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JOURNAL OF ECONOMIC ENTOMOLOGY 
[Vol. 16 
I know now that that result was not entirely reliable. In other words, 
the borers themselves having been taken from a cool storage room had 
not responded in activity to the 76 degrees temperature. Likewise the 
good results obtained when fumigating at lower temperatures were not 
always reliable because the borers had sometimes been subjected to warm¬ 
er weather for two or three days just prior to fumigation and were more 
easily killed than they would otherwise have been. 
Much more exhaustive experiments with the corn borers in 1922 were 
made, taking advantage of the knowledge already gained the previous 
year, but the results were equally unsatisfactory. Sixty-five experiments 
were made from February 6 to June 8. From them it was determined 
definitely that borers taken from a storeroom at a temperature of 40 
to 45 degrees Fahr. and fumigated in an atmosphere of 65 to 70 degrees 
Fahr. could not all be killed. It was also determined that borers which 
survived one fumigation at any temperature were often able to survive 
a second fumigation, some times at a higher temperature, and the records 
show that one individual borer was fumigated five times before it was 
finally killed at a temperature of 78 dgrees Fahr. I am forced to con¬ 
clude that vacuum fumigation with a six ounce charge of cyanide is not 
effective against corn borers. 
In the course of these experiments a surprising condition was dis¬ 
covered. Borers were frequently counted dead for from two to fourteen 
days after fumigation and then recovered. Many borers that did re¬ 
cover in this manner were placed under incubation conditions and were 
frequently reared to moths at the Arlington Com Borer laboratory. It 
must be concluded that if borers survive the cyanide fumigation they 
are not weakened to any appreciable extent. It was also found that the 
large mature-looking borers were no more resistant to the gas than the 
small immature specimens. It should be explained that all the experi¬ 
ments, with a very few exceptions, represented two-hour fumigation 
periods. Much better results were obtained in general in the few ex¬ 
periments made when the time of fumigation was from six to ten hours. 
I feel safe in asserting that a continuous four-hour fumigation is more 
effective than two separate two-hour fumigations, other conditions 
being equal. 
In view of all my experiments I believe that imported nursery stock 
may be safeguarded against brown tail moth larvae by fumigation at a 
suitable temperature, but I do not believe that importation of any 
