310 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 12 



that contained a considerable amount of wheat that might be used 

 for feed, especially if we could in some way destroy the beetles so they 

 would not be a source of danger wherever the feed was used. 



Carbon bisulphide could not be used for this purpose as the mills 

 would not take the fire risk. Cyanide seemed to be out of the question 

 as the screenings were so finely packed in the sacks that it would be 

 very hard, if not impossible, to get sufficient penetration of the gas, 

 unless the vacuum system was used and that was considered too 

 expensive for the purpose. 



We urged that all of the mills that were handling this wheat make 

 some provision for treating the screenings with heat to destroy the 

 insects and some of them complied with this request. One firm, 

 instead of building a small room or partitioning off a small part of a 

 large room, constructed a tight box 16 feet long, 5 feet high and 3 feet 

 from front to back. The front side of the box was provided with 

 eight doors which opened practically the whole side of the box. These 

 doors were secured by fasteners which clamped them close to their 

 frames when closed. There was shelf room for 16 sacks of wheat in 

 this box. Close to the bottom were 28, 9-foot lengths of 3/4-inch pipe. 

 The cost of such a box including material and labor was about $200. 

 The engineer said that the cost of operating it was inconsiderable 

 as it took but little steam to maintain the required temperature. 



The sacks of screenings to be treated were placed in this box about 

 9 o'clock in the morning and left there until 3 or 4 o'clock of the same 

 day, sometimes they were left there until the next morning. The 

 steam was turned on as soon as the box was filled and left until 4.30 

 or 5 o'clock in the evening. 



An examination of the screenings that had been subjected to this 

 treatment showed that, when the sacks were left in the box for only 

 six or eight hours, all of the beetles were not kill^, but when they 

 were left in twelve hours or longer, no living insects could be found. A 

 series of tests and experiments showed that with a steam pressure of 

 80 pounds the temperature in the box was raised to about 53° C. in a 

 very short time; with an increased pressure the temperature rises 

 very rapidly. With 150 pounds pressure the thermometer soon read 

 90° or 92° C. 



The weevils and other beetles that were on the outside of the sacks 

 began to die when the temperature reached 50° to 52° C. and before 

 it reached 60° C. all that were exposed were dead. But it was found 

 that the heat penetrates the screenings very slowly, so that after an 

 exposure of six hours to a temperature of 53° to 80° C. a thermometer 

 that had been placed in the center of the sack showed no increase 

 of temperature. After about seven or eight hours the heat began to 



