500 THE SMALL GRAINS 



ing to a high temperature, (2) fumigation with hydrocyanic 

 acid gas, and (3) fumigation with carbon bisulfid. 



545. Heating to a high temperature. Apparently 

 the most efficient method yet known for completely 

 eradicating all kinds of indoor cereal insects is the appli- 

 cation of high temperatures, which method has been 

 much developed in the last 4 or 5 years. Dean (1913, 

 pp. 145-176) has thoroughly investigated the method 

 and demonstrated its success. After determining the 

 best way of applying the heat in 2 different series of 

 experiments, a third series was conducted under condi- 

 tions that could more nearly be produced in a mill or 

 other large building. The insects employed were 15 speci- 

 mens each of the larvae, pupse, and adults of the confused 

 flour beetle, the adults of the saw-toothed grain beetle, 

 and the adults of the Mediterranean flour moth. The 

 specimens were placed in shell vials, so the actions of the 

 insects under the slowly rising temperature could be ob- 

 served, and the vials placed in a paraffin oven which was 

 heated to higher temperatures gradually. The temper- 

 ature at the beginning of the experiments was 87, the 

 same as that of the place from which the insects were 

 taken. Heat was applied at 8 o'clock in the morning, 

 and the temperature noted at intervals of a half hour. 

 At 5.45 P.M., with a temperature of 122.5, all insects 

 in all stages were dead. 



546. Demonstration in mills. The heating of sev- 

 eral mills, as a demonstration, proved that no stage of a 

 mill insect, even in the most inaccessible places, could 

 withstand the heat. Mills in Ohio, Illinois, Nebraska, 

 Iowa, Indiana, and southern Canada confirmed the 

 results secured in Kansas. 



In one instance heat was applied from 6 A.M. until 



