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JOURNAL OF ECONOMIC ENTOMOLOGY 
[Vol. 16 
and even complete their transformations. The experiments, with few exceptions, 
represented two hour fumigation periods, much better results being obtained when 
the time was extended to from six to ten hours. 
On February 8, 1921, Mr. E. R. Sasscer of the Federal Horticultural 
Board wrote that French fruit seedlings had been arriving at frequent 
intervals infested with the brown tail moth nests. He said the question 
had arisen at the Board meeting that day as to whether or not it would 
be possible to safeguard nursery stock bearing brown tail nests by 
fumigating at the vacuum fumigation plants with the same dosage of 
cyanide as employed in the fumigation of cotton. He had been instruct¬ 
ed by the Board to ask me to immediately secure brown tail nests and 
commence a series of experiments to settle the point in question. I 
made plans immediately and a large supply of nests containing at least 
85% living larvae were furnished at my request, by Mr. A. F Burgess 
of Melrose Highlands. 
It should be clearly understood that all the experiments I shall mention 
today were made in connection with the commercial fumigation of im¬ 
ported cotton as required by the Federal Horticultural Board. The 
method, as many of you know, is the introduction of hydrocyanic acid 
gas into the cotton while under a 25" vacuum. A dosage of six ounces 
NaCN to 100 cubic feet and a period of two hours is required for all 
ordinary raw cotton. All of my experiments with brown tail and Euro- 
pean corn borer larvae were made with the above charge of cyanide. 
My first experiment with brown tail nests was made February 15, 
1921. The temperature was 27 degrees Fahr. Fifty nests were fumi¬ 
gated. None of the larvae were killed. Two days later, February 17th, 
over 150 nests were fumigated at a temperature of 50 degrees Fahr. and 
all larvae were apparently killed. On February 23d about 100 nests 
were fumigated at 38 to 39 degrees Fahr. In one nest 173 living larvae 
and 411 dead were found. In seven other nests the average number of 
larvae alive was less than 12 each. Sixteen other nests were examined 
with the result that all the larvae were found dead. On March 1st out 
of 50 nests fumigated at 45 degrees Fahr. only 2 larvae were found alive 
in 13 nests examined. On March 7th, 50 nests fumigated at 43 degrees 
Fahr. resulted in finding 7 larvae alive in three of the ten nests examined. 
On March 11th, among 50 nests fumigated at 48 to 49 degrees Fahr. 
we found all larvae dead in ten nests examined. On March 17th, 50 
nests were fumigated at 49 degrees Fahr. and all larvae found dead in 
ten nests examined. On March 22d, 50 nests were fumigated at 42 
to 43 degrees Fahr. with the result that all larvae were found dead in five 
