144 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 4 



larvse and adults were becoming passive, and at a temperature of 118° 

 all adults were lying on their backs apparently dead, while four or 

 five larvse showed very feeble movements. At a temperature of 

 119° there was no sign of Hfe; however, the temperature was raised to 

 120° and then the insects were removed and given a chance to recover, 

 but none did. This experiment was repeated several times and each 

 time as soon as a temperature of from 119° to 120° was reached it 

 proved fatal to all stages of the insects. It required from twelve to 

 fifteen minutes to reach this fatal temperature. 



Similar experiments were conducted and repeated with the larvse, 

 pupae, and adults of Silvanus surinamensis, Ephestia kuehniella, Ten- 

 ehrioides mauritanicus, and the adults of Calandra oryza. As soon as 

 a temperature of 116° was reached it proved fatal to the adults of 

 Ephestia kuehniella while it required a temperature of 118° to prove 

 fatal to the larvse and pupse. A temperature of 118° was fatal to the 

 adults of Calandra oryza, and a temperature of 119° proved fatal 

 to all stages of Silvanus surinamensis. At a temperature of 120° 

 the majority of the Tenebrioides mauritanicus perished, but it required 

 a temperature of 120° for a period of three minutes to prove fatal to 

 all. 



In a second series of experiments a paraffin oven or incubator was 

 used, and after the oven was heated to a required temperature, 

 the insects were placed in it and the oven held to a constant 

 temperature throughout the experiment. In this experiment about 

 twenty-five specimens of the eggs, larvse, pupse and adults of Tribolium 

 confusum, larvse and pupse of the Ephestia kuehniella, and the adults 

 of Calandra oryza, and Tenebrioides mauritanicus were used. Experi- 

 ments were made not only with these various stages of insects on 

 .top of the flour, but one and two inches below the surface. After a 

 series of experiments it was found that a temperature of 115° for a 

 period of twelve hours proved fatal to all the insects in their various 

 stages. 



Since in practical use it would be impossible to actually heat a 

 mill in a few minutes as in the first series of experiments, or subject 

 them to such a sudden change as in the second series, a third set of 

 experiments was conducted to determine the fatal temperature under 

 conditions that could actually be produced in a mill. In these experi- 

 ments the larvse, pupae, and adults of Tribolium confusum, the adults 

 of Silvanus surinamensis, and Ephestia kuehniella were used. The 

 various stages of the different insects were placed in shell vials, so. 

 that their actions under the slowly rising temperature of the oven 

 could be observed. The heat was applied at 8 a. m. and the temper- 

 ature noted at intervals of every half hour. The temperature at the 



