THE TOBACCO BEETLE. 61 



time most of the beetles will have emerged from the cells, and the 

 adults, eggs, or newly hatched larva? 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. 1 (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 



1 A 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. 



