4 THE POTATO-TUBER MOTH. 
acid gas. If bisulphid of carbon is used, it should be at the rate of 
3 pounds to 1,000 cubic feet of air space, including the potatoes; 
1 ounce to a barrel of 96 pounds’ capacity would not be excessive. 
With an exposure of not more than 24 hours, no harm should be done 
to the potatoes for planting. The bisulphid should be evaporated in 
Fic. 3.—Fumigator used for stored products infested by insects. (Author's illustration. ) 
tins, like pie plates, and a cover should be placed on the top of the 
fumieatmne barrel or box so as to make it as nearly air-tight as possi- 
ble. At the end of 24 hours the potatoes should be removed, placed 
in a fresh barrel, and closed up. 
Where it can be conveniently done hydrocyanic-acid gas chant 
be used in a specially constructed fumigator (see fig. 3), also gas- 
