and bolls before they enter, theoretically it seemed 
possible that a large number of young larvse might be poisoned. 
Average plats were selected at San Isidera, Tlahualilo, and at the 
laboratory for poisoning the plants. Weekly applications of pow- 
dered calcium arsenate were made with hand dusters. These appli- 
cations were begun about July 15 and continued until the last week 
in October. The gauges on the machines were opened to their fullest 
extent and as heavy an application as possible was made each time. 
(Table XXVIII.) 
