August, '19] DOANE: AUSTRALIAN WHEAT WEEVILS 311 



reach the center of the sack and in about twelve or fourteen hours the 

 temperature would go as high as 53° to 58° C. while the temperature 

 in the box outside the sacks would be 80° to 90° C. Under these 

 conditions all the insects in the screenings were killed. 



The screenings after being taken from the hot-box gave up their 

 heat, seemingly, as slowly as they took it, for we found that the tem- 

 perature in one of the sacks dropped only 3° C. in five hours, although 

 the sack was placed near an outside door in a cool store room. 



The results of these experiments showed that with a box as described 

 above and with a steam pressure of 80 to 150 pounds the screenings 

 should be exposed to the heat twelve hours. 



One of the Los Angeles mills built a small brick walled room about 

 6 feet by 10 feet by 8 feet high. It was heated by short coils of pipe 

 on one side of the room 4 or 5 feet from the floor. The»cost of building 

 this room and instalhng the pipes was about $225. The miller said 

 that it took several hours to heat the room and that he had found it 

 necessary to raise the temperature to 190° F. (88° C.) in order to kill 

 the insects. The thermometer from which his readings were taken 

 was placed on the wall near the steam coils and on the same level 

 with them. Tests made with other thermometers showed that one 

 placed on a level with the coils but some distance from them, soon 

 reached 71°C. Another placed about 2 feet from the floor, on a sack 

 of screenings registered 48° C. while a third that had been thrust into 

 the center of the sack of screenings registered only 28° C. This showed 

 that the unusual and unsatisfactory results that were being obtained 

 were due to the steam coils being placed high on the sides of the wall, 

 instead of on the floor or very close to it. It is believed that when 

 these coils are placed lower down, as recommended, no further trouble 

 will be met with. 



Some other mills have already installed, or propose to install, small 

 heat rooms for treating infested flour or other material that may be 

 returned to the mill from dealers or elsewhere. 



One company has been spraying all of the Australian wheat received 

 by its various mills with carbon tetrachloride. The work is done 

 with small hand pumps -and the wheat is sprayed as it is poured from 

 the conveyers into the bins. The aim is to use about 2 gallons of the 

 liquid to about 1000 bushels or 30 tons of the grain. In this way they 

 figure that the cost of the material for treating a ton of grain is about 

 20 cents. If the bins in which wheat, that has been treated in this 

 way, is stored, are tight and can be kept closed for a few days, nearly 

 ail of the weevils are killed. If the wheat is drawn from the bins 

 within twenty-four or thirty-six hours after it has been treated, many 

 live weevils are often found. The wheat should lie in the bin at least 



