198 INSECT PESTS OF FARM, GARDEN AND ORCHARD 



leave it forty-eight hours, which will do it no injury for food. 

 After treating, keep the grain covered to prevent reinfestation. 



Amount to Use. It was formerly recommended that the bisul- 

 fide be applied at the rate of 1 to 3 pounds to 100 bushels of grain 

 or 1000 cubic feet of open space. Recent experiments, however, 

 have shown the total inadequacy of this dosage. Experiments 

 made by Hinds and Hunter * show that the effectiveness of the 

 gas is in direct proportion to the temperature. Below 60 F. the 

 fumigation is ineffective and inadvisable. A dosage which will, 

 kill practically all the weevil at 67 to 70 will kill but 60 to 70 per 

 cent at 60 to 65. They recommend the use of 5 pounds per 

 1000 cubic feet where the room or bin is quite tight and the tem- 

 perature is 70 or above. For loose rooms and lower tempera- 

 tures, the dosage must be largely increased and may not be profit- 

 able. The above estimates are based upon the grain being in a 

 cubical shape; if it is spread out shallow, more bisulfide will be 

 necessary. 



Caution. " Certain precautions should always bie observed. 

 The vapor of carbon bisulfide is deadly to all forms of animal 

 life if inhaled in sufficient quantity, but there is no danger in 

 inhaling a small amount. The vapor is highly inflammable, 

 but with proper care that no fire of any kind, as, for example, 

 a lighted cigar, lantern, or light of any kind, be brought into 

 the vicinity until the fumes have entirely passed away, no trouble 

 will be experienced." 



Hydrocyanic Acid Gas. Mills and storehouses which needed 

 treatment were formerly fumigated with carbon bisulfide, which 

 is still employed to a considerable extent, but this has been 

 largely replaced by fumigation with hydrocyanic acid gas, which 

 obviates the risk from fire. Directions for the use of this gas 

 should be obtained from the entomologist of the State experiment 

 station or from the Bureau of Entomology of the U. S. Depart- 

 ment of Agriculture. 



Sulfur Fumes. Professor R. I. Smith (l.c) has made expcri- 



* Hinds and Hunter, Journal of Economic Entomology, Vol. Ill, p. 47: 

 R. I. Smith, Bulletin 203, X. C. Agr. Exp. Sta. 



