June, ’26] 
smith: vacuum fumigating 
319 
nests examined. On March 25th, 50 nests were fumigated at 56 to 57 
degrees Fahr. and resulted in finding all larvae dead in the nests examined. 
In all, 35 experiments were made between February 15th and March 
25th, 1921, and without any exception brown tail larvae were killed 
when fumigated at 50 degrees Fahr. and in many cases when fumigated 
at temperature as low as 39 degrees Fahr. Even more careful experi¬ 
ments-were made in 1922 between the dates of March 6th and May 9th. 
On the latter date the larvae were crawling in great numbers. 
The 1922 experiments confirmed the results obtained in 1921 with 
one exception. On April 8, 1922, 40 nests fumigated at 51 degrees Fahr. 
resulted in the finding of 9 larvae alive among 716 which had emerged 
from the nests prior to fumigation. With this exception the 1922 ex¬ 
periments, 37 in all, proved that the brown tail larvae were always killed 
at temperatures of 50 degrees Fahr. or above. In many instances they 
were all killed at 47 degrees Fahr. In one instance they were all killed 
at 40 degrees and in another at 42 degrees Fahr. In each experiment 
from 30 to 40 nests were fumigated. In view of all this w T ork I feel 
absolutely assured that the brown tail larvae in their winter nests may 
ordinarily be effectively killed if fumigated at a temperature of 50 degrees 
Fahr. or higher. It should be understood that this fumigation work was 
all conducted in the large fumigation cylinders used for cotton fumi¬ 
gation. 
European Corn Borer Experiments 
About one month after commencing the brown tail experiments in 
1921, I decided to work with European corn borer larvae under the 
same conditions. A large supply of borers in corn stalks was furnished 
by Mr. Caffrey of Arlington. The com borer experiments were com¬ 
menced on March 17, 1921 and continued that year until April 25th. 
The results were very unsatisfactory. Twenty-one experiments were 
made. The number of borers removed from the infested corn stalks 
after each experiment, varied from 27 to 142, an average of about 75. 
Some very contrary results were recorded. The first experiment on 
March 17th resulted in 74 borers being all apparently killed at a temper¬ 
ature of 49 degrees Fahr. but on March 21st, 52 borers fumigated at 
76 degrees Fahr. resulted in only 94% being killed. One month later, 
April 21st, 72 borers were fumigated at a temperature of 54 degrees 
Fahr. and only one survived. On April 23d, 71 borers fumigated at 
46 degrees Fahr. were all apparently killed and on April 25th, 37 borers 
fumigated at 50 degrees Fahr. were all apparently killed. Referring 
again to the record of 52 borers fumigated March 21st at 76 degrees Fahr., 
