THE TOBACCO BEETLE. 61 
time most of the beetles will have emerged from the cells, and the 
adults, eggs, or newly hatched larve then present can be easily de- 
stroyed by fumigation. In two of the experiments already referred 
to, a second treatment was given 12 days later, resulting in the com- 
plete extermination of the beetles. Similar results were secured in 
several experiments not included in the series of tests described. 
FUMIGATING IN A VACUUM. 
In cooperation with the Federal Horticultural Board, a series of 
experiments was conducted at Washington, D. C., to determine the 
Fig. 15.—Apparatus used for fumigating in partial vacuum. 
effects on the tobacco beetle of hydrocyanic-acid gas in the presence 
of a partial vacuum. The apparatus used for the work was designed 
by Mr. E. H. Sasscer, Chief Inspector of the Federal Horticultural 
Board.t (Fig. 15.) 
By means of vacuum apparatus a very much greater penetration 
of the gas can be secured than is possible in fumigating at normal 
air pressure. It has been found in the tests made by the Federal 
Horticultural Board that hydrocyanic-acid gas when applied in 
vacuum readily penetrates to the interior of closely compressed bales 
1A detailed description of the apparatus and process of fumigation in vacuum has 
been given by the designer, Mr. E. R. Sasscer, in Service and Regulatory Announcements, 
Federal Horticultural Board, for October, 1915. 
